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Sample records for pre-launch calibration error

  1. Planck pre-launch status: High Frequency Instrument polarization calibration

    CERN Document Server

    Rosset, C; Ponthieu, N; Ade, P; Catalano, A; Conversi, L; Couchot, F; Crill, B P; Désert, F -X; Ganga, K; Giard, M; Giraud-Héraud, Y; Haïssinski, J; Henrot-Versillé, S; Holmes, W; Jones, W C; Lamarre, J -M; Lange, A; Leroy, C; Macías-Pérez, J; Maffei, B; de Marcillac, P; Miville-Deschênes, M -A; Montier, L; Noviello, F; Pajot, F; Perdereau, O; Piacentini, F; Piat, M; Plaszczynski, S; Pointecouteau, E; Puget, J -L; Ristorcelli, I; Savini, G; Sudiwala, R; Veneziani, M; Yvon, D

    2010-01-01

    The High Frequency Instrument of Planck will map the entire sky in the millimeter and sub-millimeter domain from 100 to 857 GHz with unprecedented sensitivity to polarization ($\\Delta P/T_{\\tiny cmb} \\sim 4\\cdot 10^{-6}$) at 100, 143, 217 and 353 GHz. It will lead to major improvements in our understanding of the Cosmic Microwave Background anisotropies and polarized foreground signals. Planck will make high resolution measurements of the $E$-mode spectrum (up to $\\ell \\sim 1500$) and will also play a prominent role in the search for the faint imprint of primordial gravitational waves on the CMB polarization. This paper addresses the effects of calibration of both temperature (gain) and polarization (polarization efficiency and detector orientation) on polarization measurements. The specific requirements on the polarization parameters of the instrument are set and we report on their pre-flight measurement on HFI bolometers. We present a semi-analytical method that exactly accounts for the scanning strategy of...

  2. JPSS-1 VIIRS Radiometric Characterization and Calibration Based on Pre-Launch Testing

    Directory of Open Access Journals (Sweden)

    Hassan Oudrari

    2016-01-01

    Full Text Available The Visible Infrared Imaging Radiometer Suite (VIIRS on-board the first Joint Polar Satellite System (JPSS completed its sensor level testing on December 2014. The JPSS-1 (J1 mission is scheduled to launch in December 2016, and will be very similar to the Suomi-National Polar-orbiting Partnership (SNPP mission. VIIRS instrument has 22 spectral bands covering the spectrum between 0.4 and 12.6 μm. It is a cross-track scanning radiometer capable of providing global measurements twice daily, through observations at two spatial resolutions, 375 m and 750 m at nadir for the imaging and moderate bands, respectively. This paper will briefly describe J1 VIIRS characterization and calibration performance and methodologies executed during the pre-launch testing phases by the government independent team to generate the at-launch baseline radiometric performance and the metrics needed to populate the sensor data record (SDR Look-Up-Tables (LUTs. This paper will also provide an assessment of the sensor pre-launch radiometric performance, such as the sensor signal to noise ratios (SNRs, radiance dynamic range, reflective and emissive bands calibration performance, polarization sensitivity, spectral performance, response-vs-scan (RVS, and scattered light response. A set of performance metrics generated during the pre-launch testing program will be compared to both the VIIRS sensor specification and the SNPP VIIRS pre-launch performance.

  3. Pre-Launch Absolute Calibration of CCD/CBERS-2B Sensor

    Science.gov (United States)

    Ponzoni, Flávio Jorge; Albuquerque, Bráulio Fonseca Carneiro

    2008-01-01

    Pre-launch absolute calibration coefficients for the CCD/CBERS-2B sensor have been calculated from radiometric measurements performed in a satellite integration and test hall in the Chinese Academy of Space Technology (CAST) headquarters, located in Beijing, China. An illuminated integrating sphere was positioned in the test hall facilities to allow the CCD/CBERS-2B imagery of the entire sphere aperture. Calibration images were recorded and a relative calibration procedure adopted exclusively in Brazil was applied to equalize the detectors responses. Averages of digital numbers (DN) from these images were determined and correlated to their respective radiance levels in order to calculate the absolute calibration coefficients. It has been the first time these pre-launch absolute calibration coefficients have been calculated considering the Brazilian image processing criteria. Now it will be possible to compare them to those that will be calculated from vicarious calibration campaigns. This comparison will permit the CCD/CBERS-2B monitoring and the frequently data updating to the user community. PMID:27873886

  4. Planck pre-launch status: calibration of the Low Frequency Instrument flight model radiometers

    CERN Document Server

    Villa, F; Sandri, M; Meinhold, P; Poutanen, T; Battaglia, P; Franceschet, C; Hughes, N; Laaninen, M; Lapolla, P; Bersanelli, M; Butler, R C; Cuttaia, F; D'Arcangelo, O; Frailis, M; Franceschi, E; Galeotta, S; Gregorio, A; Leonardi, R; Lowe, S R; Mandolesi, N; Maris, M; Mendes, L; Mennella, A; Morgante, G; Stringhetti, L; Tomasi, M; Valenziano, L; Zacchei, A; Zonca, A; Aja, B; Artal, E; Balasini, M; Bernardino, T; Blackhurst, E; Boschini, L; Cappellini, B; Cavaliere, F; Colin, A; Colombo, F; Davis, R J; De La Fuente, L; Edgeley, J; Gaier, T; Galtress, A; Hoyland, R; Jukkala, P; Kettle, D; Kilpia, V-H; Lawrence, C R; Lawson, D; Leahy, J P; Leutenegger, P; Levin, S; Maino, D; Malaspina, M; Mediavilla, A; Miccolis, M; Pagan, L; Pascual, J P; Pasian, F; Pecora, M; Pospieszalski, M; Roddis, N; Salmon, M J; Seiffert, M; Silvestri, R; Simonetto, A; Sjoman, P; Sozzi, C; Tuovinen, J; Varis, J; Wilkinson, A; Winder, F

    2010-01-01

    The Low Frequency Instrument (LFI) on-board the ESA Planck satellite carries eleven radiometer subsystems, called Radiometer Chain Assemblies (RCAs), each composed of a pair of pseudo-correlation receivers. We describe the on-ground calibration campaign performed to qualify the flight model RCAs and to measure their pre-launch performances. Each RCA was calibrated in a dedicated flight-like cryogenic environment with the radiometer front-end cooled to 20K and the back-end at 300K, and with an external input load cooled to 4K. A matched load simulating a blackbody at different temperatures was placed in front of the sky horn to derive basic radiometer properties such as noise temperature, gain, and noise performance, e.g. 1/f noise. The spectral response of each detector was measured as was their susceptibility to thermal variation. All eleven LFI RCAs were calibrated. Instrumental parameters measured in these tests, such as noise temperature, bandwidth, radiometer isolation, and linearity, provide essential i...

  5. Pre-Launch Calibration and Performance Study of the Polarcube 3u Temperature Sounding Radiometer Mission

    Science.gov (United States)

    Periasamy, L.; Gasiewski, A. J.; Sanders, B. T.; Rouw, C.; Alvarenga, G.; Gallaher, D. W.

    2016-12-01

    The positive impact of passive microwave observations of tropospheric temperature, water vapor and surface variables on short-term weather forecasts has been clearly demonstrated in recent forecast anomaly growth studies. The development of a fleet of such passive microwave sensors especially at V-band and higher frequencies in low earth orbit using 3U and 6U CubeSats could help accomplish the aforementioned objectives at low system cost and risk as well as provide for regularly updated radiometer technology. The University of Colorado's 3U CubeSat, PolarCube is intended to serve as a demonstrator for such a fleet of passive sounders and imagers. PolarCube supports MiniRad, an eight channel, double sideband 118.7503 GHz passive microwave sounder. The mission is focused primarily on sounding in Arctic and Antarctic regions with the following key remote sensing science and engineering objectives: (i) Collect coincident tropospheric temperature profiles above sea ice, open polar ocean, and partially open areas to develop joint sea ice concentration and lower tropospheric temperature mapping capabilities in clear and cloudy atmospheric conditions. This goal will be accomplished in conjunction with data from existing passive microwave sensors operating at complementary bands; and (ii) Assess the capabilities of small passive microwave satellite sensors for environmental monitoring in support of the future development of inexpensive Earth science missions. Performance data of the payload/spacecraft from pre-launch calibration will be presented. This will include- (i) characterization of the antenna sub-system comprising of an offset 3D printed feedhorn and spinning parabolic reflector and impact of the antenna efficiencies on radiometer performance, (ii) characterization of MiniRad's RF front-end and IF back-end with respect to temperature fluctuations and their impact on atmospheric temperature weighting functions and receiver sensitivity, (iii) results from roof

  6. Pre-Launch Phase 1 Calibration and Validation Rehearsal of Geophysical Data Products of Soil Moisture Active Passive (SMAP) Mission

    Science.gov (United States)

    Colliander, A.; Jackson, T. J.; Chan, S.; Dunbar, R.; Das, N. N.; Kim, S.; Reichle, R. H.; De Lannoy, G. J.; Liu, Q.; Kimball, J. S.; Yi, Y.; Cosh, M. H.; Bindlish, R.; Crow, W. T.; Dang, L.; Yueh, S. H.; Njoku, E. G.

    2013-12-01

    NASA's Soil Moisture Active Passive (SMAP) Mission is scheduled for launch in October 2014. The objective of the mission is global mapping of soil moisture and freeze/thaw state. SMAP utilizes an L-band radar and radiometer sharing a rotating 6-meter mesh reflector antenna. The instruments will operate onboard the SMAP spacecraft in a 685-km Sun-synchronous near-polar orbit, viewing the surface at a constant 40-degree incidence angle with a 1000-km swath width. Merging of active and passive L-band observations of the mission will enable an unprecedented combination of accuracy, resolution, coverage and revisit-time for soil moisture and freeze/thaw state retrieval. SMAP measurements will enable significantly improved estimates of water, energy and carbon transfers between the land and atmosphere. The SMAP science data product suite of geophysical parameters will include estimates of surface (top 5 cm) and root-zone (down to 1-m depth) soil moisture, net ecosystem exchange, and classification of the frozen/non-frozen state of the landscape. The primary validation reference of the data products will be ground-based measurements. Other remote sensing and model-based products will be used as additional resources. The post-launch timeline of the mission requires that the geophysical data products are validated (with respect to the mission requirements) within 12 months after a 3-month in-orbit check-out phase. SMAP is taking several preparatory steps in order to meet this schedule. One of the main steps consists of running a rehearsal to exercise calibration and validation procedures planned for the Cal/Val Phase. The rehearsal is divided into two stages. Phase 1, which was conducted in June-August 2013, focused on validation methodologies for the geophysical data products. Phase 2, which will be conducted in May-June 2014, includes operational aspects including a fully functioning SMAP Science Data System. (Note that the rehearsals do not include an airborne field

  7. Pre-Launch Algorithm and Data Format for the Level 1 Calibration Products for the EOS AM-1 Moderate Resolution Imaging Spectroradiometer (MODIS)

    Science.gov (United States)

    Guenther, Bruce W.; Godden, Gerald D.; Xiong, Xiao-Xiong; Knight, Edward J.; Qiu, Shi-Yue; Montgomery, Harry; Hopkins, M. M.; Khayat, Mohammad G.; Hao, Zhi-Dong; Smith, David E. (Technical Monitor)

    2000-01-01

    The Moderate Resolution Imaging Spectroradiometer (MODIS) radiometric calibration product is described for the thermal emissive and the reflective solar bands. Specific sensor design characteristics are identified to assist in understanding how the calibration algorithm software product is designed. The reflected solar band software products of radiance and reflectance factor both are described. The product file format is summarized and the MODIS Characterization Support Team (MCST) Homepage location for the current file format is provided.

  8. Regression calibration with heteroscedastic error variance.

    Science.gov (United States)

    Spiegelman, Donna; Logan, Roger; Grove, Douglas

    2011-01-01

    The problem of covariate measurement error with heteroscedastic measurement error variance is considered. Standard regression calibration assumes that the measurement error has a homoscedastic measurement error variance. An estimator is proposed to correct regression coefficients for covariate measurement error with heteroscedastic variance. Point and interval estimates are derived. Validation data containing the gold standard must be available. This estimator is a closed-form correction of the uncorrected primary regression coefficients, which may be of logistic or Cox proportional hazards model form, and is closely related to the version of regression calibration developed by Rosner et al. (1990). The primary regression model can include multiple covariates measured without error. The use of these estimators is illustrated in two data sets, one taken from occupational epidemiology (the ACE study) and one taken from nutritional epidemiology (the Nurses' Health Study). In both cases, although there was evidence of moderate heteroscedasticity, there was little difference in estimation or inference using this new procedure compared to standard regression calibration. It is shown theoretically that unless the relative risk is large or measurement error severe, standard regression calibration approximations will typically be adequate, even with moderate heteroscedasticity in the measurement error model variance. In a detailed simulation study, standard regression calibration performed either as well as or better than the new estimator. When the disease is rare and the errors normally distributed, or when measurement error is moderate, standard regression calibration remains the method of choice.

  9. JPSS-1 VIIRS pre-launch radiometric performance

    Science.gov (United States)

    Oudrari, Hassan; McIntire, Jeff; Xiong, Xiaoxiong; Butler, James; Efremova, Boryana; Ji, Qiang; Lee, Shihyan; Schwarting, Tom

    2015-09-01

    The Visible Infrared Imaging Radiometer Suite (VIIRS) on-board the first Joint Polar Satellite System (JPSS) completed its sensor level testing on December 2014. The JPSS-1 (J1) mission is scheduled to launch in December 2016, and will be very similar to the Suomi-National Polar-orbiting Partnership (SNPP) mission. VIIRS instrument was designed to provide measurements of the globe twice daily. It is a wide-swath (3,040 km) cross-track scanning radiometer with spatial resolutions of 370 and 740 m at nadir for imaging and moderate bands, respectively. It covers the wavelength spectrum from reflective to long-wave infrared through 22 spectral bands [0.412 μm to 12.01 μm]. VIIRS observations are used to generate 22 environmental data products (EDRs). This paper will briefly describe J1 VIIRS characterization and calibration performance and methodologies executed during the pre-launch testing phases by the independent government team, to generate the at-launch baseline radiometric performance, and the metrics needed to populate the sensor data record (SDR) Look-Up-Tables (LUTs). This paper will also provide an assessment of the sensor pre-launch radiometric performance, such as the sensor signal to noise ratios (SNRs), dynamic range, reflective and emissive bands calibration performance, polarization sensitivity, bands spectral performance, response-vs-scan (RVS), near field and stray light responses. A set of performance metrics generated during the pre-launch testing program will be compared to the SNPP VIIRS pre-launch performance.

  10. 1% calibration errors in MQY magnets

    CERN Document Server

    Bach, T; Langner, A; Levinsen, Y; McAteer, M; Maclean, E H; Persson, T; Skowronski, P; Tomás, R; Todesco, E; White, S

    2013-01-01

    Errors in the range of 1% have been observed for the MQY magnets in beam-based measurements. Furthermore, inconsistencies have been observed when comparing previous magnetic measurements to the LHC LSA database. After a revision, new calibration data have been extracted and were compared to the optics corrections that have been obtained from beam-based measurements. In 27-11-2012 a MD session has been performed to test these calibration data. This paper reports on the experimental verification of the new calibration data for the MQY quadrupole magnets.

  11. Calibration Errors in Interferometric Radio Polarimetry

    Science.gov (United States)

    Hales, Christopher A.

    2017-08-01

    Residual calibration errors are difficult to predict in interferometric radio polarimetry because they depend on the observational calibration strategy employed, encompassing the Stokes vector of the calibrator and parallactic angle coverage. This work presents analytic derivations and simulations that enable examination of residual on-axis instrumental leakage and position-angle errors for a suite of calibration strategies. The focus is on arrays comprising alt-azimuth antennas with common feeds over which parallactic angle is approximately uniform. The results indicate that calibration schemes requiring parallactic angle coverage in the linear feed basis (e.g., the Atacama Large Millimeter/submillimeter Array) need only observe over 30°, beyond which no significant improvements in calibration accuracy are obtained. In the circular feed basis (e.g., the Very Large Array above 1 GHz), 30° is also appropriate when the Stokes vector of the leakage calibrator is known a priori, but this rises to 90° when the Stokes vector is unknown. These findings illustrate and quantify concepts that were previously obscure rules of thumb.

  12. The pre-launch status of TanSat Mission: Instrument, Retrieval algorithm, Flux inversion and Validation

    Science.gov (United States)

    Liu, Yi; Yin, Zengshan; Yang, Zhongdong; Zheng, Yuquan; Yan, Changxiang; Tian, Xiangjun; Yang, Dongxu

    2016-04-01

    After 5 years development, The Chinese carbon dioxide observation satellite (TanSat), the first scientific experimental CO2 satellite of China, step into the pre-launch phase. The characters of pre-launch carbon dioxide spectrometer have been optimized during the laboratory test and calibration. Radiometric calibration shows a SNR of 440 (O2A 0.76um band), 300 (CO2 1.61um band) and 180 (CO2 2.06um band) on average in the typical radiance condition. Instrument line shape was calibrated automatically in using a well design testing system with laser control and record. After a series of test and calibration in laboratory, the instrumental performances meet the design requirements. TanSat will be launched on August 2016. The optimal estimation theory was involved in TanSat XCO2 retrieval algorithm in a full physics way with simulation of the radiance transfer in atmosphere. Gas absorption, aerosol and cirrus scattering and surface reflectance associate with wavelength dispersion have been considered in inversion for better correction the interference errors to XCO2. In order to simulate the radiance transfer precisely and efficiently, we develop a fast vector radiative transfer simulation method. Application of TanSat algorithm on GOSAT observation (ATANGO) is appropriate to evaluate the performance of algorithm. Validated with TCCON measurements, the ATANGO product achieves a 1.5 ppm precision. A Chinese carbon cycle data- assimilation system Tan-Tracker is developed based on the atmospheric chemical transport model GEOS-Chem. Tan-Tracker is a dual-pass data-assimilation system in which both CO2 concentrations and CO2 fluxes are simultaneously assimilated from atmospheric observations. A validation network has been established around China to support a series of CO2 satellite of China, which include 3 IFS-125HR and 4 Optical Spectrum Analyzer etc.

  13. JPSS-1 VIIRS Pre-Launch Response Versus Scan Angle Testing and Performance

    Directory of Open Access Journals (Sweden)

    David Moyer

    2016-02-01

    Full Text Available The Visible Infrared Imaging Radiometer Suite (VIIRS instruments on-board both the Suomi National Polar-orbiting Partnership (S-NPP and the first Joint Polar Satellite System (JPSS-1 spacecraft, with launch dates of October 2011 and December 2016 respectively, are cross-track scanners with an angular swath of ±56.06°. A four-mirror Rotating Telescope Assembly (RTA is used for scanning combined with a Half Angle Mirror (HAM that directs light exiting from the RTA into the aft-optics. It has 14 Reflective Solar Bands (RSBs, seven Thermal Emissive Bands (TEBs and a panchromatic Day Night Band (DNB. There are three internal calibration targets, the Solar Diffuser, the BlackBody and the Space View, that have fixed scan angles within the internal cavity of VIIRS. VIIRS has calibration requirements of 2% on RSB reflectance and as tight as 0.4% on TEB radiance that requires the sensor’s gain change across the scan or Response Versus Scan angle (RVS to be well quantified. A flow down of the top level calibration requirements put constraints on the characterization of the RVS to 0.2%–0.3% but there are no specified limitations on the magnitude of response change across scan. The RVS change across scan angle can vary significantly between bands with the RSBs having smaller changes of ~2% and some TEBs having ~10% variation. Within a band, the RVS has both detector and HAM side dependencies that vary across scan. Errors in the RVS characterization will contribute to image banding and striping artifacts if their magnitudes are above the noise level of the detectors. The RVS was characterized pre-launch for both S-NPP and JPSS-1 VIIRS and a comparison of the RVS curves between these two sensors will be discussed.

  14. Rectifying calibration error of Goldmann applanation tonometer is easy!

    Directory of Open Access Journals (Sweden)

    Nikhil S Choudhari

    2014-01-01

    Full Text Available Purpose: Goldmann applanation tonometer (GAT is the current Gold standard tonometer. However, its calibration error is common and can go unnoticed in clinics. Its company repair has limitations. The purpose of this report is to describe a self-taught technique of rectifying calibration error of GAT. Materials and Methods: Twenty-nine slit-lamp-mounted Haag-Streit Goldmann tonometers (Model AT 900 C/M; Haag-Streit, Switzerland were included in this cross-sectional interventional pilot study. The technique of rectification of calibration error of the tonometer involved cleaning and lubrication of the instrument followed by alignment of weights when lubrication alone didn′t suffice. We followed the South East Asia Glaucoma Interest Group′s definition of calibration error tolerance (acceptable GAT calibration error within ±2, ±3 and ±4 mm Hg at the 0, 20 and 60-mm Hg testing levels, respectively. Results: Twelve out of 29 (41.3% GATs were out of calibration. The range of positive and negative calibration error at the clinically most important 20-mm Hg testing level was 0.5 to 20 mm Hg and -0.5 to -18 mm Hg, respectively. Cleaning and lubrication alone sufficed to rectify calibration error of 11 (91.6% faulty instruments. Only one (8.3% faulty GAT required alignment of the counter-weight. Conclusions: Rectification of calibration error of GAT is possible in-house. Cleaning and lubrication of GAT can be carried out even by eye care professionals and may suffice to rectify calibration error in the majority of faulty instruments. Such an exercise may drastically reduce the downtime of the Gold standard tonometer.

  15. The Orbiting Carbon Observatory (OCO-2): spectrometer performance evaluation using pre-launch direct sun measurements

    Science.gov (United States)

    Frankenberg, C.; Pollock, R.; Lee, R. A. M.; Rosenberg, R.; Blavier, J.-F.; Crisp, D.; O'Dell, C. W.; Osterman, G. B.; Roehl, C.; Wennberg, P. O.; Wunch, D.

    2015-01-01

    The Orbiting Carbon Observatory-2 (OCO-2), launched on 2 July 2014, is a NASA mission designed to measure the column-averaged CO2 dry air mole fraction, XCO2. Towards that goal, it will collect spectra of reflected sunlight in narrow spectral ranges centered at 0.76, 1.6 and 2.0 μm with a resolving power (λ/Δ λ) of 20 000. These spectra will be used in an optimal estimation framework to retrieve XCO2. About 100 000 cloud free soundings of XCO2 each day will allow estimates of net CO2 fluxes on regional to continental scales to be determined. Here, we evaluate the OCO-2 spectrometer performance using pre-launch data acquired during instrument thermal vacuum tests in April 2012. A heliostat and a diffuser plate were used to feed direct sunlight into the OCO-2 instrument and spectra were recorded. These spectra were compared to those collected concurrently from a nearby high-resolution Fourier Transform Spectrometer that was part of the Total Carbon Column Observing Network (TCCON). Using the launch-ready OCO-2 calibration and spectroscopic parameters, we performed total column scaling fits to all spectral bands and compared these to TCCON results. On 20 April, we detected a CO2 plume from the Los Angeles basin at the JPL site with strongly enhanced short-term variability on the order of 1% (3-4 ppm). We also found good (< 0.5 ppm) inter-footprint consistency in retrieved XCO2. The variations in spectral fitting residuals are consistent with signal-to-noise estimates from instrument calibration, while average residuals are systematic and mostly attributable to remaining errors in our knowledge of the CO2 and O2 spectroscopic parameters. A few remaining inconsistencies observed during the tests may be attributable to the specific instrument setup on the ground and will be re-evaluated with in-orbit data.

  16. Error Model and Accuracy Calibration of 5-Axis Machine Tool

    Directory of Open Access Journals (Sweden)

    Fangyu Pan

    2013-08-01

    Full Text Available To improve the machining precision and reduce the geometric errors for 5-axis machinetool, error model and calibration are presented in this paper. Error model is realized by the theory of multi-body system and characteristic matrixes, which can establish the relationship between the cutting tool and the workpiece in theory. The accuracy calibration was difficult to achieve, but by a laser approach-laser interferometer and laser tracker, the errors can be displayed accurately which is benefit for later compensation.

  17. Auto-calibration of Systematic Odometry Errors in Mobile Robots

    DEFF Research Database (Denmark)

    Bak, Martin; Larsen, Thomas Dall; Andersen, Nils Axel

    1999-01-01

    This paper describes the phenomenon of systematic errors in odometry models in mobile robots and looks at various ways of avoiding it by means of auto-calibration. The systematic errors considered are incorrect knowledge of the wheel base and the gains from encoder readings to wheel displacement...... and experiments on a mobile robot....

  18. The Thermal Infrared Sensor (TIRS on Landsat 8: Design Overview and Pre-Launch Characterization

    Directory of Open Access Journals (Sweden)

    Dennis C. Reuter

    2015-01-01

    Full Text Available The Thermal Infrared Sensor (TIRS on Landsat 8 is the latest thermal sensor in that series of missions. Unlike the previous single-channel sensors, TIRS uses two channels to cover the 10–12.5 micron band. It is also a pushbroom imager; a departure from the previous whiskbroom approach. Nevertheless, the instrument requirements are defined such that data continuity is maintained. This paper describes the design of the TIRS instrument, the results of pre-launch calibration measurements and shows an example of initial on-orbit science performance compared to Landsat 7.

  19. Calibrating Car-Following Model Considering Measurement Errors

    Directory of Open Access Journals (Sweden)

    Chang-qiao Shao

    2013-01-01

    Full Text Available Car-following model has important applications in traffic and safety engineering. To enhance the accuracy of model in predicting behavior of individual driver, considerable studies strive to improve the model calibration technologies. However, microscopic car-following models are generally calibrated by using macroscopic traffic data ignoring measurement errors-in-variables that leads to unreliable and erroneous conclusions. This paper aims to develop a technology to calibrate the well-known Van Aerde model. Particularly, the effect of measurement errors-in-variables on the accuracy of estimate is considered. In order to complete calibration of the model using microscopic data, a new parameter estimate method named two-step approach is proposed. The result shows that the modified Van Aerde model to a certain extent is more reliable than the generic model.

  20. The Orbiting Carbon Observatory (OCO-2: spectrometer performance evaluation using pre-launch direct sun measurements

    Directory of Open Access Journals (Sweden)

    C. Frankenberg

    2014-07-01

    Full Text Available The Orbiting Carbon Observatory-2 (OCO-2, launched on 2 July 2014, is a NASA mission designed to measure the column-averaged CO2 dry air mole fraction, XCO2. Towards that goal, it will collect spectra of reflected sun-light in narrow spectral ranges centered at 0.76, 1.6 and 2.0 μm with a resolving power (λ/Δ λ of 20 000. These spectra will be used in an optimal estimation framework to retrieve XCO2. About 100 000 cloud free soundings of XCO2 each day will allow estimates of net CO2 fluxes on regional to continental scales to be determined. Here, we evaluate the OCO-2 spectrometer performance using pre-launch data acquired during instrument thermal vacuum tests in April 2012. A heliostat and a diffuser plate were used to feed direct sunlight into the OCO-2 instrument and spectra were recorded. These spectra were compared to those collected concurrently from a nearby high-resolution Fourier Transform Spectrometer that was part of the Total Carbon Column Observing Network (TCCON. Using the launch-ready OCO-2 calibration and spectroscopic parameters, we performed total column scaling fits to all spectral bands and compared these to TCCON results. On 20 April, we detected a CO2 plume from the Los Angeles basin at the JPL site with strongly enhanced short-term variability on the order of 1% (3–4 ppm. We also found good (2. The variations in spectral fitting residuals are consistent with signal-to-noise estimates from instrument calibration, while average residuals are systematic and mostly attributable to remaining errors in our knowledge of the CO2 and O2 spectroscopic parameters. A few remaining inconsistencies observed during TVAC may be attributable to the specific instrument setup on the ground and will be re-evaluated with in-orbit data, when the instrument is expected to be in a much more stable environment.

  1. Gafchromic film dosimetry: calibration methodology and error analysis

    CERN Document Server

    Crijns, Wouter; Heuvel, Frank Van den

    2011-01-01

    Purpose : To relate the physical transmittance parameters of the water equivalent Gafchromic EBT 2 Film with the delivered dose in a transparent absolute calibration protocol. The protocol should be easy to understand, easy to perform, and should be able to predict the residual dose error. Conclussions : The gafchromic EBT2 Films are properly calibrated with an accessible robust calibration protocol. The protocol largely deals with the uniformity problems of the Film. The proposed method allowed to relate the dose with the red channel transmittance using only T0, T_inf, and a dose scaling factor. Based on the local and global uniformity the red channel dose errors could be predicted to be smaller than 5%.

  2. Aquarius Salinity Retrieval Algorithm: Final Pre-Launch Version

    Science.gov (United States)

    Wentz, Frank J.; Le Vine, David M.

    2011-01-01

    This document provides the theoretical basis for the Aquarius salinity retrieval algorithm. The inputs to the algorithm are the Aquarius antenna temperature (T(sub A)) measurements along with a number of NCEP operational products and pre-computed tables of space radiation coming from the galaxy and sun. The output is sea-surface salinity and many intermediate variables required for the salinity calculation. This revision of the Algorithm Theoretical Basis Document (ATBD) is intended to be the final pre-launch version.

  3. Calibration of parallel kinematics machine using generalized distance error model

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    This paper focus on the accuracy enhancement of parallel kinematics machine through kinematics calibration. In the calibration processing, well-structured identification Jacobian matrix construction and end-effector position and orientation measurement are two main difficulties. In this paper, the identification Jacobian matrix is constructed easily by numerical calculation utilizing the unit virtual velocity method. The generalized distance errors model is presented for avoiding measuring the position and orientation directly which is difficult to be measured. At last, a measurement tool is given for acquiring the data points in the calibration processing.Experimental studies confirmed the effectiveness of method. It is also shown in the paper that the proposed approach can be applied to other typed parallel manipulators.

  4. A Pre-launch Analysis of NASA's SMAP Mission Data

    Science.gov (United States)

    Escobar, V. M.; Brown, M. E.

    2012-12-01

    an email-based review of expert end-users and earth science researchers to eliciting how pre-launch activities and research is being conducted in thematic group's organizations. Our focus through the SMAP Applications Program will be to (1) improve the missions understanding of the SMAP user community requirements, (2) document and communicate the perceived challenges and advantages to the mission scientists, and (3) facilitate the movement of science into policy and decision making arenas. We will analyze the data of this review to understand the perceived benefits to pre-launch efforts, user engagement and define areas were the connection between science development and user engagement can continue to improve and further benefit future mission pre launch efforts. The research will facilitate collaborative opportunities between agencies, broadening the fields of science where soil moisture observation data can be applied.

  5. Application of variance components estimation to calibrate geoid error models.

    Science.gov (United States)

    Guo, Dong-Mei; Xu, Hou-Ze

    2015-01-01

    The method of using Global Positioning System-leveling data to obtain orthometric heights has been well studied. A simple formulation for the weighted least squares problem has been presented in an earlier work. This formulation allows one directly employing the errors-in-variables models which completely descript the covariance matrices of the observables. However, an important question that what accuracy level can be achieved has not yet to be satisfactorily solved by this traditional formulation. One of the main reasons for this is the incorrectness of the stochastic models in the adjustment, which in turn allows improving the stochastic models of measurement noises. Therefore the issue of determining the stochastic modeling of observables in the combined adjustment with heterogeneous height types will be a main focus point in this paper. Firstly, the well-known method of variance component estimation is employed to calibrate the errors of heterogeneous height data in a combined least square adjustment of ellipsoidal, orthometric and gravimetric geoid. Specifically, the iterative algorithms of minimum norm quadratic unbiased estimation are used to estimate the variance components for each of heterogeneous observations. Secondly, two different statistical models are presented to illustrate the theory. The first method directly uses the errors-in-variables as a priori covariance matrices and the second method analyzes the biases of variance components and then proposes bias-corrected variance component estimators. Several numerical test results show the capability and effectiveness of the variance components estimation procedure in combined adjustment for calibrating geoid error model.

  6. Pre-Launch Radiometric Characterization of JPSS-1 VIIRS Thermal Emissive Bands

    Directory of Open Access Journals (Sweden)

    Jeff McIntire

    2016-01-01

    Full Text Available Pre-launch characterization and calibration of the thermal emissive spectral bands on the Joint Polar Satellite System (JPSS-1 Visible Infrared Imaging Radiometer Suite (VIIRS is critical to ensure high quality data products for environmental and climate data records post-launch. A comprehensive test program was conducted at the Raytheon El Segundo facility in 2013–2014, including extensive environmental testing. This work is focused on the thermal band radiometric performance and stability, including evaluation of a number of sensor performance metrics and estimation of uncertainties. Analysis has shown that JPSS-1 VIIRS thermal bands perform very well in relation to their design specifications, and comparisons to the Suomi National Polar-orbiting Partnership (SNPP VIIRS instrument have shown their performance to be comparable.

  7. Apollo Director Phillips Monitors Apollo 11 Pre-Launch Activities

    Science.gov (United States)

    1969-01-01

    From the Kennedy Space Flight Center (KSC) control room, Apollo Program Director Lieutenant General Samuel C. Phillips monitors pre-launch activities for Apollo 11. The Apollo 11 mission, the first lunar landing mission, launched from the KSC in Florida via the Marshall Space Flight Center (MSFC) developed Saturn V launch vehicle on July 16, 1969 and safely returned to Earth on July 24, 1969. Aboard the space craft were astronauts Neil A. Armstrong, commander; Michael Collins, Command Module (CM) pilot; and Edwin E. (Buzz) Aldrin Jr., Lunar Module (LM) pilot. The CM, 'Columbia', piloted by Collins, remained in a parking orbit around the Moon while the LM, 'Eagle'', carrying astronauts Armstrong and Aldrin, landed on the Moon. On July 20, 1969, Armstrong was the first human to ever stand on the lunar surface, followed by Aldrin. During 2½ hours of surface exploration, the crew collected 47 pounds of lunar surface material for analysis back on Earth. With the success of Apollo 11, the national objective to land men on the Moon and return them safely to Earth had been accomplished.

  8. Two Error Models for Calibrating SCARA Robots based on the MDH Model

    Directory of Open Access Journals (Sweden)

    Li Xiaolong

    2017-01-01

    Full Text Available This paper describes the process of using two error models for calibrating Selective Compliance Assembly Robot Arm (SCARA robots based on the modified Denavit-Hartenberg(MDH model, with the aim of improving the robot's accuracy. One of the error models is the position error model, which uses robot position errors with respect to an accurate robot base frame built before the measurement commenced. The other model is the distance error model, which uses only the robot moving distance to calculate errors. Because calibration requires the end-effector to be accurately measured, a laser tracker was used to measure the robot position and distance errors. After calibrating the robot and, the end-effector locations were measured again compensating the error models' parameters obtained from the calibration. The finding is that the robot's accuracy improved greatly after compensating the calibrated parameters.

  9. An Overview of JPSS-1 VIIRS Pre-Launch Testing and Performanc

    Science.gov (United States)

    Xiong, X.; McIntire, J.; Oudrari, H.; Thome, K.; Butler, J. J.; Ji, Q.; Schwarting, T.

    2015-12-01

    The Visible-Infrared Imaging Radiometer Suite (VIIRS) is a key instrument for the Suomi National Polar-orbiting Partnership (S-NPP) satellite launched in 2011 and future Joint Polar Satellite System (JPSS) satellites. The JPSS-1 (J1) spacecraft is scheduled to launch in January 2017. VIIRS instrument was designed to provide measurements of the globe twice daily. It is a cross-track scanning radiometer using a rotating telescope with spatial resolutions of 375 and 750 m at nadir for its imaging and moderate bands, respectively. It has 22 spectral bands covering wavelengths from 0.412 to 12.01 μm, including 14 reflective solar bands (RSB), 7 thermal emissive bands (TEB), and 1 day-night band (DNB). VIIRS observations are used to generate 22 environmental data products (EDRs), enabling a wide range of applications. This paper describes J1 VIIRS pre-launch testing program, instrument calibration and characterization strategies, and its projected performance based on independent analyses made by the NASA VIIRS Characterization Support Team (VCST). It also discusses the effort made the joint government team to produce sensor at-launch baseline performance parameters and the metrics needed to populate the Look-Up-Tables (LUTs) needed for the sensor data records (SDR) production. Sensor performance to be illustrated in this paper include signal-to-noise ratios (SNRs), dynamic range, spatial and spectral performance, response versus scan-angle (RVS), and polarization sensitivity.

  10. A Bayesian Estimator for Linear Calibration Error Effects in Thermal Remote Sensing

    CERN Document Server

    Morgan, J A

    2005-01-01

    The Bayesian Land Surface Temperature estimator previously developed has been extended to include the effects of imperfectly known gain and offset calibration errors. It is possible to treat both gain and offset as nuisance parameters and, by integrating over an uninformative range for their magnitudes, eliminate the dependence of surface temperature and emissivity estimates upon the exact calibration error.

  11. Stereo Matching in the Presence of Sub-Pixel Calibration Errors

    OpenAIRE

    Hirschmüller, Heiko; Gehrig, Stefan

    2009-01-01

    Stereo matching commonly requires rectified images that are computed from calibrated cameras. Since all under-lying parametric camera models are only approximations, calibration and rectification will never be perfect. Additionally, it is very hard to keep the calibration perfectly stable in application scenarios with large temperature changes and vibrations. We show that even small calibration errors of a quarter of a pixel are severely amplified on certain structures. We discuss a robotics ...

  12. Inference on rare errors using asymptotic expansions and bootstrap calibration

    NARCIS (Netherlands)

    Helmers, R.

    1998-01-01

    The number of items in error in an audit population is usually quite small, whereas the error distribution is typically highly skewed to the right. For applications in statistical auditing, where line item sampling is appropriate, a new upper confidence limit for the total error amount in an audit p

  13. Quantitative evaluation for accumulative calibration error and video-CT registration errors in electromagnetic-tracked endoscopy.

    Science.gov (United States)

    Liu, Sheena Xin; Gutiérrez, Luis F; Stanton, Doug

    2011-05-01

    Electromagnetic (EM)-guided endoscopy has demonstrated its value in minimally invasive interventions. Accuracy evaluation of the system is of paramount importance to clinical applications. Previously, a number of researchers have reported the results of calibrating the EM-guided endoscope; however, the accumulated errors of an integrated system, which ultimately reflect intra-operative performance, have not been characterized. To fill this vacancy, we propose a novel system to perform this evaluation and use a 3D metric to reflect the intra-operative procedural accuracy. This paper first presents a portable design and a method for calibration of an electromagnetic (EM)-tracked endoscopy system. An evaluation scheme is then described that uses the calibration results and EM-CT registration to enable real-time data fusion between CT and endoscopic video images. We present quantitative evaluation results for estimating the accuracy of this system using eight internal fiducials as the targets on an anatomical phantom: the error is obtained by comparing the positions of these targets in the CT space, EM space and endoscopy image space. To obtain 3D error estimation, the 3D locations of the targets in the endoscopy image space are reconstructed from stereo views of the EM-tracked monocular endoscope. Thus, the accumulated errors are evaluated in a controlled environment, where the ground truth information is present and systematic performance (including the calibration error) can be assessed. We obtain the mean in-plane error to be on the order of 2 pixels. To evaluate the data integration performance for virtual navigation, target video-CT registration error (TRE) is measured as the 3D Euclidean distance between the 3D-reconstructed targets of endoscopy video images and the targets identified in CT. The 3D error (TRE) encapsulates EM-CT registration error, EM-tracking error, fiducial localization error, and optical-EM calibration error. We present in this paper our

  14. Error Modeling, Calibration, and Nonlinear Interpolation Compensation Method of Ring Laser Gyroscope Inertial Navigation System

    Directory of Open Access Journals (Sweden)

    Jianli Li

    2013-01-01

    Full Text Available In order to improve the precision of Strapdown Inertial Navigation System (SINS and reduce the complexity of the traditional calibration method, a novel calibration and compensation scheme is proposed. An optimization calibration method with four-direction rotations is designed to calculate all error coefficients of Ring Laser Gyroscope (RLG SINS in a series of constant temperatures. According to the actual working environment, the temperature errors of RLG SINS are compensated by a nonlinear interpolation compensation algorithm. The experimental results show that the inertial navigation errors of the proposed method are reduced.

  15. Force calibration using errors-in-variables regression and Monte Carlo uncertainty evaluation

    Science.gov (United States)

    Bartel, Thomas; Stoudt, Sara; Possolo, Antonio

    2016-06-01

    An errors-in-variables regression method is presented as an alternative to the ordinary least-squares regression computation currently employed for determining the calibration function for force measuring instruments from data acquired during calibration. A Monte Carlo uncertainty evaluation for the errors-in-variables regression is also presented. The corresponding function (which we call measurement function, often called analysis function in gas metrology) necessary for the subsequent use of the calibrated device to measure force, and the associated uncertainty evaluation, are also derived from the calibration results. Comparisons are made, using real force calibration data, between the results from the errors-in-variables and ordinary least-squares analyses, as well as between the Monte Carlo uncertainty assessment and the conventional uncertainty propagation employed at the National Institute of Standards and Technology (NIST). The results show that the errors-in-variables analysis properly accounts for the uncertainty in the applied calibrated forces, and that the Monte Carlo method, owing to its intrinsic ability to model uncertainty contributions accurately, yields a better representation of the calibration uncertainty throughout the transducer’s force range than the methods currently in use. These improvements notwithstanding, the differences between the results produced by the current and by the proposed new methods generally are small because the relative uncertainties of the inputs are small and most contemporary load cells respond approximately linearly to such inputs. For this reason, there will be no compelling need to revise any of the force calibration reports previously issued by NIST.

  16. Optical System Error Analysis and Calibration Method of High-Accuracy Star Trackers

    Directory of Open Access Journals (Sweden)

    Zheng You

    2013-04-01

    Full Text Available The star tracker is a high-accuracy attitude measurement device widely used in spacecraft. Its performance depends largely on the precision of the optical system parameters. Therefore, the analysis of the optical system parameter errors and a precise calibration model are crucial to the accuracy of the star tracker. Research in this field is relatively lacking a systematic and universal analysis up to now. This paper proposes in detail an approach for the synthetic error analysis of the star tracker, without the complicated theoretical derivation. This approach can determine the error propagation relationship of the star tracker, and can build intuitively and systematically an error model. The analysis results can be used as a foundation and a guide for the optical design, calibration, and compensation of the star tracker. A calibration experiment is designed and conducted. Excellent calibration results are achieved based on the calibration model. To summarize, the error analysis approach and the calibration method are proved to be adequate and precise, and could provide an important guarantee for the design, manufacture, and measurement of high-accuracy star trackers.

  17. 3-PRS serial-parallel machine tool error calibration and parameter identification

    Institute of Scientific and Technical Information of China (English)

    ZHAO Jun-wei; DAI Jun; HUANG Jun-jie

    2009-01-01

    3-PRS serial-parallel machine tool consists of a 3-degree-of-freedom (DOF) implementation platform and a 2-DOF X-Y platform. The error modeling and parameter identification methods were deduced based on 3-PRS serial-parallel machine tool. 3-PRS serial-parallel machine tool was researched, and the mechanism of error analysis, modeling, identification of error parameters and measurement equipment for the use of agency error of measurement were conducted. In order to achieve the geometric parameters calibration and error compensation of the serial-parallel machine tool, the nominal structural parameters of the controller was adjusted by identifying the structure of the machine tool. With the establishment of a vector space size chain, we can do the error analysis, error modeling, error measurement and error compensation can be done.

  18. Design and Flight Performance of the Orion Pre-Launch Navigation System

    Science.gov (United States)

    Zanetti, Renato

    2016-01-01

    Launched in December 2014 atop a Delta IV Heavy from the Kennedy Space Center, the Orion vehicle's Exploration Flight Test-1 (EFT-1) successfully completed the objective to test the prelaunch and entry components of the system. Orion's pre-launch absolute navigation design is presented, together with its EFT-1 performance.

  19. Scalable in situ qubit calibration during repetitive error detection

    Science.gov (United States)

    Kelly, J.; Barends, R.; Fowler, A. G.; Megrant, A.; Jeffrey, E.; White, T. C.; Sank, D.; Mutus, J. Y.; Campbell, B.; Chen, Yu; Chen, Z.; Chiaro, B.; Dunsworth, A.; Lucero, E.; Neeley, M.; Neill, C.; O'Malley, P. J. J.; Quintana, C.; Roushan, P.; Vainsencher, A.; Wenner, J.; Martinis, John M.

    2016-09-01

    We present a method to optimize qubit control parameters during error detection which is compatible with large-scale qubit arrays. We demonstrate our method to optimize single or two-qubit gates in parallel on a nine-qubit system. Additionally, we show how parameter drift can be compensated for during computation by inserting a frequency drift and using our method to remove it. We remove both drift on a single qubit and independent drifts on all qubits simultaneously. We believe this method will be useful in keeping error rates low on all physical qubits throughout the course of a computation. Our method is O (1 ) scalable to systems of arbitrary size, providing a path towards controlling the large numbers of qubits needed for a fault-tolerant quantum computer.

  20. Neural network calibration of a snapshot birefringent Fourier transform spectrometer with periodic phase errors.

    Science.gov (United States)

    Luo, David; Kudenov, Michael W

    2016-05-16

    Systematic phase errors in Fourier transform spectroscopy can severely degrade the calculated spectra. Compensation of these errors is typically accomplished using post-processing techniques, such as Fourier deconvolution, linear unmixing, or iterative solvers. This results in increased computational complexity when reconstructing and calibrating many parallel interference patterns. In this paper, we describe a new method of calibrating a Fourier transform spectrometer based on the use of artificial neural networks (ANNs). In this way, it is demonstrated that a simpler and more straightforward reconstruction process can be achieved at the cost of additional calibration equipment. To this end, we provide a theoretical model for general systematic phase errors in a polarization birefringent interferometer. This is followed by a discussion of our experimental setup and a demonstration of our technique, as applied to data with and without phase error. The technique's utility is then supported by comparison to alternative reconstruction techniques using fast Fourier transforms (FFTs) and linear unmixing.

  1. Airborne campaigns for CryoSat pre-launch calibration and validation

    DEFF Research Database (Denmark)

    Hvidegaard, Sine Munk; Forsberg, René; Skourup, Henriette

    2010-01-01

    in the Arctic Ocean. The main goal of the airborne surveys was to acquire coincident scanning laser and CryoSat type radar elevation measurements of the surface; either sea ice or land ice. Selected lines have been surveyed along with detailed mapping of validation sites coordinated with insitu field work......From 2003 to 2008 DTU Space together with ESA and several international partners carried out airborne and ground field campaigns in preparation for CryoSat validation; called CryoVEx: CryoSat Validation Experiments covering the main ice caps in Greenland, Canada and Svalbard and sea ice...

  2. Mars Entry Atmospheric Data System Modeling, Calibration, and Error Analysis

    Science.gov (United States)

    Karlgaard, Christopher D.; VanNorman, John; Siemers, Paul M.; Schoenenberger, Mark; Munk, Michelle M.

    2014-01-01

    The Mars Science Laboratory (MSL) Entry, Descent, and Landing Instrumentation (MEDLI)/Mars Entry Atmospheric Data System (MEADS) project installed seven pressure ports through the MSL Phenolic Impregnated Carbon Ablator (PICA) heatshield to measure heatshield surface pressures during entry. These measured surface pressures are used to generate estimates of atmospheric quantities based on modeled surface pressure distributions. In particular, the quantities to be estimated from the MEADS pressure measurements include the dynamic pressure, angle of attack, and angle of sideslip. This report describes the calibration of the pressure transducers utilized to reconstruct the atmospheric data and associated uncertainty models, pressure modeling and uncertainty analysis, and system performance results. The results indicate that the MEADS pressure measurement system hardware meets the project requirements.

  3. A novel separation and calibration method for DVL and compass error in dead reckoning navigation systems

    Science.gov (United States)

    Zhang, Yanshun; Guo, Yajing; Yang, Tao; Li, Chunyu; Wang, Zhanqing

    2016-06-01

    The scale factor error δ C of the Doppler velocity log (DVL) and the heading angle error δ \\psi of a compass are so integrated in dead reckoning (DR) navigation systems that it is difficult to separate them. This paper aims to solve this problem by putting forward an online separation and calibration method for δ C and δ \\psi based on an ‘arc and linear’ trajectory. This method introduces the high-accuracy location information of a long base line (LBL) acoustic positioning system. At first, the relationship between the displacements on the ‘arc’ trajectory in directions of east and north, output by the LBL and DR systems, serves to judge the carrier direction and calibrate δ C . And then by compensating δ C , the displacement on the ‘linear’ trajectory is used to calibrate δ \\psi . Finally, a semi-physical simulation experiment is conducted to test and verify this calibration method to see how effective and accurate it is. Experimental results show that after calibration the residual error ratios of δ C and δ \\psi are 8.24% and 3.70% respectively. Therefore, online calibration of δ C and δ \\psi is realized effectively. What’s more, when the DR system is working alone in 400 s, this method reduces position error by up to 93.39%, from 18.91 m to 1.25 m.

  4. HERA Transverse Polarimeter absolute scale and error by rise-time calibration

    CERN Document Server

    Karibian, V

    2003-01-01

    We give the results of an analysis of some 18 rise-time calibrations which are based on data collected in 1996/97. Such measurements are used to determine the absolute polarization scale of the transverse electron beam polarimeter (TPOL) at HERA. The results of the 1996/97 calibrations are found to be in good agreement with earlier calibrations of the TPOL performed in 1994 with errors of 1.2% and 1.1%. Based on these calibrations and a comparison with measurements from the longitudinal polarimeter (LPOL) at HERA carried out over a two-months period in 2000, we obtain a mean LPOL/TPOL ratio of 1.018. Both polarimeters are found to agree with each other within their overall errors of about 2% each.

  5. Using self-location to calibrate the errors of observer positions for source localization

    Institute of Scientific and Technical Information of China (English)

    Wanchun Li; Wanyi Zhang; Liping Li

    2014-01-01

    The uncertainty of observers’ positions can lead to significantly degrading in source localization accuracy. This pa-per proposes a method of using self-location for calibrating the positions of observer stations in source localization to reduce the errors of the observer positions and improve the accuracy of the source localization. The relative distance measurements of the two coordinative observers are used for the linear minimum mean square error (LMMSE) estimator. The results of computer si-mulations prove the feasibility and effectiveness of the proposed method. With the general estimation errors of observers’ positions, the MSE of the source localization with self-location calibration, which is significantly lower than that without self-location calibra-tion, is approximating to the Cramer-Rao lower bound (CRLB).

  6. Calibration/Validation Error Budgets, Uncertainties, Traceability and Their Importance to Imaging Spectrometry

    Science.gov (United States)

    Thome, K.

    2016-01-01

    Knowledge of uncertainties and errors are essential for comparisons of remote sensing data across time, space, and spectral domains. Vicarious radiometric calibration is used to demonstrate the need for uncertainty knowledge and to provide an example error budget. The sample error budget serves as an example of the questions and issues that need to be addressed by the calibrationvalidation community as accuracy requirements for imaging spectroscopy data will continue to become more stringent in the future. Error budgets will also be critical to ensure consistency between the range of imaging spectrometers expected to be launched in the next five years.

  7. Assessment of measurement errors and dynamic calibration methods for three different tipping bucket rain gauges

    Science.gov (United States)

    Shedekar, Vinayak S.; King, Kevin W.; Fausey, Norman R.; Soboyejo, Alfred B. O.; Harmel, R. Daren; Brown, Larry C.

    2016-09-01

    Three different models of tipping bucket rain gauges (TBRs), viz. HS-TB3 (Hydrological Services Pty Ltd.), ISCO-674 (Isco, Inc.) and TR-525 (Texas Electronics, Inc.), were calibrated in the lab to quantify measurement errors across a range of rainfall intensities (5 mm·h- 1 to 250 mm·h- 1) and three different volumetric settings. Instantaneous and cumulative values of simulated rainfall were recorded at 1, 2, 5, 10 and 20-min intervals. All three TBR models showed a substantial deviation (α = 0.05) in measurements from actual rainfall depths, with increasing underestimation errors at greater rainfall intensities. Simple linear regression equations were developed for each TBR to correct the TBR readings based on measured intensities (R2 > 0.98). Additionally, two dynamic calibration techniques, viz. quadratic model (R2 > 0.7) and T vs. 1/Q model (R2 = > 0.98), were tested and found to be useful in situations when the volumetric settings of TBRs are unknown. The correction models were successfully applied to correct field-collected rainfall data from respective TBR models. The calibration parameters of correction models were found to be highly sensitive to changes in volumetric calibration of TBRs. Overall, the HS-TB3 model (with a better protected tipping bucket mechanism, and consistent measurement errors across a range of rainfall intensities) was found to be the most reliable and consistent for rainfall measurements, followed by the ISCO-674 (with susceptibility to clogging and relatively smaller measurement errors across a range of rainfall intensities) and the TR-525 (with high susceptibility to clogging and frequent changes in volumetric calibration, and highly intensity-dependent measurement errors). The study demonstrated that corrections based on dynamic and volumetric calibration can only help minimize-but not completely eliminate the measurement errors. The findings from this study will be useful for correcting field data from TBRs; and may have major

  8. A New Calibration Method for Microphone Array with Gain, Phase, and Position Errors

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Microphone array can be used in sound source localization and separation. But gain, phase, and position errors can seriously influence the performance of localization algorithms such as multiple signal classification (MUSIC) algorithm. In this paper, a new calibration method for microphone array with gain, phase, and position errors is proposed. Unlike traditional calibration methods for antenna array, the proposed method can be used in the broadband and near-field signal model such as microphone array with arbitrary sensor geometries in one plane. Computer simulations are presented and simulation results show the new method having good performance.

  9. The impact of modelling errors on interferometer calibration for 21 cm power spectra

    Science.gov (United States)

    Ewall-Wice, Aaron; Dillon, Joshua S.; Liu, Adrian; Hewitt, Jacqueline

    2017-09-01

    We study the impact of sky-based calibration errors from source mismodelling on 21 cm power spectrum measurements with an interferometer and propose a method for suppressing their effects. While emission from faint sources that are not accounted for in calibration catalogues is believed to be spectrally smooth, deviations of true visibilities from model visibilities are not, due to the inherent chromaticity of the interferometer's sky response (the 'wedge'). Thus, unmodelled foregrounds, below the confusion limit of many instruments, introduce frequency structure into gain solutions on the same line-of-sight scales on which we hope to observe the cosmological signal. We derive analytic expressions describing these errors using linearized approximations of the calibration equations and estimate the impact of this bias on measurements of the 21 cm power spectrum during the epoch of reionization. Given our current precision in primary beam and foreground modelling, this noise will significantly impact the sensitivity of existing experiments that rely on sky-based calibration. Our formalism describes the scaling of calibration with array and sky-model parameters and can be used to guide future instrument design and calibration strategy. We find that sky-based calibration that downweights long baselines can eliminate contamination in most of the region outside of the wedge with only a modest increase in instrumental noise.

  10. CALIBRATION ERRORS IN THE CAVITY BEAM POSITION MONITOR SYSTEM AT THE ATF2

    CERN Document Server

    Cullinan, F; Joshi, N; Lyapin, A

    2011-01-01

    It has been shown at the Accelerator Test Facility at KEK, that it is possible to run a system of 37 cavity beam position monitors (BPMs) and achieve high working resolution. However, stability of the calibration constants (position scale and radio frequency (RF) phase) over a three/four week running period is yet to be demonstrated. During the calibration procedure, random beam jitter gives rise to a statistical error in the position scale and slow orbit drift in position and tilt causes systematic errors in both the position scale and RF phase. These errors are dominant and have been evaluated for each BPM. The results are compared with the errors expected after a tested method of beam jitter subtraction has been applied.

  11. A revised 5 minute gravimetric geoid and associated errors for the North Atlantic calibration area

    Science.gov (United States)

    Mader, G. L.

    1979-01-01

    A revised 5 minute gravimetric geoid and its errors were computed for the North Atlantic calibration area using GEM-8 potential coefficients and the latest gravity data available from the Defense Mapping Agency. This effort was prompted by a number of inconsistencies and small errors found in previous calculations of this geoid. The computational method and constants used are given in detail to serve as a reference for future work.

  12. Local error calibration of EGM08 geoid using GNSS/levelling data

    Science.gov (United States)

    Eshagh, Mehdi; Zoghi, Sedigheh

    2016-07-01

    The geoid error, computed from EGM08, is unrealistically large due to the continuation of the spherical harmonic coefficient errors down to the surface of the reference ellipsoid. In this study, we try to calibrate such an error by the differences between the EGM08 and GNSS/levelling geoids over Fennoscandia. We use the variance component estimation procedure through combined adjustments of the geoid and GNSS/levelling heights using corrector surfaces of 4-, 5- and 7-parameter. We also develop a simple iterative method to calibrate the geoid error from the a posteriori variance factor and the errors of GNSS/levelling geoid. Our numerical investigations show that performing the separate adjustment and variance component estimation for each country with a two-component stochastic model is more successful than performing it in the whole area with a five-component model. The number of GNSS/levelling data over Sweden and Norway are much larger than those in Denmark and Finland. This causes that the corrector surfaces are fitted better in these countries and consequently the estimated errors for the geoid become larger than what they should be in the others. Based on a 7-parameter corrector surface model, the average error of the EGM08 geoid becomes 12, 17, 51 and 34 mm, in Sweden, Denmark, Norway and Finland, respectively. If the two-component stochastic model is used in a combined adjustment over Fennoscandia this average error will be 48 mm.

  13. The effect of biomechanical variables on force sensitive resistor error: Implications for calibration and improved accuracy.

    Science.gov (United States)

    Schofield, Jonathon S; Evans, Katherine R; Hebert, Jacqueline S; Marasco, Paul D; Carey, Jason P

    2016-03-21

    Force Sensitive Resistors (FSRs) are commercially available thin film polymer sensors commonly employed in a multitude of biomechanical measurement environments. Reasons for such wide spread usage lie in the versatility, small profile, and low cost of these sensors. Yet FSRs have limitations. It is commonly accepted that temperature, curvature and biological tissue compliance may impact sensor conductance and resulting force readings. The effect of these variables and degree to which they interact has yet to be comprehensively investigated and quantified. This work systematically assesses varying levels of temperature, sensor curvature and surface compliance using a full factorial design-of-experiments approach. Three models of Interlink FSRs were evaluated. Calibration equations under 12 unique combinations of temperature, curvature and compliance were determined for each sensor. Root mean squared error, mean absolute error, and maximum error were quantified as measures of the impact these thermo/mechanical factors have on sensor performance. It was found that all three variables have the potential to affect FSR calibration curves. The FSR model and corresponding sensor geometry are sensitive to these three mechanical factors at varying levels. Experimental results suggest that reducing sensor error requires calibration of each sensor in an environment as close to its intended use as possible and if multiple FSRs are used in a system, they must be calibrated independently.

  14. Correcting for multivariate measurement error by regression calibration in meta-analyses of epidemiological studies

    DEFF Research Database (Denmark)

    Tybjærg-Hansen, Anne

    2009-01-01

    Within-person variability in measured values of multiple risk factors can bias their associations with disease. The multivariate regression calibration (RC) approach can correct for such measurement error and has been applied to studies in which true values or independent repeat measurements of t...

  15. Calibration method of the time synchronization error of many data acquisition nodes in the chained system

    Science.gov (United States)

    Jiang, Jia-jia; Duan, Fa-jie; Chen, Jin; Zhang, Chao; Wang, Kai; Chang, Zong-jie

    2012-08-01

    Time synchronization is very important in a distributed chained seismic acquisition system with a large number of data acquisition nodes (DANs). The time synchronization error has two causes. On the one hand, there is a large accumulated propagation delay when commands propagate from the analysis and control system to multiple distant DANs, which makes it impossible for different DANs to receive the same command synchronously. Unfortunately, the propagation delay of commands (PDCs) varies in different application environments. On the other hand, the phase jitter of both the master clock and the clock recovery phase-locked loop, which is designed to extract the timing signal, may also cause the time synchronization error. In this paper, in order to achieve accurate time synchronization, a novel calibration method is proposed which can align the PDCs of all of the DANs in real time and overcome the time synchronization error caused by the phase jitter. Firstly, we give a quantitative analysis of the time synchronization error caused by both the PDCs and the phase jitter. Secondly, we propose a back and forth model (BFM) and a transmission delay measurement method (TDMM) to overcome these difficulties. Furthermore, the BFM is designed as the hardware configuration to measure the PDCs and calibrate the time synchronization error. The TDMM is used to measure the PDCs accurately. Thirdly, in order to overcome the time synchronization error caused by the phase jitter, a compression and mapping algorithm (CMA) is presented. Finally, based on the proposed BFM, TDMM and CMA, a united calibration algorithm is developed to overcome the time synchronization error caused by both the PDCs and the phase jitter. The simulation experiment results show the effectiveness of the calibration method proposed in this paper.

  16. Calibration of a neutron log in partially saturated media. Part II. Error analysis

    Energy Technology Data Exchange (ETDEWEB)

    Hearst, J.R.; Kasameyer, P.W.; Dreiling, L.A.

    1981-03-20

    Four sources or error (uncertainty) are studied in water content obtained from neutron logs calibrated in partially saturated media for holes up to 3 m. For this calibration a special facility was built and an algorithm for a commercial epithermal neutron log was developed that obtains water content from count rate, bulk density, and gap between the neutron sonde and the borehole wall. The algorithm contained errors due to the calibration and lack of fit, while the field measurements included uncertainties in the count rate (caused by statistics and a short time constant), gap, and density. There can be inhomogeneity in the material surrounding the borehole. Under normal field conditions the hole-size-corrected water content obtained from such neutron logs can have an uncertainty as large as 15% of its value.

  17. The Impact of Modeling Errors on Interferometer Calibration for 21 cm Power Spectra

    CERN Document Server

    Ewall-Wice, Aaron; Liu, Adrian; Hewitt, Jacqueline

    2016-01-01

    We study the impact of sky-based calibration errors from source mismodeling on 21 cm power spectrum measurements with an interferometer and propose a method for suppressing their effects. While emission from faint sources that are not accounted for in calibration catalogs is believed to be spectrally smooth, deviations of true visibilities from model visibilities are not, due to the inherent chromaticity of the interferometer's sky-response (the "wedge"). Thus, unmodeled foregrounds at the $\\approx 1$ mJy level introduce frequency structure into gain solutions on the same line-of-sight scales on which we hope to observe the cosmological signal. We derive analytic expressions describing these errors using linearized approximations of the calibration equations and determine the impact of this bias on measurements of the 21 cm power spectrum during the Epoch of Reionization (EoR). Given our current precision in primary beam and foreground modeling, this noise will significantly impact the sensitivity of existing...

  18. A Novel Error Model of Optical Systems and an On-Orbit Calibration Method for Star Sensors

    Directory of Open Access Journals (Sweden)

    Shuang Wang

    2015-12-01

    Full Text Available In order to improve the on-orbit measurement accuracy of star sensors, the effects of image-plane rotary error, image-plane tilt error and distortions of optical systems resulting from the on-orbit thermal environment were studied in this paper. Since these issues will affect the precision of star image point positions, in this paper, a novel measurement error model based on the traditional error model is explored. Due to the orthonormal characteristics of image-plane rotary-tilt errors and the strong nonlinearity among these error parameters, it is difficult to calibrate all the parameters simultaneously. To solve this difficulty, for the new error model, a modified two-step calibration method based on the Extended Kalman Filter (EKF and Least Square Methods (LSM is presented. The former one is used to calibrate the main point drift, focal length error and distortions of optical systems while the latter estimates the image-plane rotary-tilt errors. With this calibration method, the precision of star image point position influenced by the above errors is greatly improved from 15.42% to 1.389%. Finally, the simulation results demonstrate that the presented measurement error model for star sensors has higher precision. Moreover, the proposed two-step method can effectively calibrate model error parameters, and the calibration precision of on-orbit star sensors is also improved obviously.

  19. On Inertial Body Tracking in the Presence of Model Calibration Errors.

    Science.gov (United States)

    Miezal, Markus; Taetz, Bertram; Bleser, Gabriele

    2016-07-22

    In inertial body tracking, the human body is commonly represented as a biomechanical model consisting of rigid segments with known lengths and connecting joints. The model state is then estimated via sensor fusion methods based on data from attached inertial measurement units (IMUs). This requires the relative poses of the IMUs w.r.t. the segments-the IMU-to-segment calibrations, subsequently called I2S calibrations-to be known. Since calibration methods based on static poses, movements and manual measurements are still the most widely used, potentially large human-induced calibration errors have to be expected. This work compares three newly developed/adapted extended Kalman filter (EKF) and optimization-based sensor fusion methods with an existing EKF-based method w.r.t. their segment orientation estimation accuracy in the presence of model calibration errors with and without using magnetometer information. While the existing EKF-based method uses a segment-centered kinematic chain biomechanical model and a constant angular acceleration motion model, the newly developed/adapted methods are all based on a free segments model, where each segment is represented with six degrees of freedom in the global frame. Moreover, these methods differ in the assumed motion model (constant angular acceleration, constant angular velocity, inertial data as control input), the state representation (segment-centered, IMU-centered) and the estimation method (EKF, sliding window optimization). In addition to the free segments representation, the optimization-based method also represents each IMU with six degrees of freedom in the global frame. In the evaluation on simulated and real data from a three segment model (an arm), the optimization-based method showed the smallest mean errors, standard deviations and maximum errors throughout all tests. It also showed the lowest dependency on magnetometer information and motion agility. Moreover, it was insensitive w.r.t. I2S position and

  20. Quantifying model structural error: Efficient Bayesian calibration of a regional groundwater flow model using surrogates and a data-driven error model

    Science.gov (United States)

    Xu, Tianfang; Valocchi, Albert J.; Ye, Ming; Liang, Feng

    2017-05-01

    Groundwater model structural error is ubiquitous, due to simplification and/or misrepresentation of real aquifer systems. During model calibration, the basic hydrogeological parameters may be adjusted to compensate for structural error. This may result in biased predictions when such calibrated models are used to forecast aquifer responses to new forcing. We investigate the impact of model structural error on calibration and prediction of a real-world groundwater flow model, using a Bayesian method with a data-driven error model to explicitly account for model structural error. The error-explicit Bayesian method jointly infers model parameters and structural error and thereby reduces parameter compensation. In this study, Bayesian inference is facilitated using high performance computing and fast surrogate models (based on machine learning techniques) as a substitute for the computationally expensive groundwater model. We demonstrate that with explicit treatment of model structural error, the Bayesian method yields parameter posterior distributions that are substantially different from those derived using classical Bayesian calibration that does not account for model structural error. We also found that the error-explicit Bayesian method gives significantly more accurate prediction along with reasonable credible intervals. Finally, through variance decomposition, we provide a comprehensive assessment of prediction uncertainty contributed from parameter, model structure, and measurement uncertainty. The results suggest that the error-explicit Bayesian approach provides a solution to real-world modeling applications for which data support the presence of model structural error, yet model deficiency cannot be specifically identified or corrected.

  1. Systematic Geometric Error Modeling for Workspace Volumetric Calibration of a 5-axis Turbine Blade Grinding Machine

    Institute of Scientific and Technical Information of China (English)

    Abdul Wahid Khan; Chen Wuyi

    2010-01-01

    A systematic geometric model has been presented for calibration of a newly designed 5-axis turbine blade grinding machine.This machine is designed to serve a specific purpose to attain high accuracy and high efficiency grinding of turbine blades by eliminating the hand grinding process.Although its topology is RPPPR (P:prismatic;R:rotary),its design is quite distinct from the competitive machine tools.As error quantification is the only way to investigate,maintain and improve its accuracy,calibration is recommended for its performance assessment and acceptance testing.Systematic geometric error modeling technique is implemented and 52 position dependent and position independent errors are identified while considering the machine as five rigid bodies by eliminating the set-up errors ofworkpiece and cutting tool.39 of them are found to have influential errors and are accommodated for finding the resultant effect between the cutting tool and the workpiece in workspace volume.Rigid body kinematics techniques and homogenous transformation matrices are used for error synthesis.

  2. A Fully Bayesian Approach to Improved Calibration and Prediction of Groundwater Models With Structure Error

    Science.gov (United States)

    Xu, T.; Valocchi, A. J.

    2014-12-01

    Effective water resource management typically relies on numerical models to analyse groundwater flow and solute transport processes. These models are usually subject to model structure error due to simplification and/or misrepresentation of the real system. As a result, the model outputs may systematically deviate from measurements, thus violating a key assumption for traditional regression-based calibration and uncertainty analysis. On the other hand, model structure error induced bias can be described statistically in an inductive, data-driven way based on historical model-to-measurement misfit. We adopt a fully Bayesian approach that integrates a Gaussian process error model to account for model structure error to the calibration, prediction and uncertainty analysis of groundwater models. The posterior distributions of parameters of the groundwater model and the Gaussian process error model are jointly inferred using DREAM, an efficient Markov chain Monte Carlo sampler. We test the usefulness of the fully Bayesian approach towards a synthetic case study of surface-ground water interaction under changing pumping conditions. We first illustrate through this example that traditional least squares regression without accounting for model structure error yields biased parameter estimates due to parameter compensation as well as biased predictions. In contrast, the Bayesian approach gives less biased parameter estimates. Moreover, the integration of a Gaussian process error model significantly reduces predictive bias and leads to prediction intervals that are more consistent with observations. The results highlight the importance of explicit treatment of model structure error especially in circumstances where subsequent decision-making and risk analysis require accurate prediction and uncertainty quantification. In addition, the data-driven error modelling approach is capable of extracting more information from observation data than using a groundwater model alone.

  3. OLI Radiometric Calibration

    Science.gov (United States)

    Markham, Brian; Morfitt, Ron; Kvaran, Geir; Biggar, Stuart; Leisso, Nathan; Czapla-Myers, Jeff

    2011-01-01

    Goals: (1) Present an overview of the pre-launch radiance, reflectance & uniformity calibration of the Operational Land Imager (OLI) (1a) Transfer to orbit/heliostat (1b) Linearity (2) Discuss on-orbit plans for radiance, reflectance and uniformity calibration of the OLI

  4. A GPS-Based Pitot-Static Calibration Method Using Global Output-Error Optimization

    Science.gov (United States)

    Foster, John V.; Cunningham, Kevin

    2010-01-01

    Pressure-based airspeed and altitude measurements for aircraft typically require calibration of the installed system to account for pressure sensing errors such as those due to local flow field effects. In some cases, calibration is used to meet requirements such as those specified in Federal Aviation Regulation Part 25. Several methods are used for in-flight pitot-static calibration including tower fly-by, pacer aircraft, and trailing cone methods. In the 1990 s, the introduction of satellite-based positioning systems to the civilian market enabled new inflight calibration methods based on accurate ground speed measurements provided by Global Positioning Systems (GPS). Use of GPS for airspeed calibration has many advantages such as accuracy, ease of portability (e.g. hand-held) and the flexibility of operating in airspace without the limitations of test range boundaries or ground telemetry support. The current research was motivated by the need for a rapid and statistically accurate method for in-flight calibration of pitot-static systems for remotely piloted, dynamically-scaled research aircraft. Current calibration methods were deemed not practical for this application because of confined test range size and limited flight time available for each sortie. A method was developed that uses high data rate measurements of static and total pressure, and GPSbased ground speed measurements to compute the pressure errors over a range of airspeed. The novel application of this approach is the use of system identification methods that rapidly compute optimal pressure error models with defined confidence intervals in nearreal time. This method has been demonstrated in flight tests and has shown 2- bounds of approximately 0.2 kts with an order of magnitude reduction in test time over other methods. As part of this experiment, a unique database of wind measurements was acquired concurrently with the flight experiments, for the purpose of experimental validation of the

  5. Analysis and Calibration of Sources of Electronic Error in PSD Sensor Response

    Directory of Open Access Journals (Sweden)

    David Rodríguez-Navarro

    2016-04-01

    Full Text Available In order to obtain very precise measurements of the position of agents located at a considerable distance using a sensor system based on position sensitive detectors (PSD, it is necessary to analyze and mitigate the factors that generate substantial errors in the system’s response. These sources of error can be divided into electronic and geometric factors. The former stem from the nature and construction of the PSD as well as the performance, tolerances and electronic response of the system, while the latter are related to the sensor’s optical system. Here, we focus solely on the electrical effects, since the study, analysis and correction of these are a prerequisite for subsequently addressing geometric errors. A simple calibration method is proposed, which considers PSD response, component tolerances, temperature variations, signal frequency used, signal to noise ratio (SNR, suboptimal operational amplifier parameters, and analog to digital converter (ADC quantitation SNRQ, etc. Following an analysis of these effects and calibration of the sensor, it was possible to correct the errors, thus rendering the effects negligible, as reported in the results section.

  6. Estimating pole/zero errors in GSN-IRIS/USGS network calibration metadata

    Science.gov (United States)

    Ringler, A.T.; Hutt, C.R.; Aster, R.; Bolton, H.; Gee, L.S.; Storm, T.

    2012-01-01

    Mapping the digital record of a seismograph into true ground motion requires the correction of the data by some description of the instrument's response. For the Global Seismographic Network (Butler et al., 2004), as well as many other networks, this instrument response is represented as a Laplace domain pole–zero model and published in the Standard for the Exchange of Earthquake Data (SEED) format. This Laplace representation assumes that the seismometer behaves as a linear system, with any abrupt changes described adequately via multiple time-invariant epochs. The SEED format allows for published instrument response errors as well, but these typically have not been estimated or provided to users. We present an iterative three-step method to estimate the instrument response parameters (poles and zeros) and their associated errors using random calibration signals. First, we solve a coarse nonlinear inverse problem using a least-squares grid search to yield a first approximation to the solution. This approach reduces the likelihood of poorly estimated parameters (a local-minimum solution) caused by noise in the calibration records and enhances algorithm convergence. Second, we iteratively solve a nonlinear parameter estimation problem to obtain the least-squares best-fit Laplace pole–zero–gain model. Third, by applying the central limit theorem, we estimate the errors in this pole–zero model by solving the inverse problem at each frequency in a two-thirds octave band centered at each best-fit pole–zero frequency. This procedure yields error estimates of the 99% confidence interval. We demonstrate the method by applying it to a number of recent Incorporated Research Institutions in Seismology/United States Geological Survey (IRIS/USGS) network calibrations (network code IU).

  7. Use of Two-Part Regression Calibration Model to Correct for Measurement Error in Episodically Consumed Foods in a Single-Replicate Study Design: EPIC Case Study

    NARCIS (Netherlands)

    Agogo, G.O.; Voet, van der H.; Veer, van 't P.; Ferrari, P.; Leenders, M.; Muller, D.C.; Sánchez-Cantalejo, E.; Bamia, C.; Braaten, T.; Knüppel, S.; Johansson, I.; Eeuwijk, van F.A.; Boshuizen, H.C.

    2014-01-01

    In epidemiologic studies, measurement error in dietary variables often attenuates association between dietary intake and disease occurrence. To adjust for the attenuation caused by error in dietary intake, regression calibration is commonly used. To apply regression calibration, unbiased reference m

  8. Use of Two-Part Regression Calibration Model to Correct for Measurement Error in Episodically Consumed Foods in a Single-Replicate Study Design : EPIC Case Study

    NARCIS (Netherlands)

    Agogo, George O; der Voet, Hilko van; Veer, Pieter Van't; Ferrari, Pietro; Leenders, Max; Muller, David C; Sánchez-Cantalejo, Emilio; Bamia, Christina; Braaten, Tonje; Knüppel, Sven; Johansson, Ingegerd; van Eeuwijk, Fred A; Boshuizen, Hendriek

    2014-01-01

    In epidemiologic studies, measurement error in dietary variables often attenuates association between dietary intake and disease occurrence. To adjust for the attenuation caused by error in dietary intake, regression calibration is commonly used. To apply regression calibration, unbiased reference m

  9. Joint calibration algorithm for gain-phase and mutual coupling errors in uniform linear array

    Institute of Scientific and Technical Information of China (English)

    Li Weixing; Lin Jianzhi; Zhang Yue; Chen Zengping

    2016-01-01

    The effect of gain-phase perturbations and mutual coupling significantly degrades the performance of digital array radar (DAR). This paper investigates array calibration problems in the scenario where the true locations of auxiliary sources deviate from nominal values but the angle intervals are known. A practical algorithm is proposed to jointly calibrate gain-phase errors and mutual coupling errors. Firstly, a simplified model of the distortion matrix is developed based on its special structure in uniform linear array (ULA). Then the model is employed to derive the precise locations of the auxiliary sources by one-dimension search. Finally, the least-squares estimation of the distortion matrix is obtained. The algorithm has the potential of achieving considerable improvement in calibration accuracy due to the reduction of unknown parameters. In addition, the algorithm is feasible for practical applications, since it requires only one auxiliary source with the help of rotation platforms. Simulation results demonstrate the validity, robustness and high per-formance of the proposed algorithm. Experiments were carried out using an S-band DAR test-bed. The results of measured data show that the proposed algorithm is practical and effective in appli-cation.

  10. GOME total ozone and calibration error derived using Version 8 TOMS Algorithm

    Science.gov (United States)

    Gleason, J.; Wellemeyer, C.; Qin, W.; Ahn, C.; Gopalan, A.; Bhartia, P.

    2003-04-01

    The Global Ozone Monitoring Experiment (GOME) is a hyper-spectral satellite instrument measuring the ultraviolet backscatter at relatively high spectral resolution. GOME radiances have been slit averaged to emulate measurements of the Total Ozone Mapping Spectrometer (TOMS) made at discrete wavelengths and processed using the new TOMS Version 8 Ozone Algorithm. Compared to Differential Optical Absorption Spectroscopy (DOAS) techniques based on local structure in the Huggins Bands, the TOMS uses differential absorption between a pair of wavelengths including the local structure as well as the background continuum. This makes the TOMS Algorithm more sensitive to ozone, but it also makes the algorithm more sensitive to instrument calibration errors. While calibration adjustments are not needed for the fitting techniques like the DOAS employed in GOME algorithms, some adjustment is necessary when applying the TOMS Algorithm to GOME. Using spectral discrimination at near ultraviolet wavelength channels unabsorbed by ozone, the GOME wavelength dependent calibration drift is estimated and then checked using pair justification. In addition, the day one calibration offset is estimated based on the residuals of the Version 8 TOMS Algorithm. The estimated drift in the 2b detector of GOME is small through the first four years and then increases rapidly to +5% in normalized radiance at 331 nm relative to 385 nm by mid 2000. The 1b detector appears to be quite well behaved throughout this time period.

  11. Hand-Writing Motion Tracking with Vision-Inertial Sensor Fusion: Calibration and Error Correction

    Directory of Open Access Journals (Sweden)

    Shengli Zhou

    2014-08-01

    Full Text Available The purpose of this study was to improve the accuracy of real-time ego-motion tracking through inertial sensor and vision sensor fusion. Due to low sampling rates supported by web-based vision sensor and accumulation of errors in inertial sensors, ego-motion tracking with vision sensors is commonly afflicted by slow updating rates, while motion tracking with inertial sensor suffers from rapid deterioration in accuracy with time. This paper starts with a discussion of developed algorithms for calibrating two relative rotations of the system using only one reference image. Next, stochastic noises associated with the inertial sensor are identified using Allan Variance analysis, and modeled according to their characteristics. Finally, the proposed models are incorporated into an extended Kalman filter for inertial sensor and vision sensor fusion. Compared with results from conventional sensor fusion models, we have shown that ego-motion tracking can be greatly enhanced using the proposed error correction model.

  12. On calibrating the sensor errors of a PDR-based indoor localization system.

    Science.gov (United States)

    Lan, Kun-Chan; Shih, Wen-Yuah

    2013-04-10

    Many studies utilize the signal strength of short-range radio systems (such as WiFi, ultrasound and infrared) to build a radio map for indoor localization, by deploying a large number of beacon nodes within a building. The drawback of such an infrastructure-based approach is that the deployment and calibration of the system are costly and labor-intensive. Some prior studies proposed the use of Pedestrian Dead Reckoning (PDR) for indoor localization, which does not require the deployment of beacon nodes. In a PDR system, a small number of sensors are put on the pedestrian. These sensors (such as a G-sensor and gyroscope) are used to estimate the distance and direction that a user travels. The effectiveness of a PDR system lies in its success in accurately estimating the user's moving distance and direction. In this work, we propose a novel waist-mounted based PDR that can measure the user's step lengths with a high accuracy. We utilize vertical acceleration of the body to calculate the user's change in height during walking. Based on the Pythagorean Theorem, we can then estimate each step length using this data. Furthermore, we design a map matching algorithm to calibrate the direction errors from the gyro using building floor plans. The results of our experiment show that we can achieve about 98.26% accuracy in estimating the user's walking distance, with an overall location error of about 0.48 m.

  13. Pre-Launch Noise Characterization of the Landsat-7 Enhanced Thematic Mapper Plus (ETM Plus)

    Science.gov (United States)

    Pedelty, J. A.; Markham, B. L.; Barker, J. L.; Seiferth, J. C.

    1999-01-01

    A noise characterization of the Landsat-7 Enhanced Thematic Mapper Plus (ETM+) instrument was performed as part of a near-real time performance assessment and health monitoring program. Perl'ormance data for the integrated Landsat-7 spacecraft and ETM+ were collected before, during, and after the spacecraft thermal vacuum testing program at the Lockheed Martin Missiles and Space (LMMS) facilities in Valley Forge, PA. The Landsat-7 spacecraft and ETM+ instrument were successfully launched on April 15, 1999. The spacecraft and ETM+ are now nearing the end of the on orbit engineering checkout phase, and Landsat-7 is expected to be declared operational on or about July 15, 1999. A preliminary post-launch noise characterization was performed and compared with the pre-launch characterization. In general the overall noise levels in the ETM+ are at or below the specification levels. Coherent noise is seen in most bands, but is only operationally significant when imaging in (he panchromatic band (band 8). This coherent noise has an amplitude as high as approximately 3 DN (peak-to-peak, high gain) at the Nyquist rate of 104 kHz, and causes the noise levels in panchromatic band images at times to exceed the total noise specification by up to approximately 10%. However, this 104 kHz noise is now much weaker than it was prior to the successful repair of the ETM+ power supplies that was completed in May 1998. Weak and stable coherent noise at approximately 5 kHz is seen in all bands in the prime focal plane (bands 1-4 and 8) with the prime (side A) electronics. Very strong coherent noise at approximately 20 kHz is seen in a few detectors of bands 1 and 8, but this noise is almost entirely in the turn-around region between scans when the ETM+ is not imaging the Earth. Strong coherent noise was seen in 2 detectors of band 5 during some of the pre-launch testing; however, this noise seems to be temperature dependent, and has not been seen in the current on orbit environment. Strong

  14. On Calibrating the Sensor Errors of a PDR-Based Indoor Localization System

    Directory of Open Access Journals (Sweden)

    Wen-Yuah Shih

    2013-04-01

    Full Text Available Many studies utilize the signal strength of short-range radio systems (such as WiFi, ultrasound and infrared to build a radio map for indoor localization, by deploying a large number of beacon nodes within a building. The drawback of such an infrastructure-based approach is that the deployment and calibration of the system are costly and labor-intensive. Some prior studies proposed the use of Pedestrian Dead Reckoning (PDR for indoor localization, which does not require the deployment of beacon nodes. In a PDR system, a small number of sensors are put on the pedestrian. These sensors (such as a G-sensor and gyroscope are used to estimate the distance and direction that a user travels. The effectiveness of a PDR system lies in its success in accurately estimating the user’s moving distance and direction. In this work, we propose a novel waist-mounted based PDR that can measure the user’s step lengths with a high accuracy. We utilize vertical acceleration of the body to calculate the user’s change in height during walking. Based on the Pythagorean Theorem, we can then estimate each step length using this data. Furthermore, we design a map matching algorithm to calibrate the direction errors from the gyro using building floor plans. The results of our experiment show that we can achieve about 98.26% accuracy in estimating the user’s walking distance, with an overall location error of about 0.48 m.

  15. Design, calibration and error analysis of instrumentation for heat transfer measurements in internal combustion engines

    Science.gov (United States)

    Ferguson, C. R.; Tree, D. R.; Dewitt, D. P.; Wahiduzzaman, S. A. H.

    1987-01-01

    The paper reports the methodology and uncertainty analyses of instrumentation for heat transfer measurements in internal combustion engines. Results are presented for determining the local wall heat flux in an internal combustion engine (using a surface thermocouple-type heat flux gage) and the apparent flame-temperature and soot volume fraction path length product in a diesel engine (using two-color pyrometry). It is shown that a surface thermocouple heat transfer gage suitably constructed and calibrated will have an accuracy of 5 to 10 percent. It is also shown that, when applying two-color pyrometry to measure the apparent flame temperature and soot volume fraction-path length, it is important to choose at least one of the two wavelengths to lie in the range of 1.3 to 2.3 micrometers. Carefully calibrated two-color pyrometer can ensure that random errors in the apparent flame temperature and in the soot volume fraction path length will remain small (within about 1 percent and 10-percent, respectively).

  16. Design, calibration and error analysis of instrumentation for heat transfer measurements in internal combustion engines

    Science.gov (United States)

    Ferguson, C. R.; Tree, D. R.; Dewitt, D. P.; Wahiduzzaman, S. A. H.

    1987-01-01

    The paper reports the methodology and uncertainty analyses of instrumentation for heat transfer measurements in internal combustion engines. Results are presented for determining the local wall heat flux in an internal combustion engine (using a surface thermocouple-type heat flux gage) and the apparent flame-temperature and soot volume fraction path length product in a diesel engine (using two-color pyrometry). It is shown that a surface thermocouple heat transfer gage suitably constructed and calibrated will have an accuracy of 5 to 10 percent. It is also shown that, when applying two-color pyrometry to measure the apparent flame temperature and soot volume fraction-path length, it is important to choose at least one of the two wavelengths to lie in the range of 1.3 to 2.3 micrometers. Carefully calibrated two-color pyrometer can ensure that random errors in the apparent flame temperature and in the soot volume fraction path length will remain small (within about 1 percent and 10-percent, respectively).

  17. Solar Cell Short Circuit Current Errors and Uncertainties During High Altitude Calibrations

    Science.gov (United States)

    Snyder, David D.

    2012-01-01

    High altitude balloon based facilities can make solar cell calibration measurements above 99.5% of the atmosphere to use for adjusting laboratory solar simulators. While close to on-orbit illumination, the small attenuation to the spectra may result in under measurements of solar cell parameters. Variations of stratospheric weather, may produce flight-to-flight measurement variations. To support the NSCAP effort, this work quantifies some of the effects on solar cell short circuit current (Isc) measurements on triple junction sub-cells. This work looks at several types of high altitude methods, direct high altitude meas urements near 120 kft, and lower stratospheric Langley plots from aircraft. It also looks at Langley extrapolation from altitudes above most of the ozone, for potential small balloon payloads. A convolution of the sub-cell spectral response with the standard solar spectrum modified by several absorption processes is used to determine the relative change from AMO, lscllsc(AMO). Rayleigh scattering, molecular scatterin g from uniformly mixed gases, Ozone, and water vapor, are included in this analysis. A range of atmosph eric pressures are examined, from 0. 05 to 0.25 Atm to cover the range of atmospheric altitudes where solar cell calibrations a reperformed. Generally these errors and uncertainties are less than 0.2%

  18. The IMU Calibration Mathematical Modeling and Error Analysis%IMU标定数学建模及误差分析

    Institute of Scientific and Technical Information of China (English)

    赵桂玲; 姜雨含; 李松

    2016-01-01

    The calibration path design and data processing method for inertial measurement unit(IMU)depend on IMU calibration mathematical model. Installation error is an important factor in determining the IMU calibration model. According to the different installation forms of accelerometers and gyroscopes relative to the carrier ,an IMU calibration mathematical modeling method was proposed by coordinate transformation. The affects of IMU calibra⁃tion model error on angular rate and acceleration were derived. It analyzed the influence of IMU calibration model error on inertial navigation system navigation(SINS),and also designed calibration path and data processing meth⁃ods based on the position information provided by turntable. The simulation and turntable experiment results show that IMU calibration model error causes attitude error,velocity error and position error. Also,the expression form of installation error decides the navigation errors caused by IMU calibration model.%惯性测量单元(IMU)标定路径设计和数据处理方法取决于IMU标定数学模型,安装误差是决定IMU标定模型的重要因素。针对工程中加速度计和陀螺相对载体安装方式的不同,提出一种通过坐标系转换矩阵建立IMU标定数学模型的方法,推导IMU标定模型误差与载体角速度和加速度之间的关系,分析IMU标定模型误差对捷联惯性导航系统导航参数的影响,并利用转台提供的位置信息设计IMU标定路径和数据处理方法。仿真和转台实验结果表明:IMU标定数学模型误差引起捷联惯性导航系统速度误差、位置误差和姿态误差;安装误差的表现形式决定了IMU标定模型误差对系统导航精度的影响。

  19. Pre-Launch Assessment of User Needs for SWOT Mission Data Products

    Science.gov (United States)

    Srinivasan, M. M.; Peterson, C. A.; Doorn, B.

    2015-12-01

    In order to effectively address the applications requirements of future Surface Water and Ocean Topography (SWOT) mission data users, we must understand their needs with respect to latency, spatial scales, technical capabilities, and other practical considerations. We have developed the 1st SWOT User Survey for broad distribution to the SWOT applications community to provide the SWOT Project with an understanding of and improved ability to support users needs. Actionable knowledge for specific applications may be realized when we can determine the margins of user requirements for data products and access. The SWOT Applications team will be launching a SWOT Early Adopters program and are interested in identifying a broad community of users who will participate in pre-launch applications activities including meetings, briefings, and workshops. The SWOT applications program is designed to connect mission scientists to end users and leverage the scientific research and data management tools with operational decision-making for different thematic users and data requirements. SWOT is scheduled to launch in 2020, so simulated hydrology and ocean data sets have been and will continued to be developed by science team members and the SWOT Project in order to determine how the data will represent the physical Earth systems targeted by the mission. SWOT will produce the first global survey of Earth's surface water by measuring sea surface height and the heights, slopes, and inundated areas of rivers, lakes, and wetlands. These coastal, lake and river measurements will be used for monitoring the hydrologic cycle, flooding, and climate impacts of a changing environment. The oceanographic measurements will enhance understanding of submesoscale processes and extend the capabilities of ocean state and climate prediction models.

  20. Non-Intrusive Techniques of Inspections During the Pre-Launch Phase of Space Vehicle

    Science.gov (United States)

    Thirumalainambi, Rejkumar; Bardina, Jorge E.

    2005-01-01

    This paper addresses a method of non-intrusive local inspection of surface and sub-surface conditions, interfaces, laminations and seals in both space vehicle and ground operations with an integrated suite of imaging sensors during pre-launch operations. It employs an advanced Raman spectrophotometer with additional spectrophotometers and lidar mounted on a flying robot to constantly monitor the space hardware as well as inner surface of the vehicle and ground operations hardware. This paper addresses a team of micro flying robots with necessary sensors and photometers to monitor the entire space vehicle internally and externally. The micro flying robots can reach altitude with least amount of energy, where astronauts have difficulty in reaching and monitoring the materials and subsurface faults. The micro flying robot has an embedded fault detection system which acts as an advisory system and in many cases micro flying robots act as a Supervisor to fix the problems. As missions expand to a sustainable presence in the Moon, and extend for durations longer than one year in lunar outpost, the effectiveness of the instrumentation and hardware has to be revolutionized if NASA is to meet high levels of mission safety, reliability, and overall success. The micro flying robot uses contra-rotating propellers powered by an ultra-thin, ultrasonic motor with currently the world's highest power weight ratio, and is balanced in mid-air by means of the world's first stabilizing mechanism using a linear actuator. The essence of micromechatronics has been brought together in high-density mounting technology to minimize the size and weight. The robot can take suitable payloads of photometers, embedded chips for image analysis and micro pumps for sealing cracks or fixing other material problems. This paper also highlights advantages that this type of non-intrusive techniques offer over costly and monolithic traditional techniques.

  1. A 14-bit 200-MS/s time-interleaved ADC with sample-time error calibration

    Institute of Scientific and Technical Information of China (English)

    Zhang Yiwen; Chen Chixiao; Yu Bei; Ye Fan; Ren Junyan

    2012-01-01

    Sample-time error between channels degrades the resolution of time-interleaved analog-to-digital converters (TIADCs).A calibration method implemented in mixed circuits with low complexity and fast convergence is proposed in this paper.The algorithm for detecting sample-time error is based on correlation and widely applied to wide-sense stationary input signals.The detected sample-time error is corrected by a voltage-controlled sampling switch.The experimental result of a 2-channel 200-MS/s 14-bit TIADC shows that the signal-to-noise and distortion ratio improves by 19.1 dB,and the spurious-free dynamic range improves by 34.6 dB for a 70.12-MHz input after calibration.The calibration convergence time is about 20000 sampling intervals.

  2. Evaluation of Anomaly Detection Capability for Ground-Based Pre-Launch Shuttle Operations. Chapter 8

    Science.gov (United States)

    Martin, Rodney Alexander

    2010-01-01

    This chapter will provide a thorough end-to-end description of the process for evaluation of three different data-driven algorithms for anomaly detection to select the best candidate for deployment as part of a suite of IVHM (Integrated Vehicle Health Management) technologies. These algorithms were deemed to be sufficiently mature enough to be considered viable candidates for deployment in support of the maiden launch of Ares I-X, the successor to the Space Shuttle for NASA's Constellation program. Data-driven algorithms are just one of three different types being deployed. The other two types of algorithms being deployed include a "nile-based" expert system, and a "model-based" system. Within these two categories, the deployable candidates have already been selected based upon qualitative factors such as flight heritage. For the rule-based system, SHINE (Spacecraft High-speed Inference Engine) has been selected for deployment, which is a component of BEAM (Beacon-based Exception Analysis for Multimissions), a patented technology developed at NASA's JPL (Jet Propulsion Laboratory) and serves to aid in the management and identification of operational modes. For the "model-based" system, a commercially available package developed by QSI (Qualtech Systems, Inc.), TEAMS (Testability Engineering and Maintenance System) has been selected for deployment to aid in diagnosis. In the context of this particular deployment, distinctions among the use of the terms "data-driven," "rule-based," and "model-based," can be found in. Although there are three different categories of algorithms that have been selected for deployment, our main focus in this chapter will be on the evaluation of three candidates for data-driven anomaly detection. These algorithms will be evaluated upon their capability for robustly detecting incipient faults or failures in the ground-based phase of pre-launch space shuttle operations, rather than based oil heritage as performed in previous studies. Robust

  3. Pre-Launch phase 2 rehearsal of the calibration and validation of soil moisture active passive (SMAP) geophysical data products

    Science.gov (United States)

    NASA’s Soil Moisture Active Passive (SMAP) Mission is scheduled for launch in early November 2014. The objective of the mission is global mapping of soil moisture and landscape freeze/thaw state. SMAP utilizes L-band radar and radiometer measurements sharing a rotating 6-meter mesh reflector antenna...

  4. A simultaneously calibration approach for installation and attitude errors of an INS/GPS/LDS target tracker.

    Science.gov (United States)

    Cheng, Jianhua; Chen, Daidai; Sun, Xiangyu; Wang, Tongda

    2015-02-04

    To obtain the absolute position of a target is one of the basic topics for non-cooperated target tracking problems. In this paper, we present a simultaneously calibration method for an Inertial navigation system (INS)/Global position system (GPS)/Laser distance scanner (LDS) integrated system based target positioning approach. The INS/GPS integrated system provides the attitude and position of observer, and LDS offers the distance between the observer and the target. The two most significant errors are taken into jointly consideration and analyzed: (1) the attitude measure error of INS/GPS; (2) the installation error between INS/GPS and LDS subsystems. Consequently, a INS/GPS/LDS based target positioning approach considering these two errors is proposed. In order to improve the performance of this approach, a novel calibration method is designed to simultaneously estimate and compensate these two main errors. Finally, simulations are conducted to access the performance of the proposed target positioning approach and the designed simultaneously calibration method.

  5. Comparison of Error Estimations by DERs in One-Port S and SLO Calibrated VNA Measurements and Application

    CERN Document Server

    Yannopoulou, Nikolitsa

    2011-01-01

    In order to demonstrate the usefulness of the only one existing method for systematic error estimations in VNA (Vector Network Analyzer) measurements by using complex DERs (Differential Error Regions), we compare one-port VNA measurements after the two well-known calibration techniques: the quick reflection response, that uses only a single S (Short circuit) standard, and the time-consuming full one-port, that uses a triple of SLO standards (Short circuit, matching Load, Open circuit). For both calibration techniques, the comparison concerns: (a) a 3D geometric representation of the difference between VNA readings and measurements, and (b) a number of presentation figures for the DERs and their polar DEIs (Differential Error Intervals) of the reflection coefficient, as well as, the DERs and their rectangular DEIs of the corresponding input impedance. In this paper, we present the application of this method to an AUT (Antenna Under Test) selected to highlight the existence of practical cases in which the time ...

  6. Application of advanced shearing techniques to the calibration of autocollimators with small angle generators and investigation of error sources.

    Science.gov (United States)

    Yandayan, T; Geckeler, R D; Aksulu, M; Akgoz, S A; Ozgur, B

    2016-05-01

    The application of advanced error-separating shearing techniques to the precise calibration of autocollimators with Small Angle Generators (SAGs) was carried out for the first time. The experimental realization was achieved using the High Precision Small Angle Generator (HPSAG) of TUBITAK UME under classical dimensional metrology laboratory environmental conditions. The standard uncertainty value of 5 mas (24.2 nrad) reached by classical calibration method was improved to the level of 1.38 mas (6.7 nrad). Shearing techniques, which offer a unique opportunity to separate the errors of devices without recourse to any external standard, were first adapted by Physikalisch-Technische Bundesanstalt (PTB) to the calibration of autocollimators with angle encoders. It has been demonstrated experimentally in a clean room environment using the primary angle standard of PTB (WMT 220). The application of the technique to a different type of angle measurement system extends the range of the shearing technique further and reveals other advantages. For example, the angular scales of the SAGs are based on linear measurement systems (e.g., capacitive nanosensors for the HPSAG). Therefore, SAGs show different systematic errors when compared to angle encoders. In addition to the error-separation of HPSAG and the autocollimator, detailed investigations on error sources were carried out. Apart from determination of the systematic errors of the capacitive sensor used in the HPSAG, it was also demonstrated that the shearing method enables the unique opportunity to characterize other error sources such as errors due to temperature drift in long term measurements. This proves that the shearing technique is a very powerful method for investigating angle measuring systems, for their improvement, and for specifying precautions to be taken during the measurements.

  7. Parameterizations for reducing camera reprojection error for robot-world hand-eye calibration

    Science.gov (United States)

    Accurate robot-world, hand-eye calibration is crucial to automation tasks. In this paper, we discuss the robot-world, hand-eye calibration problem which has been modeled as the linear relationship AX equals ZB, where X and Z are the unknown calibration matrices composed of rotation and translation ...

  8. SU-E-T-550: Range Effects in Proton Therapy Caused by Systematic Errors in the Stoichiometric Calibration

    Energy Technology Data Exchange (ETDEWEB)

    Doolan, P [University College London, London (United Kingdom); Massachusetts General Hospital, Boston, MA (United States); Dias, M [Massachusetts General Hospital, Boston, MA (United States); Dipartamento di Elettronica, Informazione e Bioingegneria - DEIB, Politecnico di Milano (Italy); Collins Fekete, C [Massachusetts General Hospital, Boston, MA (United States); Departement de physique, de genie physique et d' optique et Centre de recherche sur le cancer, Universite Laval, Quebec (Canada); Seco, J [Massachusetts General Hospital, Boston, MA (United States)

    2014-06-01

    Purpose: The procedure for proton treatment planning involves the conversion of the patient's X-ray CT from Hounsfield units into relative stopping powers (RSP), using a stoichiometric calibration curve (Schneider 1996). In clinical practice a 3.5% margin is added to account for the range uncertainty introduced by this process and other errors. RSPs for real tissues are calculated using composition data and the Bethe-Bloch formula (ICRU 1993). The purpose of this work is to investigate the impact that systematic errors in the stoichiometric calibration have on the proton range. Methods: Seven tissue inserts of the Gammex 467 phantom were imaged using our CT scanner. Their known chemical compositions (Watanabe 1999) were then used to calculate the theoretical RSPs, using the same formula as would be used for human tissues in the stoichiometric procedure. The actual RSPs of these inserts were measured using a Bragg peak shift measurement in the proton beam at our institution. Results: The theoretical calculation of the RSP was lower than the measured RSP values, by a mean/max error of - 1.5/-3.6%. For all seven inserts the theoretical approach underestimated the RSP, with errors variable across the range of Hounsfield units. Systematic errors for lung (average of two inserts), adipose and cortical bone were - 3.0/-2.1/-0.5%, respectively. Conclusion: There is a systematic underestimation caused by the theoretical calculation of RSP; a crucial step in the stoichiometric calibration procedure. As such, we propose that proton calibration curves should be based on measured RSPs. Investigations will be made to see if the same systematic errors exist for biological tissues. The impact of these differences on the range of proton beams, for phantoms and patient scenarios, will be investigated. This project was funded equally by the Engineering and Physical Sciences Research Council (UK) and Ion Beam Applications (Louvain-La-Neuve, Belgium)

  9. Integrating a calibrated groundwater flow model with error-correcting data-driven models to improve predictions

    Science.gov (United States)

    Demissie, Yonas K.; Valocchi, Albert J.; Minsker, Barbara S.; Bailey, Barbara A.

    2009-01-01

    SummaryPhysically-based groundwater models (PBMs), such as MODFLOW, contain numerous parameters which are usually estimated using statistically-based methods, which assume that the underlying error is white noise. However, because of the practical difficulties of representing all the natural subsurface complexity, numerical simulations are often prone to large uncertainties that can result in both random and systematic model error. The systematic errors can be attributed to conceptual, parameter, and measurement uncertainty, and most often it can be difficult to determine their physical cause. In this paper, we have developed a framework to handle systematic error in physically-based groundwater flow model applications that uses error-correcting data-driven models (DDMs) in a complementary fashion. The data-driven models are separately developed to predict the MODFLOW head prediction errors, which were subsequently used to update the head predictions at existing and proposed observation wells. The framework is evaluated using a hypothetical case study developed based on a phytoremediation site at the Argonne National Laboratory. This case study includes structural, parameter, and measurement uncertainties. In terms of bias and prediction uncertainty range, the complementary modeling framework has shown substantial improvements (up to 64% reduction in RMSE and prediction error ranges) over the original MODFLOW model, in both the calibration and the verification periods. Moreover, the spatial and temporal correlations of the prediction errors are significantly reduced, thus resulting in reduced local biases and structures in the model prediction errors.

  10. Developing Calibration Weights and Standard-Error Estimates for a Survey of Drug-Related Emergency-Department Visits

    Directory of Open Access Journals (Sweden)

    Kott Phillip S.

    2014-09-01

    Full Text Available This article describes a two-step calibration-weighting scheme for a stratified simple random sample of hospital emergency departments. The first step adjusts for unit nonresponse. The second increases the statistical efficiency of most estimators of interest. Both use a measure of emergency-department size and other useful auxiliary variables contained in the sampling frame. Although many survey variables are roughly a linear function of the measure of size, response is better modeled as a function of the log of that measure. Consequently the log of size is a calibration variable in the nonresponse-adjustment step, while the measure of size itself is a calibration variable in the second calibration step. Nonlinear calibration procedures are employed in both steps. We show with 2010 DAWN data that estimating variances as if a one-step calibration weighting routine had been used when there were in fact two steps can, after appropriately adjusting the finite-population correct in some sense, produce standard-error estimates that tend to be slightly conservative.

  11. The Calibration and error analysis of Shallow water (less than 100m) Multibeam Echo-Sounding System

    Science.gov (United States)

    Lin, M.

    2016-12-01

    Multibeam echo-sounders(MBES) have been developed to gather bathymetric and acoustic data for more efficient and more exact mapping of the oceans. This gain in efficiency does not come without drawbacks. Indeed, the finer the resolution of remote sensing instruments, the harder they are to calibrate. This is the case for multibeam echo-sounding systems (MBES). We are no longer dealing with sounding lines where the bathymetry must be interpolated between them to engender consistent representations of the seafloor. We now need to match together strips (swaths) of totally ensonified seabed. As a consequence, misalignment and time lag problems emerge as artifacts in the bathymetry from adjacent or overlapping swaths, particularly when operating in shallow water. More importantly, one must still verify that bathymetric data meet the accuracy requirements. This paper aims to summarize the system integration involved with MBES and identify the various source of error pertaining to shallow water survey (100m and less). A systematic method for the calibration of shallow water MBES is proposed and presented as a set of field procedures. The procedures aim at detecting, quantifying and correcting systematic instrumental and installation errors. Hence, calibrating for variations of the speed of sound in the water column, which is natural in origin, is not addressed in this document. The data which used in calibration will reference International Hydrographic Organization(IHO) and other related standards to compare. This paper aims to set a model in the specific area which can calibrate the error due to instruments. We will construct a procedure in patch test and figure out all the possibilities may make sounding data with error then calculate the error value to compensate. In general, the problems which have to be solved is the patch test's 4 correction in the Hypack system 1.Roll 2.GPS Latency 3.Pitch 4.Yaw. Cause These 4 correction affect each others, we run each survey line

  12. Sensitivity analysis, calibration, and testing of a distributed hydrological model using error-based weighting and one objective function

    Science.gov (United States)

    Foglia, L.; Hill, Mary C.; Mehl, Steffen W.; Burlando, P.

    2009-01-01

    We evaluate the utility of three interrelated means of using data to calibrate the fully distributed rainfall-runoff model TOPKAPI as applied to the Maggia Valley drainage area in Switzerland. The use of error-based weighting of observation and prior information data, local sensitivity analysis, and single-objective function nonlinear regression provides quantitative evaluation of sensitivity of the 35 model parameters to the data, identification of data types most important to the calibration, and identification of correlations among parameters that contribute to nonuniqueness. Sensitivity analysis required only 71 model runs, and regression required about 50 model runs. The approach presented appears to be ideal for evaluation of models with long run times or as a preliminary step to more computationally demanding methods. The statistics used include composite scaled sensitivities, parameter correlation coefficients, leverage, Cook's D, and DFBETAS. Tests suggest predictive ability of the calibrated model typical of hydrologic models.

  13. Analysis of Calibration Errors for Both Short and Long Stroke White Light Experiments

    Science.gov (United States)

    Pan, Xaiopei

    2006-01-01

    This work will analyze focusing and tilt variations introduced by thermal changes in calibration processes. In particular the accuracy limits are presented for common short- and long-stroke experiments. A new, simple, practical calibration scheme is proposed and analyzed based on the SIM PlanetQuest's Micro-Arcsecond Metrology (MAM) testbed experiments.

  14. On the Error State Selection for Stationary SINS Alignment and Calibration Kalman Filters-Part II: Observability/Estimability Analysis.

    Science.gov (United States)

    Silva, Felipe O; Hemerly, Elder M; Leite Filho, Waldemar C

    2017-02-23

    This paper presents the second part of a study aiming at the error state selection in Kalman filters applied to the stationary self-alignment and calibration (SSAC) problem of strapdown inertial navigation systems (SINS). The observability properties of the system are systematically investigated, and the number of unobservable modes is established. Through the analytical manipulation of the full SINS error model, the unobservable modes of the system are determined, and the SSAC error states (except the velocity errors) are proven to be individually unobservable. The estimability of the system is determined through the examination of the major diagonal terms of the covariance matrix and their eigenvalues/eigenvectors. Filter order reduction based on observability analysis is shown to be inadequate, and several misconceptions regarding SSAC observability and estimability deficiencies are removed. As the main contributions of this paper, we demonstrate that, except for the position errors, all error states can be minimally estimated in the SSAC problem and, hence, should not be removed from the filter. Corroborating the conclusions of the first part of this study, a 12-state Kalman filter is found to be the optimal error state selection for SSAC purposes. Results from simulated and experimental tests support the outlined conclusions.

  15. On the Error State Selection for Stationary SINS Alignment and Calibration Kalman Filters—Part II: Observability/Estimability Analysis

    Directory of Open Access Journals (Sweden)

    Felipe O. Silva

    2017-02-01

    Full Text Available This paper presents the second part of a study aiming at the error state selection in Kalman filters applied to the stationary self-alignment and calibration (SSAC problem of strapdown inertial navigation systems (SINS. The observability properties of the system are systematically investigated, and the number of unobservable modes is established. Through the analytical manipulation of the full SINS error model, the unobservable modes of the system are determined, and the SSAC error states (except the velocity errors are proven to be individually unobservable. The estimability of the system is determined through the examination of the major diagonal terms of the covariance matrix and their eigenvalues/eigenvectors. Filter order reduction based on observability analysis is shown to be inadequate, and several misconceptions regarding SSAC observability and estimability deficiencies are removed. As the main contributions of this paper, we demonstrate that, except for the position errors, all error states can be minimally estimated in the SSAC problem and, hence, should not be removed from the filter. Corroborating the conclusions of the first part of this study, a 12-state Kalman filter is found to be the optimal error state selection for SSAC purposes. Results from simulated and experimental tests support the outlined conclusions.

  16. Nonlinear calibration transfer based on hierarchical Bayesian models and Lagrange Multipliers: Error bounds of estimates via Monte Carlo - Markov Chain sampling.

    Science.gov (United States)

    Seichter, Felicia; Vogt, Josef; Radermacher, Peter; Mizaikoff, Boris

    2017-01-25

    The calibration of analytical systems is time-consuming and the effort for daily calibration routines should therefore be minimized, while maintaining the analytical accuracy and precision. The 'calibration transfer' approach proposes to combine calibration data already recorded with actual calibrations measurements. However, this strategy was developed for the multivariate, linear analysis of spectroscopic data, and thus, cannot be applied to sensors with a single response channel and/or a non-linear relationship between signal and desired analytical concentration. To fill this gap for a non-linear calibration equation, we assume that the coefficients for the equation, collected over several calibration runs, are normally distributed. Considering that coefficients of an actual calibration are a sample of this distribution, only a few standards are needed for a complete calibration data set. The resulting calibration transfer approach is demonstrated for a fluorescence oxygen sensor and implemented as a hierarchical Bayesian model, combined with a Lagrange Multipliers technique and Monte-Carlo Markov-Chain sampling. The latter provides realistic estimates for coefficients and prediction together with accurate error bounds by simulating known measurement errors and system fluctuations. Performance criteria for validation and optimal selection of a reduced set of calibration samples were developed and lead to a setup which maintains the analytical performance of a full calibration. Strategies for a rapid determination of problems occurring in a daily calibration routine, are proposed, thereby opening the possibility of correcting the problem just in time.

  17. Electricity Price Forecast Using Combined Models with Adaptive Weights Selected and Errors Calibrated by Hidden Markov Model

    Directory of Open Access Journals (Sweden)

    Da Liu

    2013-01-01

    Full Text Available A combined forecast with weights adaptively selected and errors calibrated by Hidden Markov model (HMM is proposed to model the day-ahead electricity price. Firstly several single models were built to forecast the electricity price separately. Then the validation errors from every individual model were transformed into two discrete sequences: an emission sequence and a state sequence to build the HMM, obtaining a transmission matrix and an emission matrix, representing the forecasting ability state of the individual models. The combining weights of the individual models were decided by the state transmission matrixes in HMM and the best predict sample ratio of each individual among all the models in the validation set. The individual forecasts were averaged to get the combining forecast with the weights obtained above. The residuals of combining forecast were calibrated by the possible error calculated by the emission matrix of HMM. A case study of day-ahead electricity market of Pennsylvania-New Jersey-Maryland (PJM, USA, suggests that the proposed method outperforms individual techniques of price forecasting, such as support vector machine (SVM, generalized regression neural networks (GRNN, day-ahead modeling, and self-organized map (SOM similar days modeling.

  18. Suppression of Fiber Modal Noise Induced Radial Velocity Errors for Bright Emission-line Calibration Sources

    Science.gov (United States)

    Mahadevan, Suvrath; Halverson, Samuel; Ramsey, Lawrence; Venditti, Nick

    2014-05-01

    Modal noise in optical fibers imposes limits on the signal-to-noise ratio (S/N) and velocity precision achievable with the next generation of astronomical spectrographs. This is an increasingly pressing problem for precision radial velocity spectrographs in the near-infrared (NIR) and optical that require both high stability of the observed line profiles and high S/N. Many of these spectrographs plan to use highly coherent emission-line calibration sources like laser frequency combs and Fabry-Perot etalons to achieve precision sufficient to detect terrestrial-mass planets. These high-precision calibration sources often use single-mode fibers or highly coherent sources. Coupling light from single-mode fibers to multi-mode fibers leads to only a very low number of modes being excited, thereby exacerbating the modal noise measured by the spectrograph. We present a commercial off-the-shelf solution that significantly mitigates modal noise at all optical and NIR wavelengths, and which can be applied to spectrograph calibration systems. Our solution uses an integrating sphere in conjunction with a diffuser that is moved rapidly using electrostrictive polymers, and is generally superior to most tested forms of mechanical fiber agitation. We demonstrate a high level of modal noise reduction with a narrow bandwidth 1550 nm laser. Our relatively inexpensive solution immediately enables spectrographs to take advantage of the innate precision of bright state-of-the art calibration sources by removing a major source of systematic noise.

  19. ESA ExoMars: Pre-launch PanCam Geometric Modeling and Accuracy Assessment

    Science.gov (United States)

    Li, D.; Li, R.; Yilmaz, A.

    2014-08-01

    ExoMars is the flagship mission of the European Space Agency (ESA) Aurora Programme. The mobile scientific platform, or rover, will carry a drill and a suite of instruments dedicated to exobiology and geochemistry research. As the ExoMars rover is designed to travel kilometres over the Martian surface, high-precision rover localization and topographic mapping will be critical for traverse path planning and safe planetary surface operations. For such purposes, the ExoMars rover Panoramic Camera system (PanCam) will acquire images that are processed into an imagery network providing vision information for photogrammetric algorithms to localize the rover and generate 3-D mapping products. Since the design of the ExoMars PanCam will influence localization and mapping accuracy, quantitative error analysis of the PanCam design will improve scientists' awareness of the achievable level of accuracy, and enable the PanCam design team to optimize its design to achieve the highest possible level of localization and mapping accuracy. Based on photogrammetric principles and uncertainty propagation theory, we have developed a method to theoretically analyze how mapping and localization accuracy would be affected by various factors, such as length of stereo hard-baseline, focal length, and pixel size, etc.

  20. Performance analysis for time-frequency MUSIC algorithm in presence of both additive noise and array calibration errors

    Science.gov (United States)

    Khodja, Mohamed; Belouchrani, Adel; Abed-Meraim, Karim

    2012-12-01

    This article deals with the application of Spatial Time-Frequency Distribution (STFD) to the direction finding problem using the Multiple Signal Classification (MUSIC)algorithm. A comparative performance analysis is performed for the method under consideration with respect to that using data covariance matrix when the received array signals are subject to calibration errors in a non-stationary environment. An unified analytical expression of the Direction Of Arrival (DOA) error estimation is derived for both methods. Numerical results show the effect of the parameters intervening in the derived expression on the algorithm performance. It is particularly observed that for low Signal to Noise Ratio (SNR) and high Signal to sensor Perturbation Ratio (SPR) the STFD method gives better performance, while for high SNR and for the same SPR both methods give similar performance.

  1. Suppression of Fiber Modal Noise Induced Radial Velocity Errors for Bright Emission-Line Calibration Sources

    CERN Document Server

    Mahadevan, Suvrath; Ramsey, Lawrence; Venditti, Nick

    2014-01-01

    Modal noise in optical fibers imposes limits on the signal to noise and velocity precision achievable with the next generation of astronomical spectrographs. This is an increasingly pressing problem for precision radial velocity (RV) spectrographs in the near-infrared (NIR) and optical that require both high stability of the observed line profiles and high signal to noise. Many of these spectrographs plan to use highly coherent emission line calibration sources like laser frequency combs and Fabry-Perot etalons to achieve precision sufficient to detect terrestrial mass planets. These high precision calibration sources often use single mode fibers or highly coherent sources. Coupling light from single mode fibers to multi-mode fibers leads to only a very low number of modes being excited, thereby exacerbating the modal noise measured by the spectrograph. We present a commercial off-the-shelf (COTS) solution that significantly mitigates modal noise at all optical and NIR wavelengths, and which can be applied to...

  2. Determination of optimal samples for robot calibration based on error similarity

    Directory of Open Access Journals (Sweden)

    Tian Wei

    2015-06-01

    Full Text Available Industrial robots are used for automatic drilling and riveting. The absolute position accuracy of an industrial robot is one of the key performance indexes in aircraft assembly, and can be improved through error compensation to meet aircraft assembly requirements. The achievable accuracy and the difficulty of accuracy compensation implementation are closely related to the choice of sampling points. Therefore, based on the error similarity error compensation method, a method for choosing sampling points on a uniform grid is proposed. A simulation is conducted to analyze the influence of the sample point locations on error compensation. In addition, the grid steps of the sampling points are optimized using a statistical analysis method. The method is used to generate grids and optimize the grid steps of a Kuka KR-210 robot. The experimental results show that the method for planning sampling data can be used to effectively optimize the sampling grid. After error compensation, the position accuracy of the robot meets the position accuracy requirements.

  3. Galaxy-galaxy weak lensing in SDSS: intrinsic alignments and shear calibration errors

    CERN Document Server

    Hirata, C M; Seljak, U; Guzik, J; Padmanabhan, N; Blake, C; Brinkmann, J; Budavari, T; Connolly, A; Csabai, I; Scranton, R; Szalay, A S; Hirata, Christopher M.; Mandelbaum, Rachel; Seljak, Uros; Guzik, Jacek; Padmanabhan, Nikhil; Blake, Cullen; Brinkmann, Jonathan; Budavari, Tamas; Connolly, Andrew; Csabai, Istvan; Scranton, Ryan; Szalay, Alexander S.

    2004-01-01

    Galaxy-galaxy lensing has emerged as a powerful probe of the dark matter haloes of galaxies, but is subject to contamination if intrinsically aligned satellites of the lens galaxy are used as part of the source sample. We present a measurement of this intrinsic shear using 200,747 lens galaxies from the Sloan Digital Sky Survey (SDSS) spectroscopic sample and a sample of satellites selected using photometric redshifts. The mean intrinsic shear at transverse separations of 30--446$h^{-1}$ kpc is constrained to be $-0.0062<\\Delta\\gamma<+0.0066$ (99.9 per cent confidence, including identified systematics), which limits contamination of the galaxy-galaxy lensing signal to at most $\\sim 15$ per cent on these scales. We present these limits as a function of transverse separation and lens luminosity. We furthermore investigate shear calibration biases in the SDSS and conclude that the shear amplitude is calibrated to better than 18 per cent. This includes noise-induced calibration biases in the ellipticity, wh...

  4. A spectral synthesis method to suppress aliasing and calibrate for delay errors in Fourier transform correlators

    CERN Document Server

    Kaneko, Tak

    2008-01-01

    Context: Fourier transform (or lag) correlators in radio interferometers can serve as an efficient means of synthesising spectral channels. However aliasing corrupts the edge channels so they usually have to be excluded from the data set. In systems with around 10 channels, the loss in sensitivity can be significant. In addition, the low level of residual aliasing in the remaining channels may cause systematic errors. Moreover, delay errors have been widely reported in implementations of broadband analogue correlators and simulations have shown that delay errors exasperate the effects of aliasing. Aims: We describe a software-based approach that suppresses aliasing by oversampling the cross-correlation function. This method can be applied to interferometers with individually-tracking antennas equipped with a discrete path compensator system. It is based on the well-known property of interferometers where the drift scan response is the Fourier transform of the source's band-limited spectrum. Methods: In this p...

  5. Use of two-part regression calibration model to correct for measurement error in episodically consumed foods in a single-replicate study design: EPIC case study.

    Directory of Open Access Journals (Sweden)

    George O Agogo

    Full Text Available In epidemiologic studies, measurement error in dietary variables often attenuates association between dietary intake and disease occurrence. To adjust for the attenuation caused by error in dietary intake, regression calibration is commonly used. To apply regression calibration, unbiased reference measurements are required. Short-term reference measurements for foods that are not consumed daily contain excess zeroes that pose challenges in the calibration model. We adapted two-part regression calibration model, initially developed for multiple replicates of reference measurements per individual to a single-replicate setting. We showed how to handle excess zero reference measurements by two-step modeling approach, how to explore heteroscedasticity in the consumed amount with variance-mean graph, how to explore nonlinearity with the generalized additive modeling (GAM and the empirical logit approaches, and how to select covariates in the calibration model. The performance of two-part calibration model was compared with the one-part counterpart. We used vegetable intake and mortality data from European Prospective Investigation on Cancer and Nutrition (EPIC study. In the EPIC, reference measurements were taken with 24-hour recalls. For each of the three vegetable subgroups assessed separately, correcting for error with an appropriately specified two-part calibration model resulted in about three fold increase in the strength of association with all-cause mortality, as measured by the log hazard ratio. Further found is that the standard way of including covariates in the calibration model can lead to over fitting the two-part calibration model. Moreover, the extent of adjusting for error is influenced by the number and forms of covariates in the calibration model. For episodically consumed foods, we advise researchers to pay special attention to response distribution, nonlinearity, and covariate inclusion in specifying the calibration model.

  6. Expected linking error resulting from item parameter drift among the common Items on Rasch calibrated tests.

    Science.gov (United States)

    Miller, G Edward; Gesn, Paul Randall; Rotou, Jourania

    2005-01-01

    In state assessment programs that employ Rasch-based common item linking procedures, the linking constant is usually estimated with only those common items not identified as exhibiting item difficulty parameter drift. Since state assessments typically contain a fixed number of items, an item classified as exhibiting parameter drift during the linking process remains on the exam as a scorable item even if it is removed from the common item set. Under the assumption that item parameter drift has occurred for one or more of the common items, the expected effect of including or excluding the "affected" item(s) in the estimation of the linking constant is derived in this article. If the item parameter drift is due solely to factors not associated with a change in examinee achievement, no linking error will (be expected to) occur given that the linking constant is estimated only with the items not identified as "affected"; linking error will (be expected to) occur if the linking constant is estimated with all common items. However, if the item parameter drift is due solely to change in examinee achievement, the opposite is true: no linking error will (be expected to) occur if the linking constant is estimated with all common items; linking error will (be expected to) occur if the linking constant is estimated only with the items not identified as "affected".

  7. A Note on NCOM Temperature Forecast Error Calibration Using the Ensemble Transform

    Science.gov (United States)

    2009-01-01

    spatial distributions of the E Coelhn et a\\. ,’journal of Marine Systems 78 (2009) S272-S281 S27S t e IS ii 15 If ii .i s 51 s^ I! i| 1* 2 3...International Conference on Mathematics and Continuum Mechanics. Pub. Centro Internacional de Matematica (C1M). ISBN: 978-989-95011- 2-6, pp. 207-217. Porto...Hagerdorn. R., Palmer, T.N., 2005. The rationale behind the success of multi-model ensembles in seasonal forecasting - II . Calibration and combination

  8. The solar vector error within the SNPP Common GEO code, the correction, and the effects on the VIIRS SDR RSB calibration

    Science.gov (United States)

    Fulbright, Jon; Anderson, Samuel; Lei, Ning; Efremova, Boryana; Wang, Zhipeng; McIntire, Jeffrey; Chiang, Kwofu; Xiong, Xiaoxiong

    2014-11-01

    Due to a software error, the solar and lunar vectors reported in the on-board calibrator intermediate product (OBC-IP) files for SNPP VIIRS are incorrect. The magnitude of the error is about 0.2 degree, and the magnitude is increasing by about 0.01 degree per year. This error, although small, has an effect on the radiometric calibration of the reflective solar bands (RSB) because accurate solar angles are required for calculating the screen transmission functions and for calculating the illumination of the Solar Diffuser panel. In this paper, we describe the error in the Common GEO code, and how it may be fixed. We present evidence for the error from within the OBC-IP data. We also describe the effects of the solar vector error on the RSB calibration and the Sensor Data Record (SDR). In order to perform this evaluation, we have reanalyzed the yaw-maneuver data to compute the vignetting functions required for the on-orbit SD RSB radiometric calibration. After the reanalysis, we find effect of up to 0.5% on the shortwave infrared (SWIR) RSB calibration.

  9. Predictive error dependencies when using pilot points and singular value decomposition in groundwater model calibration

    DEFF Research Database (Denmark)

    Christensen, Steen; Doherty, John

    2008-01-01

    over the model area. Singular value decomposition (SVD) of the (possibly weighted) sensitivity matrix of the pilot point based model produces eigenvectors of which we pick a small number corresponding to significant eigenvalues. Super parameters are defined as factors through which parameter...... conditions near an inflow boundary where data is lacking and which exhibit apparent significant nonlinear behavior. It is shown that inclusion of Tikhonov regularization can stabilize and speed up the parameter estimation process. A method of linearized model analysis of predictive uncertainty...... nonlinear functions. Recommendations concerning the use of pilot points and singular value decomposition in real-world groundwater model calibration are finally given. (c) 2008 Elsevier Ltd. All rights reserved....

  10. Calibration of symmetric and non-symmetric errors for interferometry of ultra-precise imaging systems

    Energy Technology Data Exchange (ETDEWEB)

    Phillion, D W; Sommargren, G E; Johnson, M A; Decker, T A; Taylor, J S; Gomie, Y; Kakuchi, O; Takeuchi, S

    2005-06-29

    The azimuthal Zernike coefficients for shells of Zernike functions with shell numbers nerrors would then be known. Physically, the measurements in circles A and B are accomplished by rotating each pinhole aligner about an aligned axis, then about an oblique axis. Absolute measurement accuracies better than 0.2 nm were achieved.

  11. Magnetic Compass Error Analysis and Calibration for Rotorcraft Flying Robot%旋翼飞行机器人磁罗盘误差分析及校准

    Institute of Scientific and Technical Information of China (English)

    戴磊; 齐俊桐; 吴冲; 韩建达

    2012-01-01

    以旋翼飞行机器人组合导航系统为研究背景,针对电子磁罗盘的误差校准方法进行研究.通过分析其测量原理和误差来源,总结出影响磁罗盘航向解算精度的5个主要误差因素,对于上述误差因素,提出了软件和硬件解决办法.考虑到旋翼飞行机器人平台的特殊性,提出了硬磁罗差和标度因数误差的简化校准实现方法,简化后的磁罗盘校准方法,免去了校准过程中将载体竖起的步骤,且不降低校准精度.实际的磁罗盘校准测试表明,本文提出的方法能避免将大尺寸的载体竖起,降低校磁操作的难度.该方法可以有效地修正原始磁场测量值的椭球分布,从而提高组台导航系统航向解算精度.%With the research background of the rotorcraft flying robot's integrated navigation system, an error calibration method for electric magnetic compass is proposed. Based on the analysis of the magnetic compass's measurement theory and error sources, 5 main factors which affect the heading angle calculation precision of the magnetic compass, are summarized. In response to the mentioned error factors, software and hardware solutions are proposed. Considering the specialties of rotorcraft flying robot, a simplified calibration method for magnetic compass is proposed to calibrate the hard magnetism errors and scale factor errors. The simplified magnetic compass calibration method can avoid sticking up the robot during calibration process, but its calibration precision is not decreased. The actual calibration test of the magnetic compass shows that the proposed calibration method can effectively correct the measurements' ellipsoidal distribution of the original magnetic field, and it also can improve the heading angle calculation precision of integrated navigation system. This method can simplify the calibration process and avoid to stick up the huge robot.

  12. Use of Balance Calibration Certificate to Calculate the Errors of Indication and Measurement Uncertainty in Mass Determinations Performed in Medical Laboratories

    Directory of Open Access Journals (Sweden)

    Adriana VÂLCU

    2011-09-01

    Full Text Available Based on the reference document, the article proposes the way to calculate the errors of indication and associated measurement uncertainties, by resorting to the general information provided by the calibration certificate of a balance (non-automatic weighing instruments, shortly NAWI used in medical field. The paper may be also considered a useful guideline for: operators working in laboratories accredited in medical (or other various fields where the weighing operations are part of their testing activities; test houses, laboratories, or manufacturers using calibrated non-automatic weighing instruments for measurements relevant for the quality of production subject to QM requirements (e.g. ISO 9000 series, ISO 10012, ISO/IEC 17025; bodies accrediting laboratories; accredited laboratories for the calibration of NAWI. Article refers only to electronic weighing instruments having maximum capacity up to 30 kg. Starting from the results provided by a calibration certificate it is presented an example of calculation.

  13. Pre-Launch Radiometric Performance Characterization of the Advanced Technology Microwave Sounder on the Joint Polar Satellite System-1 Satellite

    Science.gov (United States)

    Smith, Craig K.; Kim, Edward; Leslie, R. Vincent; Lyu, Joseph; McCormick, Lisa M.; Anderson, Kent

    2017-01-01

    The Advanced Technology Microwave Sounder (ATMS) is a space-based, cross-track radiometer for operational atmospheric temperature and humidity sounding, utilizing 22 channels over a frequency range from 23 to 183 gigahertz. The ATMS for the Joint Polar Satellite System-1 has undergone two rounds of re-work in 2014-2015 and 2016, following performance issues discovered during and following thermal vacuum chamber (TVAC) testing at the instrument and observatory level. Final shelf-level testing, including measurement of pass band characteristics and spectral response functions, was completed in December 2016. Final instrument-level TVAC testing and calibration occurred during February 2017. Here we will describe the instrument-level TVAC calibration process, and illustrate with results from the final TVAC calibration effort.

  14. Error Calibration of Fluxgate Magnetometers in Arbitrary Attitude Situation%任意姿态变化下的磁通门传感器误差校正

    Institute of Scientific and Technical Information of China (English)

    庞鸿锋; 罗诗途; 陈棣湘; 潘孟春; 张琦

    2011-01-01

    三轴磁通门传感器随着姿态变化存在空间转向差,主要原因为轴间非正交性、各轴刻度因子误差和零偏误差,需要研究校正方法,提高测量准确度.选择稳定的磁场环境,对德国的一款DM系列高精度三轴磁通门传感器进行标定.研究了传感器姿态在空间中任意变化;提出采用最小二乘法对磁通门传感器校正参数进行准确估计并校正该点转向差;传感器在验证点姿态任意变化,采用已获取的校正权值抑制验证点转向差.实验结果表明,校正点和验证点的转向差经过校正后分别从106 nT和89 nT减少到27 nT和23nT,转向差明显得到抑制,说明了校正权值在姿态任意变化情况下校正效果良好.%Diversionary error of three-axis fluxgate magnetometer can not be avoided when its attitude changes. The main reasons are non-orthogonality between axes and different amplification of each axis. So, it is necessary to research calibration method and improve measurement precision. A stable magnetic circumstance is selected to calibrate a Germany DM-series three-axis fluxgate magnetometer. Firstly, the magnetometer attitude changes arbitrary. Secondly, the least squares method is used to estimate calibration parameters, and then, diversionary error is suppressed. Lastly, with the magnetometer attitude changing arbitrary at the validation place, the calibration parameters are used to reduce diversionary error. Experimental results show that the diversionary error at the calibration place and the validation place are suppressed from 106 nT and 89 nT to 27 nT and 23 nT, respectively. Diversionary errors are reduced greatly, which demonstrates that the calibration performance is effective.

  15. Pipeline Analog-Digital Converters Dynamic Error Modeling for Calibration : Integral Nonlinearity Modeling, Pipeline ADC Calibration, Wireless Channel K-Factor Estimation

    OpenAIRE

    Medawar, Samer

    2012-01-01

    This thesis deals with the characterization, modeling and calibration of pipeline analog-digital converters (ADC)s. The integral nonlinearity (INL) is characterized, modeled and the model is used to design a post-correction block in order to compensate the imperfections of the ADC. The INL model is divided into: a dynamic term designed by the low code frequency (LCF) component depending on the output code k and the frequency under test m, and a static term known as high code frequency (HCF) c...

  16. 精密离心机误差对石英加速度计误差标定精度分析%Relationship between Calibration Accuracy of Error Model Coefficients of Accelerometer and Errors of Precision Centrifuge

    Institute of Scientific and Technical Information of China (English)

    王世明; 任顺清

    2012-01-01

    In this paper, error sources of the precision centrifuge are analyzed at first, and a homogeneous transformation method is used to accurately calculate the centripetal acceleration, as well as components of the centripetal acceleration, the acceleration of gravity, and the Coriolis acceleration in the input, the output and the pendulum axes of the tested accelerometer. Then the error model of quartz pendulous accelerometer to be tested on the centrifuge is given, the calculated specific forces acting on three axes of the accelerometer are substituted into the error model, then the relationship between the calibration errors and the errors of the centrifuge is established. Finally, the correspondences between the calibration accuracy of each error model coefficient of accelerometer and some error sources of centrifuge are determined by using simulation results, thus laying a theoretical foundation for the determination of centrifuge accuracy according to the demand for calibration accuracy of accelerometer.%分析了离心机各个误差源,用齐次变换法精确地计算了产生的向心加速度,给出了向心加速度、重力加速度和哥氏加速度在加速度计坐标系下的分量,推导了被试加速度计输入加速度的精确表达式.在给出石英摆式加速度计在精密离心机上标定时的误差模型的基础上,着重讨论了误差模型系数的计算值与离心机误差之间的关系.根据仿真结果找出了某些离心机误差对加速度计误差系数标定的影响关系,为按照加速度计的标定精度来确定离心机的精度打下了理论基础.

  17. Error estimates for ocean surface winds: Applying Desroziers diagnostics to the Cross-Calibrated, Multi-Platform analysis of wind speed

    Science.gov (United States)

    Hoffman, Ross N.; Ardizzone, Joseph V.; Leidner, S. Mark; Smith, Deborah K.; Atlas, Robert M.

    2013-04-01

    The cross-calibrated, multi-platform (CCMP) ocean surface wind project [Atlas et al., 2011] generates high-quality, high-resolution, vector winds over the world's oceans beginning with the 1987 launch of the SSM/I F08, using Remote Sensing Systems (RSS) microwave satellite wind retrievals, as well as in situ observations from ships and buoys. The variational analysis method [VAM, Hoffman et al., 2003] is at the center of the CCMP project's analysis procedures for combining observations of the wind. The VAM was developed as a smoothing spline and so implicitly defines the background error covariance by means of several constraints with adjustable weights, and does not provide an explicit estimate of the analysis error. Here we report on our research to develop uncertainty estimates for wind speed for the VAM inputs and outputs, i.e., for the background (B), the observations (O) and the analysis (A) wind speed, based on the Desroziers et al. [2005] diagnostics (DD hereafter). The DD are applied to the CCMP ocean surface wind data sets to estimate wind speed errors of the ECMWF background, the microwave satellite observations and the resulting CCMP analysis. The DD confirm that the ECMWF operational surface wind speed error standard deviations vary with latitude in the range 0.7-1.5 m/s and that the cross-calibrated Remote Sensing Systems (RSS) wind speed retrievals standard deviations are in the range 0.5-0.8 m/s. Further the estimated CCMP analysis wind speed standard deviations are in the range 0.2-0.4 m/s. The results suggests the need to revise the parameterization of the errors due to the FGAT (first guess at the appropriate time) procedure. Errors for wind speeds S. M. Leidner, J. C. Jusem, D. K. Smith, and D. Gombos, A cross-calibrated, multi-platform ocean surface wind velocity product for meteorological and oceanographic applications, Bull. Am. Meteorol. Soc., 92, 157-174, 2011, doi:10.1175/2010BAMS2946.1. Desroziers, G., L. Berre, B. Chapnik, and P. Poli

  18. Analysis of calibration data for the uranium active neutron coincidence counting collar with attention to errors in the measured neutron coincidence rate

    Energy Technology Data Exchange (ETDEWEB)

    Croft, Stephen [Oak Ridge National Laboratory (ORNL), One Bethel Valley Road, Oak Ridge, TN (United States); Burr, Tom [International Atomic Energy Agency (IAEA), Vienna (Austria); Favalli, Andrea [Los Alamos National Laboratory (LANL), MS E540, Los Alamos, NM 87545 (United States); Nicholson, Andrew [Oak Ridge National Laboratory (ORNL), One Bethel Valley Road, Oak Ridge, TN (United States)

    2016-03-01

    The declared linear density of {sup 238}U and {sup 235}U in fresh low enriched uranium light water reactor fuel assemblies can be verified for nuclear safeguards purposes using a neutron coincidence counter collar in passive and active mode, respectively. The active mode calibration of the Uranium Neutron Collar – Light water reactor fuel (UNCL) instrument is normally performed using a non-linear fitting technique. The fitting technique relates the measured neutron coincidence rate (the predictor) to the linear density of {sup 235}U (the response) in order to estimate model parameters of the nonlinear Padé equation, which traditionally is used to model the calibration data. Alternatively, following a simple data transformation, the fitting can also be performed using standard linear fitting methods. This paper compares performance of the nonlinear technique to the linear technique, using a range of possible error variance magnitudes in the measured neutron coincidence rate. We develop the required formalism and then apply the traditional (nonlinear) and alternative approaches (linear) to the same experimental and corresponding simulated representative datasets. We find that, in this context, because of the magnitude of the errors in the predictor, it is preferable not to transform to a linear model, and it is preferable not to adjust for the errors in the predictor when inferring the model parameters.

  19. Calibration Error of Robotic Vision System of 3D Laser Scanner%机器人三维激光扫描视觉系统标定误差

    Institute of Scientific and Technical Information of China (English)

    齐立哲; 汤青; 贠超; 王京; 甘中学

    2011-01-01

    The 3D laser scanner is widely applied in industry robot vision system, but the calibration error of positional relationship between the scanner and the robot has important influence on the application of robot vision system. It is presented systematically how the scanning results are influenced by the robotic vision calibration position and orientation errors and how the workpiece positioning process is affected by the scanning result and then it is concluded that the position calibration of vision system is not necessary in the robot workpiece positioning system when there is no variation of robot scanning posture no matter whether the workpiece has posture variation or not. The validity of the theoretical analysis conclusion is verified by tests, thus providing the theoretical basis for explaining the influence of calibration error of vision system on the scanning result and for simplifying the calibration process of the vision system.%基于三维激光扫描仪的工业机器人视觉系统应用越来越广泛,而扫描仪与机器人之间位姿关系标定精度对于机器人视觉系统的应用有重要的影响.介绍基于三维激光扫描仪的机器人视觉系统的相关原理,然后在此基础上系统分析机器人视觉系统位置和姿态标定误差对工件扫描结果和根据扫描结果对工件进行定位过程的影响,得出在工件无姿态变化或有姿态变化但机器人扫描姿态不变情况下的机器人工件定位系统中无须进行视觉系统位置标定的结论,并试验验证了理论分析结论的有效性,为解释视觉系统标定误差对扫描结果的影响情况及简化视觉系统标定过程提供了理论依据.

  20. Calibration and errors in the detection of heavy metals in fresh and sea waters by PIXE in the ppb-ppm range

    Science.gov (United States)

    Aprilesi, Giancarlo; Cecchi, Rodolfo; Ghermandi, Grazia; Magnoni, Gaetano; Santangelo, Renato

    1984-04-01

    A methodology for the simultaneous detection of several heavy metals in water samples will be described in detail. Targets are chemically prepared by preconcentration of the metals. Characteristics of the proton beam and X-ray detection are summarized. The concentration is obtained by using an internal standard in the range ppb-ppm. The method has been tested by calibration with samples of known concentration. The subtraction of background and the data processing are discussed. The error in each concentration is evaluated. Values of the sensitivity are quoted. The method has been extended to marine samples.

  1. Measurement error in the explanatory variable of a binary regression: regression calibration and integrated conditional likelihood in studies of residential radon and lung cancer.

    Science.gov (United States)

    Fearn, T; Hill, D C; Darby, S C

    2008-05-30

    In epidemiology, one approach to investigating the dependence of disease risk on an explanatory variable in the presence of several confounding variables is by fitting a binary regression using a conditional likelihood, thus eliminating the nuisance parameters. When the explanatory variable is measured with error, the estimated regression coefficient is biased usually towards zero. Motivated by the need to correct for this bias in analyses that combine data from a number of case-control studies of lung cancer risk associated with exposure to residential radon, two approaches are investigated. Both employ the conditional distribution of the true explanatory variable given the measured one. The method of regression calibration uses the expected value of the true given measured variable as the covariate. The second approach integrates the conditional likelihood numerically by sampling from the distribution of the true given measured explanatory variable. The two approaches give very similar point estimates and confidence intervals not only for the motivating example but also for an artificial data set with known properties. These results and some further simulations that demonstrate correct coverage for the confidence intervals suggest that for studies of residential radon and lung cancer the regression calibration approach will perform very well, so that nothing more sophisticated is needed to correct for measurement error.

  2. On the Photometric Error Calibration for the Differential Light Curves of Point-like Active Galactic Nuclei

    Indian Academy of Sciences (India)

    Arti Goyal; Mukul Mhaskey; Gopal-Krishna; Paul J. Wiita; C. S. Stalin; Ram Sagar

    2013-09-01

    It is important to quantify the underestimation of rms photometric errors returned by the commonly used APPHOT algorithm in the IRAF software, in the context of differential photometry of point-like AGN, because of the crucial role it plays in evaluating their variability properties. Published values of the underestimation factor, , using several different telescopes, lie in the range 1.3–1.75. The present study aims to revisit this question by employing an exceptionally large data set of 262 differential light curves (DLCs) derived from 262 pairs of non-varying stars monitored under our ARIES AGN monitoring program for characterizing the intra-night optical variability (INOV) of prominent AGN classes. The bulk of these data were taken with the 1-m Sampurnanad Telescope (ST). We find = 1.54 ± 0.05 which is close to our recently reported value of = 1.5. Moreover, this consistency holds at least up to a brightness mismatch of 1.5 mag between the paired stars. From this we infer that a magnitude difference of at least up to 1.5 mag between a point-like AGN and comparison star(s) monitored simultaneously is within the same CCD chip acceptable, as it should not lead to spurious claims of INOV.

  3. Vetting Galactic Leavitt Law Calibrators Using Radial Velocities: On the Variability, Binarity, and Possible Parallax Error of 19 Long-period Cepheids

    Science.gov (United States)

    Anderson, R. I.; Casertano, S.; Riess, A. G.; Melis, C.; Holl, B.; Semaan, T.; Papics, P. I.; Blanco-Cuaresma, S.; Eyer, L.; Mowlavi, N.; Palaversa, L.; Roelens, M.

    2016-10-01

    We investigate the radial velocity (RV) variability and spectroscopic binarity of 19 Galactic long-period ({P}{puls} ≳ 10 days) classical Cepheid variable stars whose trigonometric parallaxes are being measured using the Hubble Space Telescope and Gaia. Our primary objective is to constrain possible parallax error due to undetected orbital motion. Using over 1600 high-precision RVs measured between 2011 and 2016, we find no indication of orbital motion on ≲5 year timescales for 18 Cepheids and determine upper limits on allowed configurations for a range of input orbital periods. The results constrain the unsigned parallax error due to orbital motion to 10 years) variations in pulsation-averaged velocity v γ via a template fitting approach using both new and literature RVs. We discover the spectroscopic binarity of XZ Car and CD Cyg, find first tentative evidence for AQ Car, and reveal KN Cen’s orbital signature. Further (mostly tentative) evidence of time-variable v γ is found for SS CMa, VY Car, SZ Cyg, and X Pup. We briefly discuss considerations regarding a vetting process of Galactic Leavitt law calibrators and show that light contributions by companions are insignificant for most distance scale applications.

  4. HIRDLS instrument radiometric calibration black body targets

    Science.gov (United States)

    Hepplewhite, Christopher L.; Watkins, Robert E. J.; Row, Frederick; Barnett, John J.; Peters, Daniel M.; Palmer, Christopher W. P.; Wolfenden, Roger; Djotni, Karim; Arter, Philip I.

    2003-11-01

    The pre-launch calibration of the HIRDLS instrument took place in a dedicated facility at the University of Oxford. One aspect of this calibration was the determination of the response of the instrument to black body radiation. This was achieved with the use of purpose built full aperture black body targets which were mounted in the vacuum chamber together with all of the calibration equipment. Special attention was placed on the absolute knowledge of the emission from these targets. This was done through a combination of thermometric sensor calibration traceable to the International Temperature Standard (ITS-90), surface emission measurements, cavity design and modeling and controlling the stray light sources in the vacuum chamber. This paper describes the design requirements, implementation and performance achieved.

  5. Further investigation on MODIS solar diffuser screen vignetting function and its implementation in RSB calibration

    Science.gov (United States)

    Wang, Zhipeng; Xiong, Xiaoxiong; Barnes, Williams L.

    2011-10-01

    The MODIS high-gain ocean color bands (B8-B16) are calibrated with its solar diffuser screen (SDS) closed to avoid saturation so that the vignetting function (VF) of SDS is necessary for the calculation of the gain coefficients of these detectors. Since there was no pre-launch system level characterization of the VF, a series of yaw maneuvers were carried out at the mission beginning for both Terra and Aqua to enable its on-orbit characterization. Current VF was derived from the low-gain bands (B1-B7 & B17-B19) data and applied to high-gain ocean color bands calibration, with the assumption that all bands and detectors should share the same VF since it is wavelength independent. As expected, error exists and it was carried over into the calibrated gain coefficients of those bands that use the SDS for their on-orbit calibration. In this paper, an improved VF calculation approach, still using the yaw data as input, is presented. The new approach takes the frame-level mismatch between different detector's footprints on the solar diffuser (SD) into account so that a proper SD image frame adjustment is made when the VF of the low-gain bands is translated into high-gain bands VF. A new set of band-and-detector dependent VFs can be derived using this approach. The implementation of the new VF into calibration of high-gain bands gain coefficient has effectively reduced the undesired seasonal oscillations in its trending from up to Terra's 0.6% and Aqua's 1.0% to nearly 0.2%.

  6. The Uncertainty Evaluation of Value Error by Mine Anemometer Calibrating Device%矿用风速表示值误差的测量不确定度评定

    Institute of Scientific and Technical Information of China (English)

    赵镇川

    2013-01-01

      通过矿用风速表检定装置对风速表示值误差进行不确定度评定。%  It processed uncertainty evaluation of wind speed value error through mine anemometer calibrating device.

  7. Calibration of gyro error model coefficients on precision centrifuge with counter-rotating platform%《中国惯性技术学报》征稿简则

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    In order to accurately calibrate the gyro drift coefficients, a coordinate system was set up based on the precision centrifuge with counter-rotating platform, and the attitude relationship between two adjacent coordinate systems were analyzed in consideration of the error sources. Precise angular velocity input for each axis of gyro was derived by using direction cosine matrices, and the nominal value of each specific force input was given as well. Combined with the gyro's static error model, various harmonic amplitude expressions were deduced including gyro drift coefficients. By using centrifuge to provide two different harmonic accelerations, and sampling the output of gyro at each sampling time, the amplitudes of 0-2nd harmonics were obtained through Fourier analysis. The drift coefficients were identified by least square method based on the relationship between harmonic amplitude expressions and drift coefficients. The test simulation results show that the calibration of the gyro drift coefficients on centrifuge with counter-rotating platform can effectively avoid some of the centrifuge errors, and other centrifuge errors only have significant impacts on D1, Ds, DIO and DOs whose accurate calibration can be achieved by compensating the centrifuge errors.

  8. Reliable long-range ensemble streamflow forecasts: Combining calibrated climate forecasts with a conceptual runoff model and a staged error model

    Science.gov (United States)

    Bennett, James C.; Wang, Q. J.; Li, Ming; Robertson, David E.; Schepen, Andrew

    2016-10-01

    We present a new streamflow forecasting system called forecast guided stochastic scenarios (FoGSS). FoGSS makes use of ensemble seasonal precipitation forecasts from a coupled ocean-atmosphere general circulation model (CGCM). The CGCM forecasts are post-processed with the method of calibration, bridging and merging (CBaM) to produce ensemble precipitation forecasts over river catchments. CBaM corrects biases and removes noise from the CGCM forecasts, and produces highly reliable ensemble precipitation forecasts. The post-processed CGCM forecasts are used to force the Wapaba monthly rainfall-runoff model. Uncertainty in the hydrological modeling is accounted for with a three-stage error model. Stage 1 applies the log-sinh transformation to normalize residuals and homogenize their variance; Stage 2 applies a conditional bias-correction to correct biases and help remove negative forecast skill; Stage 3 applies an autoregressive model to improve forecast accuracy at short lead-times and propagate uncertainty through the forecast. FoGSS generates ensemble forecasts in the form of time series for the coming 12 months. In a case study of two catchments, FoGSS produces reliable forecasts at all lead-times. Forecast skill with respect to climatology is evident to lead-times of about 3 months. At longer lead-times, forecast skill approximates that of climatology forecasts; that is, forecasts become like stochastic scenarios. Because forecast skill is virtually never negative at long lead-times, forecasts of accumulated volumes can be skillful. Forecasts of accumulated 12 month streamflow volumes are significantly skillful in several instances, and ensembles of accumulated volumes are reliable. We conclude that FoGSS forecasts could be highly useful to water managers.

  9. Comparison of ultraviolet Bi-directional Reflectance Distribution Function (BRDF) measurements of diffusers used in the calibration of the Total Ozone Mapping Spectrometer (TOMS)

    NARCIS (Netherlands)

    Butler, J.J.; Park, H.; Barnes, P.Y.; Early, E.A.; Eijk-Olij, C. van; Zoutman, A.E.; Buller-Leeuwen, S. van; Groote Schaarsberg, J.

    2002-01-01

    The measurement and long-term monitoring of global total ozone by ultraviolet albedo measuring satellite instruments require accurate and precise determination of the Bi-directional Reflectance Distribution Function (BRDF) of laboratory-based diffusers used in the pre-launch calibration of those ins

  10. Comparison of ultraviolet Bi-directional Reflectance Distribution Function (BRDF) measurements of diffusers used in the calibration of the Total Ozone Mapping Spectrometer (TOMS)

    NARCIS (Netherlands)

    Butler, J.J.; Park, H.; Barnes, P.Y.; Early, E.A.; Eijk-Olij, C. van; Zoutman, A.E.; Buller-Leeuwen, S. van; Groote Schaarsberg, J.

    2002-01-01

    The measurement and long-term monitoring of global total ozone by ultraviolet albedo measuring satellite instruments require accurate and precise determination of the Bi-directional Reflectance Distribution Function (BRDF) of laboratory-based diffusers used in the pre-launch calibration of those

  11. THE METHOD OF DETERMINATION OF ERROR IN THE REFERENCE VALUE OF THE DOSE DURING THE LINEAR ACCELERATOR RADIATION OUTPUT CALIBRATION PROCEDURE. Part 3. The dependence of the radiation beam characteristics

    Directory of Open Access Journals (Sweden)

    E. V. Titovich

    2016-01-01

    Full Text Available To ensure the radiation protection of oncology patients is needed to provide the constancy of functional characteristics of the medical linear accelerators, which affect the accuracy of dose delivery. For this purpose, their quality control procedures are realized including calibration of radiation output of the linac, so the error in determining the dose reference value during this procedure must not exceed 2 %. The aim is to develop a methodology for determining the error in determining this value, depending on the characteristics of the radiation beam. Dosimetric measurements of Trilogy S/N 3567 linac dose distributions have been carried out for achievement of the objectives, on the basis of which dose errors depending on the dose rate value, the accuracy of the beam quality and output factors determination, the symmetry and uniformity of the radiation field, the angular dependence of the linac radiation output were obtained. It was found that the greatest impact on the value of the error has the error in the output factors determination (up to 5.26 % for both photon energy. Dose errors caused by changing dose rate during treatment were different for two photon energies, and reached 1.6 % for 6 MeV and 1.4 % for 18 MeV. Dose errors caused by inaccuracies of the beam quality determination were different for two photon energies, and reached 1.1 % for 18 MeV and –0.3 % for 6 MeV. Errors caused by the remaining of the characteristic do not exceed 1 %. Thus, there is a possibility to express the results of periodic quality control of the linear accelerator in terms of dose and use them to conduct a comprehensive assessment of the possibility of clinical use of a linear accelerator for oncology patients irradiation on the basis of the calibration of radiation output.

  12. Digital cameras and measurement error in close-range photogrammetry calibration%数字近景摄影测量中相机与测量误差校准

    Institute of Scientific and Technical Information of China (English)

    薛冰融; 李斌兵

    2013-01-01

      随着科学技术的发展,数码相机被应用到了数字近景摄影测量技术之中,数码相机在使用前必须要对误差进行校准,对此,本文分析数字近景摄影测量中相机与测量误差校准,为有关工作提供借鉴。%With the development of science and technology,digital cameras are applied to digital close-range photogrammetric technique,digital cameras have to errors in calibration before use,for which this analysis in digital close-range photogrammetric camera calibration and measurement error,to provide work experience.

  13. Calibration of Angular Systematic Errors for High Resolution Satellite Imagery%高分辨率卫星遥感影像姿态角系统误差检校

    Institute of Scientific and Technical Information of China (English)

    袁修孝; 余翔

    2012-01-01

    The object positioning accuracy from high resolution satellite imagery is strongly relevant to image attitude data accuracy, but the attitude data have generally systematic errors and the object location becomes unreliable. The angular systematic error calibration model is stricter than constant angular error calibration model, based on the rigorous geometric processing model of high resolution satellite remote sensing imagery. The calibration model was tested on SPOT-5 and CBERS-02B images and both have proved its correctness. After compensating the angular systematic errors of images, the direct georeferencing accuracy can reach ±(2-3) pixels, which is much better than results of constant angular calibration.%简要介绍高分辨率卫星遥感影像的严格几何处理模型,提出较为严密的影像姿态角系统误差检校模型。通过对SPOT-5、CBERS-02B两种卫星遥感影像的试验证实模型的正确性和方法的有效性。对影像姿态角系统误差进行补偿后,可明显提高卫星遥感影像对地目标定位的精度,且优于影像姿态角常差检校的效果,目标点平面定位精度达到了±(2-~3)像素的水平。

  14. 液位传感器校准装置几何误差模型及不确定度评定%Geometric Error Model and Uncertainty Evaluation on Calibration Device of Cryogenic Liquid Level Sensor

    Institute of Scientific and Technical Information of China (English)

    于航; 李东升; 王梅宝; 马豪; 张晓丹; 王颖

    2016-01-01

    立足于接触式低温液位传感器的校准需求,设计并研制了液位传感器动态校准装置,以实现在常温及低温条件下对测量范围为1800 mm、极限误差为±2 mm的电容式传感器的校准。采用齐次坐标变换原理,从导轨直线度误差、定位误差、各连结链空间角度误差、液面波动误差等方面入手,建立了低温液位传感器校准装置的几何误差模型。对低温液位传感器校准装置的测量不确定度进行了评定,结果表明:扩展不确定度为U=0.53 mm ( k=2),满足低温液位传感器的校准精度要求。%Based on the need of calibrating the liquid level sensor , dynamic calibration device was designed and developed for liquid level sensor which applied to capacitive sensors ( measuring range is 1 800 mm, and limiting error is ±2 mm) in both normal and low temperature conditions .The principle of homogeneous coordinate transformation was used to establish geometric error model for the calibration device , which mainly contained the rail straightness error , positioning error , spatial angle error of each chain and level fluc-tuation error, and other aspects.Moreover, the uncertainty of calibration device was evaluated .The results show that the expanded un-certainty is U=0.53 mm ( k=2) , which meets the specifications of calibration accuracy of the cryogenic liquid level sensor .

  15. Statistical errors and systematic biases in the calibration of the convective core overshooting with eclipsing binaries. A case study: TZ Fornacis

    Science.gov (United States)

    Valle, G.; Dell'Omodarme, M.; Prada Moroni, P. G.; Degl'Innocenti, S.

    2017-03-01

    Context. Recently published work has made high-precision fundamental parameters available for the binary system TZ Fornacis, making it an ideal target for the calibration of stellar models. Aims: Relying on these observations, we attempt to constrain the initial helium abundance, the age and the efficiency of the convective core overshooting. Our main aim is in pointing out the biases in the results due to not accounting for some sources of uncertainty. Methods: We adopt the SCEPtER pipeline, a maximum likelihood technique based on fine grids of stellar models computed for various values of metallicity, initial helium abundance and overshooting efficiency by means of two independent stellar evolutionary codes, namely FRANEC and MESA. Results: Beside the degeneracy between the estimated age and overshooting efficiency, we found the existence of multiple independent groups of solutions. The best one suggests a system of age 1.10 ± 0.07 Gyr composed of a primary star in the central helium burning stage and a secondary in the sub-giant branch (SGB). The resulting initial helium abundance is consistent with a helium-to-metal enrichment ratio of ΔY/ ΔZ = 1; the core overshooting parameter is β = 0.15 ± 0.01 for FRANEC and fov = 0.013 ± 0.001 for MESA. The second class of solutions, characterised by a worse goodness-of-fit, still suggest a primary star in the central helium-burning stage but a secondary in the overall contraction phase, at the end of the main sequence (MS). In this case, the FRANEC grid provides an age of Gyr and a core overshooting parameter , while the MESA grid gives 1.23 ± 0.03 Gyr and fov = 0.025 ± 0.003. We analyse the impact on the results of a larger, but typical, mass uncertainty and of neglecting the uncertainty in the initial helium content of the system. We show that very precise mass determinations with uncertainty of a few thousandths of solar mass are required to obtain reliable determinations of stellar parameters, as mass errors

  16. The calibration of PIXIE

    Science.gov (United States)

    Fixsen, D. J.; Chuss, D. T.; Kogut, Alan; Mirel, Paul; Wollack, E. J.

    2016-07-01

    The FIRAS instrument demonstrated the use of an external calibrator to compare the sky to an instrumented blackbody. The PIXIE calibrator is improved from -35 dB to -65 dB. Another significant improvement is the ability to insert the calibrator into either input of the FTS. This allows detection and correction of additional errors, reduces the effective calibration noise by a factor of 2, eliminates an entire class of systematics and allows continuous observations. This paper presents the design and use of the PIXIE calibrator.

  17. An overview of Suomi NPP VIIRS calibration maneuvers

    Science.gov (United States)

    Butler, James J.; Xiong, Xiaoxiong; Barnes, Robert A.; Patt, Frederick S.; Sun, Junqiang; Chiang, Kwofu

    2012-09-01

    The first Visible Infrared Imager Radiometer Suite (VIIRS) instrument was successfully launched on-board the Suomi National Polar-orbiting Partnership (SNPP) spacecraft on October 28, 2011. Suomi NPP VIIRS observations are made in 22 spectral bands, from the visible (VIS) to the long-wave infrared (LWIR), and are used to produce 22 Environmental Data Records (EDRs) with a broad range of scientific applications. The quality of these VIIRS EDRs strongly depends on the quality of its calibrated and geo-located Sensor Date Records (SDRs). Built with a strong heritage to the NASA's EOS MODerate resolution Imaging Spectroradiometer (MODIS) instrument, the VIIRS is calibrated on-orbit using a similar set of on-board calibrators (OBC), including a solar diffuser (SD) and solar diffuser stability monitor (SDSM) system for the reflective solar bands (RSB) and a blackbody (BB) for the thermal emissive bands (TEB). Onorbit maneuvers of the SNPP spacecraft provide additional calibration and characterization data from the VIIRS instrument which cannot be obtained pre-launch and are required to produce the highest quality SDRs. These include multiorbit yaw maneuvers for the characterization of SD and SDSM screen transmission, quasi-monthly roll maneuvers to acquire lunar observations to track sensor degradation in the visible through shortwave infrared, and a driven pitch-over maneuver to acquire multiple scans of deep space to determine TEB response versus scan angle (RVS). This paper provides an overview of these three SNPP calibration maneuvers. Discussions are focused on their potential calibration and science benefits, pre-launch planning activities, and on-orbit scheduling and implementation strategies. Results from calibration maneuvers performed during the Intensive Calibration and Validation (ICV) period for the VIIRS sensor are illustrated. Also presented in this paper are lessons learned regarding the implementation of calibration spacecraft maneuvers on follow

  18. TECHNIQUE OF ESTIMATION OF ERROR IN THE REFERENCE VALUE OF THE DOSE DURING THE LINEAR ACCELERATOR RADIATION OUTPUT CALIBRATION PROCEDURE. Part 2. Dependence on the characteristics of collimator, optical sourse-distance indicator, treatment field, lasers and treatment couch

    Directory of Open Access Journals (Sweden)

    Y. V. Tsitovich

    2016-01-01

    Full Text Available To ensure the safety of radiation oncology patients needed to provide consistent functional characteristics of the medical linear accelerators, which affect the accuracy of dose delivery. To this end, their quality control procedures, which include the calibration of radiation output of the linac, the error in determining the dose reference value during which must not exceed 2 %, is provided. The aim is to develop a methodology for determining the error (difference between a measured value of quantity and its true value in determining this value, depending on the characteristics of the collimator, the source to surface distance pointer, lasers, radiation field and treatment table. To achieve the objectives have been carried out dosimetric measurements of Trilogy S/N 3567 linac dose distributions, on the basis of which dose errors depending on the accuracy setting the zero position of the collimator, the deviation of the collimator rotation isocenter, the sourcesurface distance pointer accuracy, field size accuracy, the accuracy of lasers and treatment table positioning were obtained. It was found that the greatest impact on the value of the error has the error in the optical SSD indication and the error in the lasers position in the plane perpendicular to the plane of incidence of the radiation beam (up to 3.64 % for the energy of 6 MV. Dose errors caused by error in the field size were different for two photon energies, and reached 2.54 % for 6 MeV and 1.33% for 18 MeV. Errors caused by the rest of the characteristic do not exceed 1 %. Thus, it is possible to express the results of periodic quality control of these devices integrated in linac in terms of dose and use them to conduct a comprehensive assessment of the possibility of clinical use of a linear accelerator for oncology patients irradiation on the basis of the calibration of radiation output in case of development of techniques that allow to analyze the influence dosimetric

  19. 微小型无人机三轴磁强计现场误差校正方法%In-suit Error Calibration of Three-axis Magnetometer for Unmanned Aerial Vehicle

    Institute of Scientific and Technical Information of China (English)

    吴永亮; 王田苗; 梁建宏

    2011-01-01

    详细分析微小型无人机导航用三轴磁强计的误差来源,建立三轴磁强计的等效误差模型,提出基于两步估计算法和圆约束非对准误差估计算法的三轴磁强计现场误差校正方法.在充分考虑地磁场偏转和倾斜特性的基础上,提出适合微小型无人机应用的现场数据采样策略,能够在较少的旋转操作下获得较好的采样数据.仿真表明:在所有磁场误差都存在的情况下,使用三轴磁强计现场误差校正方法对三轴磁强计输出进行校正后推算所得的航向角误差小于1.2°,仅相当于使用工程上常用的极大极小值法校正后所得的航向角误差的8%,校正精度提升92%.基于三轴磁强计实测数据的分析也验证了三轴磁强计现场误差校正方法的有效性和实用性.%The error sources of a three-axis magnetometer are systematically analyzed, and a uniform error model specially for calibration is established. An in-suit three-axis magnetometer calibration method for micro and mini unmanned aerial vehicle (UAV)based on the two-step estimation algorithm and circle restricted misalignment calibration algorithm is proposed.Taking into full consideration the inclination and declination of the earth's magnetic vector, the proposed in-suit data sampling strategy can obtain excellent sphere coverage by using the fewest rotations. The simulation results indicate that in spite of all error sources existing, including strong hard iron and soft iron disturbances, the standard deviation of the magnetic heading error obtained by the calibrated magnetic data using the in-suit three-axis magnetometer calibration method is less than 1.2°, which is a mere 8 % of the result obtained by using the usual industrial maximum and minimum calibration method.The precision is improved by 92%. The calibration result based on the real measurement data from a three-axis magnetometer also validates the effectiveness of the in-suit three

  20. A bivariate measurement error model for nitrogen and potassium intakes to evaluate the performance of regression calibration in the European Prospective Investigation into Cancer and Nutrition study

    NARCIS (Netherlands)

    Ferrari, P.; Roddam, A.; Fahey, M. T.; Jenab, M.; Bamia, C.; Ocke, M.; Amiano, P.; Hjartaker, A.; Biessy, C.; Rinaldi, S.; Huybrechts, I.; Tjonneland, A.; Dethlefsen, C.; Niravong, M.; Clavel-Chapelon, F.; Linseisen, J.; Boeing, H.; Oikonomou, E.; Orfanos, P.; Palli, D.; de Magistris, M. Santucci; Bueno-de-Mesquita, H. B.; Peeters, P. H. M.; Parr, C. L.; Braaten, T.; Dorronsoro, M.; Berenguer, T.; Gullberg, B.; Johansson, I.; Welch, A. A.; Riboli, E.; Bingham, S.; Slimani, N.

    2009-01-01

    Objectives: Within the European Prospective Investigation into Cancer and Nutrition (EPIC) study, the performance of 24-h dietary recall (24-HDR) measurements as reference measurements in a linear regression calibration model is evaluated critically at the individual (within-centre) and aggregate

  1. A bivariate measurement error model for nitrogen and potassium intakes to evaluate the performance of regression calibration in the European Prospective Investigation into Cancer and Nutrition study

    NARCIS (Netherlands)

    Ferrari, P.; Roddam, A.; Fahey, M. T.; Jenab, M.; Bamia, C.; Ocke, M.; Amiano, P.; Hjartaker, A.; Biessy, C.; Rinaldi, S.; Huybrechts, I.; Tjonneland, A.; Dethlefsen, C.; Niravong, M.; Clavel-Chapelon, F.; Linseisen, J.; Boeing, H.; Oikonomou, E.; Orfanos, P.; Palli, D.; de Magistris, M. Santucci; Bueno-de-Mesquita, H. B.; Peeters, P. H. M.; Parr, C. L.; Braaten, T.; Dorronsoro, M.; Berenguer, T.; Gullberg, B.; Johansson, I.; Welch, A. A.; Riboli, E.; Bingham, S.; Slimani, N.

    2009-01-01

    Objectives: Within the European Prospective Investigation into Cancer and Nutrition (EPIC) study, the performance of 24-h dietary recall (24-HDR) measurements as reference measurements in a linear regression calibration model is evaluated critically at the individual (within-centre) and aggregate (b

  2. MODIS Radiometric Calibration Program, Methods and Results

    Science.gov (United States)

    Xiong, Xiaoxiong; Guenther, Bruce; Angal, Amit; Barnes, William; Salomonson, Vincent; Sun, Junqiang; Wenny, Brian

    2012-01-01

    As a key instrument for NASA s Earth Observing System (EOS), the Moderate Resolution Imaging Spectroradiometer (MODIS) has made significant contributions to the remote sensing community with its unprecedented amount of data products continuously generated from its observations and freely distributed to users worldwide. MODIS observations, covering spectral regions from visible (VIS) to long-wave infrared (LWIR), have enabled a broad range of research activities and applications for studies of the earth s interactive system of land, oceans, and atmosphere. In addition to extensive pre-launch measurements, developed to characterize sensor performance, MODIS carries a set of on-board calibrators (OBC) that can be used to track on-orbit changes of various sensor characteristics. Most importantly, dedicated and continuous calibration efforts have been made to maintain sensor data quality. This paper provides an overview of the MODIS calibration program, on-orbit calibration activities, methods, and performance. Key calibration results and lessons learned from the MODIS calibration effort are also presented in this paper.

  3. Trinocular Calibration Method Based on Binocular Calibration

    Directory of Open Access Journals (Sweden)

    CAO Dan-Dan

    2012-10-01

    Full Text Available In order to solve the self-occlusion problem in plane-based multi-camera calibration system and expand the measurement range, a tri-camera vision system based on binocular calibration is proposed. The three cameras are grouped into two pairs, while the public camera is taken as the reference to build the global coordinate. By calibration of the measured absolute distance and the true absolute distance, global calibration is realized. The MRE (mean relative error of the global calibration of the two camera pairs in the experiments can be as low as 0.277% and 0.328% respectively. Experiment results show that this method is feasible, simple and effective, and has high precision.

  4. The BepiColombo mission to Mercury: ISA accelerometer on-ground and in-flight calibration procedures

    Science.gov (United States)

    Iafolla, V.; Lucchesi, D.; Fiorenza, E.; Lucente, M.; Lefevre, C.; Magnafico, C.; Peron, R.; Santoli, F.; Nozzoli, S.; Argada, A.

    2012-04-01

    The key role of the Italian Spring Accelerometer (ISA) in the radio science measurements of the ESA BepiColombo mission to Mercury is to remove, aposteriori, the non-gravitational accelerations acting on the Mercury Planetary Orbiter (MPO) due to the very strong radiation environment around Mercury. This presentation is devoted to describe the main on-ground and in-flight calibration procedures that are necessary to guarantee the accelerometer performance in order to reach the very ambitious objectives of the Radio Science Experiments (RSE) of the ESA mission: the accelerometer sensitivity has to be 10-8 m/s2/√Hz in the frequency band 3·10-5 -10-1 Hz. ISA is a three axes torsional accelerometer and the calibration procedures are necessary in order to estimate scale factors and axes misalignments and couplings. The on-ground calibration procedures are primarily finalized to the determination of the actuator transducer factor of the proof-masses capacitor plates and to the determination of the proof-masses axes orthogonality and orientation with respect to a reference optical cube. The in-flight calibration procedures are devoted to the determination of the accelerometer pick-up transducer factors, which are different from those determined on-ground during the calibration of ISA's actuators, and to the determination of the axes alignment in order to check if launch shocks have produced possible variations with respect to their nominal orientation in the MPO body-fixed frame as determined during the pre-launch characterization and calibration. A by-product of the in-flight calibration procedures is the determination of ISA proof-masses position with respect to spacecraft effective center-of-mass. This allows to check if the MPO center-of-mass variations are in line with on-ground estimates based on fuel consumption computations and the mass distribution of the spacecraft appendices and movable parts, as in the case of the orientation of the solar array panels and

  5. 8-position calibrating method for system error of digital magnetometer%一种八位置数字磁强计系统误差标定方法

    Institute of Scientific and Technical Information of China (English)

    林恒; 魏莹莹; 李保国

    2011-01-01

    Among the factors affecting the system error of digital magnetometer, the contributor comes from the precision variance of the production of the digital magnetometer and installation. Through a careful analysis and calculation of system error of digital magnetometer,a simple and effective method for system error compensation is presented which is the 8-position calibrating method. Experiments are done to verify the method. The result shows that the system error of digital magnetometer can be compensated and the heading measure precision can be improved validly by using this method.%由于数字磁强计本身制作和生产安装的精度差异,产生了数字磁强计的系统误差.通过对数字磁强计的系统误差进行详细分析和理论计算,建立了误差方程,并提出了一种简单有效的系统误差补偿方法--八位置标定方法,并对此方法进行了实验验证.实验结果表明:该方法可以较好地补偿数字磁强计的系统误差,提高航向测量精度.

  6. TECHNIQUE OF ESTIMATION OF ERROR IN THE REFERENCE VALUE OF THE DOSE DURING THE LINEAR ACCELERATOR RADIATION OUTPUT CALIBRATION PROCEDURE. PART 1. DEPENDANCE OF THE MECHANICAL PARAMETERS OF LINAC’S GANTRY

    Directory of Open Access Journals (Sweden)

    Y. V. Tsitovich

    2015-01-01

    Full Text Available To ensure the safety of radiation oncology patients needed to provide a consistent functional characteristics of the medical linear electron accelerators, which affect the accuracy of dose delivery. To this end, their quality control procedures, which include the calibration of radiation output of the linear accelerator, the error in determining the dose reference value during which must not exceed 2 %, is provided. The aim is to develop a methodology for determining the error in determining this value, depending on the mechanical charachteristics of the linac’s gantry. To achieve the objectives have been carried out dosimetric measurements of Trilogy S/N 3567 linac dose distributions, on the basis of which dose errors depending on the accuracy setting the zero position of the gantry and the deviation of the gantry rotation isocenter were obtained. It was found that the greatest impact on the value of the error has gantry rotation isocenter deviation in a plane perpendicular to the plane of incidence of the radiation beam (up to 3,64% for the energy of 6 MeV. Dose errors caused by tilting the gantry and its isocenter deviation in the plane of incidence of the beam were highest for 18 MeV energy and reached –0,7 % and –0,9 % respectively. Thus, it is possible to express the results of periodic quality control of the linear accelerator ganty in terms of dose and use them to conduct a comprehensive assessment of the possibility of clinical use of a linear accelerator for oncology patients irradiation in case of development of techniques that allow to analyze the influence of the rest of its technical and dosimetric parameters for error in dose.

  7. Measurement Error Analysis and Calibration Technique of NTC- Based Body Temperature Sensor%一种基于NTC的体温传感器测量误差分析及校准技术

    Institute of Scientific and Technical Information of China (English)

    邓迟; 胡巍; 刁盛锡; 林福江; 钱大宏

    2015-01-01

    A NTC thermistor-based wearable body temperature sensor was designed. This paper described the design principles and realization method of the NTC-based body temperature sensor. In this paper the temperature measurement error sources of the body temperature sensor were analyzed in detail. The automatic measurement and calibration method of ADC error was given. The results showed that the measurement accuracy of calibrated body temperature sensor is better than±0.04oC. The temperature sensor has high accuracy, smal size and low power consumption advantages.%该文设计了一款基于NTC热敏电阻的可穿戴式体温传感器,阐述了基于NTC的体温传感器的设计原理及实现方法。文中对体温传感器的温度测量误差来源进行了详细分析,给出了ADC误差自动测量和校准的方法。实验结果表明,经校准后的体温传感器其测量精度误差小于±0.04 oC。该体温传感器具有精度高、体积小和功耗低的优点。

  8. Calibration methods of angle measurement error of 360° laser scanner%360°激光扫描仪测角误差检校方法探讨

    Institute of Scientific and Technical Information of China (English)

    张艳亭; 马东洋; 马浩; 关艳玲

    2011-01-01

    This paper first analyzed the influence factors of angle measurement error of laser scanner, and mainly studied and discussed two calibration methods of angle measurement error of 360 ° vehicle-based laser scanner, one is dynamic method and the other is static one; then, the paper processed the point cloud data with TerraScan software and matlab and conducted a detailed analysis of the testing results; finally, it concluded that the laser scanner calibration techniques and methods would become more mature and perfect in the future.%本文在分析激光扫描仪测角误差影响因素基础上,探讨360°车载激光扫描仪测角误差的2种检校方法,即动态法和静态法;并结合TerraScan软件和matlab处理点云数据,设计数学模型对误差进行改正;最后对试验结果进行了详细分析.

  9. Error-landscape-based multi-objective calibration of the Smagorinsky eddy-viscosity using high-Reynolds-number decaying turbulence data

    NARCIS (Netherlands)

    Meyers, Johan; Meneveau, Charles; Geurts, Bernard J.

    2010-01-01

    A suite of large-eddy simulation(LESs) of decaying homogeneous isotropic turbulence at high Reynolds numbers is performed and compared to wind-tunnel experiments in the tradition of Comte-Bellot and Corrsin. The error-landscape approach is used for the evaluation of the Smagorinsky model, and the re

  10. Evaluation of a two-part regression calibration to adjust for dietary exposure measurement error in the Cox proportional hazards model

    NARCIS (Netherlands)

    Agogo, George O.; Voet, van der Hilko; Veer, van 't Pieter; Eeuwijk, van Fred A.; Boshuizen, Hendriek C.

    2016-01-01

    Dietary questionnaires are prone to measurement error, which bias the perceived association between dietary intake and risk of disease. Short-term measurements are required to adjust for the bias in the association. For foods that are not consumed daily, the short-term measurements are often char

  11. 基于高斯牛顿迭代算法的三轴磁强计校正%Error calibration of three axis magnetometer based on Gauss-Newton iteration algorithm

    Institute of Scientific and Technical Information of China (English)

    庞鸿锋; 潘孟春; 王伟; 张琦; 罗诗途

    2013-01-01

    In three axis magnetometers,scale factor,bias and non-orthogonality errors of the axes exist,so it is important to study its calibration method.The magnetometer calibration model is deduced based on scalar calibration method,and a magnetometer calibration method based on Gauss-Newton algorithm is proposed.A high precision proton magnetometer is used to provide the magnetic field intensity reference value.A nonmagnetic turntable is used to rotate the magnetometer,and during the rotation process the magnetometer records sample data continuously,which makes the measurement data more applicable and representative.Simulation results show that the magnetometer error is reduced from 162.135 nT to 1.467 nT.Experiment results show that,after calibration,the measurement errors of the magnetometer rotating three axes are reduced from 1133.887 nT,1317.554 nT,1303.994 nT to 36.964 nT,20.922 nT,15.664 nT,respectively,which shows that the proposed method can effectively reduce the measurement error of the magnetometer and obviously improve the precision of the three axis magnetometers.%三轴磁强计存在各轴刻度因子、零偏和轴间非正交性误差,需要研究其校正方法.基于标量校正法思想,对磁强计校正模型进行了推导,提出基于高斯牛顿迭代法的磁强计校正方法.采用高精度质子磁力仪提供磁场基准值.借助无磁转台转动磁强计,转动过程中磁强计连续采样,测量数据更具代表性和实用性.仿真结果表明,磁强计误差从162.135 nT降低到1.467 nT.实验结果表明,校正后,磁强计绕3个轴转动的测量值误差分别从1133.887 nT、1317.554 nT、1303.994 nT降低到36.964nT、20.922nT、15.664 nT.表明该方法能有效降低磁强计测量误差,磁强计精度明显得到提高.

  12. Error calibration of three axis magnetometer based on UKF and equipment%基于无迹卡尔曼滤波和设备的三轴磁强计校正

    Institute of Scientific and Technical Information of China (English)

    庞鸿锋; 潘孟春; 陈棣湘; 罗诗途; 罗飞路

    2012-01-01

    The model parameter estimation method based on unscented Kalman filter ( UKF) is proposed to calibrate the scalar and vector errors of three axis magnetometer. A high precision proton magnetometer is used to measure the true value of the magnetic field scalar; a nonmagnetic turntable is used to rotate the magnetometer omni-directionally and the calibration model parameters are estimated after rotation. Using this method, the parameters of a DM-050 magnetometer are estimated, and these estimated parameters are used to calibrate its scalar and vector errors. Simulation results show that the estimated parameters are consistent with the actual parameters. After calibration, the scalar error is reduced from 427.9 nT to 2.06 nT; the vector errors of X, Y, Z axes are reduced to 1.84 nT, 1.96 nT and 1.72 nT, respectively. In addition, the method using UKF to estimate magnetometer model parameters is proved to have good repeatability; and the influence of noise on the UKF performance is discussed. Experiment results show that the magnetometer error is reduced from 114. 94 nT to 14. 47 nT, which indicates that the proposed method can improve the precision of three axis magnetometer.%采用无迹卡尔曼滤波(unscented Kalman filter,UKF)磁强计模型参数估计方法,提出对三轴磁强计的总量及分量误差进行校正.采用高精度质子磁力仪提供磁场基准值,借助无磁转台实现磁强计全方位转动,对一款DM-050三轴磁强计进行了参数估计,并将参数估计值运用到总量和分量校正.仿真结果表明,参数估计值与磁强计实际参数值一致.校正后,磁强计总量误差从427.9 nT减少到2.06nT;X、Y、Z轴分量误差分别减少到1.84nT、1.96 nT、1.72 nT.而且证明了UKF对磁强计模型参数估计的重复性良好,并研究了噪声幅度大小对UKF的性能影响程度.实验结果表明,磁强计误差从114.94 nT减少到14.47 nT,表明该方法能有效提高磁强计测量精度.

  13. 炮口测速装置测速误差合格判别方法探讨%Discussion on Calibration and Judging Method of Allowable Velocity Error for Muzzle Velocity Measurement Device

    Institute of Scientific and Technical Information of China (English)

    张国平; 王茂林; 于斌

    2014-01-01

    在科研和生产过程中,炮口测速装置要在弹道炮和战斗炮上进行初速标定和测速误差检测,两个平台上初速标定系数的一致性问题、测速误差合格判断问题、合理的检测样本大小问题,应用概率论和数理统计理论及方法、语言去解释和处理。从炮口测速装置的工作原理出发,分析了影响测速误差的主要因素,确定了初速标定系数一致性判别准则和测速误差合格判别准则,在给定置信水平条件下,确定合理的检测样本大小,分析方法和思路对火炮其他试验(如初速检测、立靶密集度试验、弹药运输前后弹道一致性试验等)数据处理、指标合格判定具有借鉴作用。%In process of scientific research and production,muzzle velocity measurement device must be calibrated and the measured velocity error must be checked at the ballistic simulation gun and the combat gun.The check consistency of muzzle velocity calibration coefficients in the both guns,acceptability j udgment of measured velocity error and reasonable test sample size must be interpreted and solved by use of the probability theory and mathematical statistical method as well as the language in terms of probability and statistics.From the point view of the principle of muzzle velocity measurement device,the main factors that have influence on the measured velocity error were found out and analyzed.Judge criterion for consistency of calibra-ting coefficients and measured velocity acceptability at different guns were determined.Under the condition of the given confidence level,a reasonable test sample size was acquired.Some a-nalysis methods and resolved problem process may provide the reference for data processing and acceptability j udge of the other tests,such as muzzle velocity test,dispersion test with vertical target,consistency test of ammunition performance before and after transportation etc.

  14. Vetting Galactic Leavitt Law Calibrators using Radial Velocities: On the Variability, Binarity, and Possible Parallax Error of 19 Long-period Cepheids

    CERN Document Server

    Anderson, R I; Riess, A G; Melis, C; Holl, B; Semaan, T; Papics, P I; Blanco-Cuaresma, S; Eyer, L; Mowlavi, N; Palaversa, L; Roelens, M

    2016-01-01

    We investigate the radial velocity (RV) variability and spectroscopic binarity of 19 Galactic long-period ($P_{\\rm{puls}} \\gtrsim 10$ d) classical Cepheid variable stars whose trigonometric parallaxes are being measured using the Hubble Space Telescope and Gaia. Our primary objective is to constrain possible parallax error due to undetected orbital motion. Using $>1600$ high-precision RVs measured between 2011 and 2016, we find no indication of orbital motion on $\\lesssim 5$ yr timescales for 18 Cepheids and determine upper limits on allowed configurations for a range of input orbital periods. The results constrain the unsigned parallax error due to orbital motion to $ 10$ yr) variations in pulsation-averaged velocity $v_\\gamma$ via a template fitting approach using both new and literature RVs. We discover the spectroscopic binarity of XZ Car and CD Cyg, find first tentative evidence for AQ Car, and reveal KN Cen's orbital signature. Further (mostly tentative) evidence of time-variable $v_\\gamma$ is found for...

  15. An Overview of MODIS Radiometric Calibration and Characterization

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The Moderate Resolution Imaging Spectroradiometer (MODIS) is one of the key instruments for NASA's Earth Observing System (EOS), currently operating on both the Terra and Aqua satellites. The MODIS is a major advance over the previous generation of sensors in terms of its spectral, spatial, and temporal resolutions. It has 36 spectral bands: 20 reflective solar bands (RSB) with center wavelengths from 0.41 to 2.1μm and 16 thermal emissive bands (TEB) with center wavelengths from 3.7 to 14.4μm,making observations at three spatial resolutions: 250 m (bands 1-2), 500 m (bands 3-7), and 1km (bands 8-36). MODIS is a cross-track scanning radiometer with a wide field-of-view, providing a complete global coverage of the Earth in less than 2 days. Both Terra and Aqua MODIS went through extensive pre-launch calibration and characterization at various levels. In orbit, the calibration and characterization tasks are performed using its on-board calibrators (OBCs) that include a solar diffuser (SD) and a solar diffuser stability monitor (SDSM), a v-grooved flat panel blackbody (BB), and a spectro-radiometric calibration assembly (SRCA). In this paper, we present an overview of MODIS calibration and characterization activities, methodologies, and lessons learned from pre-launch characterization and in-orbit operation. Key issues discussed in this paper include in-orbit efforts of monitoring the noise characteristics of the detectors,tracking the solar diffuser and optics degradations, and updating the sensor's response versus scan angle.The experiences and lessons learned through MODIS have played and will continue to play major roles in the design and characterization of future sensors.

  16. An Optimal Calibration Method for a MEMS Inertial Measurement Unit

    Directory of Open Access Journals (Sweden)

    Bin Fang

    2014-02-01

    Full Text Available An optimal calibration method for a micro-electro-mechanical inertial measurement unit (MIMU is presented in this paper. The accuracy of the MIMU is highly dependent on calibration to remove the deterministic errors of systematic errors, which also contain random errors. The overlapping Allan variance is applied to characterize the types of random error terms in the measurements. The calibration model includes package misalignment error, sensor-to-sensor misalignment error and bias, and a scale factor is built. The new concept of a calibration method, which includes a calibration scheme and a calibration algorithm, is proposed. The calibration scheme is designed by D-optimal and the calibration algorithm is deduced by a Kalman filter. In addition, the thermal calibration is investigated, as the bias and scale factor varied with temperature. The simulations and real tests verify the effectiveness of the proposed calibration method and show that it is better than the traditional method.

  17. Ge well detector calibration by means of a trial and error procedure using the dead layers as a unique parameter in a Monte Carlo simulation

    Energy Technology Data Exchange (ETDEWEB)

    Courtine, Fabien; Pilleyre, Thierry; Sanzelle, Serge [Laboratoire de Physique Corpusculaire, IN2P3-CNRS, Universite Blaise Pascal, F-63177 Aubiere Cedex (France); Miallier, Didier [Laboratoire de Physique Corpusculaire, IN2P3-CNRS, Universite Blaise Pascal, F-63177 Aubiere Cedex (France)], E-mail: miallier@clermont.in2p3.fr

    2008-11-01

    The project aimed at modelling an HPGe well detector in view to predict its photon-counting efficiency by means of the Monte Carlo simulation code GEANT4. Although a qualitative and quantitative description of the crystal and housing was available, uncertainties were associated to parameters controlling the detector response. This induced poor agreement between the efficiency calculated on the basis of nominal data and the actual efficiency experimentally measured with a {sup 137}Cs point source. It was then decided to improve the model, by parameterization of a trial and error method. The distribution of the dead layers was adopted as a unique parameter, in order to explore the possibilities and pertinence of this parameter. In the course of the work, it appeared necessary to introduce the possibility that the thickness of the dead layers was not uniform for a given surface. At the end of the process, the results allowed to conclude that the approach was able to give a model adapted to practical application with a satisfactory precision in the calculated efficiency. The pattern of the 'dead layers' that was obtained is characterized by a variable thickness which seems to be physically relevant. It implicitly and partly accounts for effects that are not originated from actual dead layers, such as incomplete charge collection. But, such effects, which are uneasily accounted for, can, in a first approximation, be represented by 'dead layers'; this is an advantage of the parameterization that was adopted.

  18. A Careful Consideration of the Calibration Concept

    Science.gov (United States)

    Phillips, S. D.; Estler, W. T.; Doiron, T.; Eberhardt, K. R.; Levenson, M. S.

    2001-01-01

    This paper presents a detailed discussion of the technical aspects of the calibration process with emphasis on the definition of the measurand, the conditions under which the calibration results are valid, and the subsequent use of the calibration results in measurement uncertainty statements. The concepts of measurement uncertainty, error, systematic error, and reproducibility are also addressed as they pertain to the calibration process. PMID:27500027

  19. 基于激光跟踪仪的 Delta 并联机构运动学误差标定%Calibration of Delta Parallel Robot Kinematic Errors Based on Laser Tracker

    Institute of Scientific and Technical Information of China (English)

    张文昌; 梅江平; 刘艺; 张新

    2013-01-01

    The kinematics error model of Delta parallel robot was established first,and then the geometric errors affecting the precision of the end-effector were analyzed and simplified to 18 ones. By taking a laser tracker as meas-urement tool,a stepping iterative method is proposed to identify the geometric errors. Considering the non-linear mapping from the actuated variables in joint space to the pose of the end-effector in Cartesian space,the geometric errors were iterated by using the residual errors of the distances between every two measuring points as optimization index,and then the kinematic model of the robot was modified. The precision of the end effector is dramatically im-proved to the order of 0.1,mm from 1.0,mm after calibration,thus verifies the effectiveness and generality of this method.%  以 Delta 并联机构为研究对象,建立了 Delta 并联机构的运动学误差模型,对影响其末端精度的几何误差源进行了分析,并指出这些几何误差源可简化为18项.以激光跟踪仪作为测量工具,提出一种步进迭代的误差参数辨识方法,该方法利用 Delta 并联机构操作空间与关节空间之间的映射关系,通过优化多个检测点相互之间的理论距离与实际距离的残差,计算出 Delta 并联机构的各项几何误差参数,进而修正 Delta 并联机构的运动学模型,标定后机构末端精度由1.0,mm 数量级提高至0.1,mm 数量级,实验结果表明了文中所述方法的有效性和普遍性.

  20. Radiation calibration and error analysis for a large-aperture infrared opto-electric system%大口径红外光电系统辐射定标及误差分析

    Institute of Scientific and Technical Information of China (English)

    杨词银; 曹立华

    2011-01-01

    为了实现对大口径红外光电系统的辐射定标,建立了基于大面源黑体的辐射定标系统以及基于红外单色照明光管的光谱定标系统.利用腔型黑体、连续可变滤光片CVF和平行光管组成红外单色照明光管,对红外系统进行光谱定标,确定系统归一化相对光谱响应函数.利用大面源黑体覆盖红外系统入瞳和视场,对红外系统进行辐射定标,确定系统绝对辐射亮度响应度α.对α的误差源进行了分析计算:α的不确定度主要来自于红外系统输出数码值、大面源黑体辐射、光谱定标和背景辐射的不确定度,经测量和计算分别为0.4%、4.9%、2.5%、1.9%.计算结果表明,响应度α的不确定度为6.1%,满足红外系统10%定标精度的要求.%To perform radation calibration on infrared opto-electric system with a large-aperture, a radiation calibration system based on extended area blackbody and a spectral calibration system based on infrared monochroic collimator were established. The infrared monochroic collimator was composed of a cavity blackbody, a circular variable filter (CVF) and a collimator. It was used to calibrate the infrared opto-electric system spectrally in order to determine its normalized relative spectral response function. A large extended area blackbody, which covered the input pupil and the view field of the infrared opto-electric system, was used to perform radiation calibration on the infrared system in order to determine its absolute radiance responsivity. Analysis on error sources of the radiance responsivity was performed, and the uncertainty of the responsivity came from uncertainties for the output value of the infrared opto-electric system, radiation emitting from the extended area blackbody, the spectral calibration and the background radiation, which were 0.4% 、4.9% ,2.5% 、 1.9% respectively after measuring and calculating. The calculation results show that the uncertainty of the

  1. Calibration Under Uncertainty.

    Energy Technology Data Exchange (ETDEWEB)

    Swiler, Laura Painton; Trucano, Timothy Guy

    2005-03-01

    This report is a white paper summarizing the literature and different approaches to the problem of calibrating computer model parameters in the face of model uncertainty. Model calibration is often formulated as finding the parameters that minimize the squared difference between the model-computed data (the predicted data) and the actual experimental data. This approach does not allow for explicit treatment of uncertainty or error in the model itself: the model is considered the %22true%22 deterministic representation of reality. While this approach does have utility, it is far from an accurate mathematical treatment of the true model calibration problem in which both the computed data and experimental data have error bars. This year, we examined methods to perform calibration accounting for the error in both the computer model and the data, as well as improving our understanding of its meaning for model predictability. We call this approach Calibration under Uncertainty (CUU). This talk presents our current thinking on CUU. We outline some current approaches in the literature, and discuss the Bayesian approach to CUU in detail.

  2. Energy calibration via correlation

    CERN Document Server

    Maier, Daniel

    2015-01-01

    The main task of an energy calibration is to find a relation between pulse-height values and the corresponding energies. Doing this for each pulse-height channel individually requires an elaborated input spectrum with an excellent counting statistics and a sophisticated data analysis. This work presents an easy to handle energy calibration process which can operate reliably on calibration measurements with low counting statistics. The method uses a parameter based model for the energy calibration and concludes on the optimal parameters of the model by finding the best correlation between the measured pulse-height spectrum and multiple synthetic pulse-height spectra which are constructed with different sets of calibration parameters. A CdTe-based semiconductor detector and the line emissions of an 241 Am source were used to test the performance of the correlation method in terms of systematic calibration errors for different counting statistics. Up to energies of 60 keV systematic errors were measured to be le...

  3. Calibration uncertainty

    DEFF Research Database (Denmark)

    Heydorn, Kaj; Anglov, Thomas

    2002-01-01

    Methods recommended by the International Standardization Organisation and Eurachem are not satisfactory for the correct estimation of calibration uncertainty. A novel approach is introduced and tested on actual calibration data for the determination of Pb by ICP-AES. The improved calibration unce...

  4. Landsat-7 ETM+ On-Orbit Radiometric Calibration

    Science.gov (United States)

    Markham, Brian L.; Kaita, Ed; Miller, Jeff; Barsi, Julia; Smith, David E. (Technical Monitor)

    2000-01-01

    As of July, 2000 the Enhanced Thematic Mapper Plus (ETM+) sensor on Landsat-7 has been operating on-orbit for about 15 months. The ETM+ images the Earth in has eight spectral bands in the visible, near-infrared (IR), short wavelength infrared (SWIR), and thermal portions of the spectrum. Three on-board calibration systems are available for the reflective bands: (1) the Internal Calibrator (IC), (2) the Partial Aperture Solar Calibrator (PASC), and (3) the Full Aperture Solar Calibrator (FASC). The Internal Calibrator also provides the thermal band calibration. Several investigators on the Landsat science team are also regularly performing vicarious calibrations. The internal calibrator, which during much of the pre-launch testing and early on-orbit check out period, showed up to 15% variability with time, has since stabilized as the instrument has assumed a regular schedule of operations and is now typically showing only a few percent variation with time, mostly associated with warm-up. The PASC has been the most variable of the sources: the response to the PASC has increased by as much as 50% is some bands and is oscillating with time, perhaps due to contamination. The FASC has been the most stable of the sources: mid scan response to the FASC diffuser have varied from -4%/yr for band 4 (0.83 microns) to -2%/yr for band 1 (0.49 microns) to +1%/yr for band 7 (2.2 microns). These decreases in response in bands 1-4 would have been about half as large if measured on the right (west) side of the panel and about twice as large if measured on the left side of the panel. The current interpretation is that the FASC diffuser panel is changing non-uniformly in its reflectance characteristics. Vicarious ground measurements have generally been consistent with the pre-launch measurements of the instrument responsivity and have not shown evidence of a change in responsivity with time. The FASC, IC, and vicarious results suggest the instrument has not changed by more than two

  5. Systematic error revisited

    Energy Technology Data Exchange (ETDEWEB)

    Glosup, J.G.; Axelrod, M.C.

    1996-08-05

    The American National Standards Institute (ANSI) defines systematic error as An error which remains constant over replicative measurements. It would seem from the ANSI definition that a systematic error is not really an error at all; it is merely a failure to calibrate the measurement system properly because if error is constant why not simply correct for it? Yet systematic errors undoubtedly exist, and they differ in some fundamental way from the kind of errors we call random. Early papers by Eisenhart and by Youden discussed systematic versus random error with regard to measurements in the physical sciences, but not in a fundamental way, and the distinction remains clouded by controversy. The lack of a general agreement on definitions has led to a plethora of different and often confusing methods on how to quantify the total uncertainty of a measurement that incorporates both its systematic and random errors. Some assert that systematic error should be treated by non- statistical methods. We disagree with this approach, and we provide basic definitions based on entropy concepts, and a statistical methodology for combining errors and making statements of total measurement of uncertainty. We illustrate our methods with radiometric assay data.

  6. LOFAR facet calibration

    CERN Document Server

    van Weeren, R J; Hardcastle, M J; Shimwell, T W; Rafferty, D A; Sabater, J; Heald, G; Sridhar, S S; Dijkema, T J; Brunetti, G; Brüggen, M; Andrade-Santos, F; Ogrean, G A; Röttgering, H J A; Dawson, W A; Forman, W R; de Gasperin, F; Jones, C; Miley, G K; Rudnick, L; Sarazin, C L; Bonafede, A; Best, P N; Bîrzan, L; Cassano, R; Chyży, K T; Croston, J H; Ensslin, T; Ferrari, C; Hoeft, M; Horellou, C; Jarvis, M J; Kraft, R P; Mevius, M; Intema, H T; Murray, S S; Orrú, E; Pizzo, R; Simionescu, A; Stroe, A; van der Tol, S; White, G J

    2016-01-01

    LOFAR, the Low-Frequency Array, is a powerful new radio telescope operating between 10 and 240 MHz. LOFAR allows detailed sensitive high-resolution studies of the low-frequency radio sky. At the same time LOFAR also provides excellent short baseline coverage to map diffuse extended emission. However, producing high-quality deep images is challenging due to the presence of direction dependent calibration errors, caused by imperfect knowledge of the station beam shapes and the ionosphere. Furthermore, the large data volume and presence of station clock errors present additional difficulties. In this paper we present a new calibration scheme, which we name facet calibration, to obtain deep high-resolution LOFAR High Band Antenna images using the Dutch part of the array. This scheme solves and corrects the direction dependent errors in a number of facets that cover the observed field of view. Facet calibration provides close to thermal noise limited images for a typical 8 hr observing run at $\\sim$ 5arcsec resolu...

  7. Accurate estimation of TOA and calibration of synchronization error for multilateration%多点定位TOA精确估计及同步误差校正算法

    Institute of Scientific and Technical Information of China (English)

    王洪; 金尔文; 刘昌忠; 吴宏刚

    2013-01-01

    提出了S模式信号的数学模型,讨论了脉冲上升沿测量到达时间(time of arrival,TOA)的精度、统计方法估计TOA的最优值和最优估计的实现方法.然后,提出了一种先解码后测量TOA的改进方法,从脉冲积累的角度导出了改进方法的理论精度,与单脉冲测量的精度相比较有明显提高.针对硬件实现的问题,分析了采样对TOA测量的影响和解决方法.最后,讨论了多点定位的同步问题,将TOA的精确估计值应用于多点定位系统多部接收机之间的同步误差校正.%A mathematical model of mode S signals is built. Accuracy of time of arrival (TOA) measurements by pulse rise edge and best statistical estimation methods are discussed. The way to realize the best estimation is also introduced. Then a novel method is proposed to measure the TOA of mode S signals, in which the measurement is performed after the decoding of mode S signals. The accuracy of the proposed method is improved significantly compared with the single pulse measurement, which can be derived from pulse integration. The influence of sampling on TOA measurement is analyzed and the corresponding solving method is introduced. Finally, synchronization in a multilateration system is discussed and the accurate TOA of signals is used for calibration of synchronization errors among receivers.

  8. TARGETLESS CAMERA CALIBRATION

    Directory of Open Access Journals (Sweden)

    L. Barazzetti

    2012-09-01

    Full Text Available In photogrammetry a camera is considered calibrated if its interior orientation parameters are known. These encompass the principal distance, the principal point position and some Additional Parameters used to model possible systematic errors. The current state of the art for automated camera calibration relies on the use of coded targets to accurately determine the image correspondences. This paper presents a new methodology for the efficient and rigorous photogrammetric calibration of digital cameras which does not require any longer the use of targets. A set of images depicting a scene with a good texture are sufficient for the extraction of natural corresponding image points. These are automatically matched with feature-based approaches and robust estimation techniques. The successive photogrammetric bundle adjustment retrieves the unknown camera parameters and their theoretical accuracies. Examples, considerations and comparisons with real data and different case studies are illustrated to show the potentialities of the proposed methodology.

  9. Optimal Calibration Accuracy for Gravitational Wave Detectors

    CERN Document Server

    Lindblom, Lee

    2009-01-01

    Calibration errors in the response function of a gravitational wave detector degrade its ability to detect and then to measure the properties of any detected signals. This paper derives the needed levels of calibration accuracy for each of these data-analysis tasks. The levels derived here are optimal in the sense that lower accuracy would result in missed detections and/or a loss of measurement precision, while higher accuracy would be made irrelevant by the intrinsic noise level of the detector. Calibration errors affect the data-analysis process in much the same way as errors in theoretical waveform templates. The optimal level of calibration accuracy is expressed therefore as a joint limit on modeling and calibration errors: increased accuracy in one reduces the accuracy requirement in the other.

  10. Site characterization for calibration of radiometric sensors using vicarious method

    Science.gov (United States)

    Parihar, Shailesh; Rathore, L. S.; Mohapatra, M.; Sharma, A. K.; Mitra, A. K.; Bhatla, R.; Singh, R. S.; Desai, Yogdeep; Srivastava, Shailendra S.

    2016-05-01

    Radiometric performances of earth observation satellite/sensors vary from ground pre-launch calibration campaign to post launch period extended to lifetime of the satellite due to launching vibrations. Therefore calibration is carried out worldwide through various methods throughout satellite lifetime. In India Indian Space Research Organization (ISRO) calibrates the sensor of Resourcesat-2 satellite by vicarious method. One of these vicarious calibration methods is the reflectance-based approach that is applied in this study for radiometric calibration of sensors on-board Resouresat-2 satellite. The results of ground-based measurement of atmospheric conditions and surface reflectance are made at Bap, Rajasthan Calibration/Validation (Cal/Val) site. Cal/Val observations at site were carried out with hyper-spectral Spectroradiometer covering spectral range of 350nm- 2500nm for radiometric characterization of the site. The Sunphotometer/Ozonometer for measuring the atmospheric parameters has also been used. The calibrated radiance is converted to absolute at-sensor spectral reflectance and Top-Of-Atmosphere (TOA) radiance. TOA radiance was computed using radiative transfer model `Second simulation of the satellite signal in the solar spectrum' (6S), which can accurately simulate the problems introduced by the presence of the atmosphere along the path from Sun to target (surface) to Sensor. The methodology for band averaged reflectance retrieval and spectral reflectance fitting process are described. Then the spectral reflectance and atmospheric parameters are put into 6S code to predict TOA radiance which compare with Resourcesat-2 radiance. Spectral signature and its reflectance ratio indicate the uniformity of the site. Thus the study proves that the selected site is suitable for vicarious calibration of sensor of Resourcesat-2. Further the study demonstrates the procedure for similar exercise for site selection for Cal/Val analysis of other satellite over India

  11. In-Flight Pitot-Static Calibration

    Science.gov (United States)

    Foster, John V. (Inventor); Cunningham, Kevin (Inventor)

    2016-01-01

    A GPS-based pitot-static calibration system uses global output-error optimization. High data rate measurements of static and total pressure, ambient air conditions, and GPS-based ground speed measurements are used to compute pitot-static pressure errors over a range of airspeed. System identification methods rapidly compute optimal pressure error models with defined confidence intervals.

  12. Radio Interferometric Calibration Using The SAGE Algorithm

    CERN Document Server

    Kazemi, S; Zaroubi, S; de Bruyn, A G; Koopmans, L V E; Noordam, J

    2010-01-01

    The aim of the new generation of radio synthesis arrays such as LOFAR and SKA is to achieve much higher sensitivity, resolution and frequency coverage than what is available now. To accomplish this goal, the accuracy of the calibration techniques used is of considerable importance. Moreover, since these telescopes produce huge amounts of data, speed of convergence of calibration is a major bottleneck. The errors in calibration are due to system noise (sky and instrumental) as well as the estimation errors introduced by the calibration technique itself, which we call "solver noise". We define solver noise as the "distance" between the optimal solution, the true value of the unknowns corrupted by the system noise, and the solution obtained by calibration. We present the Space Alternating Generalized Expectation Maximization (SAGE) calibration technique, which is a modification of the Expectation Maximization algorithm, and compare its performance with the traditional Least Squares calibration based on the level...

  13. Muon Energy Calibration of the MINOS Detectors

    Energy Technology Data Exchange (ETDEWEB)

    Miyagawa, Paul S. [Somerville College, Oxford (United Kingdom)

    2004-01-01

    MINOS is a long-baseline neutrino oscillation experiment designed to search for conclusive evidence of neutrino oscillations and to measure the oscillation parameters precisely. MINOS comprises two iron tracking calorimeters located at Fermilab and Soudan. The Calibration Detector at CERN is a third MINOS detector used as part of the detector response calibration programme. A correct energy calibration between these detectors is crucial for the accurate measurement of oscillation parameters. This thesis presents a calibration developed to produce a uniform response within a detector using cosmic muons. Reconstruction of tracks in cosmic ray data is discussed. This data is utilized to calculate calibration constants for each readout channel of the Calibration Detector. These constants have an average statistical error of 1.8%. The consistency of the constants is demonstrated both within a single run and between runs separated by a few days. Results are presented from applying the calibration to test beam particles measured by the Calibration Detector. The responses are calibrated to within 1.8% systematic error. The potential impact of the calibration on the measurement of oscillation parameters by MINOS is also investigated. Applying the calibration reduces the errors in the measured parameters by ~ 10%, which is equivalent to increasing the amount of data by 20%.

  14. Muon Energy Calibration of the MINOS Detectors

    Energy Technology Data Exchange (ETDEWEB)

    Miyagawa, Paul S.

    2004-09-01

    MINOS is a long-baseline neutrino oscillation experiment designed to search for conclusive evidence of neutrino oscillations and to measure the oscillation parameters precisely. MINOS comprises two iron tracking calorimeters located at Fermilab and Soudan. The Calibration Detector at CERN is a third MINOS detector used as part of the detector response calibration programme. A correct energy calibration between these detectors is crucial for the accurate measurement of oscillation parameters. This thesis presents a calibration developed to produce a uniform response within a detector using cosmic muons. Reconstruction of tracks in cosmic ray data is discussed. This data is utilized to calculate calibration constants for each readout channel of the Calibration Detector. These constants have an average statistical error of 1.8%. The consistency of the constants is demonstrated both within a single run and between runs separated by a few days. Results are presented from applying the calibration to test beam particles measured by the Calibration Detector. The responses are calibrated to within 1.8% systematic error. The potential impact of the calibration on the measurement of oscillation parameters by MINOS is also investigated. Applying the calibration reduces the errors in the measured parameters by {approx} 10%, which is equivalent to increasing the amount of data by 20%.

  15. Sloan Digital Sky Survey Photometric Calibration Revisited

    Science.gov (United States)

    Marriner, J.

    2016-05-01

    The Sloan Digital Sky Survey calibration is revisited to obtain the most accurate photometric calibration. A small but significant error is found in the flat-fielding of the Photometric telescope used for calibration. Two SDSS star catalogs are compared and the average difference in magnitude as a function of right ascension and declination exhibits small systematic errors in relative calibration. The photometric transformation from the SDSS Photometric Telescope to the 2.5 m telescope is recomputed and compared to synthetic magnitudes computed from measured filter bandpasses.

  16. Sloan Digital Sky Survey Photometric Calibration Revisited

    Energy Technology Data Exchange (ETDEWEB)

    Marriner, John; /Fermilab

    2012-06-29

    The Sloan Digital Sky Survey calibration is revisited to obtain the most accurate photometric calibration. A small but significant error is found in the flat-fielding of the Photometric telescope used for calibration. Two SDSS star catalogs are compared and the average difference in magnitude as a function of right ascension and declination exhibits small systematic errors in relative calibration. The photometric transformation from the SDSS Photometric Telescope to the 2.5 m telescope is recomputed and compared to synthetic magnitudes computed from measured filter bandpasses.

  17. Prelaunch calibration of the HIRDLS instrument

    Science.gov (United States)

    Barnett, John J.; Darbyshire, A. G.; Hepplewhite, Christopher L.; Palmer, Christopher W.; Row, F.; Venters, P.; Watkins, R. E.; Whitney, John G.; Gille, John C.; Johnson, Brian R.

    1998-11-01

    The High Resolution Dynamics Limb Sounder (HIRDLS) instrument is being built jointly by the UK and USA, and is scheduled for launch on the NASA EOS Chem satellite in 2002. HIRDLS will measure the concentration of trace species and aerosol, and temperature and pressure variations in the Earth's atmosphere between about 8 and 100 km altitude. It is an infrared limb emission sounder, and a primary aim is that it should measure to much finder spatial resolution than has previously been achieved, with simultaneous 1 km vertical and 500 km horizontal resolutions, globally, every 12 hours. Achieving these objectives will depend upon very precise pre-launch calibration. This will be undertaken at Oxford University in a test laboratory that is currently being constructed specifically for the task. The instrument will be surrounded by cryogenically cooled walls, and mounted together with the test equipment on an optical table contained in a vacuum chamber. The table will be mounted independently of the chamber, on an inertial mass supported on pneumatic isolators. Test equipment is being manufactured to measure (1) the radiometric response (with an absolute accuracy equivalent to 70 mK) using full aperture black body targets, (2) the spectral response of each of the filter channels using a grating monochromator, (3) the spatial response of the instrument field of view, including low level out-of-field contributions, to 10 (mu) rad accuracy using a monochromator. The methods and equipment used are described together with the principal requirements.

  18. Post-Launch Calibration Support for VIIRS Onboard NASA NPP Spacecraft

    Science.gov (United States)

    Xiong, Xiaoxion; Chiang, Kwo-Fu; McIntire, Jeffrey; Schwaller, Matthew; Butler, James

    2011-01-01

    The NPP Instrument Calibration Support Element (NICSE) is one of the elements within the NASA NPP Science Data Segment (SDS). The primary responsibility of NICSE is to independently monitor and evaluate on-orbit radiometric and geometric performance of the Visible Infrared Imaging Radiometer Suite (VIIRS) instrument and to validate its Sensor Data Record (SDR) [1]. The NICSE interacts and works closely with other SDS Product Evaluation and Analysis Tools Elements (PEATE) and the NPP Science Team (ST) and supports their on-orbit data product calibration and validation efforts. The NICSE also works closely with the NPP Instrument Calibration Support Team (NICST) during sensor pre-launch testing in ambient and thermal vacuum environment [2]. This paper provides an overview of NICSE VIIRS sensor post-launch calibration support with a focus on the use of sensor on-board calibrators (OBC) for the radiometric calibration and characterization. It presents the current status of NICSE post-launch radiometric calibration tool development effort based on its design requirements

  19. Using Dome C for moderate resolution imaging spectroradiometer calibration stability and consistency

    Science.gov (United States)

    Xiong, Xiaoxiong; Wu, Aisheng; Wenny, Brian N.

    2009-03-01

    Currently, there are two nearly identical moderate resolution imaging spectroradiometer (MODIS) instruments operated in space: one on the Terra spacecraft launched in December 1999 and another on the Aqua spacecraft launched in May 2002. MODIS has 36 spectral bands with wavelengths covering from visible (VIS) to long-wave infrared (LWIR). Since launch, MODIS observations and data products have significantly enabled studies of changes in the Earth system of land, oceans, and atmosphere. In order to maintain its on-orbit calibration and data product quality, MODIS was built with a comprehensive set of on-board calibrators. MODIS reflective solar bands (RSB) are calibrated on-orbit by a system that consists of a solar diffuser (SD) and a solar diffuser stability monitor (SDSM) on a regular basis. Its thermal emissive bands (TEB) calibration is executed on a scan-by-scan basis using an on-board blackbody (BB). The MODIS Characterization Support Team (MCST) at NASA/GSFC has been responsible for supporting sensor calibration and characterization tasks from pre-launch to post launch. In this paper, we describe current MCST efforts and progress made to examine sensor stability and inter-calibration consistency using observations over Dome Concordia, Antarctica. Results show that this site can provide useful calibration reference for Earth-observing sensors.

  20. An error prediction framework for interferometric SAR data

    DEFF Research Database (Denmark)

    Mohr, Johan Jacob; Merryman Boncori, John Peter

    2008-01-01

    Three of the major error sources in interferometric synthetic aperture radar measurements of terrain elevation and displacement are baseline errors, atmospheric path length errors, and phase unwrapping errors. In many processing schemes, these errors are calibrated out by using ground control poi...

  1. In flight calibrations of Ibis/PICsIT

    Energy Technology Data Exchange (ETDEWEB)

    Malaguti, G.; Di Cocco, G.; Foschini, L.; Stephen, J.B. [Istituto di Astrofisica Spaziale e Fisica Cosmica - IASF/CNR, Sezione di Bologne (Italy); Bazzano, A.; Ubertini, P. [Istituto di Astrofisica Spaziale e Fisica Cosmica - IASF/CNR, Roma (Italy); Bird, A.J. [Southampton Univ., School of Physics and Astronomy (United Kingdom); Laurent, P. [CEA Saclay - Sap, 91 - Gif sur Yvette (France); Segreto, A. [Istituto di Astrofisica Spaziale e Fisica Cosmica - IASF/CNR, Sezione di Palermo (Italy)

    2003-11-01

    PICsIT (Pixellated Imaging Caesium Iodide Telescope) is the high energy detector of the IBIS telescope on-board the INTEGRAL satellite. It consists of 4096 independent detection units, {approx} 0.7 cm{sup 2} in cross-section, operating in the energy range between 175 keV and 10 MeV. The intrinsically low signal to noise ratio in the gamma-ray astronomy domain implies very long observations, lasting 10{sup 5}- 10{sup 6} s. Moreover, the image formation principle on which PICsIT works is that of coded imaging in which the entire detection plane contributes to each decoded sky pixel. For these two main reasons, the monitoring, and possible correction, of the spatial and temporal non-uniformity of pixel performances, especially in terms of gain and energy resolution, is of paramount importance. The IBIS on-board {sup 22}Na calibration source allows the calibration of each pixel at an accuracy of <0.5% by integrating the data from a few revolutions at constant temperature. The two calibration lines, at 511 and 1275 keV, allow also the measurement and monitoring of the PICsIT energy resolution which proves to be very stable at {approx} 19% and {approx} 9% (FWHM) respectively, and consistent with the values expected analytical predictions checked against pre-launch tests. (authors)

  2. CALIBRATION OF THE INFRARED OPTOMETER

    Science.gov (United States)

    An infrared optometer for measuring the absolute status of accommodation is subject to a constant error not associated with chromatic aberration or...on optometer accuracy as long as the pupil does not vignette the optometer beam. A modification is described for calibrating the infrared optometer ...for an individual subject without using trial lenses or a subjective optometer . (Author)

  3. Calibration of shaft alignment instruments

    Science.gov (United States)

    Hemming, Bjorn

    1998-09-01

    Correct shaft alignment is vital for most rotating machines. Several shaft alignment instruments, ranging form dial indicator based to laser based, are commercially available. At VTT Manufacturing Technology a device for calibration of shaft alignment instruments was developed during 1997. A feature of the developed device is the similarity to the typical use of shaft alignment instruments i.e. the rotation of two shafts during the calibration. The benefit of the rotation is that all errors of the shaft alignment instrument, for example the deformations of the suspension bars, are included. However, the rotation increases significantly the uncertainty of calibration because of errors in the suspension of the shafts in the developed device for calibration of shaft alignment instruments. Without rotation the uncertainty of calibration is 0.001 mm for the parallel offset scale and 0,003 mm/m for the angular scale. With rotation the uncertainty of calibration is 0.002 mm for the scale and 0.004 mm/m for the angular scale.

  4. 计算机辅助外科中手术与计划空间标定以及视觉空间的误差校正%Calibration Between Operation Space and Plan Space and Error Correction of Visual Space in Computer-aided Surgery

    Institute of Scientific and Technical Information of China (English)

    郭锥; 周宇; 席文明

    2012-01-01

    In computer-aided surgery (CAS) system,many space integrates in together,in order to improve the precision of the system operation,the effective calibration method to correct the error between the space is needed. Using the robot characteristics motion errors in visual space of navigation system to establish the mapping of visual space and robot space,and to recursion correction the local transformation matrix of visual space and robot space. Using local transformation matrix to establish optimization equatipn.and then obtaining global optimal transformation matrix. This method for all the static and dynamic error correction. According to the coupling error exists in the operation and plan space,using the designed special structure force sensor and calibration piece of decoupling to calibration its error, and according to the transformation matrix to adjust the objects position and orientation in the plan space to ensure that the objects in the plan space have the same pose with it in the operation space. The experimental results show that the dynamic calibration method can make the visual space global error reduced to 5 pixels,and the force control calibration method can make the position error is reduced to 0. 25 mm and the posture error reduced to 0. 1%计算机辅助外科(CAS)系统中,多空间集成在一起,为了提高系统的操作精度,需要有效的标定方法校正空间之间的误差.利用机器人上特征在导航系统中视觉空间的运动误差,建立视觉空间与机器人空间的映射关系,递归校正两空间之间的局部转换矩阵.利用局部转换矩阵建立优化方程,求取全局最优转换矩阵.该方法对所有动态、静态误差进行校正.针对手术与计划空间中存在的耦合误差,利用设计的特殊结构力传感器和标定块解耦标定其误差,并根据求取的转换矩阵,调整计划空间中对象的位姿,保证计划空间与手术空间中的对象位姿一致.实验结果表明,动

  5. Verification of L-band SAR calibration

    Science.gov (United States)

    Larson, R. W.; Jackson, P. L.; Kasischke, E.

    1985-01-01

    Absolute calibration of a digital L-band SAR system to an accuracy of better than 3 dB has been verified. This was accomplished with a calibration signal generator that produces the phase history of a point target. This signal relates calibration values to various SAR data sets. Values of radar cross-section (RCS) of reference reflectors were obtained using a derived calibration relationship for the L-band channel on the ERIM/CCRS X-C-L SAR system. Calibrated RCS values were compared to known RCS values of each reference reflector for verification and to obtain an error estimate. The calibration was based on the radar response to 21 calibrated reference reflectors.

  6. Camera calibration correction in shape from inconsistent silhouette

    Science.gov (United States)

    The use of shape from silhouette for reconstruction tasks is plagued by two types of real-world errors: camera calibration error and silhouette segmentation error. When either error is present, we call the problem the Shape from Inconsistent Silhouette (SfIS) problem. In this paper, we show how sm...

  7. 基于辅助阵元的方位依赖幅相误差最大似然自校正:针对确定信号模型%Maximum likelihood self-calibration for direction-dependent gain-phase errors with carry-on instrumental sensors:case of deterministic signal model

    Institute of Scientific and Technical Information of China (English)

    王鼎; 潘苗; 吴瑛

    2011-01-01

    Aim at the self-calibration of direction-dependent gm-phase errors in case of deterministic signal model, the maximum likelihood method(MLM) for calibrating the direction-dependent gain-phase errors with carry-on instrumental sensors was presented. In order to maximize the high-dimensional nonlinear cost function appearing in the MLM, an improved alternative projection iteration algorithm, which could optimize the azimuths and direc6on-dependent gain-phase errors was proposed. The closed-form expressions of the Cramér-Rao bound(CRB) for azimuths and gain-phase errors were derived. Simulation experiments show the effectiveness and advantage of the novel method.%针对确定信号模型条件下方位依赖幅相误差的自校正问题,给出了一种基于辅助阵元的方位依赖幅相误差最大似然自校正方法;针对最大似然估计器中出现的高维非线性优化问题,推导了一种改进型交替投影迭代算法,从而实现了信号方位和方位依赖幅相误差的优化计算.此外,还推导了信号方位和方位依赖幅相误差的无偏克拉美罗界(CRB).仿真实验结果验证了新方法的有效性和优越性.

  8. Giada improved calibration of measurement subsystems

    Science.gov (United States)

    Della Corte, V.; Rotundi, A.; Sordini, R.; Accolla, M.; Ferrari, M.; Ivanovski, S.; Lucarelli, F.; Mazzotta Epifani, E.; Palumbo, P.

    2014-12-01

    GIADA (Grain Impact Analyzer and Dust Accumulator) is an in-situ instrument devoted to measure the dynamical properties of the dust grains emitted by the comet. An Extended Calibration activity using the GIADA Flight Spare Model has been carried out taking into account the knowledge gained through the analyses of IDPs and cometary samples returned from comet 81P/Wild 2. GIADA consists of three measurement subsystems: Grain Detection System, an optical device measuring the optical cross-section for individual dust; Impact Sensor an aluminum plate connected to 5 piezo-sensors measuring the momentum of impacting single dust grains; Micro Balance System measuring the cumulative deposition in time of dust grains smaller than 10 μm. The results of the analyses on data acquired with the GIADA PFM and the comparison with calibration data acquired during the pre-launch campaign allowed us to improve GIADA performances and capabilities. We will report the results of the following main activities: a) definition of a correlation between the 2 GIADA Models (PFM housed in laboratory and In-Flight Model on-board ROSETTA); b) characterization of the sub-systems performances (signal elaboration, sensitivities, space environment effects); c) new calibration measurements and related curves by means of the PFM model using realistic cometary dust analogues. Acknowledgements: GIADA was built by a consortium led by the Univ. Napoli "Parthenope" & INAF-Oss. Astr. Capodimonte, IT, in collaboration with the Inst. de Astrofisica de Andalucia, ES, Selex-ES s.p.a. and SENER. GIADA is presently managed & operated by Ist. di Astrofisica e Planetologia Spaziali-INAF, IT. GIADA was funded and managed by the Agenzia Spaziale Italiana, IT, with a support of the Spanish Ministry of Education and Science MEC, ES. GIADA was developed from a University of Kent, UK, PI proposal; sci. & tech. contribution given by CISAS, IT, Lab. d'Astr. Spat., FR, and Institutions from UK, IT, FR, DE and USA. We thank

  9. A FAST FOREGROUND DIGITAL CALIBRATION TECHNIQUE FOR PIPELINED ADC

    Institute of Scientific and Technical Information of China (English)

    Wang Yu; Yang Haigang; Cheng Xin; Liu Fei; Yin Tao

    2012-01-01

    Digital calibration techniques are widely developed to cancel the non-idealities of the pipelined Analog-to-Digital Converters (ADCs).This letter presents a fast foreground digital calibration technique based on the analysis of error sources which influence the resolution of pipelined ADCs.This method estimates the gain error of the ADC prototype quickly and calibrates the ADC simultaneously in the operation time.Finally,a 10 bit,100 Ms/s pipelined ADC is implemented and calibrated.The simulation results show that the digital calibration technique has its efficiency with fewem operation cycles.

  10. Calibrating transport lines using LOCO techniques

    Energy Technology Data Exchange (ETDEWEB)

    Yves Roblin

    2011-09-01

    With the 12GeV upgrade underway at CEBAF, there is a need to re-characterize the beamlines after the modifications made to it to accommodate running at higher energies. We present a linear perturbation approach to calibrating the optics model of transport lines. This method is adapted from the LOCO method in use for storage rings. We consider the effect of quadrupole errors, dipole construction errors as well as beam position monitors and correctors calibrations. The ideal model is expanded to first order in Taylor series of the quadrupole errors. A set of difference orbits obtained by exciting the correctors along the beamline is taken, yielding the measured response matrix. An iterative procedure is invoked and the quadrupole errors as well as beam position monitors and corrector calibration factors are obtained. Here we present details of the method and results of first measurements at CEBAF in early 2011.

  11. Complete Tri-Axis Magnetometer Calibration with a Gyro Auxiliary.

    Science.gov (United States)

    Yang, Deng; You, Zheng; Li, Bin; Duan, Wenrui; Yuan, Binwen

    2017-05-26

    Magnetometers combined with inertial sensors are widely used for orientation estimation, and calibrations are necessary to achieve high accuracy. This paper presents a complete tri-axis magnetometer calibration algorithm with a gyro auxiliary. The magnetic distortions and sensor errors, including the misalignment error between the magnetometer and assembled platform, are compensated after calibration. With the gyro auxiliary, the magnetometer linear interpolation outputs are calculated, and the error parameters are evaluated under linear operations of magnetometer interpolation outputs. The simulation and experiment are performed to illustrate the efficiency of the algorithm. After calibration, the heading errors calculated by magnetometers are reduced to 0.5° (1σ). This calibration algorithm can also be applied to tri-axis accelerometers whose error model is similar to tri-axis magnetometers.

  12. Application of an Error Statistics Estimation Method to the PSAS Forecast Error Covariance Model

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    In atmospheric data assimilation systems, the forecast error covariance model is an important component. However, the parameters required by a forecast error covariance model are difficult to obtain due to the absence of the truth. This study applies an error statistics estimation method to the Physical-space Statistical Analysis System (PSAS) height-wind forecast error covariance model. This method consists of two components: the first component computes the error statistics by using the National Meteorological Center (NMC) method, which is a lagged-forecast difference approach, within the framework of the PSAS height-wind forecast error covariance model; the second obtains a calibration formula to rescale the error standard deviations provided by the NMC method. The calibration is against the error statistics estimated by using a maximum-likelihood estimation (MLE) with rawindsonde height observed-minus-forecast residuals. A complete set of formulas for estimating the error statistics and for the calibration is applied to a one-month-long dataset generated by a general circulation model of the Global Model and Assimilation Office (GMAO), NASA. There is a clear constant relationship between the error statistics estimates of the NMC-method and MLE. The final product provides a full set of 6-hour error statistics required by the PSAS height-wind forecast error covariance model over the globe. The features of these error statistics are examined and discussed.

  13. Spectral calibration for convex grating imaging spectrometer

    Science.gov (United States)

    Zhou, Jiankang; Chen, Xinhua; Ji, Yiqun; Chen, Yuheng; Shen, Weimin

    2013-12-01

    Spectral calibration of imaging spectrometer plays an important role for acquiring target accurate spectrum. There are two spectral calibration types in essence, the wavelength scanning and characteristic line sampling. Only the calibrated pixel is used for the wavelength scanning methods and he spectral response function (SRF) is constructed by the calibrated pixel itself. The different wavelength can be generated by the monochromator. The SRF is constructed by adjacent pixels of the calibrated one for the characteristic line sampling methods. And the pixels are illuminated by the narrow spectrum line and the center wavelength of the spectral line is exactly known. The calibration result comes from scanning method is precise, but it takes much time and data to deal with. The wavelength scanning method cannot be used in field or space environment. The characteristic line sampling method is simple, but the calibration precision is not easy to confirm. The standard spectroscopic lamp is used to calibrate our manufactured convex grating imaging spectrometer which has Offner concentric structure and can supply high resolution and uniform spectral signal. Gaussian fitting algorithm is used to determine the center position and the Full-Width-Half-Maximum(FWHM)of the characteristic spectrum line. The central wavelengths and FWHMs of spectral pixels are calibrated by cubic polynomial fitting. By setting a fitting error thresh hold and abandoning the maximum deviation point, an optimization calculation is achieved. The integrated calibration experiment equipment for spectral calibration is developed to enhance calibration efficiency. The spectral calibration result comes from spectral lamp method are verified by monochromator wavelength scanning calibration technique. The result shows that spectral calibration uncertainty of FWHM and center wavelength are both less than 0.08nm, or 5.2% of spectral FWHM.

  14. Calibration Monitor for Dark Energy Experiments

    Energy Technology Data Exchange (ETDEWEB)

    Kaiser, M. E.

    2009-11-23

    The goal of this program was to design, build, test, and characterize a flight qualified calibration source and monitor for a Dark Energy related experiment: ACCESS - 'Absolute Color Calibration Experiment for Standard Stars'. This calibration source, the On-board Calibration Monitor (OCM), is a key component of our ACCESS spectrophotometric calibration program. The OCM will be flown as part of the ACCESS sub-orbital rocket payload in addition to monitoring instrument sensitivity on the ground. The objective of the OCM is to minimize systematic errors associated with any potential changes in the ACCESS instrument sensitivity. Importantly, the OCM will be used to monitor instrument sensitivity immediately after astronomical observations while the instrument payload is parachuting to the ground. Through monitoring, we can detect, track, characterize, and thus correct for any changes in instrument senstivity over the proposed 5-year duration of the assembled and calibrated instrument.

  15. Herschel SPIRE FTS Relative Spectral Response Calibration

    CERN Document Server

    Fulton, Trevor; Baluteau, Jean-Paul; Benielli, Dominique; Imhof, Peter; Lim, Tanya; Lu, Nanyao; Marchili, Nicola; Naylor, David; Polehampton, Edward; Swinyard, Bruce; Valtchanov, Ivan

    2014-01-01

    Herschel/SPIRE Fourier transform spectrometer (FTS) observations contain emission from both the Herschel Telescope and the SPIRE Instrument itself, both of which are typically orders of magnitude greater than the emission from the astronomical source, and must be removed in order to recover the source spectrum. The effects of the Herschel Telescope and the SPIRE Instrument are removed during data reduction using relative spectral response calibration curves and emission models. We present the evolution of the methods used to derive the relative spectral response calibration curves for the SPIRE FTS. The relationship between the calibration curves and the ultimate sensitivity of calibrated SPIRE FTS data is discussed and the results from the derivation methods are compared. These comparisons show that the latest derivation methods result in calibration curves that impart a factor of between 2 and 100 less noise to the overall error budget, which results in calibrated spectra for individual observations whose n...

  16. AFFTC Standard Airspeed Calibration Procedures

    Science.gov (United States)

    1981-06-01

    25x0UIXQXQ Results of groundLpeed course calibration are normally pre- sented in the following plots: 1. .AvP vs Vi Ŗ. All vs V ic 3. AMPC vs Mic .4...8217Average AfPeavgpo, tion correction AM /AH 10-5 per and figure V 9 PC PC feet . fu V AYpc" x q3 @ , Average position avg corred ion (AM @ AMPC /AVPC...instrument error 0 M ic From and 0), Mach number p Chart 8.5 in reference’l (AFTR 6273) (DO AMPPacer poqition error calibra- Pc tion at9 S( AMpc /’,HpC)p

  17. Crowd-Sourced Calibration: The GEDI Strategy for Empirical Biomass Estimation Using Spaceborne Lidar

    Science.gov (United States)

    Dubayah, R.

    2015-12-01

    The central task in estimating forest biomass from spaceborne sensors is the development of calibration equations that relate observed forest structure to biomass at a variety of spatial scales. Empirical methods generally rely on statistical estimation or machine learning techniques where field-based estimates of biomass at the plot level are associated with post-launch observations of variables such as canopy height and cover. For global-scale mapping the process is complex and leads to a number of questions: How many calibrations are required to capture non-stationarity in the relationships? Where does one calibration begin and another end? Should calibrations be conditioned by biome? Vegetation type? Land-use? Post-launch calibrations lead to further complications, such as the requirement to have sufficient field plot data underneath potentially sparse satellite observations, spatial and temporal mismatches in scale between field plots and pixels, and geolocation uncertainty, both in the plots and the satellite data. The Global Ecosystem Dynamics Investigation (GEDI) is under development by NASA to estimate forest biomass. GEDI will deploy a multi-beam lidar on the International Space Station and provide billions of observations of forest structure per year. Because GEDI uses relatively small footprints, about 25 m diameter, post-launch calibration is exceptionally problematic for the reasons listed earlier. Instead, GEDI will use a kind of "crowd-sourced" calibration strategy where existing lidar observations and the corresponding plot biomass will be assembled from data contributed by the science community. Through a process of continuous updating, calibrations will be refined as more data is ingested. This talk will focus on the GEDI pre-launch calibration strategy and present initial progress on its development, and how it forms the basis for meeting mission biomass requirements.

  18. On chromatic and geometrical calibration

    DEFF Research Database (Denmark)

    Folm-Hansen, Jørgen

    1999-01-01

    of non-uniformity of the illumination of the image plane. Only the image deforming aberrations and the non-uniformity of illumination are included in the calibration models. The topics of the pinhole camera model and the extension to the Direct Linear Transform (DLT) are described. It is shown how......The main subject of the present thesis is different methods for the geometrical and chromatic calibration of cameras in various environments. For the monochromatic issues of the calibration we present the acquisition of monochrome images, the classic monochrome aberrations and the various sources...... the DLT can be extended with non-linear models of the common lens aberrations/errors some of them caused by manufacturing defects like decentering and thin prism distortion. The relation between a warping and the non-linear defects are shown. The issue of making a good resampling of an image by using...

  19. Curiosity’s robotic arm-mounted Mars Hand Lens Imager (MAHLI): Characterization and calibration status

    Science.gov (United States)

    Edgett, Kenneth S.; Caplinger, Michael A.; Maki, Justin N.; Ravine, Michael A.; Ghaemi, F. Tony; McNair, Sean; Herkenhoff, Kenneth E.; Duston, Brian M.; Wilson, Reg G.; Yingst, R. Aileen; Kennedy, Megan R.; Minitti, Michelle E.; Sengstacken, Aaron J.; Supulver, Kimberley D.; Lipkaman, Leslie J.; Krezoski, Gillian M.; McBride, Marie J.; Jones, Tessa L.; Nixon, Brian E.; Van Beek, Jason K.; Krysak, Daniel J.; Kirk, Randolph L.

    2015-01-01

    MAHLI (Mars Hand Lens Imager) is a 2-megapixel, Bayer pattern color CCD camera with a macro lens mounted on a rotatable turret at the end of the 2-meters-long robotic arm aboard the Mars Science Laboratory rover, Curiosity. The camera includes white and longwave ultraviolet LEDs to illuminate targets at night. Onboard data processing services include focus stack merging and data compression. Here we report on the results and status of MAHLI characterization and calibration, covering the pre-launch period from August 2008 through the early months of the extended surface mission through February 2015. Since landing in Gale crater in August 2012, MAHLI has been used for a wide range of science and engineering applications, including distinction among a variety of mafic, siliciclastic sedimentary rocks; investigation of grain-scale rock, regolith, and eolian sediment textures and structures; imaging of the landscape; inspection and monitoring of rover and science instrument hardware concerns; and supporting geologic sample selection, extraction, analysis, delivery, and documentation. The camera has a dust cover and focus mechanism actuated by a single stepper motor. The transparent cover was coated with a thin film of dust during landing, thus MAHLI is usually operated with the cover open. The camera focuses over a range from a working distance of 2.04 cm to infinity; the highest resolution images are at 13.9 µm per pixel; images acquired from 6.9 cm show features at the same scale as the Mars Exploration Rover Microscopic Imagers at 31 µm/pixel; and 100 µm/pixel is achieved at a working distance of ~26.5 cm. The very highest resolution images returned from Mars permit distinction of high contrast silt grains in the 30–40 µm size range. MAHLI has performed well; the images need no calibration in order to achieve most of the investigation’s science and engineering goals. The positioning and repeatability of robotic arm placement of the MAHLI camera head have

  20. Refractive Errors

    Science.gov (United States)

    ... does the eye focus light? In order to see clearly, light rays from an object must focus onto the ... The refractive errors are: myopia, hyperopia and astigmatism [See figures 2 and 3]. What is hyperopia (farsightedness)? Hyperopia occurs when light rays focus behind the retina (because the eye ...

  1. Medication Errors

    Science.gov (United States)

    ... Proprietary Names (PDF - 146KB) Draft Guidance for Industry: Best Practices in Developing Proprietary Names for Drugs (PDF - 279KB) ... or (301) 796-3400 druginfo@fda.hhs.gov Human Drug ... in Medication Errors Resources for You Agency for Healthcare Research and Quality: ...

  2. Nonlinear Observers for Gyro Calibration

    Science.gov (United States)

    Thienel, Julie; Sanner, Robert M.

    2003-01-01

    Nonlinear observers for gyro calibration are presented. The first observer estimates a constant gyro bias. The second observer estimates scale factor errors. The third observer estimates the gyro alignment for three orthogonal gyros. The convergence properties of all three observers are discussed. Additionally, all three observers are coupled with a nonlinear control algorithm. The stability of each of the resulting closed loop systems is analyzed. Simulated test results are presented for each system.

  3. Systematic error mitigation in multiple field astrometry

    CERN Document Server

    Gai, Mario

    2011-01-01

    Combination of more than two fields provides constraints on the systematic error of simultaneous observations. The concept is investigated in the context of the Gravitation Astrometric Measurement Experiment (GAME), which aims at measurement of the PPN parameter $\\gamma$ at the $10^{-7}-10^{-8}$ level. Robust self-calibration and control of systematic error is crucial to the achievement of the precision goal. The present work is focused on the concept investigation and practical implementation strategy of systematic error control over four simultaneously observed fields, implementing a "double differential" measurement technique. Some basic requirements on geometry, observing and calibration strategy are derived, discussing the fundamental characteristics of the proposed concept.

  4. Simple transfer calibration method for a Cimel Sun-Moon photometer: calculating lunar calibration coefficients from Sun calibration constants.

    Science.gov (United States)

    Li, Zhengqiang; Li, Kaitao; Li, Donghui; Yang, Jiuchun; Xu, Hua; Goloub, Philippe; Victori, Stephane

    2016-09-20

    The Cimel new technologies allow both daytime and nighttime aerosol optical depth (AOD) measurements. Although the daytime AOD calibration protocols are well established, accurate and simple nighttime calibration is still a challenging task. Standard lunar-Langley and intercomparison calibration methods both require specific conditions in terms of atmospheric stability and site condition. Additionally, the lunar irradiance model also has some known limits on its uncertainty. This paper presents a simple calibration method that transfers the direct-Sun calibration constant, V0,Sun, to the lunar irradiance calibration coefficient, CMoon. Our approach is a pure calculation method, independent of site limits, e.g., Moon phase. The method is also not affected by the lunar irradiance model limitations, which is the largest error source of traditional calibration methods. Besides, this new transfer calibration approach is easy to use in the field since CMoon can be obtained directly once V0,Sun is known. Error analysis suggests that the average uncertainty of CMoon over the 440-1640 nm bands obtained with the transfer method is 2.4%-2.8%, depending on the V0,Sun approach (Langley or intercomparison), which is comparable with that of lunar-Langley approach, theoretically. In this paper, the Sun-Moon transfer and the Langley methods are compared based on site measurements in Beijing, and the day-night measurement continuity and performance are analyzed.

  5. Sensor Calibration Design Based on D-Optimality Criterion

    Directory of Open Access Journals (Sweden)

    Hajiyev Chingiz

    2016-09-01

    Full Text Available In this study, a procedure for optimal selection of measurement points using the D-optimality criterion to find the best calibration curves of measurement sensors is proposed. The coefficients of calibration curve are evaluated by applying the classical Least Squares Method (LSM. As an example, the problem of optimal selection for standard pressure setters when calibrating a differential pressure sensor is solved. The values obtained from the D-optimum measurement points for calibration of the differential pressure sensor are compared with those from actual experiments. Comparison of the calibration errors corresponding to the D-optimal, A-optimal and Equidistant calibration curves is done.

  6. Traceable Pyrgeometer Calibrations

    Energy Technology Data Exchange (ETDEWEB)

    Dooraghi, Mike; Kutchenreiter, Mark; Reda, Ibrahim; Habte, Aron; Sengupta, Manajit; Andreas, Afshin; Newman, Martina

    2016-05-02

    This poster presents the development, implementation, and operation of the Broadband Outdoor Radiometer Calibrations (BORCAL) Longwave (LW) system at the Southern Great Plains Radiometric Calibration Facility for the calibration of pyrgeometers that provide traceability to the World Infrared Standard Group.

  7. Traceable Pyrgeometer Calibrations

    Energy Technology Data Exchange (ETDEWEB)

    Dooraghi, Mike; Kutchenreiter, Mark; Reda, Ibrahim; Habte, Aron; Sengupta, Manajit; Andreas, Afshin; Newman, Martina

    2016-05-02

    This poster presents the development, implementation, and operation of the Broadband Outdoor Radiometer Calibrations (BORCAL) Longwave (LW) system at the Southern Great Plains Radiometric Calibration Facility for the calibration of pyrgeometers that provide traceability to the World Infrared Standard Group.

  8. Calibration of sound calibrators: an overview

    Science.gov (United States)

    Milhomem, T. A. B.; Soares, Z. M. D.

    2016-07-01

    This paper presents an overview of calibration of sound calibrators. Initially, traditional calibration methods are presented. Following, the international standard IEC 60942 is discussed emphasizing parameters, target measurement uncertainty and criteria for conformance to the requirements of the standard. Last, Regional Metrology Organizations comparisons are summarized.

  9. Quantile Regression With Measurement Error

    KAUST Repository

    Wei, Ying

    2009-08-27

    Regression quantiles can be substantially biased when the covariates are measured with error. In this paper we propose a new method that produces consistent linear quantile estimation in the presence of covariate measurement error. The method corrects the measurement error induced bias by constructing joint estimating equations that simultaneously hold for all the quantile levels. An iterative EM-type estimation algorithm to obtain the solutions to such joint estimation equations is provided. The finite sample performance of the proposed method is investigated in a simulation study, and compared to the standard regression calibration approach. Finally, we apply our methodology to part of the National Collaborative Perinatal Project growth data, a longitudinal study with an unusual measurement error structure. © 2009 American Statistical Association.

  10. Geometric Calibration and Accuracy Verification of the GF-3 Satellite.

    Science.gov (United States)

    Zhao, Ruishan; Zhang, Guo; Deng, Mingjun; Xu, Kai; Guo, Fengcheng

    2017-08-29

    The GF-3 satellite is the first multi-polarization synthetic aperture radar (SAR) imaging satellite in China, which operates in the C band with a resolution of 1 m. Although the SAR satellite system was geometrically calibrated during the in-orbit commissioning phase, there are still some system errors that affect its geometric positioning accuracy. In this study, these errors are classified into three categories: fixed system error, time-varying system error, and random error. Using a multimode hybrid geometric calibration of spaceborne SAR, and considering the atmospheric propagation delay, all system errors can be effectively corrected through high-precision ground control points and global atmospheric reference data. The geometric calibration experiments and accuracy evaluation for the GF-3 satellite are performed using ground control data from several regions. The experimental results show that the residual system errors of the GF-3 SAR satellite have been effectively eliminated, and the geometric positioning accuracy can be better than 3 m.

  11. Error Analysis and On-Board Calibration of Magnetometer in Space Environment Exploration Satellite%空间环境探测卫星用磁强计误差分析及在线标定

    Institute of Scientific and Technical Information of China (English)

    杨照华; 余远金; 祁振强

    2012-01-01

    A magnetometer used in the sun-earth space exploration satellite is usually assembled at the tip of the boom by the action of space disturbance torque and maneuver, the installation matrix magnetometer of varies dramatically, which may lead to the low attitude determination accuracy. Based on the analysis of the magnetometer attitude determination errors, a 19 state high-fidelity measurement model of magnetometer is proposed. Combined with satellite attitude dynamics and kinematics, a 19 state Extended Kalman Filter is adopted to estimate installation matrix on-board and compensate magnetometer measurement. Then the innovative magnetometer measurement model is used to estimate satellite attitude. Finally the algorithm is validated by using the turntable experiment. Results of turntable experiment show that this method can estimate installation matrix errors under the computational requirement of On-board Computer and dramatically improve the accuracy of attitude determination and magnetometer error estimation.%用于探测日地空间磁环境的磁强计多数安装在伸杆的末端,长期受太阳辐射等空间环境干扰力矩以及机动等影响,磁强计安装矩阵随时间发生较大的变化,从而导致卫星定姿精度下降.为此,在分析空间环境干扰力矩和磁强计定姿误差特性的基础上,建立了19维高精度的磁强计误差模型,结合卫星的运动学和姿态动力学特性,采用EKF滤波方法对安装矩阵进行实时估计与修正补偿,并利用该磁强计模型实现卫星的姿态确定,最后利用实验进行验证.实验结果表明,该方法能够在满足星载计算机的计算量要求的同时,在线估计安装矩阵误差,显著提高了磁强计的误差估计精度与定姿精度.

  12. Metop-BAVHRR IR channel post-launch calibration and verification tests

    Science.gov (United States)

    Chang, Tiejun; Wu, Xiangqian; Weng, Fuzhong

    2013-09-01

    Meteorological Operational (METOP)-B spacecraft was launched on September 17, 2012, and the Advanced Very High Resolution Radiometer (AVHRR) IR channels were activated October 18. AVHRR instrument has been tested and characterized pre-launch under thermal vacuum (TV) condition by the instrument vender. The instrument dynamic range, noise equivalent differential temperature (NEDT), and nonlinear response have been characterized in the test. Basing on the TV test data, the calibration coefficients are generated for post-launch. The on-orbit verification tests have been performed to verify the instrument response and performance, including the dynamic range, NEDT, on-board blackbody (BB) temperature, instrument response calibration, and instrument status from the telemetry data. The post-launch Cal/Val test is to improve the calibration accuracy and enhance the L1B data quality. These tests include stray light analysis, instrument gain verification, and uncertainty assessment. The stray light impact on the calibration is estimated as 0.2% for 11 μm channel, 0.3% for 12 μm channel, and 3% for 3.7μm channel. The inter-comparison AVHRR IR channel radiances with the radiance derived from Infrared Atmospheric Sounding Interferometer (IASI) measurement has been performed and the AVHRR bias shoes brightness temperature dependency.

  13. Exploration of new multivariate spectral calibration algorithms.

    Energy Technology Data Exchange (ETDEWEB)

    Van Benthem, Mark Hilary; Haaland, David Michael; Melgaard, David Kennett; Martin, Laura Elizabeth; Wehlburg, Christine Marie; Pell, Randy J. (The Dow Chemical Company, Midland, MI); Guenard, Robert D. (Merck & Co. Inc., West Point, PA)

    2004-03-01

    A variety of multivariate calibration algorithms for quantitative spectral analyses were investigated and compared, and new algorithms were developed in the course of this Laboratory Directed Research and Development project. We were able to demonstrate the ability of the hybrid classical least squares/partial least squares (CLSIPLS) calibration algorithms to maintain calibrations in the presence of spectrometer drift and to transfer calibrations between spectrometers from the same or different manufacturers. These methods were found to be as good or better in prediction ability as the commonly used partial least squares (PLS) method. We also present the theory for an entirely new class of algorithms labeled augmented classical least squares (ACLS) methods. New factor selection methods are developed and described for the ACLS algorithms. These factor selection methods are demonstrated using near-infrared spectra collected from a system of dilute aqueous solutions. The ACLS algorithm is also shown to provide improved ease of use and better prediction ability than PLS when transferring calibrations between near-infrared calibrations from the same manufacturer. Finally, simulations incorporating either ideal or realistic errors in the spectra were used to compare the prediction abilities of the new ACLS algorithm with that of PLS. We found that in the presence of realistic errors with non-uniform spectral error variance across spectral channels or with spectral errors correlated between frequency channels, ACLS methods generally out-performed the more commonly used PLS method. These results demonstrate the need for realistic error structure in simulations when the prediction abilities of various algorithms are compared. The combination of equal or superior prediction ability and the ease of use of the ACLS algorithms make the new ACLS methods the preferred algorithms to use for multivariate spectral calibrations.

  14. Lidar to lidar calibration phase 1

    DEFF Research Database (Denmark)

    Yordanova, Ginka; Courtney, Michael

    This report presents a feasibility study of a lidar to lidar (L2L) calibration procedure. Phase one of the project was conducted at Høvsøre, Denmark. Two windcubes were placed next to the 116m met mast and different methods were applied to obtain the sensing height error of the lidars. The purpose...... is to find the most consistent method and use it in a potential lidar to lidar calibration procedure....

  15. Robust radio interferometric calibration using the t-distribution

    NARCIS (Netherlands)

    Kazemi, S.; Yatawatta, S.

    2013-01-01

    A major stage of radio interferometric data processing is calibration or the estimation of systematic errors in the data and the correction for such errors. A stochastic error (noise) model is assumed, and in most cases, this underlying model is assumed to be Gaussian. However, outliers in the data

  16. Research on self-calibration error ratio method of infrared thermometer%红外线测温仪自校准误差比对方法的研究

    Institute of Scientific and Technical Information of China (English)

    肖艳红

    2012-01-01

    红外线测温仪由于长期用于生产一线进行现场测试,使用环境恶劣,以及日常维护保养不当,可能导致栓定有效期内的红外线测温仪不能准确测量甚至设备故障,导致测量失准,影响电网安全稳定运行。根据红外测温原理研究了运行中的红外线测温仪自校准方法,使用者可用简易自制设备随时对红外线测温仪进行定性测试分析,方法简单易行。确保红外线测温仪处于良好工作状态,准确测量,减少安全隐患。%Infrared thermometer is usually used for testing in the production field. Because of harsh environment as well as improper maintenance, the Infrared thermometer in the test within the validity period can not be accurately measured , even equipment failure and measurement inaccurate , the power grid security and stabilityoperation are also affected. The operation of the infrared thermometer calibration method based on its principle is researched. It can be qualitatively tested and analysed in simple homemade device at any time. It make sure that the infrared thermometer is in good working condition and accurately measuring. The security risks are reduced.

  17. CryoSat-2: Post launch performance of SIRAL-2 and its calibration/validation

    Science.gov (United States)

    Cullen, Robert; Francis, Richard; Davidson, Malcolm; Wingham, Duncan

    2010-05-01

    the use of ocean calibration zones and radar transponders. 3. CRYOSAT-2 OVERALL PERFORMANCE & VALIDATION PLANNING Validating such retrievals derived from a phase coherent pulse-width limited polar observing radar altimeter, such as SIRAL, is not a simple one [4]. In order to fully understand all the respective error co-variances it is necessary to acquire many different types of in-situ measurements (GPR, neutron probe density profiles, drilled and electromagnetic derived sea-ice thicknesses, for example) in highly inhospitable regions of the cryosphere at key times of the year. In order to correlate retrievals from CryoSat with the in-situ data it was decided early in the CryoSat development that an aircraft borne radar altimeter with similar functionality to SIRAL would provide the necessary link, albeit on the smaller scale, and provide pre-launch incite into expected performances and issues. In 2001 ESA commenced the development of its own prototype radar altimeter that mimics the functionality of SIRAL. Similar to SIRAL, but with subtle functional differences, the airborne SAR/Interferometric Radar Altimeter System (ASIRAS) has now been the centre piece instrument for a number of large scale land and sea ice field campaigns in the Arctic during spring and autumn 2004, 2006 and 2008. Additional smaller science/test campaigns have taken place in March 2003 (Svalbard), March 2005 (Bay of Bothnia), March 2006 (Western Greenland) and April 2007 (CryoVEx 2007 in Svalbard). It is a credit to all parties that constitute the CryoSat Validation and Retrieval Team (CVRT) for the coordination, planning, acquisition of in-situ and airborne measurements and the subsequent processing and distributing of its data for analysis. CVRT has a robust infrastructure in place for validating its level 2 products derived from an operational CryoSat-2. 4. REFERENCES [1] http://www.esa.int/livingplanet/cryosat [2] Wingham, D. J., Francis, C. R., Baker, S., Bouzinac, C., Cullen, R., de

  18. Vicarious Calibration Based Cross Calibration of Solar Reflective Channels of Radiometers Onboard Remote Sensing Satellite and Evaluation of Cross Calibration Accuracy through Band-to-Band Data Comparisons

    Directory of Open Access Journals (Sweden)

    Kohei Arai

    2013-04-01

    Full Text Available Accuracy evaluation of cross calibration through band-to-band data comparison for visible and near infrared radiometers which onboard earth observation satellites is conducted. The conventional cross calibration for visible to near infrared radiometers onboard earth observation satellites is conducted through comparisons of band-to-band data of which spectral response functions are overlapped mostly. There are the following major error sources due to observation time difference, spectral response function difference in conjunction of surface reflectance and atmospheric optical depth, observation area difference. These error sources are assessed with dataset acquired through ground measurements of surface reflectance and optical depth. Then the accuracy of the conventional cross calibration is evaluated with vicarious calibration data. The results show that cross calibration accuracy can be done more precisely if the influences due to the aforementioned three major error sources are taken into account.

  19. Vicarious Calibration of Beijing-1 Multispectral Imagers

    Directory of Open Access Journals (Sweden)

    Zhengchao Chen

    2014-02-01

    Full Text Available For on-orbit calibration of the Beijing-1 multispectral imagers (Beijing-1/MS, a field calibration campaign was performed at the Dunhuang calibration site during September and October of 2008. Based on the in situ data and images from Beijing-1 and Terra/Moderate Resolution Imaging Spectroradiometer (MODIS, three vicarious calibration methods (i.e., reflectance-based, irradiance-based, and cross-calibration were used to calculate the top-of-atmosphere (TOA radiance of Beijing-1. An analysis was then performed to determine or identify systematic and accidental errors, and the overall uncertainty was assessed for each individual method. The findings show that the reflectance-based method has an uncertainty of more than 10% if the aerosol optical depth (AOD exceeds 0.2. The cross-calibration method is able to reach an error level within 7% if the images are selected carefully. The final calibration coefficients were derived from the irradiance-based data for 6 September 2008, with an uncertainty estimated to be less than 5%.

  20. Medication Errors - A Review

    OpenAIRE

    Vinay BC; Nikhitha MK; Patel Sunil B

    2015-01-01

    In this present review article, regarding medication errors its definition, medication error problem, types of medication errors, common causes of medication errors, monitoring medication errors, consequences of medication errors, prevention of medication error and managing medication errors have been explained neatly and legibly with proper tables which is easy to understand.

  1. Medication Errors - A Review

    OpenAIRE

    Vinay BC; Nikhitha MK; Patel Sunil B

    2015-01-01

    In this present review article, regarding medication errors its definition, medication error problem, types of medication errors, common causes of medication errors, monitoring medication errors, consequences of medication errors, prevention of medication error and managing medication errors have been explained neatly and legibly with proper tables which is easy to understand.

  2. An Improved Photometric Calibration of the Sloan Digital Sky Survey Imaging Data

    Energy Technology Data Exchange (ETDEWEB)

    Padmanabhan, Nikhil; Schlegel, D.J.; Finkbeiner, D.P.; Barentine, J.C.; Blanton, M.R.; Brewington, H.J.; Gunn, J.E.; Harvanek, M.; Hogg, D.W.; Ivezic, Z.; Johnston, D.; /LBL, Berkeley /Princeton U. /Harvard-Smithsonian Ctr. Astrophys. /Texas U., Astron. Dept. /Apache Point Observ. /New York U. /Washington U., Seattle, Astron. Dept. /Caltech, JPL

    2007-03-01

    We present an algorithm to photometrically calibrate wide field optical imaging surveys, that simultaneously solves for the calibration parameters and relative stellar fluxes using overlapping observations. The algorithm decouples the problem of ''relative'' calibrations from that of ''absolute'' calibrations; the absolute calibration is reduced to determining a few numbers for the entire survey. We pay special attention to the spatial structure of the calibration errors, allowing one to isolate particular error modes in downstream analyses. Applying this to the Sloan Digital Sky Survey imaging data, we achieve {approx}1% relative calibration errors across 8500 deg{sup 2} in griz; the errors are {approx}2% for the u band. These errors are dominated by unmodeled atmospheric variations at Apache Point Observatory.

  3. Calibrating page sized Gafchromic EBT3 films

    Energy Technology Data Exchange (ETDEWEB)

    Crijns, W.; Maes, F.; Heide, U. A. van der; Van den Heuvel, F. [Department of Radiation Oncology, University Hospitals Leuven, Herestraat 49, 3000 Leuven (Belgium); Department ESAT/PSI-Medical Image Computing, Medical Imaging Research Center, KU Leuven, Herestraat 49, 3000 Leuven (Belgium); Department of Radiation Oncology, The Netherlands Cancer Institute-Antoni van Leeuwenhoek Hospital, Plesmanlaan 121, 1066 CX Amsterdam (Netherlands); Department of Radiation Oncology, University Hospitals Leuven, Herestraat 49, 3000 Leuven (Belgium)

    2013-01-15

    Purpose: The purpose is the development of a novel calibration method for dosimetry with Gafchromic EBT3 films. The method should be applicable for pretreatment verification of volumetric modulated arc, and intensity modulated radiotherapy. Because the exposed area on film can be large for such treatments, lateral scan errors must be taken into account. The correction for the lateral scan effect is obtained from the calibration data itself. Methods: In this work, the film measurements were modeled using their relative scan values (Transmittance, T). Inside the transmittance domain a linear combination and a parabolic lateral scan correction described the observed transmittance values. The linear combination model, combined a monomer transmittance state (T{sub 0}) and a polymer transmittance state (T{sub {infinity}}) of the film. The dose domain was associated with the observed effects in the transmittance domain through a rational calibration function. On the calibration film only simple static fields were applied and page sized films were used for calibration and measurements (treatment verification). Four different calibration setups were considered and compared with respect to dose estimation accuracy. The first (I) used a calibration table from 32 regions of interest (ROIs) spread on 4 calibration films, the second (II) used 16 ROIs spread on 2 calibration films, the third (III), and fourth (IV) used 8 ROIs spread on a single calibration film. The calibration tables of the setups I, II, and IV contained eight dose levels delivered to different positions on the films, while for setup III only four dose levels were applied. Validation was performed by irradiating film strips with known doses at two different time points over the course of a week. Accuracy of the dose response and the lateral effect correction was estimated using the dose difference and the root mean squared error (RMSE), respectively. Results: A calibration based on two films was the optimal

  4. Luminosity monitoring and calibration of BLM

    Institute of Scientific and Technical Information of China (English)

    XUE Zhen; CAI Xiao; YU Bo-Xiang; FANG Jian; SUN Xi-Lei; SHI Feng; WANG Zhi-Gang; AN Zheng-Hua; SUN Li-Jun; LIU Hong-Bang; ZHANG Ai-Wu; XU Zi-Zong; WANG Xiao-Dong; WANG Xiao-Lian; HU Tao; WANG Zhi-Yong; FU Cheng-Dong; YAN Wen-Biao; L(U) Jun-Guang; ZHOU Li

    2011-01-01

    The BEPCⅡLuminosity Monitor(BLM)monitors relative luminosity per bunch.The counting rates of gamma photons,which are proportional to the luminosities from the BLM at the center of mass system energy of the ψ(3770)resonance,are obtained with a statistical error of 0.01% and a systematic error of 4.1%.Absolute luminosities are also determined by the BESⅢ End-cap Electro-Magnetic Calorimeter(EEMC)using Bhabha events with a statistical error of 2.3% and a systematic error of 3.5%.The calibration constant between the luminosities obtained with the EEMC and the counting rates of the BLM are found to be 0.84±0.03(x1026 cm-2·count-1).With the calibration constant,the counting rates of the BLM can be scaled up to absolute luminosities.

  5. Planck pre-launch status: The optical system

    DEFF Research Database (Denmark)

    Tauber, J. A.; Nørgaard-Nielsen, Hans Ulrik; Ade, P. A. R.

    2010-01-01

    Planck is a scientific satellite that represents the next milestone in space-based research related to the cosmic microwave background, and in many other astrophysical fields. Planck was launched on 14 May of 2009 and is now operational. The uncertainty in the optical response of its detectors...

  6. Planck pre-launch status: The Planck mission

    DEFF Research Database (Denmark)

    Tauber, J. A.; Mandoles, N.; Puget, J.-L.

    2010-01-01

    The European Space Agency's Planck satellite, launched on 14 May 2009, is the third-generation space experiment in the field of cosmic microwave background (CMB) research. It will image the anisotropies of the CMB over the whole sky, with unprecedented sensitivity ( ~ 2 × 10-6) and angular...

  7. Calibration of Nanopositioning Stages

    Directory of Open Access Journals (Sweden)

    Ning Tan

    2015-12-01

    Full Text Available Accuracy is one of the most important criteria for the performance evaluation of micro- and nanorobots or systems. Nanopositioning stages are used to achieve the high positioning resolution and accuracy for a wide and growing scope of applications. However, their positioning accuracy and repeatability are not well known and difficult to guarantee, which induces many drawbacks for many applications. For example, in the mechanical characterisation of biological samples, it is difficult to perform several cycles in a repeatable way so as not to induce negative influences on the study. It also prevents one from controlling accurately a tool with respect to a sample without adding additional sensors for closed loop control. This paper aims at quantifying the positioning repeatability and accuracy based on the ISO 9283:1998 standard, and analyzing factors influencing positioning accuracy onto a case study of 1-DoF (Degree-of-Freedom nanopositioning stage. The influence of thermal drift is notably quantified. Performances improvement of the nanopositioning stage are then investigated through robot calibration (i.e., open-loop approach. Two models (static and adaptive models are proposed to compensate for both geometric errors and thermal drift. Validation experiments are conducted over a long period (several days showing that the accuracy of the stage is improved from typical micrometer range to 400 nm using the static model and even down to 100 nm using the adaptive model. In addition, we extend the 1-DoF calibration to multi-DoF with a case study of a 2-DoF nanopositioning robot. Results demonstrate that the model efficiently improved the 2D accuracy from 1400 nm to 200 nm.

  8. Automated intraoperative calibration for prostate cancer brachytherapy

    Energy Technology Data Exchange (ETDEWEB)

    Kuiran Chen, Thomas; Heffter, Tamas; Lasso, Andras; Pinter, Csaba; Abolmaesumi, Purang; Burdette, E. Clif; Fichtinger, Gabor [Queen' s University, Kingston, Ontario K7L 3N6 (Canada); University of British Columbia, Vancouver, British Columbia V6T 1Z4 (Canada); Acoustic MedSystems, Inc., Champaign, Illinois 61820-3979 (United States); Queen' s University, Kingston, Ontario K7L 3N6 (Canada) and Johns Hopkins University, Baltimore, Maryland 21218-2682 (United States)

    2011-11-15

    Purpose: Prostate cancer brachytherapy relies on an accurate spatial registration between the implant needles and the TRUS image, called ''calibration''. The authors propose a new device and a fast, automatic method to calibrate the brachytherapy system in the operating room, with instant error feedback. Methods: A device was CAD-designed and precision-engineered, which mechanically couples a calibration phantom with an exact replica of the standard brachytherapy template. From real-time TRUS images acquired from the calibration device and processed by the calibration system, the coordinate transformation between the brachytherapy template and the TRUS images was computed automatically. The system instantly generated a report of the target reconstruction accuracy based on the current calibration outcome. Results: Four types of validation tests were conducted. First, 50 independent, real-time calibration trials yielded an average of 0.57 {+-} 0.13 mm line reconstruction error (LRE) relative to ground truth. Second, the averaged LRE was 0.37 {+-} 0.25 mm relative to ground truth in tests with six different commercial TRUS scanners operating at similar imaging settings. Furthermore, testing with five different commercial stepper systems yielded an average of 0.29 {+-} 0.16 mm LRE relative to ground truth. Finally, the system achieved an average of 0.56 {+-} 0.27 mm target registration error (TRE) relative to ground truth in needle insertion tests through the template in a water tank. Conclusions: The proposed automatic, intraoperative calibration system for prostate cancer brachytherapy has achieved high accuracy, precision, and robustness.

  9. Effect of calibration method on Tekscan sensor accuracy.

    Science.gov (United States)

    Brimacombe, Jill M; Wilson, David R; Hodgson, Antony J; Ho, Karen C T; Anglin, Carolyn

    2009-03-01

    Tekscan pressure sensors are used in biomechanics research to measure joint contact loads. While the overall accuracy of these sensors has been reported previously, the effects of different calibration algorithms on sensor accuracy have not been compared. The objectives of this validation study were to determine the most appropriate calibration method supplied in the Tekscan program software and to compare its accuracy to the accuracy obtained with two user-defined calibration protocols. We evaluated the calibration accuracies for test loads within the low range, high range, and full range of the sensor. Our experimental setup used materials representing those found in standard prosthetic joints, i.e., metal against plastic. The Tekscan power calibration was the most accurate of the algorithms provided with the system software, with an overall rms error of 2.7% of the tested sensor range, whereas the linear calibrations resulted in an overall rms error of up to 24% of the tested range. The user-defined ten-point cubic calibration was almost five times more accurate, on average, than the power calibration over the full range, with an overall rms error of 0.6% of the tested range. The user-defined three-point quadratic calibration was almost twice as accurate as the Tekscan power calibration, but was sensitive to the calibration loads used. We recommend that investigators design their own calibration curves not only to improve accuracy but also to understand the range(s) of highest error and to choose the optimal points within the expected sensing range for calibration. Since output and sensor nonlinearity depend on the experimental protocol (sensor type, interface shape and materials, sensor range in use, loading method, etc.), sensor behavior should be investigated for each different application.

  10. Infrared stereo calibration for unmanned ground vehicle navigation

    Science.gov (United States)

    Harguess, Josh; Strange, Shawn

    2014-06-01

    The problem of calibrating two color cameras as a stereo pair has been heavily researched and many off-the-shelf software packages, such as Robot Operating System and OpenCV, include calibration routines that work in most cases. However, the problem of calibrating two infrared (IR) cameras for the purposes of sensor fusion and point could generation is relatively new and many challenges exist. We present a comparison of color camera and IR camera stereo calibration using data from an unmanned ground vehicle. There are two main challenges in IR stereo calibration; the calibration board (material, design, etc.) and the accuracy of calibration pattern detection. We present our analysis of these challenges along with our IR stereo calibration methodology. Finally, we present our results both visually and analytically with computed reprojection errors.

  11. An improved outdoor calibration procedure for broadband ultraviolet radiometers.

    Science.gov (United States)

    Cancillo, M L; Serrano, A; Antón, M; García, J A; Vilaplana, J M; de la Morena, B

    2005-01-01

    This article aims at improving the broadband ultraviolet radiometer's calibration methodology. For this goal, three broadband radiometers are calibrated against a spectrophotometer of reference. Three different one-step calibration models are tested: ratio, first order and second order. The latter is proposed in order to adequately reproduce the high dependence on the solar zenith angle shown by the other two models and, therefore, to improve the calibration performance at high solar elevations. The proposed new second-order model requires no additional information and, thus, keeps the operational character of the one-step methodology. The models are compared in terms of their root mean square error and the most qualified is subsequently validated by comparing its predictions with the spectrophotometer measurements within an independent validation data subset. Results show that the best calibration is achieved by the second-order model, with a mean bias error and mean absolute bias error lower than 2.2 and 6.7%, respectively.

  12. A self-calibration method for tri-axis rotational inertial navigation system

    Science.gov (United States)

    Gao, Pengyu; Li, Kui; Wang, Lei; Liu, Zengjun

    2016-11-01

    The navigation accuracy of the rotational inertial navigation system (RINS) could be greatly improved by periodically rotating the inertial measurement unit (IMU) with gimbals. However, error parameters in RINS should be effectively calibrated and compensated. In this paper, a self-calibration method is proposed for tri-axis RINS using attitude errors and velocity errors as measurements. The proposed calibration scheme is designed as three separate steps, and a certain gimbal rotates continuously in each step. All the error parameters in the RINS are calibrated when the whole scheme finishes. The separate calibration steps reduce the correlations between error parameters, and the observability of errors in this method is clear to demonstrate according to the relations between navigation errors and error parameters when gimbals rotate. Each calibration step only lasts 12 min, thus gyro drifts and accelerometers biases could be regarded as constant. The proposed calibration scheme is tested in both simulation and actual tri-axis RINS, and simulation and experimental results show that all 23 error parameters could be well estimated in tri-axis RINS. A long-term vehicle navigation experiment results show that after calibration and compensation, the navigation performance has doubled approximately, and the velocity accuracy is less than 2 m s-1 while the position accuracy is less than 1500 m, fully illustrating the significance of the proposed self-calibration method in improving the navigation performance of RINS.

  13. System modeling based measurement error analysis of digital sun sensors

    Institute of Scientific and Technical Information of China (English)

    WEI; M; insong; XING; Fei; WANG; Geng; YOU; Zheng

    2015-01-01

    Stringent attitude determination accuracy is required for the development of the advanced space technologies and thus the accuracy improvement of digital sun sensors is necessary.In this paper,we presented a proposal for measurement error analysis of a digital sun sensor.A system modeling including three different error sources was built and employed for system error analysis.Numerical simulations were also conducted to study the measurement error introduced by different sources of error.Based on our model and study,the system errors from different error sources are coupled and the system calibration should be elaborately designed to realize a digital sun sensor with extra-high accuracy.

  14. Landsat TM and ETM+ thermal band calibration

    Science.gov (United States)

    Barsi, J.A.; Schott, J.R.; Palluconi, F. D.; Helder, D.L.; Hook, S.J.; Markham, B.L.; Chander, G.; O'Donnell, E. M.

    2003-01-01

    Landsat-5 has been imaging the Earth since March 1984, and Landsat-7 was added to the series of Landsat instruments in April 1999. The Landsat Project Science Office and the Landsat-7 Image Assessment System have been monitoring the on-board calibration of Landsat-7 since launch. Additionally, two separate university teams have been evaluating the on-board thermal calibration of Landsat-7 through ground-based measurements since launch. Although not monitored as closely over its lifetime, a new effort is currently being made to validate the calibration of Landsat-5. Two university teams are beginning to collect ground truth under Landsat-5, along with using other vicarious calibration methods to go back into the archive to validate the history of the calibration of Landsat-5. This paper considers the calibration efforts for the thermal band, band 6, of both the Landsat-5 and Landsat-7 instruments. Though stable since launch, Landsat-7 had an initial calibration error of about 3 K, and changes were made to correct for this beginning 1 October 2000 for data processed with the National Landsat Archive Production System (NLAPS) and beginning 20 December 2000 for data processed with the Landsat Product Generation System (LPGS). Recent results from Landsat-5 vicarious calibration efforts show an offset of –0.7 K over the lifetime of the instrument. This suggests that historical calibration efforts may have been detecting errors in processing systems rather than changes in the instrument. A correction to the Landsat-5 processing has not yet been implemented but will be in the near future.

  15. Initial SAM Calibration Gas Experiments on Mars: Quadrupole Mass Spectrometer Results and Implications

    Science.gov (United States)

    Franz, Heather B.; Trainer, Melissa G.; Malespin, Charles A.; Mahaffy, Paul R.; Atreya, Sushil K.; Becker, Richard H,; Benna, Mehdi; Conrad, Pamela G.; Eigenbrode, Jennifer L.; Freissinet, Caroline; hide

    2017-01-01

    The Sample Analysis at Mars (SAM) instrument suite of the Mars Science Laboratory (MSL) Curiosity rover is equipped to analyze both martian atmospheric gases and volatiles released by pyrolysis of solid surface materials, with target measurements including chemical and isotopic composition (Mahaffy et al., 2012). To facilitate assessment of instrument performance and validation of results obtained on Mars, SAM houses a calibration cell containing CO2, Ar, N2, Xe, and several fluorinated hydrocarbon compounds (Franz et al., 2014; Mahaffy et al., 2012). This report describes the first two experiments utilizing this calibration cell on Mars and gives results from analysis of data acquired with the SAM Quadrupole Mass Spectrometer (QMS). These data support the accuracy of isotope ratios obtained with the QMS (Conrad et al., 2016; Mahaffy et al., 2013) and provide ground-truth for reassessment of analytical constants required for atmospheric measurements, which were reported in previous contributions (Franz et al., 2015, 2014). The most significant implication of the QMS data involves reinterpretation of pre-launch contamination previously believed to affect only CO abundance measurements (Franz et al., 2015) to affect N2 abundances, as well. The corresponding adjustment to the N2 calibration constant presented here brings the atmospheric volume mixing ratios for Ar and N2 retrieved by SAM into closer agreement with those reported by the Viking mission (Owen et al., 1977; Oyama and Berdahl, 1977).

  16. Initial SAM calibration gas experiments on Mars: Quadrupole mass spectrometer results and implications

    Science.gov (United States)

    Franz, Heather B.; Trainer, Melissa G.; Malespin, Charles A.; Mahaffy, Paul R.; Atreya, Sushil K.; Becker, Richard H.; Benna, Mehdi; Conrad, Pamela G.; Eigenbrode, Jennifer L.; Freissinet, Caroline; Manning, Heidi L. K.; Prats, Benito D.; Raaen, Eric; Wong, Michael H.

    2017-04-01

    The Sample Analysis at Mars (SAM) instrument suite of the Mars Science Laboratory (MSL) Curiosity rover is equipped to analyze both martian atmospheric gases and volatiles released by pyrolysis of solid surface materials, with target measurements including chemical and isotopic composition (Mahaffy et al., 2012). To facilitate assessment of instrument performance and validation of results obtained on Mars, SAM houses a calibration cell containing CO2, Ar, N2, Xe, and several fluorinated hydrocarbon compounds (Franz et al., 2014; Mahaffy et al., 2012). This report describes the first two experiments utilizing this calibration cell on Mars and gives results from analysis of data acquired with the SAM Quadrupole Mass Spectrometer (QMS). These data support the accuracy of isotope ratios obtained with the QMS (Conrad et al., 2016; Mahaffy et al., 2013) and provide ground-truth for reassessment of analytical constants required for atmospheric measurements, which were reported in previous contributions (Franz et al., 2015, 2014). The most significant implication of the QMS data involves reinterpretation of pre-launch contamination previously believed to affect only CO abundance measurements (Franz et al., 2015) to affect N2 abundances, as well. The corresponding adjustment to the N2 calibration constant presented here brings the atmospheric volume mixing ratios for Ar and N2 retrieved by SAM into closer agreement with those reported by the Viking mission (Owen et al., 1977; Oyama and Berdahl, 1977).

  17. Three-point bridge calibration with one resistor

    Science.gov (United States)

    Harrison, D. R.; Brown, R. M.

    1974-01-01

    Method calibrates transducer bridge curing unbalanced condition and line resistance errors are negligible. Series resistance method can be automated easily and controlled by 2-bit information source which provide 4 states for switches.

  18. Calibration of the fluxgate CSC vector magnetometers

    DEFF Research Database (Denmark)

    Merayo, José M.G.; Risbo, Torben; Primdahl, Fritz

    1995-01-01

    sensor giving an error corresponding to 5 to 10 nT in full scale field. It rotates as well the CSC sensor axes. In principle this is due to the presence of soft magnetic material. No remanent magnetization has been observed. Hermann Luehr has ratified this fact and recommended a final calibration...

  19. Phase calibration scheme for a ``T'' array

    Science.gov (United States)

    Ramesh, R.; Subramanian, K. R.; Sastry, Ch. V.

    1999-10-01

    A calibration scheme based on closure and redundancy techniques is described for correcting the phase errors in the complex visibilities observed with a T-shaped radio interferometer array. Practical details of the scheme are illustrated with reference to the Gauribidanur radioheliograph (GRH).

  20. Novel calibration algorithm for a three-axis strapdown magnetometer.

    Science.gov (United States)

    Liu, Yan Xia; Li, Xi Sheng; Zhang, Xiao Juan; Feng, Yi Bo

    2014-05-14

    A complete error calibration model with 12 independent parameters is established by analyzing the three-axis magnetometer error mechanism. The said model conforms to an ellipsoid restriction, the parameters of the ellipsoid equation are estimated, and the ellipsoid coefficient matrix is derived. However, the calibration matrix cannot be determined completely, as there are fewer ellipsoid parameters than calibration model parameters. Mathematically, the calibration matrix derived from the ellipsoid coefficient matrix by a different matrix decomposition method is not unique, and there exists an unknown rotation matrix R between them. This paper puts forward a constant intersection angle method (angles between the geomagnetic field and gravitational field are fixed) to estimate R. The Tikhonov method is adopted to solve the problem that rounding errors or other errors may seriously affect the calculation results of R when the condition number of the matrix is very large. The geomagnetic field vector and heading error are further corrected by R. The constant intersection angle method is convenient and practical, as it is free from any additional calibration procedure or coordinate transformation. In addition, the simulation experiment indicates that the heading error declines from ±1° calibrated by classical ellipsoid fitting to ±0.2° calibrated by a constant intersection angle method, and the signal-to-noise ratio is 50 dB. The actual experiment exhibits that the heading error is further corrected from ±0.8° calibrated by the classical ellipsoid fitting to ±0.3° calibrated by a constant intersection angle method.

  1. Cumulative sum quality control for calibrated breast density measurements

    Energy Technology Data Exchange (ETDEWEB)

    Heine, John J.; Cao Ke; Beam, Craig [Cancer Prevention and Control Division, Moffitt Cancer Center, 12902 Magnolia Drive, Tampa, Florida 33612 (United States); Division of Epidemiology and Biostatistics, School of Public Health, University of Illinois at Chicago, 1603 W. Taylor St., Chicago, Illinois 60612 (United States)

    2009-12-15

    Purpose: Breast density is a significant breast cancer risk factor. Although various methods are used to estimate breast density, there is no standard measurement for this important factor. The authors are developing a breast density standardization method for use in full field digital mammography (FFDM). The approach calibrates for interpatient acquisition technique differences. The calibration produces a normalized breast density pixel value scale. The method relies on first generating a baseline (BL) calibration dataset, which required extensive phantom imaging. Standardizing prospective mammograms with calibration data generated in the past could introduce unanticipated error in the standardized output if the calibration dataset is no longer valid. Methods: Sample points from the BL calibration dataset were imaged approximately biweekly over an extended timeframe. These serial samples were used to evaluate the BL dataset reproducibility and quantify the serial calibration accuracy. The cumulative sum (Cusum) quality control method was used to evaluate the serial sampling. Results: There is considerable drift in the serial sample points from the BL calibration dataset that is x-ray beam dependent. Systematic deviation from the BL dataset caused significant calibration errors. This system drift was not captured with routine system quality control measures. Cusum analysis indicated that the drift is a sign of system wear and eventual x-ray tube failure. Conclusions: The BL calibration dataset must be monitored and periodically updated, when necessary, to account for sustained system variations to maintain the calibration accuracy.

  2. Systematic Calibration for Ultra-High Accuracy Inertial Measurement Units.

    Science.gov (United States)

    Cai, Qingzhong; Yang, Gongliu; Song, Ningfang; Liu, Yiliang

    2016-06-22

    An inertial navigation system (INS) has been widely used in challenging GPS environments. With the rapid development of modern physics, an atomic gyroscope will come into use in the near future with a predicted accuracy of 5 × 10(-6)°/h or better. However, existing calibration methods and devices can not satisfy the accuracy requirements of future ultra-high accuracy inertial sensors. In this paper, an improved calibration model is established by introducing gyro g-sensitivity errors, accelerometer cross-coupling errors and lever arm errors. A systematic calibration method is proposed based on a 51-state Kalman filter and smoother. Simulation results show that the proposed calibration method can realize the estimation of all the parameters using a common dual-axis turntable. Laboratory and sailing tests prove that the position accuracy in a five-day inertial navigation can be improved about 8% by the proposed calibration method. The accuracy can be improved at least 20% when the position accuracy of the atomic gyro INS can reach a level of 0.1 nautical miles/5 d. Compared with the existing calibration methods, the proposed method, with more error sources and high order small error parameters calibrated for ultra-high accuracy inertial measurement units (IMUs) using common turntables, has a great application potential in future atomic gyro INSs.

  3. Systematic Calibration for Ultra-High Accuracy Inertial Measurement Units

    Directory of Open Access Journals (Sweden)

    Qingzhong Cai

    2016-06-01

    Full Text Available An inertial navigation system (INS has been widely used in challenging GPS environments. With the rapid development of modern physics, an atomic gyroscope will come into use in the near future with a predicted accuracy of 5 × 10−6°/h or better. However, existing calibration methods and devices can not satisfy the accuracy requirements of future ultra-high accuracy inertial sensors. In this paper, an improved calibration model is established by introducing gyro g-sensitivity errors, accelerometer cross-coupling errors and lever arm errors. A systematic calibration method is proposed based on a 51-state Kalman filter and smoother. Simulation results show that the proposed calibration method can realize the estimation of all the parameters using a common dual-axis turntable. Laboratory and sailing tests prove that the position accuracy in a five-day inertial navigation can be improved about 8% by the proposed calibration method. The accuracy can be improved at least 20% when the position accuracy of the atomic gyro INS can reach a level of 0.1 nautical miles/5 d. Compared with the existing calibration methods, the proposed method, with more error sources and high order small error parameters calibrated for ultra-high accuracy inertial measurement units (IMUs using common turntables, has a great application potential in future atomic gyro INSs.

  4. SIM-Lite Mission Spectral Calibration Sensitivities and Refinements

    Science.gov (United States)

    Zhai, C.; An, X.; Goullioud, R.; Nemati, B.; Shao, M.; Shen, J.; Wehmeier, U.; Wang, X.; Weiler, M.; Werne, T.; Wu, J.

    2010-01-01

    SIM-Lite missions will perform astrometry at microarcsecond accuracy using star light interferometry. For typical baselines that are shorter than 10 meters, this requires to measure optical path difference (OPD) accurate to tens of picometers calling for highly accurate calibration. A major challenge is to calibrate the star spectral dependency in fringe measurements -- the spectral calibration. Previously, we have developed a spectral calibration and estimation scheme achieving picometer level accuracy. In this paper, we present the improvements regarding the application of this scheme from sensitivity studies. Data from the SIM Spectral Calibration Development Unit (SCDU) test facility shows that the fringe OPD is very sensitive to pointings of both beams from the two arms of the interferometer. This sensitivity coupled with a systematic pointing error provides a mechanism to explain the bias changes in 2007. Improving system alignment can effectively reduce this sensitivity and thus errors due to pointing errors. Modeling this sensitivity can lead to further improvement in data processing. We then investigate the sensitivity to a model parameter, the bandwidth used in the fringe model, which presents an interesting trade between systematic and random errors. Finally we show the mitigation of calibration errors due to system drifts by interpolating instrument calibrations. These improvements enable us to use SCDU data to demonstrate that SIM-Lite missions can meet the 1pm noise floor requirement for detecting earth-like exoplanets.

  5. A New Technique for CCD Camera Auto-Calibration

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    A novel feature-round-based coplanar drone for the CCD camera auto-calibration is designed. Based on the ellipse similarity, an ellipse recognition algorithm is proposed. The experiment indicates the calibration error is less than 0.4 pixel.

  6. Performance of MODIS Thermal Emissive Bands On-orbit Calibration Algorithms

    Science.gov (United States)

    Xiong, Xiaoxiong; Chang, T.

    2009-01-01

    serves as the thermal calibration source and the SV provides measurements for the sensor's background and offsets. MODIS on-board BB is a v-grooved plate with its temperature measured using 12 platinum resistive thermistors (PRT) uniformly embedded in the BB substrate. All the BB thermistors were characterized pre-launch with reference to the NIST temperature standards. Unlike typical BB operations in many heritage sensors, which have no temperature control capability, the MODIS on-board BB can be operated at any temperatures between instrument ambient (about 270K) and 315K and can also be varied continuously within this range. This feature has significantly enhanced the MODIS' capability of tracking and updating the TEB nonlinear calibration coefficients over its entire mission. Following a brief description of MODIS TEB on-orbit calibration methodologies and its onboard BB operational activities, this paper provides a comprehensive performance assessment of MODIS TEB quadratic calibration algorithm. It examines the scan-by-scan, orbit-by-orbit, daily, and seasonal variations of detector responses and associated impact due changes in the CFPA and instrument temperatures. Specifically, this paper will analyze the contribution by each individual thermal emissive source term (BB, scan cavity, and scan mirror), the impact on the Level 1 B data product quality due to pre-launch and on-orbit calibration uncertainties. A comparison of Terra and Aqua TEB on-orbit performance, lessons learned, and suggestions for future improvements will also be made.

  7. Error handling strategies in multiphase inverse modeling

    Energy Technology Data Exchange (ETDEWEB)

    Finsterle, S.; Zhang, Y.

    2010-12-01

    Parameter estimation by inverse modeling involves the repeated evaluation of a function of residuals. These residuals represent both errors in the model and errors in the data. In practical applications of inverse modeling of multiphase flow and transport, the error structure of the final residuals often significantly deviates from the statistical assumptions that underlie standard maximum likelihood estimation using the least-squares method. Large random or systematic errors are likely to lead to convergence problems, biased parameter estimates, misleading uncertainty measures, or poor predictive capabilities of the calibrated model. The multiphase inverse modeling code iTOUGH2 supports strategies that identify and mitigate the impact of systematic or non-normal error structures. We discuss these approaches and provide an overview of the error handling features implemented in iTOUGH2.

  8. Calibrating Photometric Redshifts of Luminous Red Galaxies

    CERN Document Server

    Padmanabhan, N; Schlegel, D J; Bridges, T J; Brinkmann, J; Cannon, R; Connolly, A J; Croom, S M; Csabai, I; Drinkwater, M; Eisenstein, D J; Hewett, P C; Loveday, J; Nichol, R C; Pimbblet, K A; De Propris, R; Schneider, D P; Scranton, R; Seljak, U; Shanks, T; Szapudi, I; Szalay, A S; Wake, D; Padmanabhan, Nikhil; Budavari, Tamas; Schlegel, David J.; Bridges, Terry; Brinkmann, Jonathan; Cannon, Russell; Connolly, Andrew J.; Croom, Scott M.; Csabai, Istvan; Drinkwater, Michael; Eisenstein, Daniel J.; Hewett, Paul C.; Loveday, Jon; Nichol, Robert C.; Pimbblet, Kevin A.; Propris, Roberto De; Schneider, Donald P.; Scranton, Ryan; Seljak, Uros; Shanks, Tom; Szapudi, Istvan; Szalay, Alexander S.; Wake, David

    2004-01-01

    We discuss the construction of a photometric redshift catalogue of Luminous Red Galaxies (LRGs) from the Sloan Digital Sky Survey (SDSS), emphasizing the principal steps necessary for constructing such a catalogue -- (i) photometrically selecting the sample, (ii) measuring photometric redshifts and their error distributions, (iii) and estimating the true redshift distribution. We compare two photometric redshift algorithms for these data and find that they give comparable results. Calibrating against the SDSS and SDSS-2dF spectroscopic surveys, we find that the photometric redshift accuracy is $\\sigma \\sim 0.03$ for redshifts less than 0.55 and worsens at higher redshift ($\\sim 0.06$). These errors are caused by photometric scatter, as well as systematic errors in the templates, filter curves, and photometric zeropoints. We also parametrize the photometric redshift error distribution with a sum of Gaussians, and use this model to deconvolve the errors from the measured photometric redshift distribution to est...

  9. Analysis of errors in forensic science

    Directory of Open Access Journals (Sweden)

    Mingxiao Du

    2017-01-01

    Full Text Available Reliability of expert testimony is one of the foundations of judicial justice. Both expert bias and scientific errors affect the reliability of expert opinion, which in turn affects the trustworthiness of the findings of fact in legal proceedings. Expert bias can be eliminated by replacing experts; however, it may be more difficult to eliminate scientific errors. From the perspective of statistics, errors in operation of forensic science include systematic errors, random errors, and gross errors. In general, process repetition and abiding by the standard ISO/IEC:17025: 2005, general requirements for the competence of testing and calibration laboratories, during operation are common measures used to reduce errors that originate from experts and equipment, respectively. For example, to reduce gross errors, the laboratory can ensure that a test is repeated several times by different experts. In applying for forensic principles and methods, the Federal Rules of Evidence 702 mandate that judges consider factors such as peer review, to ensure the reliability of the expert testimony. As the scientific principles and methods may not undergo professional review by specialists in a certain field, peer review serves as an exclusive standard. This study also examines two types of statistical errors. As false-positive errors involve a higher possibility of an unfair decision-making, they should receive more attention than false-negative errors.

  10. Landsat-7 ETM+ radiometric calibration status

    Science.gov (United States)

    Barsi, Julia A.; Markham, Brian L.; Czapla-Myers, Jeffrey S.; Helder, Dennis L.; Hook, Simon J.; Schott, John R.; Haque, Md. Obaidul

    2016-09-01

    Now in its 17th year of operation, the Enhanced Thematic Mapper + (ETM+), on board the Landsat-7 satellite, continues to systematically acquire imagery of the Earth to add to the 40+ year archive of Landsat data. Characterization of the ETM+ on-orbit radiometric performance has been on-going since its launch in 1999. The radiometric calibration of the reflective bands is still monitored using on-board calibration devices, though the Pseudo-Invariant Calibration Sites (PICS) method has proven to be an effective tool as well. The calibration gains were updated in April 2013 based primarily on PICS results, which corrected for a change of as much as -0.2%/year degradation in the worst case bands. A new comparison with the SADE database of PICS results indicates no additional degradation in the updated calibration. PICS data are still being tracked though the recent trends are not well understood. The thermal band calibration was updated last in October 2013 based on a continued calibration effort by NASA/Jet Propulsion Lab and Rochester Institute of Technology. The update accounted for a 0.036 W/m2 sr μm or 0.26K at 300K bias error. The updated lifetime trend is now stable to within +/- 0.4K.

  11. Increased Automation in Stereo Camera Calibration Techniques

    Directory of Open Access Journals (Sweden)

    Brandi House

    2006-08-01

    Full Text Available Robotic vision has become a very popular field in recent years due to the numerous promising applications it may enhance. However, errors within the cameras and in their perception of their environment can cause applications in robotics to fail. To help correct these internal and external imperfections, stereo camera calibrations are performed. There are currently many accurate methods of camera calibration available; however, most or all of them are time consuming and labor intensive. This research seeks to automate the most labor intensive aspects of a popular calibration technique developed by Jean-Yves Bouguet. His process requires manual selection of the extreme corners of a checkerboard pattern. The modified process uses embedded LEDs in the checkerboard pattern to act as active fiducials. Images are captured of the checkerboard with the LEDs on and off in rapid succession. The difference of the two images automatically highlights the location of the four extreme corners, and these corner locations take the place of the manual selections. With this modification to the calibration routine, upwards of eighty mouse clicks are eliminated per stereo calibration. Preliminary test results indicate that accuracy is not substantially affected by the modified procedure. Improved automation to camera calibration procedures may finally penetrate the barriers to the use of calibration in practice.

  12. Increased Automation in Stereo Camera Calibration Techniques

    Directory of Open Access Journals (Sweden)

    Brandi House

    2006-08-01

    Full Text Available Robotic vision has become a very popular field in recent years due to the numerous promising applications it may enhance. However, errors within the cameras and in their perception of their environment can cause applications in robotics to fail. To help correct these internal and external imperfections, stereo camera calibrations are performed. There are currently many accurate methods of camera calibration available; however, most or all of them are time consuming and labor intensive. This research seeks to automate the most labor intensive aspects of a popular calibration technique developed by Jean-Yves Bouguet. His process requires manual selection of the extreme corners of a checkerboard pattern. The modified process uses embedded LEDs in the checkerboard pattern to act as active fiducials. Images are captured of the checkerboard with the LEDs on and off in rapid succession. The difference of the two images automatically highlights the location of the four extreme corners, and these corner locations take the place of the manual selections. With this modification to the calibration routine, upwards of eighty mouse clicks are eliminated per stereo calibration. Preliminary test results indicate that accuracy is not substantially affected by the modified procedure. Improved automation to camera calibration procedures may finally penetrate the barriers to the use of calibration in practice.

  13. Calibrators and control samples for bilirubinometers.

    Science.gov (United States)

    Blijenberg, B G; Brügmann, G; Geilenkeuser, W J; Kusyschyn, R; Röhle, G; Schlebusch, H; Schneider, C

    1993-06-01

    The different matrix properties of neonatal serum and commercial control samples can lead to considerable errors in the calibration and control of bilirubinometers. These difficulties can be avoided by calibration with serum from healthy adults which is supplemented with unconjugated bilirubin. But this procedure is impracticable for most routine laboratories. Under certain preconditions, control samples, with bilirubin concentrations determined with correctly calibrated bilirubinometers or spectrophotometers, are also suitable as calibrators. This was established by determination of the bilirubin concentration of 16 different control samples, using both the reference method and correctly calibrated bilirubinometers or spectrophotometers in three or four specialist laboratories. This was also confirmed in several interlaboratory surveys, some involving up to 72 laboratories. The results of these investigations show that a control sample should be used for the calibration of a bilirubinometer only if it meets the following preconditions: 1. There should be no significant difference between the bilirubin values determined with the reference method and with a correctly calibrated spectrophotometer or bilirubinometer. 2. The bilirubin concentration should lie in the range 230-300 mumol/l. The photometric response of bilirubinometers has a limited linear range, so that analytical results greater than 300 mumol/l must be rated as basically unreliable.

  14. Consequences of Secondary Calibrations on Divergence Time Estimates.

    Directory of Open Access Journals (Sweden)

    John J Schenk

    Full Text Available Secondary calibrations (calibrations based on the results of previous molecular dating studies are commonly applied in divergence time analyses in groups that lack fossil data; however, the consequences of applying secondary calibrations in a relaxed-clock approach are not fully understood. I tested whether applying the posterior estimate from a primary study as a prior distribution in a secondary study results in consistent age and uncertainty estimates. I compared age estimates from simulations with 100 randomly replicated secondary trees. On average, the 95% credible intervals of node ages for secondary estimates were significantly younger and narrower than primary estimates. The primary and secondary age estimates were significantly different in 97% of the replicates after Bonferroni corrections. Greater error in magnitude was associated with deeper than shallower nodes, but the opposite was found when standardized by median node age, and a significant positive relationship was determined between the number of tips/age of secondary trees and the total amount of error. When two secondary calibrated nodes were analyzed, estimates remained significantly different, and although the minimum and median estimates were associated with less error, maximum age estimates and credible interval widths had greater error. The shape of the prior also influenced error, in which applying a normal, rather than uniform, prior distribution resulted in greater error. Secondary calibrations, in summary, lead to a false impression of precision and the distribution of age estimates shift away from those that would be inferred by the primary analysis. These results suggest that secondary calibrations should not be applied as the only source of calibration in divergence time analyses that test time-dependent hypotheses until the additional error associated with secondary calibrations is more properly modeled to take into account increased uncertainty in age estimates.

  15. A Novel Calibrator for Electronic Transformers Based on IEC 61850

    Directory of Open Access Journals (Sweden)

    Baoxiang PAN

    2013-01-01

    Full Text Available It is necessary for electronic transformer to make calibration before putting it into practice. To solve the problems in actual calibration process, a novel electronic transformer calibrator is designed. In principle, this system adopts both the direct method and the difference method, which are two popular methods for electronic transformer calibration, by this way the application of the system is extended with its reliability improved. In the system design, based on virtual instrument technology, LabVIEW and WinPCap toolkit are used to develop the application software, and it is able to calibrate those electronic transformers following the standard of IEC 61850. In the calculation of ratio and phase error based on fast Fourier transform, a new window function is introduced, and thus the accuracy of calibration, influenced by the frequency vibration, is improved. This research provides theoretic support and practical reference to the development of intelligent calibrator for electronic transformers.

  16. Calibration of Geodetic Instruments

    Directory of Open Access Journals (Sweden)

    Marek Bajtala

    2005-06-01

    Full Text Available The problem of metrology and security systems of unification, correctness and standard reproducibilities belong to the preferred requirements of theory and technical practice in geodesy. Requirements on the control and verification of measured instruments and equipments increase and the importance and up-to-date of calibration get into the foreground. Calibration possibilities of length-scales (of electronic rangefinders and angle-scales (of horizontal circles of geodetic instruments. Calibration of electronic rangefinders on the linear comparative baseline in terrain. Primary standard of planar angle – optical traverse and its exploitation for calibration of the horizontal circles of theodolites. The calibration equipment of the Institute of Slovak Metrology in Bratislava. The Calibration process and results from the calibration of horizontal circles of selected geodetic instruments.

  17. Analysis of error-prone survival data under additive hazards models: measurement error effects and adjustments.

    Science.gov (United States)

    Yan, Ying; Yi, Grace Y

    2016-07-01

    Covariate measurement error occurs commonly in survival analysis. Under the proportional hazards model, measurement error effects have been well studied, and various inference methods have been developed to correct for error effects under such a model. In contrast, error-contaminated survival data under the additive hazards model have received relatively less attention. In this paper, we investigate this problem by exploring measurement error effects on parameter estimation and the change of the hazard function. New insights of measurement error effects are revealed, as opposed to well-documented results for the Cox proportional hazards model. We propose a class of bias correction estimators that embraces certain existing estimators as special cases. In addition, we exploit the regression calibration method to reduce measurement error effects. Theoretical results for the developed methods are established, and numerical assessments are conducted to illustrate the finite sample performance of our methods.

  18. The VTTVIS line imaging spectrometer - principles, error sources, and calibration

    DEFF Research Database (Denmark)

    Jørgensen, R.N.

    2002-01-01

    Hyperspectral imaging with a spatial resolution of a few mm2 has proved to have a great potential within crop and weed classification and also within nutrient diagnostics. A commonly used hyperspectral imaging system is based on the Prism-Grating-Prism(PGP) principles produced by Specim Ltd....... Finland. One of the novel systems based on the PGP spectrograph (VTTVIS) was build by The Department of Agricultural Sciences, AgroTechnology, KVL, Denmark, in 1995. Several other agricultural institutions havenow implemented the technology in their research. None of these has published any thoroughly...

  19. Skew redundant MEMS IMU calibration using a Kalman filter

    Science.gov (United States)

    Jafari, M.; Sahebjameyan, M.; Moshiri, B.; Najafabadi, T. A.

    2015-10-01

    In this paper, a novel calibration procedure for skew redundant inertial measurement units (SRIMUs) based on micro-electro mechanical systems (MEMS) is proposed. A general model of the SRIMU measurements is derived which contains the effects of bias, scale factor error and misalignments. For more accuracy, the effect of lever arms of the accelerometers to the center of the table are modeled and compensated in the calibration procedure. Two separate Kalman filters (KFs) are proposed to perform the estimation of error parameters for gyroscopes and accelerometers. The predictive error minimization (PEM) stochastic modeling method is used to simultaneously model the effect of bias instability and random walk noise on the calibration Kalman filters to diminish the biased estimations. The proposed procedure is simulated numerically and has expected experimental results. The calibration maneuvers are applied using a two-axis angle turntable in a way that the persistency of excitation (PE) condition for parameter estimation is met. For this purpose, a trapezoidal calibration profile is utilized to excite different deterministic error parameters of the accelerometers and a pulse profile is used for the gyroscopes. Furthermore, to evaluate the performance of the proposed KF calibration method, a conventional least squares (LS) calibration procedure is derived for the SRIMUs and the simulation and experimental results compare the functionality of the two proposed methods with each other.

  20. An Overview of MODIS Calibration and Characterization and Lessons Learned

    Science.gov (United States)

    Xiong, Xiaxiong; Wenny, B.; Barnes, W. L.; Salomonson, V. V.

    2009-01-01

    The Moderate Resolution Imaging Spectroradiometer (MODIS) is a key instrument for NASA's EOS missions. Two nearly identical copies have flown on the Terra and Aqua spacecraft for more than 9 years and 6 years since their launch in December 1999 and May 2002, respectively. MODIS observations and associated data products have been widely used by the science community and users worldwide for studies of Earth's system of land, oceans, and atmosphere. MODIS was developed based on the desire of the science community to extend and enhance heritage sensors' data records. It was designed with enhancements made over its heritage sensors in terms of its spectral, spatial, and radiometric characteristics. It is a cross-track scanning radiometer, that uses a two-sided scan mirror, collecting data in 36 spectral bands covering spectral regions of visible (VIS), near-infrared (NIR), short-wave infrared (SWIR), mid-wave infrared (MWIR), and long-wave infrared (LWIR). The VIS, NIR, and SWIR bands (bands 1-19 and 26), which make measurements of daytime surface reflected radiances, are referred to as the reflective solar bands (RSB). The MWIR and LWIR bands (20-25 and 27-36), which measure both the daytime and nighttime scene emissive radiances, are thus referred to as the thermal emissive bands (TEB). In this paper, we provide an overview of MODIS instrument calibration and characterization methodologies, activities, and results from pre-launch to post launch, with emphasis on the lessons learned from its design to on-orbit operation. Currently, both instruments are operated normally and all the on-orbit calibration activities are performed on a regular basis with some at slightly reduced frequencies. The TEB responses have been extremely stable with less than 0.3% change per year. For the RSB, the changes are wavelength and scan angle dependent with the largest changes in the VIS spectral bands. As both Terra and Aqua MODIS continue to operate beyond their prime missions, constant

  1. Computer Generated Hologram System for Wavefront Measurement System Calibration

    Science.gov (United States)

    Olczak, Gene

    2011-01-01

    Computer Generated Holograms (CGHs) have been used for some time to calibrate interferometers that require nulling optics. A typical scenario is the testing of aspheric surfaces with an interferometer placed near the paraxial center of curvature. Existing CGH technology suffers from a reduced capacity to calibrate middle and high spatial frequencies. The root cause of this shortcoming is as follows: the CGH is not placed at an image conjugate of the asphere due to limitations imposed by the geometry of the test and the allowable size of the CGH. This innovation provides a calibration system where the imaging properties in calibration can be made comparable to the test configuration. Thus, if the test is designed to have good imaging properties, then middle and high spatial frequency errors in the test system can be well calibrated. The improved imaging properties are provided by a rudimentary auxiliary optic as part of the calibration system. The auxiliary optic is simple to characterize and align to the CGH. Use of the auxiliary optic also reduces the size of the CGH required for calibration and the density of the lines required for the CGH. The resulting CGH is less expensive than the existing technology and has reduced write error and alignment error sensitivities. This CGH system is suitable for any kind of calibration using an interferometer when high spatial resolution is required. It is especially well suited for tests that include segmented optical components or large apertures.

  2. Simultaneous calibration phantom commission and geometry calibration in cone beam CT

    Science.gov (United States)

    Xu, Yuan; Yang, Shuai; Ma, Jianhui; Li, Bin; Wu, Shuyu; Qi, Hongliang; Zhou, Linghong

    2017-09-01

    Geometry calibration is a vital step for describing the geometry of a cone beam computed tomography (CBCT) system and is a prerequisite for CBCT reconstruction. In current methods, calibration phantom commission and geometry calibration are divided into two independent tasks. Small errors in ball-bearing (BB) positioning in the phantom-making step will severely degrade the quality of phantom calibration. To solve this problem, we propose an integrated method to simultaneously realize geometry phantom commission and geometry calibration. Instead of assuming the accuracy of the geometry phantom, the integrated method considers BB centers in the phantom as an optimized parameter in the workflow. Specifically, an evaluation phantom and the corresponding evaluation contrast index are used to evaluate geometry artifacts for optimizing the BB coordinates in the geometry phantom. After utilizing particle swarm optimization, the CBCT geometry and BB coordinates in the geometry phantom are calibrated accurately and are then directly used for the next geometry calibration task in other CBCT systems. To evaluate the proposed method, both qualitative and quantitative studies were performed on simulated and realistic CBCT data. The spatial resolution of reconstructed images using dental CBCT can reach up to 15 line pair cm-1. The proposed method is also superior to the Wiesent method in experiments. This paper shows that the proposed method is attractive for simultaneous and accurate geometry phantom commission and geometry calibration.

  3. Shear calibration biases in weak lensing surveys

    CERN Document Server

    Hirata, C M; Hirata, Christopher M.; Seljak, Uros

    2003-01-01

    We investigate biases induced by the conversion between the observed image shape to shear distortion in current weak lensing analysis methods. Such overall calibration biases cannot be detected by the standard tests such as E/B decomposition or calibration with stars. We find that the non-Gaussianity of point spread function has a significant effect and can lead to up to 15 per cent error on the linear amplitude of fluctuations sigma_8 depending on the method of analysis. This could explain some of the discrepancies seen in recent amplitude determinations from weak lensing. Using an elliptical Laguerre expansion method we develop a re-Gaussianization method which reduces the error to calibration error of order 1 per cent even for poorly resolved galaxies. We also discuss a new type of shear selection bias which results in up to roughly 8 percent underestimation of the signal. It is expected to scale with redshift, inducing errors in the growth factor extraction if not properly corrected for. Understanding and...

  4. Aquarius L-Band Radiometers Calibration Using Cold Sky Observations

    Science.gov (United States)

    Dinnat, Emmanuel P.; Le Vine, David M.; Piepmeier, Jeffrey R.; Brown, Shannon T.; Hong, Liang

    2015-01-01

    An important element in the calibration plan for the Aquarius radiometers is to look at the cold sky. This involves rotating the satellite 180 degrees from its nominal Earth viewing configuration to point the main beams at the celestial sky. At L-band, the cold sky provides a stable, well-characterized scene to be used as a calibration reference. This paper describes the cold sky calibration for Aquarius and how it is used as part of the absolute calibration. Cold sky observations helped establish the radiometer bias, by correcting for an error in the spillover lobe of the antenna pattern, and monitor the long-term radiometer drift.

  5. SMAP RADAR Calibration and Validation

    Science.gov (United States)

    West, R. D.; Jaruwatanadilok, S.; Chaubel, M. J.; Spencer, M.; Chan, S. F.; Chen, C. W.; Fore, A.

    2015-12-01

    The Soil Moisture Active Passive (SMAP) mission launched on Jan 31, 2015. The mission employs L-band radar and radiometer measurements to estimate soil moisture with 4% volumetric accuracy at a resolution of 10 km, and freeze-thaw state at a resolution of 1-3 km. Immediately following launch, there was a three month instrument checkout period, followed by six months of level 1 (L1) calibration and validation. In this presentation, we will discuss the calibration and validation activities and results for the L1 radar data. Early SMAP radar data were used to check commanded timing parameters, and to work out issues in the low- and high-resolution radar processors. From April 3-13 the radar collected receive only mode data to conduct a survey of RFI sources. Analysis of the RFI environment led to a preferred operating frequency. The RFI survey data were also used to validate noise subtraction and scaling operations in the radar processors. Normal radar operations resumed on April 13. All radar data were examined closely for image quality and calibration issues which led to improvements in the radar data products for the beta release at the end of July. Radar data were used to determine and correct for small biases in the reported spacecraft attitude. Geo-location was validated against coastline positions and the known positions of corner reflectors. Residual errors at the time of the beta release are about 350 m. Intra-swath biases in the high-resolution backscatter images are reduced to less than 0.3 dB for all polarizations. Radiometric cross-calibration with Aquarius was performed using areas of the Amazon rain forest. Cross-calibration was also examined using ocean data from the low-resolution processor and comparing with the Aquarius wind model function. Using all a-priori calibration constants provided good results with co-polarized measurements matching to better than 1 dB, and cross-polarized measurements matching to about 1 dB in the beta release. During the

  6. SCIAMACHY Level 1 data: calibration concept and in-flight calibration

    Directory of Open Access Journals (Sweden)

    G. Lichtenberg

    2006-01-01

    Full Text Available The calibration of SCIAMACHY was thoroughly checked since the instrument was launched on-board ENVISAT in February 2002. While SCIAMACHY's functional performance is excellent since launch, a number of technical difficulties have appeared, that required adjustments to the calibration. The problems can be separated into three types: (1 Those caused by the instrument and/or platform environment. Among these are the high water content in the satellite structure and/or MLI layer. This results in the deposition of ice on the detectors in channels 7 and 8 which seriously affects the retrievals in the IR, mostly because of the continuous change of the slit function caused by scattering of the light through the ice layer. Additionally a light leak in channel 7 severely hampers any retrieval from this channel. (2 Problems due to errors in the on-ground calibration and/or data processing affecting for example the radiometric calibration. A new approach based on a mixture of on-ground and in-flight data is shortly described here. (3 Problems caused by principal limitations of the calibration concept, e.g. the possible appearance of spectral structures after the polarisation correction due to unavoidable errors in the determination of atmospheric polarisation. In this paper we give a complete overview of the calibration and problems that still have to be solved. We will also give an indication of the effect of calibration problems on retrievals where possible. Since the operational processing chain is currently being updated and no newly processed data are available at this point in time, for some calibration issues only a rough estimate of the effect on Level 2 products can be given. However, it is the intention of this paper to serve as a future reference for detailed studies into specific calibration issues.

  7. [Survey in hospitals. Nursing errors, error culture and error management].

    Science.gov (United States)

    Habermann, Monika; Cramer, Henning

    2010-09-01

    Knowledge on errors is important to design safe nursing practice and its framework. This article presents results of a survey on this topic, including data of a representative sample of 724 nurses from 30 German hospitals. Participants predominantly remembered medication errors. Structural and organizational factors were rated as most important causes of errors. Reporting rates were considered low; this was explained by organizational barriers. Nurses in large part expressed having suffered from mental problems after error events. Nurses' perception focussing on medication errors seems to be influenced by current discussions which are mainly medication-related. This priority should be revised. Hospitals' risk management should concentrate on organizational deficits and positive error cultures. Decision makers are requested to tackle structural problems such as staff shortage.

  8. Calibration of mass spectrometric peptide mass fingerprint data without specific external or internal calibrants

    Directory of Open Access Journals (Sweden)

    Lalowski Maciej

    2005-08-01

    Full Text Available Abstract Background Peptide Mass Fingerprinting (PMF is a widely used mass spectrometry (MS method of analysis of proteins and peptides. It relies on the comparison between experimentally determined and theoretical mass spectra. The PMF process requires calibration, usually performed with external or internal calibrants of known molecular masses. Results We have introduced two novel MS calibration methods. The first method utilises the local similarity of peptide maps generated after separation of complex protein samples by two-dimensional gel electrophoresis. It computes a multiple peak-list alignment of the data set using a modified Minimum Spanning Tree (MST algorithm. The second method exploits the idea that hundreds of MS samples are measured in parallel on one sample support. It improves the calibration coefficients by applying a two-dimensional Thin Plate Splines (TPS smoothing algorithm. We studied the novel calibration methods utilising data generated by three different MALDI-TOF-MS instruments. We demonstrate that a PMF data set can be calibrated without resorting to external or relying on widely occurring internal calibrants. The methods developed here were implemented in R and are part of the BioConductor package mscalib available from http://www.bioconductor.org. Conclusion The MST calibration algorithm is well suited to calibrate MS spectra of protein samples resulting from two-dimensional gel electrophoretic separation. The TPS based calibration algorithm might be used to correct systematic mass measurement errors observed for large MS sample supports. As compared to other methods, our combined MS spectra calibration strategy increases the peptide/protein identification rate by an additional 5 – 15%.

  9. Calibration of rings using multi-step and reversal

    DEFF Research Database (Denmark)

    Savio, Enrico; Tosello, Guido; De Chiffre, Leonardo

    2003-01-01

    This work concerns the application of multi-orientation techniques on CMMs for form error calibration of high accuracy workpieces. The form measurement capability of commercial CMMs is typically limited to some micrometer, e.g. for the inspection of roundness. The method presented herein deals...... with achieving sub-micrometer uncertainties in the calibration of rings on CMMs. The method is based on: i) systematic error separation using multi-step and reversal measurements, and ii) gaussian filtering of random errors. Validation of the method was provided through investigations on uncertainty contribution...

  10. Distributed Radio Interferometric Calibration

    CERN Document Server

    Yatawatta, Sarod

    2015-01-01

    Increasing data volumes delivered by a new generation of radio interferometers require computationally efficient and robust calibration algorithms. In this paper, we propose distributed calibration as a way of improving both computational cost as well as robustness in calibration. We exploit the data parallelism across frequency that is inherent in radio astronomical observations that are recorded as multiple channels at different frequencies. Moreover, we also exploit the smoothness of the variation of calibration parameters across frequency. Data parallelism enables us to distribute the computing load across a network of compute agents. Smoothness in frequency enables us reformulate calibration as a consensus optimization problem. With this formulation, we enable flow of information between compute agents calibrating data at different frequencies, without actually passing the data, and thereby improving robustness. We present simulation results to show the feasibility as well as the advantages of distribute...

  11. An Overview of the Joint Polar Satellite System (JPSS Science Data Product Calibration and Validation

    Directory of Open Access Journals (Sweden)

    Lihang Zhou

    2016-02-01

    Full Text Available The Joint Polar Satellite System (JPSS will launch its first JPSS-1 satellite in early 2017. The JPSS-1 and follow-on satellites will carry aboard an array of instruments including the Visible Infrared Imaging Radiometer Suite (VIIRS, the Cross-track Infrared Sounder (CrIS, the Advanced Technology Microwave Sounder (ATMS, and the Ozone Mapping and Profiler Suite (OMPS. These instruments are similar to the instruments currently operating on the Suomi National Polar-orbiting Partnership (S-NPP satellite. In preparation for the JPSS-1 launch, the JPSS program at the Center for Satellite Applications and Research (JSTAR Calibration/Validation (Cal/Val teams, have laid out the Cal/Val plans to oversee JPSS-1 science products’ algorithm development efforts, verification and characterization of these algorithms during the pre-launch period, calibration and validation of the products during post-launch, and long-term science maintenance (LTSM. In addition, the team has developed the necessary schedules, deliverables and infrastructure for routing JPSS-1 science product algorithms for operational implementation. This paper presents an overview of these efforts. In addition, this paper will provide insight into the processes of both adapting S-NPP science products for JPSS-1 and performing upgrades for enterprise solutions, and will discuss Cal/Val processes and quality assurance procedures.

  12. Influence of camera calibration conditions on the accuracy of 3D reconstruction.

    Science.gov (United States)

    Poulin-Girard, Anne-Sophie; Thibault, Simon; Laurendeau, Denis

    2016-02-01

    For stereoscopic systems designed for metrology applications, the accuracy of camera calibration dictates the precision of the 3D reconstruction. In this paper, the impact of various calibration conditions on the reconstruction quality is studied using a virtual camera calibration technique and the design file of a commercially available lens. This technique enables the study of the statistical behavior of the reconstruction task in selected calibration conditions. The data show that the mean reprojection error should not always be used to evaluate the performance of the calibration process and that a low quality of feature detection does not always lead to a high mean reconstruction error.

  13. Accuracy Analysis and Calibration of Gantry Hybrid Machine Tool

    Institute of Scientific and Technical Information of China (English)

    唐晓强; 李铁民; 尹文生; 汪劲松

    2003-01-01

    The kinematic accuracy is a key factor in the design of parallel or hybrid machine tools. This analysis improved the accuracy of a 4-DOF (degree of freedom) gantry hybrid machine tool based on a 3-DOF planar parallel manipulator by compensating for various positioning errors. The machine tool architecture was described with the inverse kinematic solution. The control parameter error model was used to analyze the accuracy of the 3-DOF planar parallel manipulator and to develop a kinematic calibration method. The experimental results prove that the calibration method reduces the cutter nose errors from ±0.50 mm to ±0.03 mm for a horizontal movement of 600 mm by compensating for errors in the slider home position, the guide way distance and the extensible strut home position. The calibration method will be useful for similar types of parallel kinematic machines.

  14. Calibrator Design for the COBE Far Infrared Absolute Spectrophotometer ($FIRAS$)

    CERN Document Server

    Mather, J C; Shafer, R A; Mosier, C; Wilkinson, D T

    1999-01-01

    The photometric errors of the external calibrator for the FIRAS instrument on the COBE are smaller than the measurement errors on the cosmic microwave background (CMBR) spectrum (typically 0.02 MJy/sr, 1 sigma), and smaller than 0.01% of the peak brightness of the CMBR. The calibrator is a re-entrant cone, shaped like a trumpet mute, made of Eccosorb iron-loaded epoxy. It fills the entire beam of the instrument and is the source of its accuracy. Its known errors are caused by reflections, temperature gradients, and leakage through the material and around the edge. Estimates and limits are given for all known error sources. Improvements in understanding the temperature measurements of the calibrator allow an improved CMBR temperature determination of 2.725 +/- 0.002 K.

  15. The Science of Calibration

    Science.gov (United States)

    Kent, S. M.

    2016-05-01

    This paper presents a broad overview of the many issues involved in calibrating astronomical data, covering the full electromagnetic spectrum from radio waves to gamma rays, and considering both ground-based and space-based missions. These issues include the science drivers for absolute and relative calibration, the physics behind calibration and the mechanisms used to transfer it from the laboratory to an astronomical source, the need for networks of calibrated astronomical standards, and some of the challenges faced by large surveys and missions.

  16. Camera calibration for multidirectional flame chemiluminescence tomography

    Science.gov (United States)

    Wang, Jia; Zhang, Weiguang; Zhang, Yuhong; Yu, Xun

    2017-04-01

    Flame chemiluminescence tomography (FCT), which combines computerized tomography theory and multidirectional chemiluminescence emission measurements, can realize instantaneous three-dimensional (3-D) diagnostics for flames with high spatial and temporal resolutions. One critical step of FCT is to record the projections by multiple cameras from different view angles. For high accuracy reconstructions, it requires that extrinsic parameters (the positions and orientations) and intrinsic parameters (especially the image distances) of cameras be accurately calibrated first. Taking the focus effect of the camera into account, a modified camera calibration method was presented for FCT, and a 3-D calibration pattern was designed to solve the parameters. The precision of the method was evaluated by reprojections of feature points to cameras with the calibration results. The maximum root mean square error of the feature points' position is 1.42 pixels and 0.0064 mm for the image distance. An FCT system with 12 cameras was calibrated by the proposed method and the 3-D CH* intensity of a propane flame was measured. The results showed that the FCT system provides reasonable reconstruction accuracy using the camera's calibration results.

  17. INFLUENCE OF MECHANICAL ERRORS IN A ZOOM CAMERA

    Directory of Open Access Journals (Sweden)

    Alfredo Gardel

    2011-05-01

    Full Text Available As it is well known, varying the focus and zoom of a camera lens system changes the alignment of the lens components resulting in a displacement of the image centre and field of view. Thus, knowledge of how the image centre shifts may be important for some aspects of camera calibration. As shown in other papers, the pinhole model is not adequate for zoom lenses. To ensure a calibration model for these lenses, the calibration parameters must be adjusted. The geometrical modelling of a zoom lens is realized from its lens specifications. The influence on the calibration parameters is calculated by introducing mechanical errors in the mobile lenses. Figures are given describing the errors obtained in the principal point coordinates and also in its standard deviation. A comparison is then made with the errors that come from the incorrect detection of the calibration points. It is concluded that mechanical errors of actual zoom lenses can be neglected in the calibration process because detection errors have more influence on the camera parameters.

  18. Error measuring system of rotary Inductosyn

    Science.gov (United States)

    Liu, Chengjun; Zou, Jibin; Fu, Xinghe

    2008-10-01

    The inductosyn is a kind of high-precision angle-position sensor. It has important applications in servo table, precision machine tool and other products. The precision of inductosyn is calibrated by its error. It's an important problem about the error measurement in the process of production and application of the inductosyn. At present, it mainly depends on the method of artificial measurement to obtain the error of inductosyn. Therefore, the disadvantages can't be ignored such as the high labour intensity of the operator, the occurrent error which is easy occurred and the poor repeatability, and so on. In order to solve these problems, a new automatic measurement method is put forward in this paper which based on a high precision optical dividing head. Error signal can be obtained by processing the output signal of inductosyn and optical dividing head precisely. When inductosyn rotating continuously, its zero position error can be measured dynamically, and zero error curves can be output automatically. The measuring and calculating errors caused by man-made factor can be overcome by this method, and it makes measuring process more quickly, exactly and reliably. Experiment proves that the accuracy of error measuring system is 1.1 arc-second (peak - peak value).

  19. Application of composite small calibration objects in traffic accident scene photogrammetry.

    Directory of Open Access Journals (Sweden)

    Qiang Chen

    Full Text Available In order to address the difficulty of arranging large calibration objects and the low measurement accuracy of small calibration objects in traffic accident scene photogrammetry, a photogrammetric method based on a composite of small calibration objects is proposed. Several small calibration objects are placed around the traffic accident scene, and the coordinate system of the composite calibration object is given based on one of them. By maintaining the relative position and coplanar relationship of the small calibration objects, the local coordinate system of each small calibration object is transformed into the coordinate system of the composite calibration object. The two-dimensional direct linear transformation method is improved based on minimizing the reprojection error of the calibration points of all objects. A rectified image is obtained using the nonlinear optimization method. The increased accuracy of traffic accident scene photogrammetry using a composite small calibration object is demonstrated through the analysis of field experiments and case studies.

  20. Angular diameter estimation of interferometric calibrators - Example of lambda Gruis, calibrator for VLTI-AMBER

    CERN Document Server

    Cruzalebes, P; Sacuto, S; Bonneau, D; 10.1051/0004-6361/200913686

    2010-01-01

    Context. Accurate long-baseline interferometric measurements require careful calibration with reference stars. Small calibrators with high angular diameter accuracy ensure the true visibility uncertainty to be dominated by the measurement errors. Aims. We review some indirect methods for estimating angular diameter, using various types of input data. Each diameter estimate, obtained for the test-case calibrator star lambda Gru, is compared with the value 2.71 mas found in the Bord\\'e calibrator catalogue published in 2002. Methods. Angular size estimations from spectral type, spectral index, in-band magnitude, broadband photometry, and spectrophotometry give close estimates of the angular diameter, with slightly variable uncertainties. Fits on photometry and spectrophotometry need physical atmosphere models with "plausible" stellar parameters. Angular diameter uncertainties were estimated by means of residual bootstrapping confidence intervals. All numerical results and graphical outputs presented in this pap...

  1. HJ-1A HSI on-orbit radiometric calibration and validation research

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    The calibration experiment data at Dunhuang radiometric calibration site in October, 2008 were used to achieve the on-orbit radiometric calibration for HJ-1A hyper spectral imager (HSI). Two other field experiments data were used to validate the Dunhuang calibration results. One field experiment took place in Inner-Mongolia, China in September, 2008, and the other field experiment took place in Lake Frome, Australia in February, 2009. Finally, the ‘confidence interval of calibration error’ concept was put forward for quantitatively computing the calibration coefficient error confidence interval. The results showed that the Dunhuang calibration results in 2008 had high reliability. The confidence intervals of calibration error for all HSI channels were between 2% to 12%, which could satisfy the requirement of the HSI quantitative applications.

  2. Comparative study of camera calibration algorithms with application to spacecraft navigation

    Science.gov (United States)

    Poelzleitner, Wolfgang; Ulm, Michael

    1994-10-01

    This paper deals with the problem of camera calibration based on 3D feature measurements. It occurs in industrial 3D measurement systems, as well as in autonomous navigation systems, where the estimation of motion parameters is required. We have selected the problem of extrinsic calibration (exterior orientation) of a camera that is looking at flat or almost flat surfaces (or terrain). This situation causes numerical and stability problems to many of the known calibration methods. To study the impact of flatness of the reference surface (or calibration target) on the calibration errors we have done a comparative study using sixteen available calibration procedures. The major emphasis was on robustness with respect to 3D measurement errors and sensitivity to flatness. A new calibration method is also investigated, which can be used independently of whether the calibration reference surface is flat, almost flat, or rugged.

  3. [In-flight absolute radiometric calibration of UAV multispectral sensor].

    Science.gov (United States)

    Chen, Wei; Yan, Lei; Gou, Zhi-Yang; Zhao, Hong-Ying; Liu, Da-Ping; Duan, Yi-Ni

    2012-12-01

    Based on the data of the scientific experiment in Urad Front Banner for UAV Remote Sensing Load Calibration Field project, with the help of 6 hyperspectral radiometric targets with good Lambertian property, the wide-view multispectral camera in UAV was calibrated adopting reflectance-based method. The result reveals that for green, red and infrared channel, whose images were successfully captured, the linear correlation coefficients between the DN and radiance are all larger than 99%. In final analysis, the comprehensive error is no more than 6%. The calibration results demonstrate that the hyperspectral targets equipped by the calibration field are well suitable for air-borne multispectral load in-flight calibration. The calibration result is reliable and could be used in the retrieval of geophysical parameters.

  4. CCD camera automatic calibration technology and ellipse recognition algorithm

    Institute of Scientific and Technical Information of China (English)

    Changku Sun; Xiaodong Zhang; Yunxia Qu

    2005-01-01

    A novel two-dimensional (2D) pattern used in camera calibration is presented. With one feature circle located at the center, an array of circles is photo-etched on this pattern. An ellipse recognition algorithm is proposed to implement the acquisition of interest calibration points without human intervention. According to the circle arrangement of the pattern, the relation between three-dimensional (3D) and 2D coordinates of these points can be established automatically and accurately. These calibration points are computed for intrinsic parameters calibration of charge-coupled device (CCD) camera with Tsai method. A series of experiments have shown that the algorithm is robust and reliable with the calibration error less than 0.4 pixel. This new calibration pattern and ellipse recognition algorithm can be widely used in computer vision.

  5. Handheld temperature calibrator

    National Research Council Canada - National Science Library

    Martella, Melanie

    2003-01-01

    ... you sign on. What are you waiting for? JOFRA ETC Series dry-block calibrators from AMETEK Test & Calibration Instruments, Largo, FL, are small enough to be handheld and feature easy-to-read displays, multiple bore blocks, programmable test setup, RS-232 communications, and software. Two versions are available: the ETC 125A that ranges from -10[degrees]C to 125[d...

  6. Sentinel-2 diffuser on-ground calibration

    Science.gov (United States)

    Mazy, E.; Camus, F.; Chorvalli, V.; Domken, I.; Laborie, A.; Marcotte, S.; Stockman, Y.

    2013-10-01

    The Sentinel-2 multi-spectral instrument (MSI) will provide Earth imagery in the frame of the Global Monitoring for Environment and Security (GMES) initiative which is a joint undertaking of the European Commission and the Agency. MSI instrument, under Astrium SAS responsibility, is a push-broom spectro imager in 13 spectral channels in VNIR and SWIR. The instrument radiometric calibration is based on in-flight calibration with sunlight through a quasi Lambertian diffuser. The diffuser covers the full pupil and the full field of view of the instrument. The on-ground calibration of the diffuser BRDF is mandatory to fulfil the in-flight performances. The diffuser is a 779 x 278 mm2 rectangular flat area in Zenith-A material. It is mounted on a motorised door in front of the instrument optical system entrance. The diffuser manufacturing and calibration is under the Centre Spatial of Liege (CSL) responsibility. The CSL has designed and built a completely remote controlled BRDF test bench able to handle large diffusers in their mount. As the diffuser is calibrated directly in its mount with respect to a reference cube, the error budget is significantly improved. The BRDF calibration is performed directly in MSI instrument spectral bands by using dedicated band-pass filters (VNIR and SWIR up to 2200 nm). Absolute accuracy is better than 0.5% in VNIR spectral bands and 1% in SWIR spectral bands. Performances were cross checked with other laboratories. The first MSI diffuser for flight model was calibrated mid 2013 on CSL BRDF measurement bench. The calibration of the diffuser consists mainly in thermal vacuum cycles, BRDF uniformity characterisation and BRDF angular characterisation. The total amount of measurement for the first flight model diffuser corresponds to more than 17500 BRDF acquisitions. Performance results are discussed in comparison with requirements.

  7. Multiyear On-orbit Calibration and Performance of Terra MODIS Thermal Emissive Bands

    Science.gov (United States)

    Xiong, Xiaoxiong; Chiang, Kwo-Fu; Wu, Aisheng; Barnes, William; Guenther, Bruce; Salomonson, Vincent

    2007-01-01

    Since launch in December 1999, Terra MODIS has been making continuous Earth observations for more than seven years. It has produced a broad range of land, ocean, and atmospheric science data products for improvements in studies of global climate and environmental change. Among its 36 spectral bands, there are 20 reflective solar bands (RSB) and 16 thermal emissive bands (TEB). MODIS thermal emissive bands cover the mid-wave infrared (MWIR) and long-wave infrared (LWIR) spectral regions with wavelengths from 3.7 to 14.4pm. They are calibrated on-orbit using an on-board blackbody (BB) with its temperature measured by a set of thermistors on a scan-by-scan basis. This paper will provide a brief overview of MODIS TEB calibration and characterization methodologies and illustrate on-board BB functions and TEB performance over more than seven years of on-orbit operation and calibration. Discussions will be focused on TEB detector short-term stability and noise characterization, and changes in long-term response (or system gain). Results show that Terra MODIS BB operation has been extremely stable since launch. When operated at its nominal controlled temperature of 290K, the BB temperature variation is typically less than +0.30mK on a scan-by-scan basis and there has been no time-dependent temperature drift. In addition to excellent short-term stability, most TEB detectors continue to meet or exceed their specified noise characterization requirements, thus enabling calibration accuracy and science data product quality to be maintained. Excluding the noisy detectors identified pre-launch and those that occurred post-launch, the changes in TEB responses have been less than 0.7% on an annual basis. The optical leak corrections applied to bands 32-36 have been effective and stable over the entire mission

  8. WFPC2 Polarization Calibration

    Science.gov (United States)

    Biretta, J.; McMaster, M.

    1997-12-01

    We derive a detailed calibration for WFPC2 polarization data which is accurate to about 1.5%. We begin by computing polarizer flats, and show how they are applied to data. A physical model for the polarization effects of the WFPC2 optics is then created using Mueller matricies. This model includes corrections for the instrumental polarization (diattenuation and phase retardance) of the pick-off mirror, as well as the high cross-polarization transmission of the polarizer filter. We compare this model against the on-orbit observations of polarization calibrators, and show it predicts relative counts in the different polarizer/aperture settings to 1.5% RMS accuracy. We then show how this model can be used to calibrate GO data, and present two WWW tools which allow observers to easily calibrate their data. Detailed examples are given illustrationg the calibration and display of WFPC2 polarization data. In closing we describe future plans and possible improvements.

  9. Sandia WIPP calibration traceability

    Energy Technology Data Exchange (ETDEWEB)

    Schuhen, M.D. [Sandia National Labs., Albuquerque, NM (United States); Dean, T.A. [RE/SPEC, Inc., Albuquerque, NM (United States)

    1996-05-01

    This report summarizes the work performed to establish calibration traceability for the instrumentation used by Sandia National Laboratories at the Waste Isolation Pilot Plant (WIPP) during testing from 1980-1985. Identifying the calibration traceability is an important part of establishing a pedigree for the data and is part of the qualification of existing data. In general, the requirement states that the calibration of Measuring and Test equipment must have a valid relationship to nationally recognized standards or the basis for the calibration must be documented. Sandia recognized that just establishing calibration traceability would not necessarily mean that all QA requirements were met during the certification of test instrumentation. To address this concern, the assessment was expanded to include various activities.

  10. Colorimetric calibration of coupled infrared simulation system

    Science.gov (United States)

    Zhang, Ying; Fei, Jindong; Gao, Yang; Du, Jian

    2015-10-01

    In order to test 2-color infrared sensors, a coupled infrared simulation system can generate radiometric outputs with wavelengths that range from less than 3 microns to more than 12 microns. There are two channels in the coupled simulation system, optically combined by a diachronic beam combiner. Each channel has an infrared blackbody, a filter, a diaphragm, and diaphragm-motors. The system is projected to the sensor under testing by a collimator. This makes it difficult to calibrate the system with only one-band thermal imager. Errors will be caused in the radiance levels measured by the narrow band thermal imager. This paper describes colorimetric temperature measurement techniques that have been developed to perform radiometric calibrations of these infrared simulation systems above. The calibration system consists of two infrared thermal imagers; one is operated at the wavelength range of MW-IR, and the other at the range of LW-IR.

  11. Precision Calibration of Infrared Synchrotron Radiation Detectors

    CERN Document Server

    Maltsev, A A; Maslova, M V

    2003-01-01

    The technique of calibration of synchrotron radiation precision detectors on a tungsten source based on similarity (close similarity) of character of spectral distributions of synchrotron and thermal radiations is given. The characteristics of various commonly used lamps, used as "standard" ones, are given. The errors of measurements are analyzed. The detectors are intended for absolute measurements of the number of electrons in a ring-shaped bunch.

  12. Probe Error Modeling Research Based on Bayesian Network

    Institute of Scientific and Technical Information of China (English)

    Wu Huaiqiang; Xing Zilong; Zhang Jian; Yan Yan

    2015-01-01

    Probe calibration is carried out under specific conditions; most of the error caused by the change of speed parameter has not been corrected. In order to reduce the measuring error influence on measurement accuracy, this article analyzes the relationship between speed parameter and probe error, and use Bayesian network to establish the model of probe error. Model takes account of prior knowledge and sample data, with the updating of data, which can reflect the change of the errors of the probe and constantly revised modeling results.

  13. Generalized Gaussian Error Calculus

    CERN Document Server

    Grabe, Michael

    2010-01-01

    For the first time in 200 years Generalized Gaussian Error Calculus addresses a rigorous, complete and self-consistent revision of the Gaussian error calculus. Since experimentalists realized that measurements in general are burdened by unknown systematic errors, the classical, widespread used evaluation procedures scrutinizing the consequences of random errors alone turned out to be obsolete. As a matter of course, the error calculus to-be, treating random and unknown systematic errors side by side, should ensure the consistency and traceability of physical units, physical constants and physical quantities at large. The generalized Gaussian error calculus considers unknown systematic errors to spawn biased estimators. Beyond, random errors are asked to conform to the idea of what the author calls well-defined measuring conditions. The approach features the properties of a building kit: any overall uncertainty turns out to be the sum of a contribution due to random errors, to be taken from a confidence inter...

  14. Calibration of atmospheric hydrogen measurements

    Directory of Open Access Journals (Sweden)

    A. Jordan

    2011-03-01

    Full Text Available Interest in atmospheric hydrogen (H2 has been growing in recent years with the prospect of H2 being a potential alternative to fossil fuels as an energy carrier. This has intensified research for a quantitative understanding of the atmospheric hydrogen cycle and its total budget, including the expansion of the global atmospheric measurement network. However, inconsistencies in published observational data constitute a major limitation in exploring such data sets. The discrepancies can be mainly attributed to difficulties in the calibration of the measurements. In this study various factors that may interfere with accurate quantification of atmospheric H2 were investigated including drifts of standard gases in high pressure cylinders. As an experimental basis a procedure to generate precise mixtures of H2 within the atmospheric concentration range was established. Application of this method has enabled a thorough linearity characterization of the commonly used GC-HgO reduction detector. We discovered that the detector response was sensitive to the composition of the matrix gas. Addressing these systematic errors, a new calibration scale has been generated defined by thirteen standards with dry air mole fractions ranging from 139–1226 nmol mol−1. This new scale has been accepted as the official World Meteorological Organisation's (WMO Global Atmospheric Watch (GAW H2 mole fraction scale.

  15. Segment Based Camera Calibration

    Institute of Scientific and Technical Information of China (English)

    马颂德; 魏国庆; 等

    1993-01-01

    The basic idea of calibrating a camera system in previous approaches is to determine camera parmeters by using a set of known 3D points as calibration reference.In this paper,we present a method of camera calibration in whih camera parameters are determined by a set of 3D lines.A set of constraints is derived on camea parameters in terms of perspective line mapping.Form these constraints,the same perspective transformation matrix as that for point mapping can be computed linearly.The minimum number of calibration lines is 6.This result generalizes that of Liu,Huang and Faugeras[12] for camera location determination in which at least 8 line correspondences are required for linear computation of camera location.Since line segments in an image can be located easily and more accurately than points,the use of lines as calibration reference tends to ease the computation in inage preprocessing and to improve calibration accuracy.Experimental results on the calibration along with stereo reconstruction are reported.

  16. Classification of Spreadsheet Errors

    OpenAIRE

    Rajalingham, Kamalasen; Chadwick, David R.; Knight, Brian

    2008-01-01

    This paper describes a framework for a systematic classification of spreadsheet errors. This classification or taxonomy of errors is aimed at facilitating analysis and comprehension of the different types of spreadsheet errors. The taxonomy is an outcome of an investigation of the widespread problem of spreadsheet errors and an analysis of specific types of these errors. This paper contains a description of the various elements and categories of the classification and is supported by appropri...

  17. Site Calibration report

    DEFF Research Database (Denmark)

    Gómez Arranz, Paula; Vesth, Allan

    This report describes the site calibration carried out at Østerild, during a given period. The site calibration was performed with two Windcube WLS7 (v1) lidars at ten measurements heights. The lidar is not a sensor approved by the current version of the IEC 61400-12-1 [1] and therefore the site...... calibration with lidars does not comply with the standard. However, the measurements are carried out following the guidelines of IEC 61400-12-1 where possible, but with some deviations presented in the following chapters....

  18. Lidar to lidar calibration

    DEFF Research Database (Denmark)

    Fernandez Garcia, Sergio; Villanueva, Héctor

    This report presents the result of the lidar to lidar calibration performed for ground-based lidar. Calibration is here understood as the establishment of a relation between the reference lidar wind speed measurements with measurement uncertainties provided by measurement standard and corresponding...... lidar wind speed indications with associated measurement uncertainties. The lidar calibration concerns the 10 minute mean wind speed measurements. The comparison of the lidar measurements of the wind direction with that from the reference lidar measurements are given for information only....

  19. Lidar to lidar calibration

    DEFF Research Database (Denmark)

    Georgieva Yankova, Ginka; Courtney, Michael

    This report presents the result of the lidar to lidar calibration performed for ground-based lidar. Calibration is here understood as the establishment of a relation between the reference lidar wind speed measurements with measurement uncertainties provided by measurement standard and corresponding...... lidar wind speed indications with associated measurement uncertainties. The lidar calibration concerns the 10 minute mean wind speed measurements. The comparison of the lidar measurements of the wind direction with that from the reference lidar measurements are given for information only....

  20. Measurement error in longitudinal film badge data

    CERN Document Server

    Marsh, J L

    2002-01-01

    Initial logistic regressions turned up some surprising contradictory results which led to a re-sampling of Sellafield mortality controls without the date of employment matching factor. It is suggested that over matching is the cause of the contradictory results. Comparisons of the two measurements of radiation exposure suggest a strongly linear relationship with non-Normal errors. A method has been developed using the technique of Regression Calibration to deal with these in a case-control study context, and applied to this Sellafield study. The classical measurement error model is that of a simple linear regression with unobservable variables. Information about the covariates is available only through error-prone measurements, usually with an additive structure. Ignoring errors has been shown to result in biased regression coefficients, reduced power of hypothesis tests and increased variability of parameter estimates. Radiation is known to be a causal factor for certain types of leukaemia. This link is main...

  1. Calibration Fixture For Anemometer Probes

    Science.gov (United States)

    Lewis, Charles R.; Nagel, Robert T.

    1993-01-01

    Fixture facilitates calibration of three-dimensional sideflow thermal anemometer probes. With fixture, probe oriented at number of angles throughout its design range. Readings calibrated as function of orientation in airflow. Calibration repeatable and verifiable.

  2. An Improved Photometric Calibration of the Sloan Digital SkySurvey Imaging Data

    Energy Technology Data Exchange (ETDEWEB)

    Padmanabhan, Nikhil; Schlegel, David J.; Finkbeiner, Douglas P.; Barentine, J.C.; Blanton, Michael R.; Brewington, Howard J.; Gunn, JamesE.; Harvanek, Michael; Hogg, David W.; Ivezic, Zeljko; Johnston, David; Kent, Stephen M.; Kleinman, S.J.; Knapp, Gillian R.; Krzesinski, Jurek; Long, Dan; Neilsen Jr., Eric H.; Nitta, Atsuko; Loomis, Craig; Lupton,Robert H.; Roweis, Sam; Snedden, Stephanie A.; Strauss, Michael A.; Tucker, Douglas L.

    2007-09-30

    We present an algorithm to photometrically calibrate widefield optical imaging surveys, that simultaneously solves for thecalibration parameters and relative stellar fluxes using overlappingobservations. The algorithm decouples the problem of "relative"calibrations from that of "absolute" calibrations; the absolutecalibration is reduced to determining a few numbers for the entiresurvey. We pay special attention to the spatial structure of thecalibration errors, allowing one to isolate particular error modes indownstream analyses. Applying this to the SloanDigital Sky Survey imagingdata, we achieve ~;1 percent relative calibration errors across 8500sq.deg/ in griz; the errors are ~;2 percent for the u band. These errorsare dominated by unmodelled atmospheric variations at Apache PointObservatory. These calibrations, dubbed ubercalibration, are now publicwith SDSS Data Release 6, and will be a part of subsequent SDSS datareleases.

  3. Calibrating nacelle lidars

    DEFF Research Database (Denmark)

    Courtney, Michael

    Nacelle mounted, forward looking wind lidars are beginning to be used to provide reference wind speed measurements for the power performance testing of wind turbines. In such applications, a formal calibration procedure with a corresponding uncertainty assessment will be necessary. This report...... presents four concepts for performing such a nacelle lidar calibration. Of the four methods, two are found to be immediately relevant and are pursued in some detail. The first of these is a line of sight calibration method in which both lines of sight (for a two beam lidar) are individually calibrated...... a representative distribution of radial wind speeds. An alternative method is to place the nacelle lidar on the ground and incline the beams upwards to bisect a mast equipped with reference instrumentation at a known height and range. This method will be easier and faster to implement and execute but the beam...

  4. SRHA calibration curve

    Data.gov (United States)

    U.S. Environmental Protection Agency — an UV calibration curve for SRHA quantitation. This dataset is associated with the following publication: Chang, X., and D. Bouchard. Surfactant-Wrapped Multiwalled...

  5. Air Data Calibration Facility

    Data.gov (United States)

    Federal Laboratory Consortium — This facility is for low altitude subsonic altimeter system calibrations of air vehicles. Mission is a direct support of the AFFTC mission. Postflight data merge is...

  6. SPOTS Calibration Example

    Directory of Open Access Journals (Sweden)

    Patterson E.

    2010-06-01

    Full Text Available The results are presented using the procedure outlined by the Standardisation Project for Optical Techniques of Strain measurement to calibrate a digital image correlation system. The process involves comparing the experimental data obtained with the optical measurement system to the theoretical values for a specially designed specimen. The standard states the criteria which must be met in order to achieve successful calibration, in addition to quantifying the measurement uncertainty in the system. The system was evaluated at three different displacement load levels, generating strain ranges from 289 µstrain to 2110 µstrain. At the 289 µstrain range, the calibration uncertainty was found to be 14.1 µstrain, and at the 2110 µstrain range it was found to be 28.9 µstrain. This calibration procedure was performed without painting a speckle pattern on the surface of the metal. Instead, the specimen surface was prepared using different grades of grit paper to produce the desired texture.

  7. Calibrated Properties Model

    Energy Technology Data Exchange (ETDEWEB)

    C. Ahlers; H. Liu

    2000-03-12

    The purpose of this Analysis/Model Report (AMR) is to document the Calibrated Properties Model that provides calibrated parameter sets for unsaturated zone (UZ) flow and transport process models for the Yucca Mountain Site Characterization Project (YMP). This work was performed in accordance with the ''AMR Development Plan for U0035 Calibrated Properties Model REV00. These calibrated property sets include matrix and fracture parameters for the UZ Flow and Transport Model (UZ Model), drift seepage models, drift-scale and mountain-scale coupled-processes models, and Total System Performance Assessment (TSPA) models as well as Performance Assessment (PA) and other participating national laboratories and government agencies. These process models provide the necessary framework to test conceptual hypotheses of flow and transport at different scales and predict flow and transport behavior under a variety of climatic and thermal-loading conditions.

  8. Traceable Pyrgeometer Calibrations

    Energy Technology Data Exchange (ETDEWEB)

    Dooraghi, Mike; Kutchenreiter, Mark; Reda, Ibrahim; Habte, Aron; Sengupta, Manajit; Andreas, Afshin; Newman, Martina; Webb, Craig

    2016-05-02

    This presentation provides a high-level overview of the progress on the Broadband Outdoor Radiometer Calibrations for all shortwave and longwave radiometers that are deployed by the Atmospheric Radiation Measurement program.

  9. Calibrating nacelle lidars

    OpenAIRE

    Courtney, Michael

    2013-01-01

    Nacelle mounted, forward looking wind lidars are beginning to be used to provide reference wind speed measurements for the power performance testing of wind turbines. In such applications, a formal calibration procedure with a corresponding uncertainty assessment will be necessary. This report presents four concepts for performing such a nacelle lidar calibration. Of the four methods, two are found to be immediately relevant and are pursued in some detail.The first of these is a line of sight...

  10. Scanner calibration revisited.

    Science.gov (United States)

    Pozhitkov, Alexander E

    2010-07-01

    Calibration of a microarray scanner is critical for accurate interpretation of microarray results. Shi et al. (BMC Bioinformatics, 2005, 6, Art. No. S11 Suppl. 2.) reported usage of a Full Moon BioSystems slide for calibration. Inspired by the Shi et al. work, we have calibrated microarray scanners in our previous research. We were puzzled however, that most of the signal intensities from a biological sample fell below the sensitivity threshold level determined by the calibration slide. This conundrum led us to re-investigate the quality of calibration provided by the Full Moon BioSystems slide as well as the accuracy of the analysis performed by Shi et al. Signal intensities were recorded on three different microarray scanners at various photomultiplier gain levels using the same calibration slide from Full Moon BioSystems. Data analysis was conducted on raw signal intensities without normalization or transformation of any kind. Weighted least-squares method was used to fit the data. We found that initial analysis performed by Shi et al. did not take into account autofluorescence of the Full Moon BioSystems slide, which led to a grossly distorted microarray scanner response. Our analysis revealed that a power-law function, which is explicitly accounting for the slide autofluorescence, perfectly described a relationship between signal intensities and fluorophore quantities. Microarray scanners respond in a much less distorted fashion than was reported by Shi et al. Full Moon BioSystems calibration slides are inadequate for performing calibration. We recommend against using these slides.

  11. Scanner calibration revisited

    Directory of Open Access Journals (Sweden)

    Pozhitkov Alexander E

    2010-07-01

    Full Text Available Abstract Background Calibration of a microarray scanner is critical for accurate interpretation of microarray results. Shi et al. (BMC Bioinformatics, 2005, 6, Art. No. S11 Suppl. 2. reported usage of a Full Moon BioSystems slide for calibration. Inspired by the Shi et al. work, we have calibrated microarray scanners in our previous research. We were puzzled however, that most of the signal intensities from a biological sample fell below the sensitivity threshold level determined by the calibration slide. This conundrum led us to re-investigate the quality of calibration provided by the Full Moon BioSystems slide as well as the accuracy of the analysis performed by Shi et al. Methods Signal intensities were recorded on three different microarray scanners at various photomultiplier gain levels using the same calibration slide from Full Moon BioSystems. Data analysis was conducted on raw signal intensities without normalization or transformation of any kind. Weighted least-squares method was used to fit the data. Results We found that initial analysis performed by Shi et al. did not take into account autofluorescence of the Full Moon BioSystems slide, which led to a grossly distorted microarray scanner response. Our analysis revealed that a power-law function, which is explicitly accounting for the slide autofluorescence, perfectly described a relationship between signal intensities and fluorophore quantities. Conclusions Microarray scanners respond in a much less distorted fashion than was reported by Shi et al. Full Moon BioSystems calibration slides are inadequate for performing calibration. We recommend against using these slides.

  12. TWSTFT Link Calibration Report

    Science.gov (United States)

    2015-09-01

    box calibrator with unknown but constant total delay during a calibration tour Total Delay: The total electrical delay from the antenna phase center...to the UTCp including all the devices/cables that the satellite and clock signals pass through. It numerically equals the sum of all the sub-delays...PTB. To average out the dimnal effects and measurement noise , 5-7 days of continuous measurements is required. 3 Setups at the Lab(k) The setup

  13. Approximation Behooves Calibration

    DEFF Research Database (Denmark)

    da Silva Ribeiro, André Manuel; Poulsen, Rolf

    2013-01-01

    Calibration based on an expansion approximation for option prices in the Heston stochastic volatility model gives stable, accurate, and fast results for S&P500-index option data over the period 2005–2009.......Calibration based on an expansion approximation for option prices in the Heston stochastic volatility model gives stable, accurate, and fast results for S&P500-index option data over the period 2005–2009....

  14. FY-3气象卫星紫外臭氧总量探测仪辐亮度在轨定标与反演结果分析%Calibration in-orbit and retrieval result study of FY-3 Total Ozone Unit (TOU)

    Institute of Scientific and Technical Information of China (English)

    江芳; 王维和; 王咏梅; 王英鉴

    2012-01-01

    FY-3气象卫星上搭载的紫外臭氧总量探测仪TOU是我国自主开发研制的首台用于全球臭氧总量定量测量的探测仪,自发射以来已成功在轨运行近两年.由于TOU发射前辐亮度定标存在偏差,为了得到高精度的产品,TOU必须进行在轨定标.本文介绍了基于辐射传输模式计算对TOU辐亮度进行在轨道定标的方法,定标过程中用于模拟辐亮度计算的臭氧总量由与TOU观测时刻相近的国外臭氧总量探测仪器MetOp/GOME-2提供.文章将在轨定标后TOU的反演结果与AURA/OMI以及地基的产品进行比较,结果表明,用辐射传输模式对TOU辐亮度进行在轨定标的方法是可行的,反演结果能够真实地反映臭氧的时空分布特性,在全球部分地基观测站所处的位置上对TOU,OMI以及地基的臭氧总量进行比较的结果表明,TOU与OM1的相对偏差均方根约为2.52%,TOU与地基以及OMI与地基观测结果之间的相对偏差均方根分别为4.45%和3.89%.%Ultraviolet Total Ozone Unit (TOU) is one of the main payloads on FY-3 satellite and the first instrument for daily global coverage of total ozone monitoring in China. TOU has been operating in-orbit about two years. Because pre-launch calibration has serious error in high ranges of radiance, an in-orbit calibration method based on radiative transfer model calculation was introduced in the paper, the total ozone column used to calculate the simulation radiance was produced from MetOp/GOME-2. The retrieval results were compared with AURA/OMI global ozone products and ground-based ozone measurement data, the results show that the calibration method is feasible and the spatial and temporal distribution characteristics are consistent with OMI and GOME-2 products. The quantitative comparisons with ground-based measurements and AURA/OMI ozone product were made over 74 stations, the TOU total ozone retrieval has a 2.52% RMS relative error compared with AURA/OMI ozone

  15. The effect of uncertainty and systematic errors in hydrological modelling

    Science.gov (United States)

    Steinsland, I.; Engeland, K.; Johansen, S. S.; Øverleir-Petersen, A.; Kolberg, S. A.

    2014-12-01

    The aims of hydrological model identification and calibration are to find the best possible set of process parametrization and parameter values that transform inputs (e.g. precipitation and temperature) to outputs (e.g. streamflow). These models enable us to make predictions of streamflow. Several sources of uncertainties have the potential to hamper the possibility of a robust model calibration and identification. In order to grasp the interaction between model parameters, inputs and streamflow, it is important to account for both systematic and random errors in inputs (e.g. precipitation and temperatures) and streamflows. By random errors we mean errors that are independent from time step to time step whereas by systematic errors we mean errors that persists for a longer period. Both random and systematic errors are important in the observation and interpolation of precipitation and temperature inputs. Important random errors comes from the measurements themselves and from the network of gauges. Important systematic errors originate from the under-catch in precipitation gauges and from unknown spatial trends that are approximated in the interpolation. For streamflow observations, the water level recordings might give random errors whereas the rating curve contributes mainly with a systematic error. In this study we want to answer the question "What is the effect of random and systematic errors in inputs and observed streamflow on estimated model parameters and streamflow predictions?". To answer we test systematically the effect of including uncertainties in inputs and streamflow during model calibration and simulation in distributed HBV model operating on daily time steps for the Osali catchment in Norway. The case study is based on observations from, uncertainty carefullt quantified, and increased uncertainties and systmatical errors are done realistically by for example removing a precipitation gauge from the network.We find that the systematical errors in

  16. Calibrating nacelle lidars

    Energy Technology Data Exchange (ETDEWEB)

    Courtney, M.

    2013-01-15

    Nacelle mounted, forward looking wind lidars are beginning to be used to provide reference wind speed measurements for the power performance testing of wind turbines. In such applications, a formal calibration procedure with a corresponding uncertainty assessment will be necessary. This report presents four concepts for performing such a nacelle lidar calibration. Of the four methods, two are found to be immediately relevant and are pursued in some detail. The first of these is a line of sight calibration method in which both lines of sight (for a two beam lidar) are individually calibrated by accurately aligning the beam to pass close to a reference wind speed sensor. A testing procedure is presented, reporting requirements outlined and the uncertainty of the method analysed. It is seen that the main limitation of the line of sight calibration method is the time required to obtain a representative distribution of radial wind speeds. An alternative method is to place the nacelle lidar on the ground and incline the beams upwards to bisect a mast equipped with reference instrumentation at a known height and range. This method will be easier and faster to implement and execute but the beam inclination introduces extra uncertainties. A procedure for conducting such a calibration is presented and initial indications of the uncertainties given. A discussion of the merits and weaknesses of the two methods is given together with some proposals for the next important steps to be taken in this work. (Author)

  17. (abstract) A VLBI Test of Tropospheric Delay Calibration with WVRs

    Science.gov (United States)

    Linfield, R. P.; Teitelbaum, L. P.; Keihm, S. J.; Resch, G. M.; Mahoney, M. J.; Treuhaft, R. N.

    1994-01-01

    Dual frequency (S/X band) very long baseline interferometry (VLBI) observations were used to test troposphere calibration by water vapor radiometers (WVRs). Comparison of the VLBI and WVR measurements show a statistical agreement (specifically, their structure functions agree) on time scales less than 700 seconds. On longer time scales, VLBI instrumental errors become important. The improvement in VLBI residual delays from WVR calibration was consistent with the measured level of tropospheric fluctuations.

  18. Predictive error analysis for a water resource management model

    Science.gov (United States)

    Gallagher, Mark; Doherty, John

    2007-02-01

    SummaryIn calibrating a model, a set of parameters is assigned to the model which will be employed for the making of all future predictions. If these parameters are estimated through solution of an inverse problem, formulated to be properly posed through either pre-calibration or mathematical regularisation, then solution of this inverse problem will, of necessity, lead to a simplified parameter set that omits the details of reality, while still fitting historical data acceptably well. Furthermore, estimates of parameters so obtained will be contaminated by measurement noise. Both of these phenomena will lead to errors in predictions made by the model, with the potential for error increasing with the hydraulic property detail on which the prediction depends. Integrity of model usage demands that model predictions be accompanied by some estimate of the possible errors associated with them. The present paper applies theory developed in a previous work to the analysis of predictive error associated with a real world, water resource management model. The analysis offers many challenges, including the fact that the model is a complex one that was partly calibrated by hand. Nevertheless, it is typical of models which are commonly employed as the basis for the making of important decisions, and for which such an analysis must be made. The potential errors associated with point-based and averaged water level and creek inflow predictions are examined, together with the dependence of these errors on the amount of averaging involved. Error variances associated with predictions made by the existing model are compared with "optimized error variances" that could have been obtained had calibration been undertaken in such a way as to minimize predictive error variance. The contributions by different parameter types to the overall error variance of selected predictions are also examined.

  19. Beowulf - Beta-Gamma Detector Calibration Graphical User Interface

    Energy Technology Data Exchange (ETDEWEB)

    McIntyre, Justin I.; Schrom, Brian T.; Cooper, Matthew W.; Haas, Derek A.; Hayes, James C.

    2009-09-21

    Pacific Northwest National Laboratory (PNNL) has demonstrated significant advancement in using beta-gamma coincidence detectors to detect a wide range of radioxenon isotopes. To obtain accurate activities with the detector it must be properly calibrated by measuring a series of calibration gas samples. The data is analyzed to create the calibration block used in the International Monitoring System file format. Doing the calibration manually has proven to be tedious and prone to errors, requiring a high degree of expertise. The Beowulf graphical user interface (GUI) is a software application that encompasses several components of the calibration task and generates a calibration block, as well as, a detailed report describing the specific calibration process used. This additional document can be used as a Quality assurance certificate to assist in auditing the calibration. This paper consists of two sections. Section 1 will describe the capabilities of Beowulf and section 2 will be a representative report generated or the 137Cs calibration and quality assurance source.

  20. New in-situ, non-intrusive calibration

    Science.gov (United States)

    Zunino, Heather; Adrian, Ronald; Ding, Liuyang; Prestridge, Kathy

    2014-11-01

    Tomographic particle image velocimetry (PIV) experiments require precise and accurate camera calibration. Standard techniques make assumptions about hard-to-measure camera parameters (i.e. optical axis angle, distortions, etc.)-reducing the calibration accuracy. Additionally, vibrations and slight movements after calibration may cause significant errors-particularly for tomographic PIV. These problems are exacerbated when a calibration target cannot be placed within the test section. A new PIV camera calibration method has been developed to permit precise calibration without placing a calibration target inside the test section or scanning the target over a volume. The method is capable of correcting for dynamic calibration changes occurring between PIV laser pulses. A transparent calibration plate with fine marks on both sides is positioned on the test section window. Dual-plane mapping makes it possible to determine a mapping function containing both position and angular direction of central rays from particles. From this information, central rays can be traced into the test section with high accuracy. Image distortion by the lens and refraction at various air-glass-liquid interfaces are accounted for, and no information about the position or angle of the camera(s) is required.

  1. Outdoor relative radiometric calibration method using gray scale targets

    Institute of Scientific and Technical Information of China (English)

    DUAN; YiNi; YAN; Lei; YANG; Bin; JING; Xin; CHEN; Wei

    2013-01-01

    The radiometric calibration of remote sensors is a basis and prerequisite of information quantification in remote sensing. This paper proposes a method for outdoor relative radiometric calibration using gray scale targets. In this method, the idea of two substitutions is adopted. Sunlight is used to replace the integrating sphere light source, and gray scale targets are used to re-place the diffuser. In this way, images at different radiance levels obtained outdoors can calculate the relative radiometric cali-bration coefficients using the least square method. The characteristics of this method are as follows. Firstly, compared with la-boratory calibration, it greatly reduces the complexity of the calibration method and the test cost. Secondly, compared with the existing outdoor relative radiometric calibration of a single radiance level, it uses test images of different radiance levels to re-duce errors. Thirdly, it is easy to operate with fewer environmental requirements, has obvious advantages in the rapid calibra-tion of airborne remote sensors before or after flight and is practical in engineering. This paper theoretically and experimental-ly proves the feasibility of this method. Calibration experiments were conducted on the wide-view multispectral imager (WVMI) using this method, and the precision of this method was evaluated by analyzing the corrected images of large uniform targets on ground. The experiment results have demonstrated that the new method is effective and its precision meets the re-quirement of the absolute radiometric calibration.

  2. Effective Calibration of Low-Cost Soil Water Content Sensors

    Directory of Open Access Journals (Sweden)

    Heye Reemt Bogena

    2017-01-01

    Full Text Available Soil water content is a key variable for understanding and modelling ecohydrological processes. Low-cost electromagnetic sensors are increasingly being used to characterize the spatio-temporal dynamics of soil water content, despite the reduced accuracy of such sensors as compared to reference electromagnetic soil water content sensing methods such as time domain reflectometry. Here, we present an effective calibration method to improve the measurement accuracy of low-cost soil water content sensors taking the recently developed SMT100 sensor (Truebner GmbH, Neustadt, Germany as an example. We calibrated the sensor output of more than 700 SMT100 sensors to permittivity using a standard procedure based on five reference media with a known apparent dielectric permittivity (1 < Ka < 34.8. Our results showed that a sensor-specific calibration improved the accuracy of the calibration compared to single “universal” calibration. The associated additional effort in calibrating each sensor individually is relaxed by a dedicated calibration setup that enables the calibration of large numbers of sensors in limited time while minimizing errors in the calibration process.

  3. Reducing medication errors.

    Science.gov (United States)

    Nute, Christine

    2014-11-25

    Most nurses are involved in medicines management, which is integral to promoting patient safety. Medicines management is prone to errors, which depending on the error can cause patient injury, increased hospital stay and significant legal expenses. This article describes a new approach to help minimise drug errors within healthcare settings where medications are prescribed, dispensed or administered. The acronym DRAINS, which considers all aspects of medicines management before administration, was devised to reduce medication errors on a cardiothoracic intensive care unit.

  4. Calibration of PIXE yields using binary thin films on Si

    Energy Technology Data Exchange (ETDEWEB)

    Meersschaut, J., E-mail: Johan.Meersschaut@imec.be [Imec, Kapeldreef 75, B-3001 Leuven (Belgium); Carbonel, J.; Popovici, M. [Imec, Kapeldreef 75, B-3001 Leuven (Belgium); Zhao, Q.; Vantomme, A. [IKS, KU Leuven, Celestijnenlaan 200D, B-3001 Leuven (Belgium); Vandervorst, W. [Imec, Kapeldreef 75, B-3001 Leuven (Belgium); IKS, KU Leuven, Celestijnenlaan 200D, B-3001 Leuven (Belgium)

    2014-07-15

    We describe the use of binary thin films on Si to calibrate the yields in proton-induced X-ray emission (PIXE) measurements. Besides of the element to be calibrated, the standards also contain a common reference element. The incorporation of a common reference element allows one to eliminate errors in the accumulated beam charge during the calibration of the PIXE set-up. The binary calibration standards allow us to determine the response function with an accuracy close to 1%. As an example, we will perform the calibration for Fe and Co, and we will determine the Co concentration in Fe{sub 1−x}Co{sub x} thin films.

  5. A HistogramBased Static Error Correction Technique for Flash ADCs: Implementation

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    In this paper, we focus on practical issues in implementing a calibration technique for medium-resolution, highspeed flash analogtodigital converters (ADCs). In [1], we theoretically describ the calibration technique and perform a behaviorallevel simulation to test its functionality [1]. In this work, we discuss some issues in transistorlevel implementation. The predominant factors that contribute to static errors such as reference generator mismatch and trackandhold (T/H) gain error can be treated as inputreferred offsets of each comparator. Using the proposed calibration technique, these errors can be calibrated with minimal detriment to the dynamic performance of the converter. We simulate a transistorlevel implementation of a 5-bit, 1 GHz ADC in a 1.2 V, 65 nm CMOS process. The results show that DNL can be improved from 2.5 LSB to below 0.7 LSB after calibration, and INL can be improved from 1.6 LSB to below 0.6 LSB after calibration.

  6. Controlled calibration method for laser induced breakdown spectroscopy

    Institute of Scientific and Technical Information of China (English)

    Li Wang; Chijian Zhang; Yuan Feng

    2008-01-01

    Laser induced breakdown spectroscopy (LIBS) is a potential technique for rapid analysis of samples present in solids, gases and liquids. In the last two decades it was an object of extensive studies. Controlled calibration method used to analysis the LIBS spectra is investigated. Compared with the inner calibration and calibration-free (CF) methods, this new method overcomes "matrix effect", and demonstrates a better ability to cope with the spectra. It is used to analyze natural soil, and errors of the concentration are decreased about 5%. The result shows that the new method is feasible and accurate.

  7. Demand Forecasting Errors

    OpenAIRE

    Mackie, Peter; Nellthorp, John; Laird, James

    2005-01-01

    Demand forecasts form a key input to the economic appraisal. As such any errors present within the demand forecasts will undermine the reliability of the economic appraisal. The minimization of demand forecasting errors is therefore important in the delivery of a robust appraisal. This issue is addressed in this note by introducing the key issues, and error types present within demand fore...

  8. When errors are rewarding

    NARCIS (Netherlands)

    Bruijn, E.R.A. de; Lange, F.P. de; Cramon, D.Y. von; Ullsperger, M.

    2009-01-01

    For social beings like humans, detecting one's own and others' errors is essential for efficient goal-directed behavior. Although one's own errors are always negative events, errors from other persons may be negative or positive depending on the social context. We used neuroimaging to disentangle br

  9. Accurate and simple calibration of DLP projector systems

    Science.gov (United States)

    Wilm, Jakob; Olesen, Oline V.; Larsen, Rasmus

    2014-03-01

    Much work has been devoted to the calibration of optical cameras, and accurate and simple methods are now available which require only a small number of calibration targets. The problem of obtaining these parameters for light projectors has not been studied as extensively and most current methods require a camera and involve feature extraction from a known projected pattern. In this work we present a novel calibration technique for DLP Projector systems based on phase shifting profilometry projection onto a printed calibration target. In contrast to most current methods, the one presented here does not rely on an initial camera calibration, and so does not carry over the error into projector calibration. A radial interpolation scheme is used to convert features coordinates into projector space, thereby allowing for a very accurate procedure. This allows for highly accurate determination of parameters including lens distortion. Our implementation acquires printed planar calibration scenes in less than 1s. This makes our method both fast and convenient. We evaluate our method in terms of reprojection errors and structured light image reconstruction quality.

  10. HAWC Timing Calibration

    CERN Document Server

    Huentemeyer, Petra; Dingus, Brenda

    2009-01-01

    The High-Altitude Water Cherenkov (HAWC) Experiment is a second-generation highsensitivity gamma-ray and cosmic-ray detector that builds on the experience and technology of the Milagro observatory. Like Milagro, HAWC utilizes the water Cherenkov technique to measure extensive air showers. Instead of a pond filled with water (as in Milagro) an array of closely packed water tanks is used. The event direction will be reconstructed using the times when the PMTs in each tank are triggered. Therefore, the timing calibration will be crucial for reaching an angular resolution as low as 0.25 degrees.We propose to use a laser calibration system, patterned after the calibration system in Milagro. Like Milagro, the HAWC optical calibration system will use ~1 ns laser light pulses. Unlike Milagro, the PMTs are optically isolated and require their own optical fiber calibration. For HAWC the laser light pulses will be directed through a series of optical fan-outs and fibers to illuminate the PMTs in approximately one half o...

  11. Relevance of ellipse eccentricity for camera calibration

    Science.gov (United States)

    Mordwinzew, W.; Tietz, B.; Boochs, F.; Paulus, D.

    2015-05-01

    Plane circular targets are widely used within calibrations of optical sensors through photogrammetric set-ups. Due to this popularity, their advantages and disadvantages are also well studied in the scientific community. One main disadvantage occurs when the projected target is not parallel to the image plane. In this geometric constellation, the target has an elliptic geometry with an offset between its geometric and its projected center. This difference is referred to as ellipse eccentricity and is a systematic error which, if not treated accordingly, has a negative impact on the overall achievable accuracy. The magnitude and direction of eccentricity errors are dependent on various factors. The most important one is the target size. The bigger an ellipse in the image is, the bigger the error will be. Although correction models dealing with eccentricity have been available for decades, it is mostly seen as a planning task in which the aim is to choose the target size small enough so that the resulting eccentricity error remains negligible. Besides the fact that advanced mathematical models are available and that the influence of this error on camera calibration results is still not completely investigated, there are various additional reasons why bigger targets can or should not be avoided. One of them is the growing image resolution as a by-product from advancements in the sensor development. Here, smaller pixels have a lower S/N ratio, necessitating more pixels to assure geometric quality. Another scenario might need bigger targets due to larger scale differences whereas distant targets should still contain enough information in the image. In general, bigger ellipses contain more contour pixels and therefore more information. This supports the target-detection algorithms to perform better even at non-optimal conditions such as data from sensors with a high noise level. In contrast to rather simple measuring situations in a stereo or multi-image mode, the impact

  12. Gemini Planet Imager Observational Calibrations VI: Photometric and Spectroscopic Calibration for the Integral Field Spectrograph

    CERN Document Server

    Maire, Jérôme; De Rosa, Robert J; Perrin, Marshall D; Rajan, Abhijith; Savransky, Dmitry; Wang, Jason J; Ruffio, Jean-Baptiste; Wolff, Schuyler G; Chilcote, Jeffrey K; Doyon, René; Graham, James R; Greenbaum, Alexandra Z; Konopacky, Quinn M; Larkin, James E; Macintosh, Bruce A; Marois, Christian; Millar-Blanchaer, Max; Patience, Jennifer; Pueyo, Laurent A; Sivaramakrishnan, Anand; Thomas, Sandrine J; Weiss, Jason L

    2014-01-01

    The Gemini Planet Imager (GPI) is a new facility instrument for the Gemini Observatory designed to provide direct detection and characterization of planets and debris disks around stars in the solar neighborhood. In addition to its extreme adaptive optics and corona graphic systems which give access to high angular resolution and high-contrast imaging capabilities, GPI contains an integral field spectrograph providing low resolution spectroscopy across five bands between 0.95 and 2.5 $\\mu$m. This paper describes the sequence of processing steps required for the spectro-photometric calibration of GPI science data, and the necessary calibration files. Based on calibration observations of the white dwarf HD 8049B we estimate that the systematic error in spectra extracted from GPI observations is less than 5%. The flux ratio of the occulted star and fiducial satellite spots within coronagraphic GPI observations, required to estimate the magnitude difference between a target and any resolved companions, was measur...

  13. Design and Ground Calibration of the Helioseismic and Magnetic Imager (HMI) Instrument on the Solar Dynamics Observatory (SDO)

    Science.gov (United States)

    Schou, J.; Scherrer, P. H.; Bush, R. I.; Wachter, R.; Couvidat, S.; Rabello-Soares, M. C.; Bogart, R. S.; Hoeksema, J. T.; Liu, Y.; Duvall, T. L., Jr.; Akin, D. J.; Allard, B. A.; Miles, J. W.; Rairden, R.; Shine, R. A.; Tarbell, T. D.; Title, A. M.; Wolfson, C. J.; Elmore, D. F.; Norton, A. A..; Tomczyk, S.

    2012-01-01

    The Helioseismic and Magnetic Imager (HMI) investigation will study the solar interior using helioseismic techniques as well as the magnetic field near the solar surface. The HMI instrument is part of the Solar Dynamics Observatory (SDO) that was launched on 11 February 2010. The instrument is designed to measure the Doppler shift, intensity, and vector magnetic field at the solar photosphere using the 6173 Fe I absorption line. The instrument consists of a front-window filter, a telescope, a set of wave plates for polarimetry, an image-stabilization system, a blocking filter, a five-stage Lyot filter with one tunable element, two wide-field tunable Michelson interferometers, a pair of 4096(exo 2) pixel cameras with independent shutters, and associated electronics. Each camera takes a full-disk image roughly every 3.75 seconds giving an overall cadence of 45 seconds for the Doppler, intensity, and line-of-sight magnetic-field measurements and a slower cadence for the full vector magnetic field. This article describes the design of the HMI instrument and provides an overview of the pre-launch calibration efforts. Overviews of the investigation, details of the calibrations, data handling, and the science analysis are provided in accompanying articles.

  14. Calibration Systems Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Myers, Tanya L.; Broocks, Bryan T.; Phillips, Mark C.

    2006-02-01

    The Calibration Systems project at Pacific Northwest National Laboratory (PNNL) is aimed towards developing and demonstrating compact Quantum Cascade (QC) laser-based calibration systems for infrared imaging systems. These on-board systems will improve the calibration technology for passive sensors, which enable stand-off detection for the proliferation or use of weapons of mass destruction, by replacing on-board blackbodies with QC laser-based systems. This alternative technology can minimize the impact on instrument size and weight while improving the quality of instruments for a variety of missions. The potential of replacing flight blackbodies is made feasible by the high output, stability, and repeatability of the QC laser spectral radiance.

  15. Ibis ground calibration

    Energy Technology Data Exchange (ETDEWEB)

    Bird, A.J.; Barlow, E.J.; Tikkanen, T. [Southampton Univ., School of Physics and Astronomy (United Kingdom); Bazzano, A.; Del Santo, M.; Ubertini, P. [Istituto di Astrofisica Spaziale e Fisica Cosmica - IASF/CNR, Roma (Italy); Blondel, C.; Laurent, P.; Lebrun, F. [CEA Saclay - Sap, 91 - Gif sur Yvette (France); Di Cocco, G.; Malaguti, E. [Istituto di Astrofisica Spaziale e Fisica-Bologna - IASF/CNR (Italy); Gabriele, M.; La Rosa, G.; Segreto, A. [Istituto di Astrofisica Spaziale e Fisica- IASF/CNR, Palermo (Italy); Quadrini, E. [Istituto di Astrofisica Spaziale e Fisica-Cosmica, EASF/CNR, Milano (Italy); Volkmer, R. [Institut fur Astronomie und Astrophysik, Tubingen (Germany)

    2003-11-01

    We present an overview of results obtained from IBIS ground calibrations. The spectral and spatial characteristics of the detector planes and surrounding passive materials have been determined through a series of calibration campaigns. Measurements of pixel gain, energy resolution, detection uniformity, efficiency and imaging capability are presented. The key results obtained from the ground calibration have been: - optimization of the instrument tunable parameters, - determination of energy linearity for all detection modes, - determination of energy resolution as a function of energy through the range 20 keV - 3 MeV, - demonstration of imaging capability in each mode, - measurement of intrinsic detector non-uniformity and understanding of the effects of passive materials surrounding the detector plane, and - discovery (and closure) of various leakage paths through the passive shielding system.

  16. Automatic magnetometer calibration with small space coverage

    Science.gov (United States)

    Wahdan, Ahmed

    The use of a standalone Global Navigation Satellite System (GNSS) has proved to be insufficient when navigating indoors or in urban canyons due to multipath or obstruction. Recent technological advances in low cost micro-electro-mechanical system (MEMS) -- based sensors (like accelerometers, gyroscopes and magnetometers) enabled the development of sensor-based navigation systems. Although MEMS sensors are low-cost, lightweight, small size, and have low-power consumption, they have complex error characteristics. Accurate computation of the heading angle (azimuth) is one of the most important aspects of any navigation system. It can be computed either by gyroscopes or magnetometers. Gyroscopes are inertial sensors that can provide the angular rate from which the heading can be calculated, however, their outputs drift with time. Moreover, the accumulated errors due to mathematical integration, performed to obtain the heading angle, lead to large heading errors. On the other hand, magnetometers do not suffer from drift and the calculation of heading does not suffer from error accumulation. They can provide an absolute heading from the magnetic north by sensing the earth's magnetic field. However, magnetometer readings are usually affected by magnetic fields, other than the earth magnetic field, and by other error sources; therefore magnetometer calibration is required to use magnetometer as a reliable source of heading in navigation applications. In this thesis, a framework for fast magnetometer calibration is proposed. This framework requires little space coverage with no user involvement in the calibration process, and does not need specific movements to be performed. The proposed techniques are capable of performing both 2-dimensional (2D) and 3-dimensional (3D) calibration for magnetometers. They are developed to consider different scenarios suitable for different applications, and can benefit from natural device movements. Some applications involve tethering the

  17. Calibrating Legal Judgments

    Directory of Open Access Journals (Sweden)

    Frederick Schauer

    2017-09-01

    Full Text Available Objective to study the notion and essence of legal judgments calibration the possibilities of using it in the lawenforcement activity to explore the expenses and advantages of using it. Methods dialectic approach to the cognition of social phenomena which enables to analyze them in historical development and functioning in the context of the integrity of objective and subjective factors it determined the choice of the following research methods formallegal comparative legal sociological methods of cognitive psychology and philosophy. Results In ordinary life people who assess other peoplersaquos judgments typically take into account the other judgments of those they are assessing in order to calibrate the judgment presently being assessed. The restaurant and hotel rating website TripAdvisor is exemplary because it facilitates calibration by providing access to a raterrsaquos previous ratings. Such information allows a user to see whether a particular rating comes from a rater who is enthusiastic about every place she patronizes or instead from someone who is incessantly hard to please. And even when less systematized as in assessing a letter of recommendation or college transcript calibration by recourse to the decisional history of those whose judgments are being assessed is ubiquitous. Yet despite the ubiquity and utility of such calibration the legal system seems perversely to reject it. Appellate courts do not openly adjust their standard of review based on the previous judgments of the judge whose decision they are reviewing nor do judges in reviewing legislative or administrative decisions magistrates in evaluating search warrant representations or jurors in assessing witness perception. In most legal domains calibration by reference to the prior decisions of the reviewee is invisible either because it does not exist or because reviewing bodies are unwilling to admit using what they in fact know and employ. Scientific novelty for the first

  18. Iterative Magnetometer Calibration

    Science.gov (United States)

    Sedlak, Joseph

    2006-01-01

    This paper presents an iterative method for three-axis magnetometer (TAM) calibration that makes use of three existing utilities recently incorporated into the attitude ground support system used at NASA's Goddard Space Flight Center. The method combines attitude-independent and attitude-dependent calibration algorithms with a new spinning spacecraft Kalman filter to solve for biases, scale factors, nonorthogonal corrections to the alignment, and the orthogonal sensor alignment. The method is particularly well-suited to spin-stabilized spacecraft, but may also be useful for three-axis stabilized missions given sufficient data to provide observability.

  19. Importance dosimetry of the systematic error in the twist of collimator on treatments VMAT; Importancia dosimetrica del error sistematico en el giro de colimador en tratamientos VMAT

    Energy Technology Data Exchange (ETDEWEB)

    Puchades Puchades, V.; Serna Berna, A.; Mata Colodro, F.; Ramos Amores, D.

    2013-07-01

    The aim of this study is to assess the dosimetric impact produced by the presence of systematic errors associated to poor calibration of rotation of collimator with the VMAT treatment technique. (Author)

  20. Radiometric inter-sensor cross-calibration uncertainty using a traceable high accuracy reference hyperspectral imager

    Science.gov (United States)

    Gorroño, Javier; Banks, Andrew C.; Fox, Nigel P.; Underwood, Craig

    2017-08-01

    Optical earth observation (EO) satellite sensors generally suffer from drifts and biases relative to their pre-launch calibration, caused by launch and/or time in the space environment. This places a severe limitation on the fundamental reliability and accuracy that can be assigned to satellite derived information, and is particularly critical for long time base studies for climate change and enabling interoperability and Analysis Ready Data. The proposed TRUTHS (Traceable Radiometry Underpinning Terrestrial and Helio-Studies) mission is explicitly designed to address this issue through re-calibrating itself directly to a primary standard of the international system of units (SI) in-orbit and then through the extension of this SI-traceability to other sensors through in-flight cross-calibration using a selection of Committee on Earth Observation Satellites (CEOS) recommended test sites. Where the characteristics of the sensor under test allows, this will result in a significant improvement in accuracy. This paper describes a set of tools, algorithms and methodologies that have been developed and used in order to estimate the radiometric uncertainty achievable for an indicative target sensor through in-flight cross-calibration using a well-calibrated hyperspectral SI-traceable reference sensor with observational characteristics such as TRUTHS. In this study, Multi-Spectral Imager (MSI) of Sentinel-2 and Landsat-8 Operational Land Imager (OLI) is evaluated as an example, however the analysis is readily translatable to larger-footprint sensors such as Sentinel-3 Ocean and Land Colour Instrument (OLCI) and Visible Infrared Imaging Radiometer Suite (VIIRS). This study considers the criticality of the instrumental and observational characteristics on pixel level reflectance factors, within a defined spatial region of interest (ROI) within the target site. It quantifies the main uncertainty contributors in the spectral, spatial, and temporal domains. The resultant tool

  1. Measurement Errors and Uncertainties Theory and Practice

    CERN Document Server

    Rabinovich, Semyon G

    2006-01-01

    Measurement Errors and Uncertainties addresses the most important problems that physicists and engineers encounter when estimating errors and uncertainty. Building from the fundamentals of measurement theory, the author develops the theory of accuracy of measurements and offers a wealth of practical recommendations and examples of applications. This new edition covers a wide range of subjects, including: - Basic concepts of metrology - Measuring instruments characterization, standardization and calibration -Estimation of errors and uncertainty of single and multiple measurements - Modern probability-based methods of estimating measurement uncertainty With this new edition, the author completes the development of the new theory of indirect measurements. This theory provides more accurate and efficient methods for processing indirect measurement data. It eliminates the need to calculate the correlation coefficient - a stumbling block in measurement data processing - and offers for the first time a way to obtain...

  2. Heliostat kinematic system calibration using uncalibrated cameras

    Science.gov (United States)

    Burisch, Michael; Gomez, Luis; Olasolo, David; Villasante, Cristobal

    2017-06-01

    The efficiency of the solar field greatly depends on the ability of the heliostats to precisely reflect solar radiation onto a central receiver. To control the heliostats with such a precision accurate knowledge of the motion of each of them modeled as a kinematic system is required. Determining the parameters of this system for each heliostat by a calibration system is crucial for the efficient operation of the solar field. For small sized heliostats being able to make such a calibration in a fast and automatic manner is imperative as the solar field potentially contain tens or even hundreds of thousands of them. A calibration system which can rapidly recalibrate a whole solar field would also allow reducing costs. Heliostats are generally designed to provide stability over a large period of time. Being able to relax this requirement and compensate any occurring error by adapting parameters in a model, the costs of the heliostat can be reduced. The presented method describes such an automatic calibration system using uncalibrated cameras rigidly attached to each heliostat. The cameras are used to observe targets spread out through the solar field; based on this the kinematic system of the heliostat can be estimated with high precision. A comparison of this approach to similar solutions shows the viability of the proposed solution.

  3. Effective radiation attenuation calibration for breast density: compression thickness influences and correction

    Directory of Open Access Journals (Sweden)

    Thomas Jerry A

    2010-11-01

    Full Text Available Abstract Background Calibrating mammograms to produce a standardized breast density measurement for breast cancer risk analysis requires an accurate spatial measure of the compressed breast thickness. Thickness inaccuracies due to the nominal system readout value and compression paddle orientation induce unacceptable errors in the calibration. Method A thickness correction was developed and evaluated using a fully specified two-component surrogate breast model. A previously developed calibration approach based on effective radiation attenuation coefficient measurements was used in the analysis. Water and oil were used to construct phantoms to replicate the deformable properties of the breast. Phantoms consisting of measured proportions of water and oil were used to estimate calibration errors without correction, evaluate the thickness correction, and investigate the reproducibility of the various calibration representations under compression thickness variations. Results The average thickness uncertainty due to compression paddle warp was characterized to within 0.5 mm. The relative calibration error was reduced to 7% from 48-68% with the correction. The normalized effective radiation attenuation coefficient (planar representation was reproducible under intra-sample compression thickness variations compared with calibrated volume measures. Conclusion Incorporating this thickness correction into the rigid breast tissue equivalent calibration method should improve the calibration accuracy of mammograms for risk assessments using the reproducible planar calibration measure.

  4. In-situ Broadband Cryogenic Calibration for Two-port Superconducting Microwave Resonators

    CERN Document Server

    Yeh, Jen-Hao

    2012-01-01

    In this paper we introduce an improved microwave calibration method for use in a cryogenic environment, based on a traditional three-standard calibration, the Thru-Reflection-Line (TRL) calibration. The modified calibration method takes advantage of additional information from multiple measurements of an ensemble of realizations of a superconducting resonator, as a new pseudo-Open standard, to correct errors in the TRL calibration. We also demonstrate an experimental realization of this in-situ broadband cryogenic calibration system utilizing cryogenic switches. All calibration measurements are done in the same thermal cycle as the measurement of the resonator (requiring only an additional 20 minutes), thus avoiding 4 additional thermal cycles for traditional TRL calibration (which would require an additional 12 days). The experimental measurements on a wave chaotic microwave billiard verify that the new method significantly improves the measured scattering matrix of a high-quality-factor superconducting reso...

  5. In situ broadband cryogenic calibration for two-port superconducting microwave resonators.

    Science.gov (United States)

    Yeh, Jen-Hao; Anlage, Steven M

    2013-03-01

    We introduce an improved microwave calibration method for use in a cryogenic environment, based on a traditional three-standard calibration, the Thru-Reflect-Line (TRL) calibration. The modified calibration method takes advantage of additional information from multiple measurements of an ensemble of realizations of a superconducting resonator, as a new pseudo-Open standard, to correct errors in the TRL calibration. We also demonstrate an experimental realization of this in situ broadband cryogenic calibration system utilizing cryogenic switches. All calibration measurements are done in the same thermal cycle as the measurement of the resonator (requiring only an additional 20 min), thus avoiding 4 additional thermal cycles for traditional TRL calibration (which would require an additional 12 days). The experimental measurements on a wave-chaotic microwave billiard verify that the new method significantly improves the measured scattering matrix of a high-quality-factor superconducting resonator.

  6. Errors of measurement by laser goniometer

    Science.gov (United States)

    Agapov, Mikhail Y.; Bournashev, Milhail N.

    2000-11-01

    The report is dedicated to research of systematic errors of angle measurement by a dynamic laser goniometer (DLG) on the basis of a ring laser (RL), intended of certification of optical angle encoders (OE), and development of methods of separation the errors of different types and their algorithmic compensation. The OE was of the absolute photoelectric angle encoder type with an informational capacity of 14 bits. Cinematic connection with a rotary platform was made through mechanical connection unit (CU). The measurement and separation of a systematic error to components was carried out with applying of a method of cross-calibration at mutual turns OE in relation to DLG base and CU in relation to OE rotor. Then the Fourier analysis of observed data was made. The research of dynamic errors of angle measurements was made with use of dependence of measured angle between reference direction assigned by the interference null-indicator (NI) with an 8-faced optical polygon (OP), and direction defined by means of the OE, on angular rate of rotation. The obtained results allow to make algorithmic compensation of a systematic error and in the total considerably to reduce a total error of measurements.

  7. Smart Calibration of Excavators

    DEFF Research Database (Denmark)

    Bro, Marie; Døring, Kasper; Ellekilde, Lars-Peter

    2005-01-01

    Excavators dig holes. But where is the bucket? The purpose of this report is to treat four different problems concerning calibrations of position indicators for excavators in operation at concrete construction sites. All four problems are related to the question of how to determine the precise ge...

  8. Calibration with Absolute Shrinkage

    DEFF Research Database (Denmark)

    Øjelund, Henrik; Madsen, Henrik; Thyregod, Poul

    2001-01-01

    is suggested to cope with the singular design matrix most often seen in chemometric calibration. Furthermore, the proposed algorithm may be generalized to all convex norms like Sigma/beta (j)/(gamma) where gamma greater than or equal to 1, i.e. a method that continuously varies from ridge regression...

  9. Calibrating Communication Competencies

    Science.gov (United States)

    Surges Tatum, Donna

    2016-11-01

    The Many-faceted Rasch measurement model is used in the creation of a diagnostic instrument by which communication competencies can be calibrated, the severity of observers/raters can be determined, the ability of speakers measured, and comparisons made between various groups.

  10. NVLAP calibration laboratory program

    Energy Technology Data Exchange (ETDEWEB)

    Cigler, J.L.

    1993-12-31

    This paper presents an overview of the progress up to April 1993 in the development of the Calibration Laboratories Accreditation Program within the framework of the National Voluntary Laboratory Accreditation Program (NVLAP) at the National Institute of Standards and Technology (NIST).

  11. CALIBRATION OF PHOSWICH DETECTORS

    NARCIS (Netherlands)

    LEEGTE, HKW; KOLDENHOF, EE; BOONSTRA, AL; WILSCHUT, HW

    1992-01-01

    Two important aspects for the calibration of phoswich detector arrays have been investigated. It is shown that common gate ADCs can be used: The loss in particle identification due to fluctuations in the gate timing in multi-hit events can be corrected for by a simple procedure using the measured ti

  12. Measurement System & Calibration report

    DEFF Research Database (Denmark)

    Kock, Carsten Weber; Vesth, Allan

    This Measurement System & Calibration report is describing DTU’s measurement system installed at a specific wind turbine. A major part of the sensors has been installed by others (see [1]) the rest of the sensors have been installed by DTU. The results of the measurements, described in this report...

  13. Entropic calibration revisited

    Energy Technology Data Exchange (ETDEWEB)

    Brody, Dorje C. [Blackett Laboratory, Imperial College, London SW7 2BZ (United Kingdom)]. E-mail: d.brody@imperial.ac.uk; Buckley, Ian R.C. [Centre for Quantitative Finance, Imperial College, London SW7 2AZ (United Kingdom); Constantinou, Irene C. [Blackett Laboratory, Imperial College, London SW7 2BZ (United Kingdom); Meister, Bernhard K. [Blackett Laboratory, Imperial College, London SW7 2BZ (United Kingdom)

    2005-04-11

    The entropic calibration of the risk-neutral density function is effective in recovering the strike dependence of options, but encounters difficulties in determining the relevant greeks. By use of put-call reversal we apply the entropic method to the time reversed economy, which allows us to obtain the spot price dependence of options and the relevant greeks.

  14. Landsat-8 Thermal Infrared Sensor (TIRS Vicarious Radiometric Calibration

    Directory of Open Access Journals (Sweden)

    Julia A. Barsi

    2014-11-01

    Full Text Available Launched in February 2013, the Landsat-8 carries on-board the Thermal Infrared Sensor (TIRS, a two-band thermal pushbroom imager, to maintain the thermal imaging capability of the Landsat program. The TIRS bands are centered at roughly 10.9 and 12 μm (Bands 10 and 11 respectively. They have 100 m spatial resolution and image coincidently with the Operational Land Imager (OLI, also on-board Landsat-8. The TIRS instrument has an internal calibration system consisting of a variable temperature blackbody and a special viewport with which it can see deep space; a two point calibration can be performed twice an orbit. Immediately after launch, a rigorous vicarious calibration program was started to validate the absolute calibration of the system. The two vicarious calibration teams, NASA/Jet Propulsion Laboratory (JPL and the Rochester Institute of Technology (RIT, both make use of buoys deployed on large water bodies as the primary monitoring technique. RIT took advantage of cross-calibration opportunity soon after launch when Landsat-8 and Landsat-7 were imaging the same targets within a few minutes of each other to perform a validation of the absolute calibration. Terra MODIS is also being used for regular monitoring of the TIRS absolute calibration. The buoy initial results showed a large error in both bands, 0.29 and 0.51 W/m2·sr·μm or −2.1 K and −4.4 K at 300 K in Band 10 and 11 respectively, where TIRS data was too hot. A calibration update was recommended for both bands to correct for a bias error and was implemented on 3 February 2014 in the USGS/EROS processing system, but the residual variability is still larger than desired for both bands (0.12 and 0.2 W/m2·sr·μm or 0.87 and 1.67 K at 300 K. Additional work has uncovered the source of the calibration error: out-of-field stray light. While analysis continues to characterize the stray light contribution, the vicarious calibration work proceeds. The additional data have not changed

  15. Method for large-range structured light system calibration.

    Science.gov (United States)

    An, Yatong; Bell, Tyler; Li, Beiwen; Xu, Jing; Zhang, Song

    2016-11-20

    Structured light system calibration often requires the usage of a calibration target with a similar size as the field of view (FOV), which brings challenges to a large-range structured light system calibration since fabricating large calibration targets is difficult and expensive. This paper presents a large-range system calibration method that does not need a large calibration target. The proposed method includes two stages: (1) accurately calibrate intrinsics (i.e., focal lengths and principle points) at a near range where both the camera and projector are out of focus, and (2) calibrate the extrinsic parameters (translation and rotation) from camera to projector with the assistance of a low-accuracy, large-range three-dimensional (3D) sensor (e.g., Microsoft Kinect). We have developed a large-scale 3D shape measurement system with a FOV of 1120  mm×1900  mm×1000  mm. Experiments demonstrate our system can achieve measurement accuracy as high as 0.07 mm with a standard deviation of 0.80 mm by measuring a 304.8 mm diameter sphere. As a comparison, Kinect V2 only achieved mean error of 0.80 mm with a standard deviation of 3.41 mm for the FOV of measurement.

  16. Quantitative Analysis of Carbon Steel with Multi-Line Internal Standard Calibration Method Using Laser-Induced Breakdown Spectroscopy.

    Science.gov (United States)

    Pan, Congyuan; Du, Xuewei; An, Ning; Zeng, Qiang; Wang, Shengbo; Wang, Qiuping

    2016-04-01

    A multi-line internal standard calibration method is proposed for the quantitative analysis of carbon steel using laser-induced breakdown spectroscopy (LIBS). A procedure based on the method was adopted to select the best calibration curves and the corresponding emission lines pairs automatically. Laser-induced breakdown spectroscopy experiments with carbon steel samples were performed, and C, Cr, and Mn were analyzed via the proposed method. Calibration curves of these elements were constructed via a traditional single line internal standard calibration method and a multi-line internal standard calibration method. The calibration curves obtained were evaluated with the determination coefficient, the root mean square error of cross-validation, and the average relative error of cross-validation. All of the parameters were improved significantly with the proposed method. The results show that accurate and stable calibration curves can be obtained efficiently via the multi-line internal standard calibration method. © The Author(s) 2016.

  17. Mercury CEM Calibration

    Energy Technology Data Exchange (ETDEWEB)

    John F. Schabron; Joseph F. Rovani; Susan S. Sorini

    2007-03-31

    The Clean Air Mercury Rule (CAMR) which was published in the Federal Register on May 18, 2005, requires that calibration of mercury continuous emissions monitors (CEMs) be performed with NIST-traceable standards. Western Research Institute (WRI) is working closely with the Electric Power Research Institute (EPRI), the National Institute of Standards and Technology (NIST), and the Environmental Protection Agency (EPA) to facilitate the development of the experimental criteria for a NIST traceability protocol for dynamic elemental mercury vapor generators. The traceability protocol will be written by EPA. Traceability will be based on the actual analysis of the output of each calibration unit at several concentration levels ranging from about 2-40 ug/m{sup 3}, and this analysis will be directly traceable to analyses by NIST using isotope dilution inductively coupled plasma/mass spectrometry (ID ICP/MS) through a chain of analyses linking the calibration unit in the power plant to the NIST ID ICP/MS. Prior to this project, NIST did not provide a recommended mercury vapor pressure equation or list mercury vapor pressure in its vapor pressure database. The NIST Physical and Chemical Properties Division in Boulder, Colorado was subcontracted under this project to study the issue in detail and to recommend a mercury vapor pressure equation that the vendors of mercury vapor pressure calibration units can use to calculate the elemental mercury vapor concentration in an equilibrium chamber at a particular temperature. As part of this study, a preliminary evaluation of calibration units from five vendors was made. The work was performed by NIST in Gaithersburg, MD and Joe Rovani from WRI who traveled to NIST as a Visiting Scientist.

  18. Calibration of Laser Beam Direction for Inner Diameter Measuring Device

    Directory of Open Access Journals (Sweden)

    Tongyu Yang

    2017-02-01

    Full Text Available The laser triangulation method is one of the most advanced methods for large inner diameter measurement. Our research group proposed a kind of inner diameter measuring device that is principally composed of three laser displacement sensors known to be fixed in the same plane measurement position. It is necessary to calibrate the direction of the laser beams that are emitted by laser displacement sensors because they do not meet the theoretical model accurately. For the purpose of calibrating the direction of laser beams, a calibration method and mathematical model were proposed. The inner diameter measuring device is equipped with the spindle of the machine tool. The laser beams rotate and translate in the plane and constitute the rotary rays which are driven to scan the inner surface of the ring gauge. The direction calibration of the laser beams can be completed by the sensors’ distance information and corresponding data processing method. The corresponding error sources are analyzed and the validity of the method is verified. After the calibration, the measurement error of the inner diameter measuring device reduced from ± 25 μ m to ± 15 μ m and the relative error was not more than 0.011%.

  19. Angular diameter estimation of interferometric calibrators. Example of λ Gruis, calibrator for VLTI-AMBER

    Science.gov (United States)

    Cruzalèbes, P.; Jorissen, A.; Sacuto, S.; Bonneau, D.

    2010-06-01

    Context. Accurate long-baseline interferometric measurements require careful calibration with reference stars. Small calibrators with high angular diameter accuracy ensure the true visibility uncertainty to be dominated by the measurement errors. Aims: We review some indirect methods for estimating angular diameter, using various types of input data. Each diameter estimate, obtained for the test-case calibrator star λ Gru, is compared with the value 2.71 mas found in the Bordé calibrator catalogue published in 2002. Methods: Angular size estimations from spectral type, spectral index, in-band magnitude, broadband photometry, and spectrophotometry give close estimates of the angular diameter, with slightly variable uncertainties. Fits on photometry and spectrophotometry need physical atmosphere models with “plausible” stellar parameters. Angular diameter uncertainties were estimated by means of residual bootstrapping confidence intervals. All numerical results and graphical outputs presented in this paper were obtained using the routines developed under PV-WAVE®, which compose the modular software suite SPIDAST, created to calibrate and interprete spectroscopic and interferometric measurements, particularly those obtained with VLTI-AMBER. Results: The final angular diameter estimate 2.70 mas of λ Gru, with 68% confidence interval 2.65-2.81 mas, is obtained by fit of the MARCS model on the ISO-SWS 2.38-27.5 μm spectrum, with the stellar parameters Te = 4250 K, log g = 2.0, z = 0.0 dex, M = 1.0 M⊙, and ξ_t = 2.0 km s-1.

  20. Improved Evaluation of Planar Calibration Standards Using the TDR Preselection Method

    Directory of Open Access Journals (Sweden)

    J. Vancl

    2007-01-01

    Full Text Available Calibration and correction methods for the Vector Network Analyzer (VNA are based on the fundamental assumption of the constant error model, which is independent of connected calibration standards and/or devices under test (DUT. Unfortunately, this assumption is not satisfied well for planar calibration standards fabricated by etching technology on soft substrates. An evaluation of the error model is affected especially by variations in the manufacturing process and also by the reproducibility of an assembly. In this paper, we propose error minimization by selecting the best combination of available calibration standards based on time domain reflection (TDR measurement, which can also be obtained by the fourier transformation from the measured S-parameters. The proposed method was verified experimentally using short, open, load and thru (SOLT standards fabricated on an FR4 laminate substrate which achieves the essential reduction of the measurement error in the frequency range up to 15 GHz. 

  1. Calibrating ground-based microwave radiometers: Uncertainty and drifts

    Science.gov (United States)

    Küchler, N.; Turner, D. D.; Löhnert, U.; Crewell, S.

    2016-04-01

    The quality of microwave radiometer (MWR) calibrations, including both the absolute radiometric accuracy and the spectral consistency, determines the accuracy of geophysical retrievals. The Microwave Radiometer Calibration Experiment (MiRaCalE) was conducted to evaluate the performance of MWR calibration techniques, especially of the so-called Tipping Curve Calibrations (TCC) and Liquid Nitrogen Calibrations (LN2cal), by repeatedly calibrating a fourth-generation Humidity and Temperature Profiler (HATPRO-G4) that measures downwelling radiance between 20 GHz and 60 GHz. MiRaCalE revealed two major points to improve MWR calibrations: (i) the necessary repetition frequency for MWR calibration techniques to correct drifts, which ensures stable long-term measurements; and (ii) the spectral consistency of control measurements of a well known reference is useful to estimate calibration accuracy. Besides, we determined the accuracy of the HATPRO's liquid nitrogen-cooled blackbody's temperature. TCCs and LN2cals were found to agree within 0.5 K when observing the liquid nitrogen-cooled blackbody with a physical temperature of 77 K. This agreement of two different calibration techniques suggests that the brightness temperature of the LN2 cooled blackbody is accurate within at least 0.5 K, which is a significant reduction of the uncertainties that have been assumed to vary between 0.6 K and 1.5 K when calibrating the HATPRO-G4. The error propagation of both techniques was found to behave almost linearly, leading to maximum uncertainties of 0.7 K when observing a scene that is associated with a brightness temperature of 15 K.

  2. Towards automatic calibration of 2-dimensional flood propagation models

    Directory of Open Access Journals (Sweden)

    P. Fabio

    2009-11-01

    Full Text Available Hydraulic models for flood propagation description are an essential tool in many fields, e.g. civil engineering, flood hazard and risk assessments, evaluation of flood control measures, etc. Nowadays there are many models of different complexity regarding the mathematical foundation and spatial dimensions available, and most of them are comparatively easy to operate due to sophisticated tools for model setup and control. However, the calibration of these models is still underdeveloped in contrast to other models like e.g. hydrological models or models used in ecosystem analysis. This has basically two reasons: first, the lack of relevant data against the models can be calibrated, because flood events are very rarely monitored due to the disturbances inflicted by them and the lack of appropriate measuring equipment in place. Secondly, especially the two-dimensional models are computationally very demanding and therefore the use of available sophisticated automatic calibration procedures is restricted in many cases. This study takes a well documented flood event in August 2002 at the Mulde River in Germany as an example and investigates the most appropriate calibration strategy for a full 2-D hyperbolic finite element model. The model independent optimiser PEST, that gives the possibility of automatic calibrations, is used. The application of the parallel version of the optimiser to the model and calibration data showed that a it is possible to use automatic calibration in combination of 2-D hydraulic model, and b equifinality of model parameterisation can also be caused by a too large number of degrees of freedom in the calibration data in contrast to a too simple model setup. In order to improve model calibration and reduce equifinality a method was developed to identify calibration data with likely errors that obstruct model calibration.

  3. Field calibration of cup anemometers

    DEFF Research Database (Denmark)

    Schmidt Paulsen, Uwe; Mortensen, Niels Gylling; Hansen, Jens Carsten

    2007-01-01

    A field calibration method and results are described along with the experience gained with the method. The cup anemometers to be calibrated are mounted in a row on a 10-m high rig and calibrated in the free wind against a reference cup anemometer. The method has been reported [1] to improve...... the statistical bias on the data relative to calibrations carried out in a wind tunnel. The methodology is sufficiently accurate for calibration of cup anemometers used for wind resource assessments and provides a simple, reliable and cost-effective solution to cup anemometer calibration, especially suited...

  4. Probabilistic quantum error correction

    CERN Document Server

    Fern, J; Fern, Jesse; Terilla, John

    2002-01-01

    There are well known necessary and sufficient conditions for a quantum code to correct a set of errors. We study weaker conditions under which a quantum code may correct errors with probabilities that may be less than one. We work with stabilizer codes and as an application study how the nine qubit code, the seven qubit code, and the five qubit code perform when there are errors on more than one qubit. As a second application, we discuss the concept of syndrome quality and use it to suggest a way that quantum error correction can be practically improved.

  5. Calibration of high-heat-flux sensors in a solar furnace

    Energy Technology Data Exchange (ETDEWEB)

    Ballestrin, J.; Rodriguez-Alonso, M.; Rodriguez, J.; Canadas, I. [Centro de Investigaciones Energeticas, Medioambientales y Tecnologicas (CIEMAT), Almeria (Spain); Barbero, F.J. [Almeria Univ., Dept. de Fisica (Spain); Langley, L.W.; Barnes, A. [Vatell Corporation, Christiansburg, VA (United States)

    2006-12-15

    The most common sensors used for the measurement of high solar irradiance are the Gardon gauges, which are usually calibrated using a black body at a certain temperature as the radiant source. This calibration procedure is assumed to produce a systematic error when solar irradiance measurements are taken using these sensors. This paper demonstrates a calorimetric method for calibrating these high-heat-flux gauges in a solar furnace. This procedure has enabled these sensors to be calibrated under concentrated solar radiation at higher irradiances under non-laboratory conditions in the CIEMAT solar furnace at the Plataforma Solar de Almeria. Working at higher irradiances has allowed the uncertainty in the calibration constant of these sensors to be reduced. This work experimentally confirms the predicted systematic errors committed when measuring high solar irradiances using Gardon sensors calibrated with a black body. (authors)

  6. Calibration of high-heat-flux sensors in a solar furnace

    Science.gov (United States)

    Ballestrín, J.; Rodríguez-Alonso, M.; Rodríguez, J.; Cañadas, I.; Barbero, F. J.; Langley, L. W.; Barnes, A.

    2006-12-01

    The most common sensors used for the measurement of high solar irradiance are the Gardon gauges, which are usually calibrated using a black body at a certain temperature as the radiant source. This calibration procedure is assumed to produce a systematic error when solar irradiance measurements are taken using these sensors. This paper demonstrates a calorimetric method for calibrating these high-heat-flux gauges in a solar furnace. This procedure has enabled these sensors to be calibrated under concentrated solar radiation at higher irradiances under non-laboratory conditions in the CIEMAT solar furnace at the Plataforma Solar de Almería. Working at higher irradiances has allowed the uncertainty in the calibration constant of these sensors to be reduced. This work experimentally confirms the predicted systematic errors committed when measuring high solar irradiances using Gardon sensors calibrated with a black body.

  7. STUDY ON A PRECISE ON-SPOT CALIBRATION METHOD FOR DISTRIBUTED STEREO REFERENCE POSITION-SETTING

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A high precision method used for on-spot calibration of distributed stereo reference position Setting is pre-sented. The high measuring accuracy in stereo reference calibration is derived from using a high precision water level in-strument and an accurate height vernier caliper. It settles the problem of reference calibration effectively and accurately,without using large coordinate measuring machines (CMM). It is more adaptable and precise than traditional calibrationmethods applying theodolites or autocollimators. The error sources of this method are analyzed in detail and severalmethods are developed to eliminate the calibration error. An optimizing swallowtail-like anchor target is developed. Ex-periments show that the calibration accuracy can be limited within 0.06 mm in the range of 3~5 m and 0.03 mm withoptimizing anchor target. This method can be widely used in on-spot calibration.

  8. Robust Radio Interferometric Calibration Using the t-Distribution

    CERN Document Server

    Kazemi, S

    2013-01-01

    A major stage of radio interferometric data processing is calibration or the estimation of systematic errors in the data and the correction for such errors. A stochastic error (noise) model is assumed, and in most cases, this underlying model is assumed to be Gaussian. However, outliers in the data due to interference or due to errors in the sky model would have adverse effects on processing based on a Gaussian noise model. Most of the shortcomings of calibration such as the loss in flux or coherence, and the appearance of spurious sources, could be attributed to the deviations of the underlying noise model. In this paper, we propose to improve the robustness of calibration by using a noise model based on Student's t distribution. Student's t noise is a special case of Gaussian noise when the variance is unknown. Unlike Gaussian noise model based calibration, traditional least squares minimization would not directly extend to a case when we have a Student's t noise model. Therefore, we use a variant of the Ex...

  9. Calibrating the ECCO ocean general circulation model using Green's functions

    Science.gov (United States)

    Menemenlis, D.; Fu, L. L.; Lee, T.; Fukumori, I.

    2002-01-01

    Green's functions provide a simple, yet effective, method to test and calibrate General-Circulation-Model(GCM) parameterizations, to study and quantify model and data errors, to correct model biases and trends, and to blend estimates from different solutions and data products.

  10. Mercury Calibration System

    Energy Technology Data Exchange (ETDEWEB)

    John Schabron; Eric Kalberer; Joseph Rovani; Mark Sanderson; Ryan Boysen; William Schuster

    2009-03-11

    U.S. Environmental Protection Agency (EPA) Performance Specification 12 in the Clean Air Mercury Rule (CAMR) states that a mercury CEM must be calibrated with National Institute for Standards and Technology (NIST)-traceable standards. In early 2009, a NIST traceable standard for elemental mercury CEM calibration still does not exist. Despite the vacature of CAMR by a Federal appeals court in early 2008, a NIST traceable standard is still needed for whatever regulation is implemented in the future. Thermo Fisher is a major vendor providing complete integrated mercury continuous emissions monitoring (CEM) systems to the industry. WRI is participating with EPA, EPRI, NIST, and Thermo Fisher towards the development of the criteria that will be used in the traceability protocols to be issued by EPA. An initial draft of an elemental mercury calibration traceability protocol was distributed for comment to the participating research groups and vendors on a limited basis in early May 2007. In August 2007, EPA issued an interim traceability protocol for elemental mercury calibrators. Various working drafts of the new interim traceability protocols were distributed in late 2008 and early 2009 to participants in the Mercury Standards Working Committee project. The protocols include sections on qualification and certification. The qualification section describes in general terms tests that must be conducted by the calibrator vendors to demonstrate that their calibration equipment meets the minimum requirements to be established by EPA for use in CAMR monitoring. Variables to be examined include linearity, ambient temperature, back pressure, ambient pressure, line voltage, and effects of shipping. None of the procedures were described in detail in the draft interim documents; however they describe what EPA would like to eventually develop. WRI is providing the data and results to EPA for use in developing revised experimental procedures and realistic acceptance criteria based on

  11. Calibration of robotic drilling systems with a moving rail

    Directory of Open Access Journals (Sweden)

    Tian Wei

    2014-12-01

    Full Text Available Industrial robots are widely used in aircraft assembly systems such as robotic drilling systems. It is necessary to expand a robot’s working range with a moving rail. A method for improving the position accuracy of an automated assembly system with an industrial robot mounted on a moving rail is proposed. A multi-station method is used to control the robot in this study. The robot only works at stations which are certain positions defined on the moving rail. The calibration of the robot system is composed by the calibration of the robot and the calibration of the stations. The calibration of the robot is based on error similarity and inverse distance weighted interpolation. The calibration of the stations is based on a magnetic strip and a magnetic sensor. Validation tests were performed in this study, which showed that the accuracy of the robot system gained significant improvement using the proposed method. The absolute position errors were reduced by about 85% to less than 0.3 mm compared with the maximum nearly 2 mm before calibration.

  12. Calibration of robotic drilling systems with a moving rail

    Institute of Scientific and Technical Information of China (English)

    Tian Wei; Zeng Yuanfan; Zhou Wei; Liao Wenhe

    2014-01-01

    Industrial robots are widely used in aircraft assembly systems such as robotic drilling sys-tems. It is necessary to expand a robot’s working range with a moving rail. A method for improving the position accuracy of an automated assembly system with an industrial robot mounted on a mov-ing rail is proposed. A multi-station method is used to control the robot in this study. The robot only works at stations which are certain positions defined on the moving rail. The calibration of the robot system is composed by the calibration of the robot and the calibration of the stations. The calibration of the robot is based on error similarity and inverse distance weighted interpolation. The calibration of the stations is based on a magnetic strip and a magnetic sensor. Validation tests were performed in this study, which showed that the accuracy of the robot system gained significant improvement using the proposed method. The absolute position errors were reduced by about 85%to less than 0.3 mm compared with the maximum nearly 2 mm before calibration.

  13. Calibration procedure for a laser triangulation scanner with uncertainty evaluation

    Science.gov (United States)

    Genta, Gianfranco; Minetola, Paolo; Barbato, Giulio

    2016-11-01

    Most of low cost 3D scanning devices that are nowadays available on the market are sold without a user calibration procedure to correct measurement errors related to changes in environmental conditions. In addition, there is no specific international standard defining a procedure to check the performance of a 3D scanner along time. This paper aims at detailing a thorough methodology to calibrate a 3D scanner and assess its measurement uncertainty. The proposed procedure is based on the use of a reference ball plate and applied to a triangulation laser scanner. Experimental results show that the metrological performance of the instrument can be greatly improved by the application of the calibration procedure that corrects systematic errors and reduces the device's measurement uncertainty.

  14. Calibration of rings using multi-step and reversal

    DEFF Research Database (Denmark)

    Savio, Enrico; Tosello, Guido; De Chiffre, Leonardo;

    2003-01-01

    with achieving sub-micrometer uncertainties in the calibration of rings on CMMs. The method is based on: i) systematic error separation using multi-step and reversal measurements, and ii) gaussian filtering of random errors. Validation of the method was provided through investigations on uncertainty contribution......, implementation of the method on two different CMMs, and comparison using roundness testers. Measurements on a 100 mm diameter master ring with a form error of approximately 0.2 µm were carried out to illustrate the procedure. Measuring uncertainty better than 0.7 µm for diameter and 0.07 µm for roundness were...

  15. True logarithmic amplification of frequency clock in SS-OCT for calibration

    OpenAIRE

    2011-01-01

    With swept source optical coherence tomography (SS-OCT), imprecise signal calibration prevents optimal imaging of biological tissues such as coronary artery. This work demonstrates an approach using a true logarithmic amplifier to precondition the clock signal, with the effort to minimize the noises and phase errors for optimal calibration. This method was validated and tested with a high-speed SS-OCT. The experimental results manifest its superior ability on optimization of the calibration a...

  16. On site calibration for new fluorescence detectors of the telescope array experiment

    Energy Technology Data Exchange (ETDEWEB)

    Tokuno, H. [Institute for Cosmic Ray Research, University of Tokyo, Kashiwa, Chiba 277-8582 (Japan)], E-mail: htokuno@icrr.u-tokyo.ac.jp; Murano, Y. [Graduate School of Science and Engineering, Tokyo Institute of Technology, Meguro, Tokyo 152-8551 (Japan); Kawana, S. [Graduate School of Science and Engineering, Saitama University, Saitama 338-8570 (Japan); Tameda, Y. [Graduate School of Science and Engineering, Tokyo Institute of Technology, Meguro, Tokyo 152-8551 (Japan); Taketa, A.; Ikeda, D.; Udo, S. [Institute for Cosmic Ray Research, University of Tokyo, Kashiwa, Chiba 277-8582 (Japan); Ogio, S. [Graduate School of Science, Osaka City University, Sumiyoshi, Osaka 558-8585 (Japan); Fukushima, M. [Institute for Cosmic Ray Research, University of Tokyo, Kashiwa, Chiba 277-8582 (Japan); Azuma, R.; Fukuda, M. [Graduate School of Science and Engineering, Tokyo Institute of Technology, Meguro, Tokyo 152-8551 (Japan); Inoue, N. [Graduate School of Science and Engineering, Saitama University, Saitama 338-8570 (Japan); Kadota, K. [Faculty of Knowledge Engineering, Musashi Institute of Technology, Setagaya, Tokyo 158-8557 (Japan); Kakimoto, F. [Graduate School of Science and Engineering, Tokyo Institute of Technology, Meguro, Tokyo 152-8551 (Japan); Sagawa, H.; Sakurai, N.; Shibata, T.; Takeda, M. [Institute for Cosmic Ray Research, University of Tokyo, Kashiwa, Chiba 277-8582 (Japan); Tsunesada, Y. [Graduate School of Science and Engineering, Tokyo Institute of Technology, Meguro, Tokyo 152-8551 (Japan)

    2009-04-01

    The Telescope Array experiment is searching for the origin of ultra-high energy cosmic rays using a ground array of particle detectors and three fluorescence telescope stations. The precise calibration of the fluorescence detectors is important for small systematic errors in shower reconstruction. This paper details the process of calibrating cameras for two of the fluorescence telescope stations. This paper provides the operational results of these camera calibrations.

  17. Combined calibration and sensitivity analysis for a water quality model of the Biebrza River, Poland

    NARCIS (Netherlands)

    Perk, van der M.; Bierkens, M.F.P.

    1995-01-01

    A study was performed to quantify the error in results of a water quality model of the Biebrza River, Poland, due to uncertainties in calibrated model parameters. The procedure used in this study combines calibration and sensitivity analysis. Finally,the model was validated to test the model capabil

  18. The Calibration Reference Data System

    Science.gov (United States)

    Greenfield, P.; Miller, T.

    2016-07-01

    We describe a software architecture and implementation for using rules to determine which calibration files are appropriate for calibrating a given observation. This new system, the Calibration Reference Data System (CRDS), replaces what had been previously used for the Hubble Space Telescope (HST) calibration pipelines, the Calibration Database System (CDBS). CRDS will be used for the James Webb Space Telescope (JWST) calibration pipelines, and is currently being used for HST calibration pipelines. CRDS can be easily generalized for use in similar applications that need a rules-based system for selecting the appropriate item for a given dataset; we give some examples of such generalizations that will likely be used for JWST. The core functionality of the Calibration Reference Data System is available under an Open Source license. CRDS is briefly contrasted with a sampling of other similar systems used at other observatories.

  19. Correction for quadrature errors

    DEFF Research Database (Denmark)

    Netterstrøm, A.; Christensen, Erik Lintz

    1994-01-01

    In high bandwidth radar systems it is necessary to use quadrature devices to convert the signal to/from baseband. Practical problems make it difficult to implement a perfect quadrature system. Channel imbalance and quadrature phase errors in the transmitter and the receiver result in error signal...

  20. ERRORS AND CORRECTION

    Institute of Scientific and Technical Information of China (English)

    1998-01-01

    To err is human . Since the 1960s, most second language teachers or language theorists have regarded errors as natural and inevitable in the language learning process . Instead of regarding them as terrible and disappointing, teachers have come to realize their value. This paper will consider these values, analyze some errors and propose some effective correction techniques.

  1. Large Hadron Collider momentum calibration and accuracy

    CERN Document Server

    AUTHOR|(CDS)2051266; Todesco, Ezio

    2017-01-01

    As a result of the excellent quality of the Large Hadron Collider (LHC) experimental detectors and the accurate calibration of the luminosity at the LHC, uncertainties on the LHC beam energy may contribute significantly to the measurement errors on certain observables unless the relative uncertainty is well below 1%. Direct measurements of the beam energy using the revolution frequency difference of proton and lead beams combined with the magnetic model errors are used to provide the energy uncertainty of the LHC beams. Above injection energy the relative uncertainty on the beam energy is determined to be ±0.1%. The energy values as reconstructed and distributed online to the LHC experiments do not require any correction above injection energy. At injection a correction of +0.31 GeV/c must be applied to the online energy values.

  2. Large Hadron Collider momentum calibration and accuracy

    Science.gov (United States)

    Todesco, E.; Wenninger, J.

    2017-08-01

    As a result of the excellent quality of the Large Hadron Collider (LHC) experimental detectors and the accurate calibration of the luminosity at the LHC, uncertainties on the LHC beam energy may contribute significantly to the measurement errors on certain observables unless the relative uncertainty is well below 1%. Direct measurements of the beam energy using the revolution frequency difference of proton and lead beams combined with the magnetic model errors are used to provide the energy uncertainty of the LHC beams. Above injection energy the relative uncertainty on the beam energy is determined to be ±0.1 %. The energy values as reconstructed and distributed online to the LHC experiments do not require any correction above injection energy. At injection a correction of +0.31 GeV /c must be applied to the online energy values.

  3. Factory-Calibrated Continuous Glucose Sensors: The Science Behind the Technology.

    Science.gov (United States)

    Hoss, Udo; Budiman, Erwin Satrya

    2017-05-01

    The use of commercially available continuous glucose monitors for diabetes management requires sensor calibrations, which until recently are exclusively performed by the patient. A new development is the implementation of factory calibration for subcutaneous glucose sensors, which eliminates the need for user calibrations and the associated blood glucose tests. Factory calibration means that the calibration process is part of the sensor manufacturing process and performed under controlled laboratory conditions. The ability to move from a user calibration to factory calibration is based on several technical requirements related to sensor stability and the robustness of the sensor manufacturing process. The main advantages of factory calibration over the conventional user calibration are: (a) more convenience for the user, since no more fingersticks are required for calibration and (b) elimination of use errors related to the execution of the calibration process, which can lead to sensor inaccuracies. The FreeStyle Libre(™) and FreeStyle Libre Pro(™) flash continuous glucose monitoring systems are the first commercially available sensor systems using factory-calibrated sensors. For these sensor systems, no user calibrations are required throughout the sensor wear duration.

  4. ERROR AND ERROR CORRECTION AT ELEMENTARY LEVEL

    Institute of Scientific and Technical Information of China (English)

    1994-01-01

    Introduction Errors are unavoidable in language learning, however, to a great extent, teachers in most middle schools in China regard errors as undesirable, a sign of failure in language learning. Most middle schools are still using the grammar-translation method which aims at encouraging students to read scientific works and enjoy literary works. The other goals of this method are to gain a greater understanding of the first language and to improve the students’ ability to cope with difficult subjects and materials, i.e. to develop the students’ minds. The practical purpose of using this method is to help learners pass the annual entrance examination. "To achieve these goals, the students must first learn grammar and vocabulary,... Grammar is taught deductively by means of long and elaborate explanations... students learn the rules of the language rather than its use." (Tang Lixing, 1983:11-12)

  5. Errors on errors - Estimating cosmological parameter covariance

    CERN Document Server

    Joachimi, Benjamin

    2014-01-01

    Current and forthcoming cosmological data analyses share the challenge of huge datasets alongside increasingly tight requirements on the precision and accuracy of extracted cosmological parameters. The community is becoming increasingly aware that these requirements not only apply to the central values of parameters but, equally important, also to the error bars. Due to non-linear effects in the astrophysics, the instrument, and the analysis pipeline, data covariance matrices are usually not well known a priori and need to be estimated from the data itself, or from suites of large simulations. In either case, the finite number of realisations available to determine data covariances introduces significant biases and additional variance in the errors on cosmological parameters in a standard likelihood analysis. Here, we review recent work on quantifying these biases and additional variances and discuss approaches to remedy these effects.

  6. [In-Flight Radiometric Calibration for ZY-3 Satellite Multispectral Sensor by Modified Reflectance-Based Method].

    Science.gov (United States)

    Han, Jie; Xie, Yong; Gu, Xing-fa; Yu, Tao; Liu, Qi-yue; Gao, Rong-jun

    2015-03-01

    Through integrating multi-spectral sensor characteristics of ZY-3 satellite, a modified reflectance-based method is proposed and used to achieve ZY-3 satellite multispectral sensor in-flight radiometric calibration. This method chooses level 1A image as data source and establishes geometric model to get an accurate observation geometric parameters at calibration site according to the information provided in image auxiliary documentation, which can reduce the influences on the calibration accuracy from image resampling and observation geometry errors. We use two-point and multi-points methods to calculate the absolute radiometric calibration coefficients of ZY-3 satellite multispectral sensor based on the large campaign at Dongying city, Shan Dong province. Compared with ZY-3 official calibration coefficients, multi-points method has higher accuracy than two-point method. Through analyzing the dispersion between each calibration point and the fitting line, we find that the residual error of water calibration site is larger than others, which of green band is approximately 67.39%. Treating water calibration site as an error, we filter it out using 95.4% confidence level as standard and recalculate the calibration coefficients with multi-points method. The final calibration coefficients show that the relative differences of the first three bands are less than 2% and the last band is less than 5%, which manifests that the proposed radiometric calibration method can obtain accurate and reliable calibration coefficients and is useful for other similar satellites in future.

  7. Lidar calibration experiments

    DEFF Research Database (Denmark)

    Ejsing Jørgensen, Hans; Mikkelsen, T.; Streicher, J.

    1997-01-01

    A series of atmospheric aerosol diffusion experiments combined with lidar detection was conducted to evaluate and calibrate an existing retrieval algorithm for aerosol backscatter lidar systems. The calibration experiments made use of two (almost) identical mini-lidar systems for aerosol cloud...... detection to test the reproducibility and uncertainty of lidars. Lidar data were obtained from both single-ended and double-ended Lidar configurations. A backstop was introduced in one of the experiments and a new method was developed where information obtained from the backstop can be used in the inversion...... algorithm. Independent in-situ aerosol plume concentrations were obtained from a simultaneous tracer gas experiment with SF6, and comparisons with the two lidars were made. The study shows that the reproducibility of the lidars is within 15%, including measurements from both sides of a plume...

  8. HIRDLS monochromator calibration equipment

    Science.gov (United States)

    Hepplewhite, Christopher L.; Barnett, John J.; Djotni, Karim; Whitney, John G.; Bracken, Justain N.; Wolfenden, Roger; Row, Frederick; Palmer, Christopher W. P.; Watkins, Robert E. J.; Knight, Rodney J.; Gray, Peter F.; Hammond, Geoffory

    2003-11-01

    A specially designed and built monochromator was developed for the spectral calibration of the HIRDLS instrument. The High Resolution Dynamics Limb Sounder (HIRDLS) is a precision infra-red remote sensing instrument with very tight requirements on the knowledge of the response to received radiation. A high performance, vacuum compatible monochromator, was developed with a wavelength range from 4 to 20 microns to encompass that of the HIRDLS instrument. The monochromator is integrated into a collimating system which is shared with a set of tiny broad band sources used for independent spatial response measurements (reported elsewhere). This paper describes the design and implementation of the monochromator and the performance obtained during the period of calibration of the HIRDLS instrument at Oxford University in 2002.

  9. Optical tweezers absolute calibration

    CERN Document Server

    Dutra, R S; Neto, P A Maia; Nussenzveig, H M

    2014-01-01

    Optical tweezers are highly versatile laser traps for neutral microparticles, with fundamental applications in physics and in single molecule cell biology. Force measurements are performed by converting the stiffness response to displacement of trapped transparent microspheres, employed as force transducers. Usually, calibration is indirect, by comparison with fluid drag forces. This can lead to discrepancies by sizable factors. Progress achieved in a program aiming at absolute calibration, conducted over the past fifteen years, is briefly reviewed. Here we overcome its last major obstacle, a theoretical overestimation of the peak stiffness, within the most employed range for applications, and we perform experimental validation. The discrepancy is traced to the effect of primary aberrations of the optical system, which are now included in the theory. All required experimental parameters are readily accessible. Astigmatism, the dominant effect, is measured by analyzing reflected images of the focused laser spo...

  10. Radiometric calibration status of Landsat-7 and Landsat-5

    Science.gov (United States)

    Barsi, J.A.; Markham, B.L.; Helder, D.L.; Chander, G.

    2007-01-01

    Launched in April 1999, Landsat-7 ETM+ continues to acquire data globally. The Scan Line Corrector in failure in 2003 has affected ground coverage and the recent switch to Bumper Mode operations in April 2007 has degraded the internal geometric accuracy of the data, but the radiometry has been unaffected. The best of the three on-board calibrators for the reflective bands, the Full Aperture Solar Calibrator, has indicated slow changes in the ETM+, but this is believed to be due to contamination on the panel rather then instrument degradation. The Internal Calibrator lamp 2, though it has not been used regularly throughout the whole mission, indicates smaller changes than the FASC since 2003. The changes indicated by lamp 2 are only statistically significant in band 1, circa 0.3% per year, and may be lamp as opposed to instrument degradations. Regular observations of desert targets in the Saharan and Arabian deserts indicate the no change in the ETM+ reflective band response, though the uncertainty is larger and does not preclude the small changes indicated by lamp 2. The thermal band continues to be stable and well-calibrated since an offset error was corrected in late-2000. Launched in 1984, Landsat-5 TM also continues to acquire global data; though without the benefit of an on-board recorder, data can only be acquired where a ground station is within range. Historically, the calibration of the TM reflective bands has used an onboard calibration system with multiple lamps. The calibration procedure for the TM reflective bands was updated in 2003 based on the best estimate at the time, using only one of the three lamps and a cross-calibration with Landsat-7 ETM+. Since then, the Saharan desert sites have been used to validate this calibration model. Problems were found with the lamp based model of up to 13% in band 1. Using the Saharan data, a new model was developed and implemented in the US processing system in April 2007. The TM thermal band was found to have a

  11. Regression calibration with more surrogates than mismeasured variables

    KAUST Repository

    Kipnis, Victor

    2012-06-29

    In a recent paper (Weller EA, Milton DK, Eisen EA, Spiegelman D. Regression calibration for logistic regression with multiple surrogates for one exposure. Journal of Statistical Planning and Inference 2007; 137: 449-461), the authors discussed fitting logistic regression models when a scalar main explanatory variable is measured with error by several surrogates, that is, a situation with more surrogates than variables measured with error. They compared two methods of adjusting for measurement error using a regression calibration approximate model as if it were exact. One is the standard regression calibration approach consisting of substituting an estimated conditional expectation of the true covariate given observed data in the logistic regression. The other is a novel two-stage approach when the logistic regression is fitted to multiple surrogates, and then a linear combination of estimated slopes is formed as the estimate of interest. Applying estimated asymptotic variances for both methods in a single data set with some sensitivity analysis, the authors asserted superiority of their two-stage approach. We investigate this claim in some detail. A troubling aspect of the proposed two-stage method is that, unlike standard regression calibration and a natural form of maximum likelihood, the resulting estimates are not invariant to reparameterization of nuisance parameters in the model. We show, however, that, under the regression calibration approximation, the two-stage method is asymptotically equivalent to a maximum likelihood formulation, and is therefore in theory superior to standard regression calibration. However, our extensive finite-sample simulations in the practically important parameter space where the regression calibration model provides a good approximation failed to uncover such superiority of the two-stage method. We also discuss extensions to different data structures.

  12. Proofreading for word errors.

    Science.gov (United States)

    Pilotti, Maura; Chodorow, Martin; Agpawa, Ian; Krajniak, Marta; Mahamane, Salif

    2012-04-01

    Proofreading (i.e., reading text for the purpose of detecting and correcting typographical errors) is viewed as a component of the activity of revising text and thus is a necessary (albeit not sufficient) procedural step for enhancing the quality of a written product. The purpose of the present research was to test competing accounts of word-error detection which predict factors that may influence reading and proofreading differently. Word errors, which change a word into another word (e.g., from --> form), were selected for examination because they are unlikely to be detected by automatic spell-checking functions. Consequently, their detection still rests mostly in the hands of the human proofreader. Findings highlighted the weaknesses of existing accounts of proofreading and identified factors, such as length and frequency of the error in the English language relative to frequency of the correct word, which might play a key role in detection of word errors.

  13. Calibration Facilities for NIF

    Energy Technology Data Exchange (ETDEWEB)

    Perry, T.S.

    2000-06-15

    The calibration facilities will be dynamic and will change to meet the needs of experiments. Small sources, such as the Manson Source should be available to everyone at any time. Carrying out experiments at Omega is providing ample opportunity for practice in pre-shot preparation. Hopefully, the needs that are demonstrated in these experiments will assure the development of (or keep in service) facilities at each of the laboratories that will be essential for in-house preparation for experiments at NIF.

  14. Mesoscale hybrid calibration artifact

    Science.gov (United States)

    Tran, Hy D.; Claudet, Andre A.; Oliver, Andrew D.

    2010-09-07

    A mesoscale calibration artifact, also called a hybrid artifact, suitable for hybrid dimensional measurement and the method for make the artifact. The hybrid artifact has structural characteristics that make it suitable for dimensional measurement in both vision-based systems and touch-probe-based systems. The hybrid artifact employs the intersection of bulk-micromachined planes to fabricate edges that are sharp to the nanometer level and intersecting planes with crystal-lattice-defined angles.

  15. Astrid-2 SSC ASUMagnetic Calibration

    DEFF Research Database (Denmark)

    Primdahl, Fritz

    1997-01-01

    Report of the inter calibration between the starcamera and the fluxgate magnetometer onboard the ASTRID-2 satellite. This calibration was performed in the night between the 15. and 16. May 1997 at the Lovö magnetic observatory.......Report of the inter calibration between the starcamera and the fluxgate magnetometer onboard the ASTRID-2 satellite. This calibration was performed in the night between the 15. and 16. May 1997 at the Lovö magnetic observatory....

  16. Online calibration technique for LDV in SINS/LDV integrated navigation systems

    Science.gov (United States)

    Wang, Qi; Gao, Chunfeng; Wei, Guo; Long, Xingwu

    2017-05-01

    There are the scale factor error of LDV (laser Doppler velocimeter) and the misalignment between the SINS (Strapdown inertial navigation system) and the vehicle in a SINS/LDV integrated navigation system. In this paper, the effects of these errors on the attitude, velocity and position of dead reckoning are derived, and a new online calibration method aiming to calibrate the scale factor of LDV and the misalignment between the SINS and the vehicle for the integrated system is put forward. This method, which is utilize the velocity and position of the Global Position System (GPS) as references, use the velocity error and position error of dead reckoning to estimate these errors. Through simulation and experiment, the validity and feasibility of the method are verified. The results show that the scale factor and the misalignment can be calibrated with satisfying accuracy, and the related research can provide technical support for high precision navigation of SINS/LDV integrated navigation systems.

  17. Evaluation of several calibration procedures for a portable soil moisture sensor

    Science.gov (United States)

    Rowlandson, Tracy L.; Berg, Aaron A.; Bullock, Paul R.; Ojo, E. RoTimi; McNairn, Heather; Wiseman, Grant; Cosh, Michael H.

    2013-08-01

    The calibration and validation of remotely sensed soil moisture products relies upon an accurate source of ground truth data. The primary method of providing this ground truth is to conduct intensive field campaigns with manual surface soil moisture sampling measurements, which utilize gravimetric sampling, soil moisture probes, or both, to estimate the volumetric soil water content. Soil moisture probes eliminate the need for labor-intensive gravimetric sampling. To ensure the accuracy of these probes, several studies have determined these probes need various degrees of localized calibration. This study examines six possible calibration techniques using data collected during a field campaign conducted in 2012, with soil moisture samples being collected over 55 fields in southern Manitoba, as part of the Soil Moisture Active Passive Validation Experiment 2012 (SMAPVEX12). The use of a general equation, applied to all collected data, resulted in the largest error regardless of whether a linear or third order polynomial relationship was established for the calibration of the soil moisture probes. Calibration equations based on soil texture or vegetation land cover reduced the error; however, the individual calibration equations established for each field in the study had the lowest error of all the calibration techniques. Although average bias was low for all of the calibration techniques, the use of the general equation to calibrate individual fields resulted in high biases for some fields.

  18. Calibration of Underwater Sound Transducers

    Directory of Open Access Journals (Sweden)

    H.R.S. Sastry

    1983-07-01

    Full Text Available The techniques of calibration of underwater sound transducers for farfield, near-field and closed environment conditions are reviewed in this paper .The design of acoustic calibration tank is mentioned. The facilities available at Naval Physical & Oceanographic Laboratory, Cochin for calibration of transducers are also listed.

  19. Radiometric Calibrations, Measurements, and Standards Development at NREL: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Myers, D. R.; Andreas, A.; Stoffel, T.; Reda, I.; Wilcox, S.; Gotseff, P.; Kay, B.

    2001-10-01

    Presented at the 2001 NCPV Program Review Meeting: Radiometric calibrations, measurements, and standards development at NREL. We describe proposed revisions to current reference standard spectral distributions used to evaluate photovoltaic device performance and durability of materials. Improvements in broadband outdoor radiometer calibrations reduce uncertainties in broadband radiometer calibrations. We report a method to quantify the rate of change of broadband radiometer responsivities as a function of integrated exposure to irradiance and thermal energy. The results of applying a vector of calibration factors or responsivities to field data to remove zenith-angle dependent errors in global solar radiation measurements are shown. We report on the relative sensitivity of radiometers to daily versus biweekly cleaning.

  20. Digital background calibration of charge pump based pipelined ADC

    Science.gov (United States)

    Singh, Anil; Agarwal, Alpana

    2016-11-01

    In the presented work, digital background calibration of a charge pump based pipelined ADC is presented. A 10-bit 100 MS/s pipelined ADC is designed using TSMC 0.18 µm CMOS technology operating on a 1.8 V power supply voltage. A power efficient opamp-less charge pump based technique is chosen to achieve the desired stage voltage gain of 2 and digital background calibration is used to calibrate the inter-stage gain error. After calibration, the ADC achieves an SNDR of 66.78 dB and SFDR of 79.3 dB. Also, DNL improves to +0.6/-0.4 LSB and INL improves from +9.3/-9.6 LSB to within ±0.5 LSB, consuming 16.53 mW of power.

  1. Internet-based calibration of a multifunction calibrator

    Energy Technology Data Exchange (ETDEWEB)

    BUNTING BACA,LISA A.; DUDA JR.,LEONARD E.; WALKER,RUSSELL M.; OLDHAM,NILE; PARKER,MARK

    2000-04-17

    A new way of providing calibration services is evolving which employs the Internet to expand present capabilities and make the calibration process more interactive. Sandia National Laboratories and the National Institute of Standards and Technology are collaborating to set up and demonstrate a remote calibration of multifunction calibrators using this Internet-based technique that is becoming known as e-calibration. This paper describes the measurement philosophy and the Internet resources that can provide real-time audio/video/data exchange, consultation and training, as well as web-accessible test procedures, software and calibration reports. The communication system utilizes commercial hardware and software that should be easy to integrate into most calibration laboratories.

  2. Gravity field determination and error assessment techniques

    Science.gov (United States)

    Yuan, D. N.; Shum, C. K.; Tapley, B. D.

    1989-01-01

    Linear estimation theory, along with a new technique to compute relative data weights, was applied to the determination of the Earth's geopotential field and other geophysical model parameters using a combination of satellite ground-based tracking data, satellite altimetry data, and the surface gravimetry data. The relative data weights for the inhomogeneous data sets are estimated simultaneously with the gravity field and other geophysical and orbit parameters in a least squares approach to produce the University of Texas gravity field models. New techniques to perform calibration of the formal covariance matrix for the geopotential solution were developed to obtain a reliable gravity field error estimate. Different techniques, which include orbit residual analysis, surface gravity anomaly residual analysis, subset gravity solution comparisons and consider covariance analysis, were applied to investigate the reliability of the calibration.

  3. Effects of temporal variability on HBV model calibration

    Directory of Open Access Journals (Sweden)

    Steven Reinaldo Rusli

    2015-10-01

    Full Text Available This study aimed to investigate the effect of temporal variability on the optimization of the Hydrologiska Byråns Vattenbalansavedlning (HBV model, as well as the calibration performance using manual optimization and average parameter values. By applying the HBV model to the Jiangwan Catchment, whose geological features include lots of cracks and gaps, simulations under various schemes were developed: short, medium-length, and long temporal calibrations. The results show that, with long temporal calibration, the objective function values of the Nash-Sutcliffe efficiency coefficient (NSE, relative error (RE, root mean square error (RMSE, and high flow ratio generally deliver a preferable simulation. Although NSE and RMSE are relatively stable with different temporal scales, significant improvements to RE and the high flow ratio are seen with longer temporal calibration. It is also noted that use of average parameter values does not lead to better simulation results compared with manual optimization. With medium-length temporal calibration, manual optimization delivers the best simulation results, with NSE, RE, RMSE, and the high flow ratio being 0.563 6, 0.122 3, 0.978 8, and 0.854 7, respectively; and calibration using average parameter values delivers NSE, RE, RMSE, and the high flow ratio of 0.481 1, 0.467 6, 1.021 0, and 2.784 0, respectively. Similar behavior is found with long temporal calibration, when NSE, RE, RMSE, and the high flow ratio using manual optimization are 0.525 3, −0.069 2, 1.058 0, and 0.980 0, respectively, as compared with 0.490 3, 0.224 8, 1.096 2, and 0.547 9, respectively, using average parameter values. This study shows that selection of longer periods of temporal calibration in hydrological analysis delivers better simulation in general for water balance analysis.

  4. Uncorrected refractive errors

    Directory of Open Access Journals (Sweden)

    Kovin S Naidoo

    2012-01-01

    Full Text Available Global estimates indicate that more than 2.3 billion people in the world suffer from poor vision due to refractive error; of which 670 million people are considered visually impaired because they do not have access to corrective treatment. Refractive errors, if uncorrected, results in an impaired quality of life for millions of people worldwide, irrespective of their age, sex and ethnicity. Over the past decade, a series of studies using a survey methodology, referred to as Refractive Error Study in Children (RESC, were performed in populations with different ethnic origins and cultural settings. These studies confirmed that the prevalence of uncorrected refractive errors is considerably high for children in low-and-middle-income countries. Furthermore, uncorrected refractive error has been noted to have extensive social and economic impacts, such as limiting educational and employment opportunities of economically active persons, healthy individuals and communities. The key public health challenges presented by uncorrected refractive errors, the leading cause of vision impairment across the world, require urgent attention. To address these issues, it is critical to focus on the development of human resources and sustainable methods of service delivery. This paper discusses three core pillars to addressing the challenges posed by uncorrected refractive errors: Human Resource (HR Development, Service Development and Social Entrepreneurship.

  5. Uncorrected refractive errors.

    Science.gov (United States)

    Naidoo, Kovin S; Jaggernath, Jyoti

    2012-01-01

    Global estimates indicate that more than 2.3 billion people in the world suffer from poor vision due to refractive error; of which 670 million people are considered visually impaired because they do not have access to corrective treatment. Refractive errors, if uncorrected, results in an impaired quality of life for millions of people worldwide, irrespective of their age, sex and ethnicity. Over the past decade, a series of studies using a survey methodology, referred to as Refractive Error Study in Children (RESC), were performed in populations with different ethnic origins and cultural settings. These studies confirmed that the prevalence of uncorrected refractive errors is considerably high for children in low-and-middle-income countries. Furthermore, uncorrected refractive error has been noted to have extensive social and economic impacts, such as limiting educational and employment opportunities of economically active persons, healthy individuals and communities. The key public health challenges presented by uncorrected refractive errors, the leading cause of vision impairment across the world, require urgent attention. To address these issues, it is critical to focus on the development of human resources and sustainable methods of service delivery. This paper discusses three core pillars to addressing the challenges posed by uncorrected refractive errors: Human Resource (HR) Development, Service Development and Social Entrepreneurship.

  6. Errors in Radiologic Reporting

    Directory of Open Access Journals (Sweden)

    Esmaeel Shokrollahi

    2010-05-01

    Full Text Available Given that the report is a professional document and bears the associated responsibilities, all of the radiologist's errors appear in it, either directly or indirectly. It is not easy to distinguish and classify the mistakes made when a report is prepared, because in most cases the errors are complex and attributable to more than one cause and because many errors depend on the individual radiologists' professional, behavioral and psychological traits."nIn fact, anyone can make a mistake, but some radiologists make more mistakes, and some types of mistakes are predictable to some extent."nReporting errors can be categorized differently:"nUniversal vs. individual"nHuman related vs. system related"nPerceptive vs. cognitive errors"n1. Descriptive "n2. Interpretative "n3. Decision related Perceptive errors"n1. False positive "n2. False negative"n Nonidentification "n Erroneous identification "nCognitive errors "n Knowledge-based"n Psychological  

  7. Errors in neuroradiology.

    Science.gov (United States)

    Caranci, Ferdinando; Tedeschi, Enrico; Leone, Giuseppe; Reginelli, Alfonso; Gatta, Gianluca; Pinto, Antonio; Squillaci, Ettore; Briganti, Francesco; Brunese, Luca

    2015-09-01

    Approximately 4 % of radiologic interpretation in daily practice contains errors and discrepancies that should occur in 2-20 % of reports. Fortunately, most of them are minor degree errors, or if serious, are found and corrected with sufficient promptness; obviously, diagnostic errors become critical when misinterpretation or misidentification should significantly delay medical or surgical treatments. Errors can be summarized into four main categories: observer errors, errors in interpretation, failure to suggest the next appropriate procedure, failure to communicate in a timely and a clinically appropriate manner. Misdiagnosis/misinterpretation percentage should rise up in emergency setting and in the first moments of the learning curve, as in residency. Para-physiological and pathological pitfalls in neuroradiology include calcification and brain stones, pseudofractures, and enlargement of subarachnoid or epidural spaces, ventricular system abnormalities, vascular system abnormalities, intracranial lesions or pseudolesions, and finally neuroradiological emergencies. In order to minimize the possibility of error, it is important to be aware of various presentations of pathology, obtain clinical information, know current practice guidelines, review after interpreting a diagnostic study, suggest follow-up studies when appropriate, communicate significant abnormal findings appropriately and in a timely fashion directly with the treatment team.

  8. Calibration of a Stereo Radiation Detection Camera Using Planar Homography

    Directory of Open Access Journals (Sweden)

    Seung-Hae Baek

    2016-01-01

    Full Text Available This paper proposes a calibration technique of a stereo gamma detection camera. Calibration of the internal and external parameters of a stereo vision camera is a well-known research problem in the computer vision society. However, few or no stereo calibration has been investigated in the radiation measurement research. Since no visual information can be obtained from a stereo radiation camera, it is impossible to use a general stereo calibration algorithm directly. In this paper, we develop a hybrid-type stereo system which is equipped with both radiation and vision cameras. To calibrate the stereo radiation cameras, stereo images of a calibration pattern captured from the vision cameras are transformed in the view of the radiation cameras. The homography transformation is calibrated based on the geometric relationship between visual and radiation camera coordinates. The accuracy of the stereo parameters of the radiation camera is analyzed by distance measurements to both visual light and gamma sources. The experimental results show that the measurement error is about 3%.

  9. Systematic Calibration for a Backpacked Spherical Photogrammetry Imaging System

    Science.gov (United States)

    Rau, J. Y.; Su, B. W.; Hsiao, K. W.; Jhan, J. P.

    2016-06-01

    A spherical camera can observe the environment for almost 720 degrees' field of view in one shoot, which is useful for augmented reality, environment documentation, or mobile mapping applications. This paper aims to develop a spherical photogrammetry imaging system for the purpose of 3D measurement through a backpacked mobile mapping system (MMS). The used equipment contains a Ladybug-5 spherical camera, a tactical grade positioning and orientation system (POS), i.e. SPAN-CPT, and an odometer, etc. This research aims to directly apply photogrammetric space intersection technique for 3D mapping from a spherical image stereo-pair. For this purpose, several systematic calibration procedures are required, including lens distortion calibration, relative orientation calibration, boresight calibration for direct georeferencing, and spherical image calibration. The lens distortion is serious on the ladybug-5 camera's original 6 images. Meanwhile, for spherical image mosaicking from these original 6 images, we propose the use of their relative orientation and correct their lens distortion at the same time. However, the constructed spherical image still contains systematic error, which will reduce the 3D measurement accuracy. Later for direct georeferencing purpose, we need to establish a ground control field for boresight/lever-arm calibration. Then, we can apply the calibrated parameters to obtain the exterior orientation parameters (EOPs) of all spherical images. In the end, the 3D positioning accuracy after space intersection will be evaluated, including EOPs obtained by structure from motion method.

  10. SYSTEMATIC CALIBRATION FOR A BACKPACKED SPHERICAL PHOTOGRAMMETRY IMAGING SYSTEM

    Directory of Open Access Journals (Sweden)

    J. Y. Rau

    2016-06-01

    Full Text Available A spherical camera can observe the environment for almost 720 degrees’ field of view in one shoot, which is useful for augmented reality, environment documentation, or mobile mapping applications. This paper aims to develop a spherical photogrammetry imaging system for the purpose of 3D measurement through a backpacked mobile mapping system (MMS. The used equipment contains a Ladybug-5 spherical camera, a tactical grade positioning and orientation system (POS, i.e. SPAN-CPT, and an odometer, etc. This research aims to directly apply photogrammetric space intersection technique for 3D mapping from a spherical image stereo-pair. For this purpose, several systematic calibration procedures are required, including lens distortion calibration, relative orientation calibration, boresight calibration for direct georeferencing, and spherical image calibration. The lens distortion is serious on the ladybug-5 camera’s original 6 images. Meanwhile, for spherical image mosaicking from these original 6 images, we propose the use of their relative orientation and correct their lens distortion at the same time. However, the constructed spherical image still contains systematic error, which will reduce the 3D measurement accuracy. Later for direct georeferencing purpose, we need to establish a ground control field for boresight/lever-arm calibration. Then, we can apply the calibrated parameters to obtain the exterior orientation parameters (EOPs of all spherical images. In the end, the 3D positioning accuracy after space intersection will be evaluated, including EOPs obtained by structure from motion method.

  11. Uniform calibration of night vision goggles and test sets

    Science.gov (United States)

    Eppeldauer, George P.

    2007-10-01

    There are orders of magnitude differences between the ~0.1 % (k=2) uncertainty of NIST reference detector calibrations and the uncertainty of night vision (NV) goggle measurements. NIST developed a night vision radiometer calibration facility including NV radiometer transfer standards. The transfer standards, that propagate the radiance responsivity scale to the military primary standards laboratories, are calibrated against a NIST reference radiometer. The reference radiometer has been calibrated on the NIST Spectral Comparator Facility (SCF) for spectral power and irradiance responsivities. Spectral considerations are discussed to lower the uncertainties of the radiance responsivity scale transfer to the test sets and then to the goggles. Since direct determination of the final uncertainties in goggle calibrations and measurements is difficult, models have been made to estimate the most important uncertainty components based on individual spectral measurements of the applied source distributions and radiometer spectral responsivities. It is also shown, that because of source spectral mismatch problems, the goggle measurement uncertainty at applications can be much higher than at calibration. A suggestion is being made to mimic the no-moon (stars only) night sky radiation distribution using several LEDs in the test-sets to decrease the large spectral mismatch errors. A broad-band correction factor has been developed to further decrease calibration uncertainty when the goggles to be used have different spectral responsivities than the standard. Geometrical considerations to optimize the radiance measurement angle and the out-of-target blocking are also discussed to decrease the uncertainty in the radiance responsivity transfer.

  12. Is your system calibrated? MRI gradient system calibration for pre-clinical, high-resolution imaging.

    Directory of Open Access Journals (Sweden)

    James O'Callaghan

    Full Text Available High-field, pre-clinical MRI systems are widely used to characterise tissue structure and volume in small animals, using high resolution imaging. Both applications rely heavily on the consistent, accurate calibration of imaging gradients, yet such calibrations are typically only performed during maintenance sessions by equipment manufacturers, and potentially with acceptance limits that are inadequate for phenotyping. To overcome this difficulty, we present a protocol for gradient calibration quality assurance testing, based on a 3D-printed, open source, structural phantom that can be customised to the dimensions of individual scanners and RF coils. In trials on a 9.4 T system, the gradient scaling errors were reduced by an order of magnitude, and displacements of greater than 100 µm, caused by gradient non-linearity, were corrected using a post-processing technique. The step-by-step protocol can be integrated into routine pre-clinical MRI quality assurance to measure and correct for these errors. We suggest that this type of quality assurance is essential for robust pre-clinical MRI experiments that rely on accurate imaging gradients, including small animal phenotyping and diffusion MR.

  13. Mercury CEM Calibration

    Energy Technology Data Exchange (ETDEWEB)

    John Schabron; Joseph Rovani; Mark Sanderson

    2008-02-29

    Mercury continuous emissions monitoring systems (CEMS) are being implemented in over 800 coal-fired power plant stacks. The power industry desires to conduct at least a full year of monitoring before the formal monitoring and reporting requirement begins on January 1, 2009. It is important for the industry to have available reliable, turnkey equipment from CEM vendors. Western Research Institute (WRI) is working closely with the Electric Power Research Institute (EPRI), the National Institute of Standards and Technology (NIST), and the Environmental Protection Agency (EPA) to facilitate the development of the experimental criteria for a NIST traceability protocol for dynamic elemental mercury vapor generators. The generators are used to calibrate mercury CEMs at power plant sites. The Clean Air Mercury Rule (CAMR) which was published in the Federal Register on May 18, 2005 requires that calibration be performed with NIST-traceable standards (Federal Register 2007). Traceability procedures will be defined by EPA. An initial draft traceability protocol was issued by EPA in May 2007 for comment. In August 2007, EPA issued an interim traceability protocol for elemental mercury generators (EPA 2007). The protocol is based on the actual analysis of the output of each calibration unit at several concentration levels ranging initially from about 2-40 {micro}g/m{sup 3} elemental mercury, and in the future down to 0.2 {micro}g/m{sup 3}, and this analysis will be directly traceable to analyses by NIST. The document is divided into two separate sections. The first deals with the qualification of generators by the vendors for use in mercury CEM calibration. The second describes the procedure that the vendors must use to certify the generator models that meet the qualification specifications. The NIST traceable certification is performance based, traceable to analysis using isotope dilution inductively coupled plasma/mass spectrometry performed by NIST in Gaithersburg, MD. The

  14. Precise calibration of LIGO test mass actuators using photon radiation pressure

    CERN Document Server

    Goetz, E; Erickson, S; Savage, R L; González, G; Kawabe, K; Landry, M; Marka, S; O'Reilly, B; Riles, K; Sigg, D; Willems, P

    2009-01-01

    Precise calibration of kilometer-scale interferometric gravitational wave detectors is crucial for source localization and waveform reconstruction. A technique that uses the radiation pressure of a power-modulated auxiliary laser to induce calibrated displacements of one of the ~10 kg arm cavity mirrors, a so-called photon calibrator, has been demonstrated previously and has recently been implemented on the LIGO detectors. In this article, we discuss the inherent precision and accuracy of the LIGO photon calibrators and several improvements that have been developed to reduce the estimated voice coil actuator calibration uncertainties to less than 2 percent (1-sigma). These improvements include accounting for rotation-induced apparent length variations caused by interferometer and photon calibrator beam centering offsets, absolute laser power measurement using temperature-controlled InGaAs photodetectors mounted on integrating spheres and calibrated by NIST, minimizing errors induced by localized elastic defor...

  15. Simple and accurate empirical absolute volume calibration of a multi-sensor fringe projection system

    Science.gov (United States)

    Gdeisat, Munther; Qudeisat, Mohammad; AlSa`d, Mohammed; Burton, David; Lilley, Francis; Ammous, Marwan M. M.

    2016-05-01

    This paper suggests a novel absolute empirical calibration method for a multi-sensor fringe projection system. The optical setup of the projector-camera sensor can be arbitrary. The term absolute calibration here means that the centre of the three dimensional coordinates in the resultant calibrated volume coincides with a preset centre to the three-dimensional real-world coordinate system. The use of a zero-phase fringe marking spot is proposed to increase depth calibration accuracy, where the spot centre is determined with sub-pixel accuracy. Also, a new method is proposed for transversal calibration. Depth and transversal calibration methods have been tested using both single sensor and three-sensor fringe projection systems. The standard deviation of the error produced by this system is 0.25 mm. The calibrated volume produced by this method is 400 mm×400 mm×140 mm.

  16. Self-Calibrating Pressure Transducer

    Science.gov (United States)

    Lueck, Dale E. (Inventor)

    2006-01-01

    A self-calibrating pressure transducer is disclosed. The device uses an embedded zirconia membrane which pumps a determined quantity of oxygen into the device. The associated pressure can be determined, and thus, the transducer pressure readings can be calibrated. The zirconia membrane obtains oxygen .from the surrounding environment when possible. Otherwise, an oxygen reservoir or other source is utilized. In another embodiment, a reversible fuel cell assembly is used to pump oxygen and hydrogen into the system. Since a known amount of gas is pumped across the cell, the pressure produced can be determined, and thus, the device can be calibrated. An isolation valve system is used to allow the device to be calibrated in situ. Calibration is optionally automated so that calibration can be continuously monitored. The device is preferably a fully integrated MEMS device. Since the device can be calibrated without removing it from the process, reductions in costs and down time are realized.

  17. Laser Doppler anemometer measurements using nonorthogonal velocity components: error estimates.

    Science.gov (United States)

    Orloff, K L; Snyder, P K

    1982-01-15

    Laser Doppler anemometers (LDAs) that are arranged to measure nonorthogonal velocity components (from which orthogonal components are computed through transformation equations) are more susceptible to calibration and sampling errors than are systems with uncoupled channels. In this paper uncertainty methods and estimation theory are used to evaluate, respectively, the systematic and statistical errors that are present when such devices are applied to the measurement of mean velocities in turbulent flows. Statistical errors are estimated for two-channel LDA data that are either correlated or uncorrelated. For uncorrelated data the directional uncertainty of the measured velocity vector is considered for applications where mean streamline patterns are desired.

  18. RF Reference Switch for Spaceflight Radiometer Calibration

    Science.gov (United States)

    Knuble, Joseph

    2013-01-01

    The goal of this technology is to provide improved calibration and measurement sensitivity to the Soil Moisture Active Passive Mission (SMAP) radiometer. While RF switches have been used in the past to calibrate microwave radiometers, the switch used on SMAP employs several techniques uniquely tailored to the instrument requirements and passive remote-sensing in general to improve radiometer performance. Measurement error and sensitivity are improved by employing techniques to reduce thermal gradients within the device, reduce insertion loss during antenna observations, increase insertion loss temporal stability, and increase rejection of radar and RFI (radio-frequency interference) signals during calibration. The two legs of the single-pole double-throw reference switch employ three PIN diodes per leg in a parallel-shunt configuration to minimize insertion loss and increase stability while exceeding rejection requirements at 1,413 MHz. The high-speed packaged diodes are selected to minimize junction capacitance and resistance while ensuring the parallel devices have very similar I-V curves. Switch rejection is improved by adding high-impedance quarter-wave tapers before and after the diodes, along with replacing the ground via of one diode per leg with an open circuit stub. Errors due to thermal gradients in the switch are reduced by embedding the 50-ohm reference load within the switch, along with using a 0.25-in. (approximately equal to 0.6-cm) aluminum prebacked substrate. Previous spaceflight microwave radiometers did not embed the reference load and thermocouple directly within the calibration switch. In doing so, the SMAP switch reduces error caused by thermal gradients between the load and switch. Thermal issues are further reduced by moving the custom, highspeed regulated driver circuit to a physically separate PWB (printed wiring board). Regarding RF performance, previous spaceflight reference switches have not employed high-impedance tapers to improve

  19. Calibrating the PAU Survey's 46 Filters

    Science.gov (United States)

    Bauer, A.; Castander, F.; Gaztañaga, E.; Serrano, S.; Sevilla, N.; Tonello, N.; PAU Team

    2016-05-01

    The Physics of the Accelerating Universe (PAU) Survey, being carried out by several Spanish institutions, will image an area of 100-200 square degrees in 6 broad and 40 narrow band optical filters. The team is building a camera (PAUCam) with 18 CCDs, which will be installed in the 4 meter William Herschel Telescope at La Palma in 2013. The narrow band filters will each cover 100Å, with the set spanning 4500-8500Å. The broad band set will consist of standard ugriZy filters. The narrow band filters will provide low-resolution (R˜50) photometric "spectra" for all objects observed in the survey, which will reach a depth of ˜24 mag in the broad bands and ˜22.5 mag (AB) in the narrow bands. Such precision will allow for galaxy photometric redshift errors of 0.0035(1+z), which will facilitate the measurement of cosmological parameters with precision comparable to much larger spectroscopic and photometric surveys. Accurate photometric calibration of the PAU data is vital to the survey's science goals, and is not straightforward due to the large and unusual filter set. We outline the data management pipelines being developed for the survey, both for nightly data reduction and coaddition of multiple epochs, with emphasis on the photometric calibration strategies. We also describe the tools we are developing to test the quality of the reduction and calibration.

  20. Object Detection and Tracking-Based Camera Calibration for Normalized Human Height Estimation

    Directory of Open Access Journals (Sweden)

    Jaehoon Jung

    2016-01-01

    Full Text Available This paper presents a normalized human height estimation algorithm using an uncalibrated camera. To estimate the normalized human height, the proposed algorithm detects a moving object and performs tracking-based automatic camera calibration. The proposed method consists of three steps: (i moving human detection and tracking, (ii automatic camera calibration, and (iii human height estimation and error correction. The proposed method automatically calibrates camera by detecting moving humans and estimates the human height using error correction. The proposed method can be applied to object-based video surveillance systems and digital forensic.

  1. Calibration for 3D imaging with a single-pixel camera

    Science.gov (United States)

    Gribben, Jeremy; Boate, Alan R.; Boukerche, Azzedine

    2017-02-01

    Traditional methods for calibrating structured light 3D imaging systems often suffer from various sources of error. By enabling our projector to both project images as well as capture them using the same optical path, we turn our DMD based projector into a dual-purpose projector and single-pixel camera (SPC). A coarse-to-fine SPC scanning technique based on coded apertures was developed to detect calibration target points with sub-pixel accuracy. Our new calibration approach shows improved depth measurement accuracy when used in structured light 3D imaging by reducing cumulative errors caused by multiple imaging paths.

  2. CALIBRATED HYDRODYNAMIC MODEL

    Directory of Open Access Journals (Sweden)

    Sezar Gülbaz

    2015-01-01

    Full Text Available The land development and increase in urbanization in a watershed affect water quantityand water quality. On one hand, urbanization provokes the adjustment of geomorphicstructure of the streams, ultimately raises peak flow rate which causes flood; on theother hand, it diminishes water quality which results in an increase in Total SuspendedSolid (TSS. Consequently, sediment accumulation in downstream of urban areas isobserved which is not preferred for longer life of dams. In order to overcome thesediment accumulation problem in dams, the amount of TSS in streams and inwatersheds should be taken under control. Low Impact Development (LID is a BestManagement Practice (BMP which may be used for this purpose. It is a land planningand engineering design method which is applied in managing storm water runoff inorder to reduce flooding as well as simultaneously improve water quality. LID includestechniques to predict suspended solid loads in surface runoff generated over imperviousurban surfaces. In this study, the impact of LID-BMPs on surface runoff and TSS isinvestigated by employing a calibrated hydrodynamic model for Sazlidere Watershedwhich is located in Istanbul, Turkey. For this purpose, a calibrated hydrodynamicmodel was developed by using Environmental Protection Agency Storm WaterManagement Model (EPA SWMM. For model calibration and validation, we set up arain gauge and a flow meter into the field and obtain rainfall and flow rate data. Andthen, we select several LID types such as retention basins, vegetative swales andpermeable pavement and we obtain their influence on peak flow rate and pollutantbuildup and washoff for TSS. Consequently, we observe the possible effects ofLID on surface runoff and TSS in Sazlidere Watershed.

  3. Rapid mapping of volumetric machine errors using distance measurements

    Energy Technology Data Exchange (ETDEWEB)

    Krulewich, D.A.

    1998-04-01

    not able to report actual error measurements. instead, we have scaled the work volume to 5OOx5OOx5OOmm and proportionally scaled the errors. The fitted model was able to predict independently measured laser body diagonals to within 3.{mu}m peak-to-valley throughout @ scaled 500 x 500 x 500 mm` volume. or approximately 88% of the total error. Furthermore, this approach performed as well as, if not better than the parametric methods, but required only four hours to collect data for calibration.

  4. Dynamic Torque Calibration Unit

    Science.gov (United States)

    Agronin, Michael L.; Marchetto, Carl A.

    1989-01-01

    Proposed dynamic torque calibration unit (DTCU) measures torque in rotary actuator components such as motors, bearings, gear trains, and flex couplings. Unique because designed specifically for testing components under low rates. Measures torque in device under test during controlled steady rotation or oscillation. Rotor oriented vertically, supported by upper angular-contact bearing and lower radial-contact bearing that floats axially to prevent thermal expansion from loading bearings. High-load capacity air bearing available to replace ball bearings when higher load capacity or reduction in rate noise required.

  5. ALTEA: The instrument calibration

    Energy Technology Data Exchange (ETDEWEB)

    Zaconte, V. [INFN and University of Rome Tor Vergata, Department of Physics, Via della Ricerca Scientifica 1, 00133 Rome (Italy)], E-mail: livio.narici@roma2.infn.it; Belli, F.; Bidoli, V.; Casolino, M.; Di Fino, L.; Narici, L.; Picozza, P.; Rinaldi, A. [INFN and University of Rome Tor Vergata, Department of Physics, Via della Ricerca Scientifica 1, 00133 Rome (Italy); Sannita, W.G. [DISM, University of Genova, Genova (Italy); Department of Psychiatry, SUNY, Stoony Brook, NY (United States); Finetti, N.; Nurzia, G.; Rantucci, E.; Scrimaglio, R.; Segreto, E. [Department of Physics, University and INFN, L' Aquila (Italy); Schardt, D. [GSI/Biophysik, Darmstadt (Germany)

    2008-05-15

    The ALTEA program is an international and multi-disciplinary project aimed at studying particle radiation in space environment and its effects on astronauts' brain functions, as the anomalous perception of light flashes first reported during Apollo missions. The ALTEA space facility includes a 6-silicon telescopes particle detector, and is onboard the International Space Station (ISS) since July 2006. In this paper, the detector calibration at the heavy-ion synchrotron SIS18 at GSI Darmstadt will be presented and compared to the Geant 3 Monte Carlo simulation. Finally, the results of a neural network analysis that was used for ion discrimination on fragmentation data will also be presented.

  6. Subaperture test of wavefront error of large telescopes: error sources and stitching performance simulations

    Science.gov (United States)

    Chen, Shanyong; Li, Shengyi; Wang, Guilin

    2014-11-01

    The wavefront error of large telescopes requires to be measured to check the system quality and also estimate the misalignment of the telescope optics including the primary, the secondary and so on. It is usually realized by a focal plane interferometer and an autocollimator flat (ACF) of the same aperture with the telescope. However, it is challenging for meter class telescopes due to high cost and technological challenges in producing the large ACF. Subaperture test with a smaller ACF is hence proposed in combination with advanced stitching algorithms. Major error sources include the surface error of the ACF, misalignment of the ACF and measurement noises. Different error sources have different impacts on the wavefront error. Basically the surface error of the ACF behaves like systematic error and the astigmatism will be cumulated and enlarged if the azimuth of subapertures remains fixed. It is difficult to accurately calibrate the ACF because it suffers considerable deformation induced by gravity or mechanical clamping force. Therefore a selfcalibrated stitching algorithm is employed to separate the ACF surface error from the subaperture wavefront error. We suggest the ACF be rotated around the optical axis of the telescope for subaperture test. The algorithm is also able to correct the subaperture tip-tilt based on the overlapping consistency. Since all subaperture measurements are obtained in the same imaging plane, lateral shift of the subapertures is always known and the real overlapping points can be recognized in this plane. Therefore lateral positioning error of subapertures has no impact on the stitched wavefront. In contrast, the angular positioning error changes the azimuth of the ACF and finally changes the systematic error. We propose an angularly uneven layout of subapertures to minimize the stitching error, which is very different from our knowledge. At last, measurement noises could never be corrected but be suppressed by means of averaging and

  7. Inpatients’ medical prescription errors

    Directory of Open Access Journals (Sweden)

    Aline Melo Santos Silva

    2009-09-01

    Full Text Available Objective: To identify and quantify the most frequent prescription errors in inpatients’ medical prescriptions. Methods: A survey of prescription errors was performed in the inpatients’ medical prescriptions, from July 2008 to May 2009 for eight hours a day. Rresults: At total of 3,931 prescriptions was analyzed and 362 (9.2% prescription errors were found, which involved the healthcare team as a whole. Among the 16 types of errors detected in prescription, the most frequent occurrences were lack of information, such as dose (66 cases, 18.2% and administration route (26 cases, 7.2%; 45 cases (12.4% of wrong transcriptions to the information system; 30 cases (8.3% of duplicate drugs; doses higher than recommended (24 events, 6.6% and 29 cases (8.0% of prescriptions with indication but not specifying allergy. Cconclusion: Medication errors are a reality at hospitals. All healthcare professionals are responsible for the identification and prevention of these errors, each one in his/her own area. The pharmacist is an essential professional in the drug therapy process. All hospital organizations need a pharmacist team responsible for medical prescription analyses before preparation, dispensation and administration of drugs to inpatients. This study showed that the pharmacist improves the inpatient’s safety and success of prescribed therapy.

  8. Bayesian Calibration of the Community Land Model using Surrogates

    Energy Technology Data Exchange (ETDEWEB)

    Ray, Jaideep; Hou, Zhangshuan; Huang, Maoyi; Sargsyan, K.; Swiler, Laura P.

    2015-01-01

    We present results from the Bayesian calibration of hydrological parameters of the Community Land Model (CLM), which is often used in climate simulations and Earth system models. A statistical inverse problem is formulated for three hydrological parameters, conditioned on observations of latent heat surface fluxes over 48 months. Our calibration method uses polynomial and Gaussian process surrogates of the CLM, and solves the parameter estimation problem using a Markov chain Monte Carlo sampler. Posterior probability densities for the parameters are developed for two sites with different soil and vegetation covers. Our method also allows us to examine the structural error in CLM under two error models. We find that accurate surrogate models can be created for CLM in most cases. The posterior distributions lead to better prediction than the default parameter values in CLM. Climatologically averaging the observations does not modify the parameters’ distributions significantly. The structural error model reveals a correlation time-scale which can potentially be used to identify physical processes that could be contributing to it. While the calibrated CLM has a higher predictive skill, the calibration is under-dispersive.

  9. Bayesian calibration of the Community Land Model using surrogates

    Energy Technology Data Exchange (ETDEWEB)

    Ray, Jaideep; Hou, Zhangshuan; Huang, Maoyi; Swiler, Laura Painton

    2014-02-01

    We present results from the Bayesian calibration of hydrological parameters of the Community Land Model (CLM), which is often used in climate simulations and Earth system models. A statistical inverse problem is formulated for three hydrological parameters, conditional on observations of latent heat surface fluxes over 48 months. Our calibration method uses polynomial and Gaussian process surrogates of the CLM, and solves the parameter estimation problem using a Markov chain Monte Carlo sampler. Posterior probability densities for the parameters are developed for two sites with different soil and vegetation covers. Our method also allows us to examine the structural error in CLM under two error models. We find that surrogate models can be created for CLM in most cases. The posterior distributions are more predictive than the default parameter values in CLM. Climatologically averaging the observations does not modify the parameters' distributions significantly. The structural error model reveals a correlation time-scale which can be used to identify the physical process that could be contributing to it. While the calibrated CLM has a higher predictive skill, the calibration is under-dispersive.

  10. MEMS IMU Error Mitigation Using Rotation Modulation Technique

    Directory of Open Access Journals (Sweden)

    Shuang Du

    2016-11-01

    Full Text Available Micro-electro-mechanical-systems (MEMS inertial measurement unit (IMU outputs are corrupted by significant sensor errors. The navigation errors of a MEMS-based inertial navigation system will therefore accumulate very quickly over time. This requires aiding from other sensors such as Global Navigation Satellite Systems (GNSS. However, it will still remain a significant challenge in the presence of GNSS outages, which are typically in urban canopies. This paper proposed a rotary inertial navigation system (INS to mitigate navigation errors caused by MEMS inertial sensor errors when external aiding information is not available. A rotary INS is an inertial navigator in which the IMU is installed on a rotation platform. Application of proper rotation schemes can effectively cancel and reduce sensor errors. A rotary INS has the potential to significantly increase the time period that INS can bridge GNSS outages and make MEMS IMU possible to maintain longer autonomous navigation performance when there is no external aiding. In this research, several IMU rotation schemes (rotation about X-, Y- and Z-axes are analyzed to mitigate the navigation errors caused by MEMS IMU sensor errors. As the IMU rotation induces additional sensor errors, a calibration process is proposed to remove the induced errors. Tests are further conducted with two MEMS IMUs installed on a tri-axial rotation table to verify the error mitigation by IMU rotations.

  11. MEMS IMU Error Mitigation Using Rotation Modulation Technique

    Science.gov (United States)

    Du, Shuang; Sun, Wei; Gao, Yang

    2016-01-01

    Micro-electro-mechanical-systems (MEMS) inertial measurement unit (IMU) outputs are corrupted by significant sensor errors. The navigation errors of a MEMS-based inertial navigation system will therefore accumulate very quickly over time. This requires aiding from other sensors such as Global Navigation Satellite Systems (GNSS). However, it will still remain a significant challenge in the presence of GNSS outages, which are typically in urban canopies. This paper proposed a rotary inertial navigation system (INS) to mitigate navigation errors caused by MEMS inertial sensor errors when external aiding information is not available. A rotary INS is an inertial navigator in which the IMU is installed on a rotation platform. Application of proper rotation schemes can effectively cancel and reduce sensor errors. A rotary INS has the potential to significantly increase the time period that INS can bridge GNSS outages and make MEMS IMU possible to maintain longer autonomous navigation performance when there is no external aiding. In this research, several IMU rotation schemes (rotation about X-, Y- and Z-axes) are analyzed to mitigate the navigation errors caused by MEMS IMU sensor errors. As the IMU rotation induces additional sensor errors, a calibration process is proposed to remove the induced errors. Tests are further conducted with two MEMS IMUs installed on a tri-axial rotation table to verify the error mitigation by IMU rotations. PMID:27916852

  12. On Nautical Observation Errors Evaluation

    Directory of Open Access Journals (Sweden)

    Wlodzimierz Filipowicz

    2015-12-01

    Full Text Available Mathematical Theory of Evidence (MTE enables upgrading models and solving crucial problems in many disciplines. MTE delivers new unique opportunity once one engages possibilistic concept. Since fuzziness is widely perceived as something that enables encoding knowledge thus models build upon fuzzy platforms accepts ones skill within given field. At the same time evidence combining scheme is a mechanism enabling enrichment initial data informative context. Therefore it can be exploited in many cases where uncertainty and lack of precision prevail. In nautical applications, for example, it can be used in order to handle data feature systematic and random deflections. Theoretical background was discussed and computer application was successfully implemented in order to cope with erroneous and uncertain data. Output of the application resulted in making a fix and a posteriori evaluating its quality. It was also proven that it can be useful for calibrating measurement appliances. Unique feature of the combination scheme proven by the author in his previous paper, enables identifying measurement systematic deflection. Based on the theorem the paper aims at further exploration of practical aspects of the problem. It concentrates on reduction of hypothesis frame reduction and random along with systematic errors identifications.

  13. Calibration of a flexible measurement system based on industrial articulated robot and structured light sensor

    Science.gov (United States)

    Mu, Nan; Wang, Kun; Xie, Zexiao; Ren, Ping

    2017-05-01

    To realize online rapid measurement for complex workpieces, a flexible measurement system based on an articulated industrial robot with a structured light sensor mounted on the end-effector is developed. A method for calibrating the system parameters is proposed in which the hand-eye transformation parameters and the robot kinematic parameters are synthesized in the calibration process. An initial hand-eye calibration is first performed using a standard sphere as the calibration target. By applying the modified complete and parametrically continuous method, we establish a synthesized kinematic model that combines the initial hand-eye transformation and distal link parameters as a whole with the sensor coordinate system as the tool frame. According to the synthesized kinematic model, an error model is constructed based on spheres' center-to-center distance errors. Consequently, the error model parameters can be identified in a calibration experiment using a three-standard-sphere target. Furthermore, the redundancy of error model parameters is eliminated to ensure the accuracy and robustness of the parameter identification. Calibration and measurement experiments are carried out based on an ER3A-C60 robot. The experimental results show that the proposed calibration method enjoys high measurement accuracy, and this efficient and flexible system is suitable for online measurement in industrial scenes.

  14. A Simple Accelerometer Calibrator

    Science.gov (United States)

    Salam, R. A.; Islamy, M. R. F.; Munir, M. M.; Latief, H.; Irsyam, M.; Khairurrijal

    2016-08-01

    High possibility of earthquake could lead to the high number of victims caused by it. It also can cause other hazards such as tsunami, landslide, etc. In that case it requires a system that can examine the earthquake occurrence. Some possible system to detect earthquake is by creating a vibration sensor system using accelerometer. However, the output of the system is usually put in the form of acceleration data. Therefore, a calibrator system for accelerometer to sense the vibration is needed. In this study, a simple accelerometer calibrator has been developed using 12 V DC motor, optocoupler, Liquid Crystal Display (LCD) and AVR 328 microcontroller as controller system. The system uses the Pulse Wave Modulation (PWM) form microcontroller to control the motor rotational speed as response to vibration frequency. The frequency of vibration was read by optocoupler and then those data was used as feedback to the system. The results show that the systems could control the rotational speed and the vibration frequencies in accordance with the defined PWM.

  15. Rotating-coil calibration in a reference quadrupole, considering roll-angle misalignment and higher-order harmonics

    CERN Document Server

    Arpaia, Pasquale; Köster, Oliver; Russenschuck, Stephan; Severino, Giordana; 10.1016/j.measurement.2016.02.061

    2016-01-01

    A method is proposed for calibrating the radius of a rotating coil sensor by relaxing the metrological constraints on alignment and field errors of the reference quadrupole. A coil radius calibration considering a roll-angle misalignment of the measurement bench, the magnet, and the motor-drive unit is analyzed. Then, the error arising from higher-order harmonic field imperfections in the reference quadrupole is assessed. The method is validated by numerical field computation for both the higher-order harmonic errors and the roll-angle misalignment. Finally, an experimental proof-of-principle demonstration is car-ried out in a calibration magnet with sextupole harmonic.

  16. Error monitoring in musicians

    Directory of Open Access Journals (Sweden)

    Clemens eMaidhof

    2013-07-01

    Full Text Available To err is human, and hence even professional musicians make errors occasionally during their performances. This paper summarizes recent work investigating error monitoring in musicians, i.e. the processes and their neural correlates associated with the monitoring of ongoing actions and the detection of deviations from intended sounds. EEG Studies reported an early component of the event-related potential (ERP occurring before the onsets of pitch errors. This component, which can be altered in musicians with focal dystonia, likely reflects processes of error detection and/or error compensation, i.e. attempts to cancel the undesired sensory consequence (a wrong tone a musician is about to perceive. Thus, auditory feedback seems not to be a prerequisite for error detection, consistent with previous behavioral results. In contrast, when auditory feedback is externally manipulated and thus unexpected, motor performance can be severely distorted, although not all feedback alterations result in performance impairments. Recent studies investigating the neural correlates of feedback processing showed that unexpected feedback elicits an ERP component after note onsets, which shows larger amplitudes during music performance than during mere perception of the same musical sequences. Hence, these results stress the role of motor actions for the processing of auditory information. Furthermore, recent methodological advances like the combination of 3D motion capture techniques with EEG will be discussed. Such combinations of different measures can potentially help to disentangle the roles of different feedback types such as proprioceptive and auditory feedback, and in general to derive at a better understanding of the complex interactions between the motor and auditory domain during error monitoring. Finally, outstanding questions and future directions in this context will be discussed.

  17. Design of a Two-Step Calibration Method of Kinematic Parameters for Serial Robots

    Science.gov (United States)

    WANG, Wei; WANG, Lei; YUN, Chao

    2017-03-01

    Serial robots are used to handle workpieces with large dimensions, and calibrating kinematic parameters is one of the most efficient ways to upgrade their accuracy. Many models are set up to investigate how many kinematic parameters can be identified to meet the minimal principle, but the base frame and the kinematic parameter are indistinctly calibrated in a one-step way. A two-step method of calibrating kinematic parameters is proposed to improve the accuracy of the robot's base frame and kinematic parameters. The forward kinematics described with respect to the measuring coordinate frame are established based on the product-of-exponential (POE) formula. In the first step the robot's base coordinate frame is calibrated by the unit quaternion form. The errors of both the robot's reference configuration and the base coordinate frame's pose are equivalently transformed to the zero-position errors of the robot's joints. The simplified model of the robot's positioning error is established in second-power explicit expressions. Then the identification model is finished by the least square method, requiring measuring position coordinates only. The complete subtasks of calibrating the robot's 39 kinematic parameters are finished in the second step. It's proved by a group of calibration experiments that by the proposed two-step calibration method the average absolute accuracy of industrial robots is updated to 0.23 mm. This paper presents that the robot's base frame should be calibrated before its kinematic parameters in order to upgrade its absolute positioning accuracy.

  18. A SVD-based method to assess the uniqueness and accuracy of SPECT geometrical calibration.

    Science.gov (United States)

    Ma, Tianyu; Yao, Rutao; Shao, Yiping; Zhou, Rong

    2009-12-01

    Geometrical calibration is critical to obtaining high resolution and artifact-free reconstructed image for SPECT and CT systems. Most published calibration methods use analytical approach to determine the uniqueness condition for a specific calibration problem, and the calibration accuracy is often evaluated through empirical studies. In this work, we present a general method to assess the characteristics of both the uniqueness and the quantitative accuracy of the calibration. The method uses a singular value decomposition (SVD) based approach to analyze the Jacobian matrix from a least-square cost function for the calibration. With this method, the uniqueness of the calibration can be identified by assessing the nonsingularity of the Jacobian matrix, and the estimation accuracy of the calibration parameters can be quantified by analyzing the SVD components. A direct application of this method is that the efficacy of a calibration configuration can be quantitatively evaluated by choosing a figure-of-merit, e.g., the minimum required number of projection samplings to achieve desired calibration accuracy. The proposed method was validated with a slit-slat SPECT system through numerical simulation studies and experimental measurements with point sources and an ultra-micro hot-rod phantom. The predicted calibration accuracy from the numerical studies was confirmed by the experimental point source calibrations at approximately 0.1 mm for both the center of rotation (COR) estimation of a rotation stage and the slit aperture position (SAP) estimation of a slit-slat collimator by an optimized system calibration protocol. The reconstructed images of a hot rod phantom showed satisfactory spatial resolution with a proper calibration and showed visible resolution degradation with artificially introduced 0.3 mm COR estimation error. The proposed method can be applied to other SPECT and CT imaging systems to analyze calibration method assessment and calibration protocol

  19. Backward-gazing method for measuring solar concentrators shape errors.

    Science.gov (United States)

    Coquand, Mathieu; Henault, François; Caliot, Cyril

    2017-03-01

    This paper describes a backward-gazing method for measuring the optomechanical errors of solar concentrating surfaces. It makes use of four cameras placed near the solar receiver and simultaneously recording images of the sun reflected by the optical surfaces. Simple data processing then allows reconstructing the slope and shape errors of the surfaces. The originality of the method is enforced by the use of generalized quad-cell formulas and approximate mathematical relations between the slope errors of the mirrors and their reflected wavefront in the case of sun-tracking heliostats at high-incidence angles. Numerical simulations demonstrate that the measurement accuracy is compliant with standard requirements of solar concentrating optics in the presence of noise or calibration errors. The method is suited to fine characterization of the optical and mechanical errors of heliostats and their facets, or to provide better control for real-time sun tracking.

  20. Two statistics for evaluating parameter identifiability and error reduction

    Science.gov (United States)

    Doherty, John; Hunt, Randall J.

    2009-01-01

    Two statistics are presented that can be used to rank input parameters utilized by a model in terms of their relative identifiability based on a given or possible future calibration dataset. Identifiability is defined here as the capability of model calibration to constrain parameters used by a model. Both statistics require that the sensitivity of each model parameter be calculated for each model output for which there are actual or presumed field measurements. Singular value decomposition (SVD) of the weighted sensitivity matrix is then undertaken to quantify the relation between the parameters and observations that, in turn, allows selection of calibration solution and null spaces spanned by unit orthogonal vectors. The first statistic presented, "parameter identifiability", is quantitatively defined as the direction cosine between a parameter and its projection onto the calibration solution space. This varies between zero and one, with zero indicating complete non-identifiability and one indicating complete identifiability. The second statistic, "relative error reduction", indicates the extent to which the calibration process reduces error in estimation of a parameter from its pre-calibration level where its value must be assigned purely on the basis of prior expert knowledge. This is more sophisticated than identifiability, in that it takes greater account of the noise associated with the calibration dataset. Like identifiability, it has a maximum value of one (which can only be achieved if there is no measurement noise). Conceptually it can fall to zero; and even below zero if a calibration problem is poorly posed. An example, based on a coupled groundwater/surface-water model, is included that demonstrates the utility of the statistics. ?? 2009 Elsevier B.V.

  1. STUDY OF CALIBRATION OF SOLAR RADIO SPECTROMETERS AND THE QUIET-SUN RADIO EMISSION

    Energy Technology Data Exchange (ETDEWEB)

    Tan, Chengming; Yan, Yihua; Tan, Baolin; Fu, Qijun; Liu, Yuying [Key Laboratory of Solar Activity, National Astronomical Observatories of Chinese Academy of Sciences, Datun Road A20, Chaoyang District, Beijing 100012 (China); Xu, Guirong [Hubei Key Laboratory for Heavy Rain Monitoring and Warning Research, Institute of Heavy Rain, China Meteorological Administration, Wuhan 430205 (China)

    2015-07-20

    This work presents a systematic investigation of the influence of weather conditions on the calibration errors by using Gaussian fitness, least chi-square linear fitness, and wavelet transform to analyze the calibration coefficients from observations of the Chinese Solar Broadband Radio Spectrometers (at frequency bands of 1.0–2.0 GHz, 2.6–3.8 GHz, and 5.2–7.6 GHz) during 1997–2007. We found that calibration coefficients are influenced by the local air temperature. Considering the temperature correction, the calibration error will reduce by about 10%–20% at 2800 MHz. Based on the above investigation and the calibration corrections, we further study the radio emission of the quiet Sun by using an appropriate hybrid model of the quiet-Sun atmosphere. The results indicate that the numerical flux of the hybrid model is much closer to the observation flux than that of other ones.

  2. Study of Calibration of Solar Radio Spectrometers and the quiet-Sun Radio Emission

    CERN Document Server

    Tan, Chengming; Tan, Baolin; Fu, Qijun; Liu, Yuying; Xu, Guirong

    2015-01-01

    This work presents a systematic investigation of the influence of weather conditions on the calibration errors by using Gaussian fitness, least chi-square linear fitness and wavelet transform to analyze the calibration coefficients from observations of the Chinese Solar Broadband Radio Spectrometers (at frequency bands of 1.0-2.0 GHz, 2.6-3.8 GHz, and 5.2-7.6 GHz) during 1997-2007. We found that calibration coefficients are influenced by the local air temperature. Considering the temperature correction, the calibration error will reduce by about $10\\%-20\\%$ at 2800 MHz. Based on the above investigation and the calibration corrections, we further study the radio emission of the quiet-Sun by using an appropriate hybrid model of the quiet-Sun atmosphere. The results indicate that the numerical flux of the hybrid model is much closer to the observation flux than that of other ones.

  3. 激发-发射矩阵荧光结合二阶校正法测定人体血浆样和牛蒡子药材中的牛蒡苷含量%Determination of arctiin in plasma samples and arctium lappa L. by using excitation-emission matrix fluorescence and second-order calibration based on parallel factor analysis/alternating normalization-weighted error algorithms

    Institute of Scientific and Technical Information of China (English)

    张燕; 吴海龙; 欧阳立群; 万瑶; 俞汝勤

    2009-01-01

    本文利用激发-发射矩阵荧光与二阶校正算法相结合,实现快速测定人体血浆样和牛蒡子对照药材中的牛蒡苷含量.采用二阶校正方法的平行因子分析(PARAFAC)和交替归一加权残差(ANWE)两种算法进行解析,所得血浆基体干扰下牛蒡苷的回收率分别为(98.7±1.4)%和(99.7±1.6)%,实现了对血浆样中的牛蒡苷含茸的直接快速定量测定.此外,用上述两种方法对牛蒡子药材中的牛蒡苷含量进行快速测定,所得结果与液相色谱方法结果进行比较,结果令人满意.实验结果表明,此方法方便快捷,可用于复杂试样中未知干扰共存下牛蒡苷含量的测定.%This paper proposed a new approach for direct determination of arctiin in plasma samples as well as a Chinese medicine (Arctium lappa L.) by the combination of excitation-emission matrix fluorescence and second-order calibration methods based on paral-lel factor analysis(PARAFAC) and alternating normalization-weighted error(ANWE) algorithms. The average recoveries of actiin in plasma samples obtained by using PARAFAC and ANWE with the estimated component number of two were 98.7 ± 1.4% and 99. 7 ± 1.6%, respectively. The methodology was used to estimate the content of arctiin in Aretium lappa L. , and the obtained results were also satisfactory compared with that of the HPLC method. It can be seen that the suggested methods can be employed to directly deter-mine arctiin, even in the presence of unknown and un-calibrated interferences, only with a simple pretreatment procedure.

  4. Study on the wavelength calibration of type III concave grating spectrometry system

    Institute of Scientific and Technical Information of China (English)

    Li Bai(白力); Ningfang Liao(廖宁放); Zhaojian Li(栗兆剑); Weiping Yang(杨卫平)

    2004-01-01

    We discuss and calibrate the spectrometry system based on concave reflection grating. The working principle, structure and parameters of the spectrometry system are introduced. For the wavelength calibration problem, three methods are put forward and discussed in detail with formulation calculation method, circular iteration method and interpolation. Interpolation is used to calibrate the concave reflection grating spectrometry system and the error is less than 1 nm. Four spectrum images that the system collected are given in this paper. The experimental results indicate that a spectrometry system can be based on concave reflection grating and be calibrated by interpolation.

  5. True logarithmic amplification of frequency clock in SS-OCT for calibration.

    Science.gov (United States)

    Liu, Bin; Azimi, Ehsan; Brezinski, Mark E

    2011-06-01

    With swept source optical coherence tomography (SS-OCT), imprecise signal calibration prevents optimal imaging of biological tissues such as coronary artery. This work demonstrates an approach using a true logarithmic amplifier to precondition the clock signal, with the effort to minimize the noises and phase errors for optimal calibration. This method was validated and tested with a high-speed SS-OCT. The experimental results manifest its superior ability on optimization of the calibration and improvement of the imaging performance. Particularly, this hardware-based approach is suitable for real-time calibration in a high-speed system where computation time is constrained.

  6. Calibrating an interferometric laser frequency stabilization to MHz precision

    CERN Document Server

    Brachmann, Johannes F S; Dieckmann, Kai; 10.1364/AO.51.005517

    2012-01-01

    We report on a calibration procedure that enhances the precision of an interferometer based frequency stabilization by several orders of magnitude. For this purpose the frequency deviations of the stabilization are measured precisely by means of a frequency comb. This allows to implement several calibration steps that compensate different systematic errors. The resulting frequency deviation is shown to be less than $5.7 $MHz (rms $1.6 $MHz) in the whole wavelength interval $750 - 795 $nm. Wide tuning of a stabilized laser at this exceptional precision is demonstrated.

  7. Design of self-calibrating controllers for heliostats in a solar power plant

    Science.gov (United States)

    Baheti, R. S.; Scott, P. F.

    1980-12-01

    A self-calibrating controller is developed for reducing installation and drive errors in a heliostat (steerable mirror used in solar/electric energy conversion). In this scheme, the heliostat periodically tracks the sun, which serves as a precision position reference. The difference between commanded and actual drive angles is used to estimate the coefficients of a model representing installation and drive errors. The calibrated model is then used to correct the drive actuator commands for these error sources when the heliostat is in a tracking mode (its principle mode of operation). Simulation results are given for a typical heliostat configuration with realistic errors. The algorithm is very effective in reducing beam steering errors. The concept is demonstrated using a prototype test apparatus and is shown to achieve an error reduction of more than 5:1.

  8. Smoothing error pitfalls

    Science.gov (United States)

    von Clarmann, T.

    2014-09-01

    The difference due to the content of a priori information between a constrained retrieval and the true atmospheric state is usually represented by a diagnostic quantity called smoothing error. In this paper it is shown that, regardless of the usefulness of the smoothing error as a diagnostic tool in its own right, the concept of the smoothing error as a component of the retrieval error budget is questionable because it is not compliant with Gaussian error propagation. The reason for this is that the smoothing error does not represent the expected deviation of the retrieval from the true state but the expected deviation of the retrieval from the atmospheric state sampled on an arbitrary grid, which is itself a smoothed representation of the true state; in other words, to characterize the full loss of information with respect to the true atmosphere, the effect of the representation of the atmospheric state on a finite grid also needs to be considered. The idea of a sufficiently fine sampling of this reference atmospheric state is problematic because atmospheric variability occurs on all scales, implying that there is no limit beyond which the sampling is fine enough. Even the idealization of infinitesimally fine sampling of the reference state does not help, because the smoothing error is applied to quantities which are only defined in a statistical sense, which implies that a finite volume of sufficient spatial extent is needed to meaningfully discuss temperature or concentration. Smoothing differences, however, which play a role when measurements are compared, are still a useful quantity if the covariance matrix involved has been evaluated on the comparison grid rather than resulting from interpolation and if the averaging kernel matrices have been evaluated on a grid fine enough to capture all atmospheric variations that the instruments are sensitive to. This is, under the assumptions stated, because the undefined component of the smoothing error, which is the

  9. Learning from Errors

    Directory of Open Access Journals (Sweden)

    MA. Lendita Kryeziu

    2015-06-01

    Full Text Available “Errare humanum est”, a well known and widespread Latin proverb which states that: to err is human, and that people make mistakes all the time. However, what counts is that people must learn from mistakes. On these grounds Steve Jobs stated: “Sometimes when you innovate, you make mistakes. It is best to admit them quickly, and get on with improving your other innovations.” Similarly, in learning new language, learners make mistakes, thus it is important to accept them, learn from them, discover the reason why they make them, improve and move on. The significance of studying errors is described by Corder as: “There have always been two justifications proposed for the study of learners' errors: the pedagogical justification, namely that a good understanding of the nature of error is necessary before a systematic means of eradicating them could be found, and the theoretical justification, which claims that a study of learners' errors is part of the systematic study of the learners' language which is itself necessary to an understanding of the process of second language acquisition” (Corder, 1982; 1. Thus the importance and the aim of this paper is analyzing errors in the process of second language acquisition and the way we teachers can benefit from mistakes to help students improve themselves while giving the proper feedback.

  10. Error Correction in Classroom

    Institute of Scientific and Technical Information of China (English)

    Dr. Grace Zhang

    2000-01-01

    Error correction is an important issue in foreign language acquisition. This paper investigates how students feel about the way in which error correction should take place in a Chinese-as-a foreign-language classroom, based on empirical data of a large scale. The study shows that there is a general consensus that error correction is necessary. In terms of correction strategy, the students preferred a combination of direct and indirect corrections, or a direct only correction. The former choice indicates that students would be happy to take either so long as the correction gets done.Most students didn't mind peer correcting provided it is conducted in a constructive way. More than halfofthe students would feel uncomfortable ifthe same error they make in class is corrected consecutively more than three times. Taking these findings into consideration, we may want to cncourage peer correcting, use a combination of correction strategies (direct only if suitable) and do it in a non-threatening and sensitive way. It is hoped that this study would contribute to the effectiveness of error correction in a Chinese language classroom and it may also have a wider implication on other languages.

  11. Landsat-7 ETM+ radiometric stability and absolute calibration

    Science.gov (United States)

    Markham, B.L.; Barker, J.L.; Barsi, J.A.; Kaita, E.; Thome, K.J.; Helder, D.L.; Palluconi, Frank Don; Schott, J.R.; Scaramuzza, P.; ,

    2002-01-01

    Launched in April 1999, the Landsat-7 ETM+ instrument is in its fourth year of operation. The quality of the acquired calibrated imagery continues to be high, especially with respect to its three most important radiometric performance parameters: reflective band instrument stability to better than ??1%, reflective band absolute calibration to better than ??5%, and thermal band absolute calibration to better than ??0.6 K. The ETM+ instrument has been the most stable of any of the Landsat instruments, in both the reflective and thermal channels. To date, the best on-board calibration source for the reflective bands has been the Full Aperture Solar Calibrator, which has indicated changes of at most -1.8% to -2.0% (95% C.I.) change per year in the ETM+ gain (band 4). However, this change is believed to be caused by changes in the solar diffuser panel, as opposed to a change in the instrument's gain. This belief is based partially on ground observations, which bound the changes in gain in band 4 at -0.7% to +1.5%. Also, ETM+ stability is indicated by the monitoring of desert targets. These image-based results for four Saharan and Arabian sites, for a collection of 35 scenes over the three years since launch, bound the gain change at -0.7% to +0.5% in band 4. Thermal calibration from ground observations revealed an offset error of +0.31 W/m 2 sr um soon after launch. This offset was corrected within the U. S. ground processing system at EROS Data Center on 21-Dec-00, and since then, the band 6 on-board calibration has indicated changes of at most +0.02% to +0.04% (95% C.I.) per year. The latest ground observations have detected no remaining offset error with an RMS error of ??0.6 K. The stability and absolute calibration of the Landsat-7 ETM+ sensor make it an ideal candidate to be used as a reference source for radiometric cross-calibrating to other land remote sensing satellite systems.

  12. Internal Water Vapor Photoacoustic Calibration

    Science.gov (United States)

    Pilgrim, Jeffrey S.

    2009-01-01

    Water vapor absorption is ubiquitous in the infrared wavelength range where photoacoustic trace gas detectors operate. This technique allows for discontinuous wavelength tuning by temperature-jumping a laser diode from one range to another within a time span suitable for photoacoustic calibration. The use of an internal calibration eliminates the need for external calibrated reference gases. Commercial applications include an improvement of photoacoustic spectrometers in all fields of use.

  13. RX130 Robot Calibration

    Science.gov (United States)

    Fugal, Mario

    2012-10-01

    In order to create precision magnets for an experiment at Oak Ridge National Laboratory, a new reverse engineering method has been proposed that uses the magnetic scalar potential to solve for the currents necessary to produce the desired field. To make the magnet it is proposed to use a copper coated G10 form, upon which a drill, mounted on a robotic arm, will carve wires. The accuracy required in the manufacturing of the wires exceeds nominal robot capabilities. However, due to the rigidity as well as the precision servo motor and harmonic gear drivers, there are robots capable of meeting this requirement with proper calibration. Improving the accuracy of an RX130 to be within 35 microns (the accuracy necessary of the wires) is the goal of this project. Using feedback from a displacement sensor, or camera and inverse kinematics it is possible to achieve this accuracy.

  14. SURF Model Calibration Strategy

    Energy Technology Data Exchange (ETDEWEB)

    Menikoff, Ralph [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2017-03-10

    SURF and SURFplus are high explosive reactive burn models for shock initiation and propagation of detonation waves. They are engineering models motivated by the ignition & growth concept of high spots and for SURFplus a second slow reaction for the energy release from carbon clustering. A key feature of the SURF model is that there is a partial decoupling between model parameters and detonation properties. This enables reduced sets of independent parameters to be calibrated sequentially for the initiation and propagation regimes. Here we focus on a methodology for tting the initiation parameters to Pop plot data based on 1-D simulations to compute a numerical Pop plot. In addition, the strategy for tting the remaining parameters for the propagation regime and failure diameter is discussed.

  15. Radiological Calibration and Standards Facility

    Data.gov (United States)

    Federal Laboratory Consortium — PNNL maintains a state-of-the-art Radiological Calibration and Standards Laboratory on the Hanford Site at Richland, Washington. Laboratory staff provide expertise...

  16. Field calibration of cup anemometers

    DEFF Research Database (Denmark)

    Kristensen, L.; Jensen, G.; Hansen, A.

    2001-01-01

    An outdoor calibration facility for cup anemometers, where the signals from 10 anemometers of which at least one is a reference can be can be recorded simultaneously, has been established. The results are discussed with special emphasis on the statisticalsignificance of the calibration expressions....... It is concluded that the method has the advantage that many anemometers can be calibrated accurately with a minimum of work and cost. The obvious disadvantage is that the calibration of a set of anemometersmay take more than one month in order to have wind speeds covering a sufficiently large magnitude range...

  17. Errors in Neonatology

    Directory of Open Access Journals (Sweden)

    Antonio Boldrini

    2013-06-01

    Full Text Available Introduction: Danger and errors are inherent in human activities. In medical practice errors can lean to adverse events for patients. Mass media echo the whole scenario. Methods: We reviewed recent published papers in PubMed database to focus on the evidence and management of errors in medical practice in general and in Neonatology in particular. We compared the results of the literature with our specific experience in Nina Simulation Centre (Pisa, Italy. Results: In Neonatology the main error domains are: medication and total parenteral nutrition, resuscitation and respiratory care, invasive procedures, nosocomial infections, patient identification, diagnostics. Risk factors include patients’ size, prematurity, vulnerability and underlying disease conditions but also multidisciplinary teams, working conditions providing fatigue, a large variety of treatment and investigative modalities needed. Discussion and Conclusions: In our opinion, it is hardly possible to change the human beings but it is likely possible to change the conditions under they work. Voluntary errors report systems can help in preventing adverse events. Education and re-training by means of simulation can be an effective strategy too. In Pisa (Italy Nina (ceNtro di FormazIone e SimulazioNe NeonAtale is a simulation center that offers the possibility of a continuous retraining for technical and non-technical skills to optimize neonatological care strategies. Furthermore, we have been working on a novel skill trainer for mechanical ventilation (MEchatronic REspiratory System SImulator for Neonatal Applications, MERESSINA. Finally, in our opinion national health policy indirectly influences risk for errors. Proceedings of the 9th International Workshop on Neonatology · Cagliari (Italy · October 23rd-26th, 2013 · Learned lessons, changing practice and cutting-edge research

  18. Error Free Software

    Science.gov (United States)

    1985-01-01

    A mathematical theory for development of "higher order" software to catch computer mistakes resulted from a Johnson Space Center contract for Apollo spacecraft navigation. Two women who were involved in the project formed Higher Order Software, Inc. to develop and market the system of error analysis and correction. They designed software which is logically error-free, which, in one instance, was found to increase productivity by 600%. USE.IT defines its objectives using AXES -- a user can write in English and the system converts to computer languages. It is employed by several large corporations.

  19. LIBERTARISMO & ERROR CATEGORIAL

    Directory of Open Access Journals (Sweden)

    Carlos G. Patarroyo G.

    2009-01-01

    Full Text Available En este artículo se ofrece una defensa del libertarismo frente a dos acusaciones según las cuales éste comete un error categorial. Para ello, se utiliza la filosofía de Gilbert Ryle como herramienta para explicar las razones que fundamentan estas acusaciones y para mostrar por qué, pese a que ciertas versiones del libertarismo que acuden a la causalidad de agentes o al dualismo cartesiano cometen estos errores, un libertarismo que busque en el indeterminismo fisicalista la base de la posibilidad de la libertad humana no necesariamente puede ser acusado de incurrir en ellos.

  20. Rapid Global Calibration Technology for Hybrid Visual Inspection System

    Directory of Open Access Journals (Sweden)

    Tao Liu

    2017-06-01

    Full Text Available Vision-based methods for product quality inspection are playing an increasingly important role in modern industries for their good performance and high efficiency. A hybrid visual inspection system, which consists of an industrial robot with a flexible sensor and several stationary sensors, has been widely applied in mass production, especially in automobile manufacturing. In this paper, a rapid global calibration method for the hybrid visual inspection system is proposed. Global calibration of a flexible sensor is performed first based on the robot kinematic. Then, with the aid of the calibrated flexible sensor, stationary sensors are calibrated globally one by one based on homography. Only a standard sphere and an auxiliary target with a 2D planar pattern are applied during the system global calibration, and the calibration process can be easily re-performed during the system’s periodical maintenance. An error compensation method is proposed for the hybrid inspection system, and the final accuracy of the hybrid system is evaluated with the deviation and correlation coefficient between the measured results of the hybrid system and Coordinate Measuring Machine (CMM. An accuracy verification experiment shows that deviation of over 95% of featured points are less than ±0.3 mm, and the correlation coefficients of over 85% of points are larger than 0.7.

  1. Data filtering with support vector machines in geometric camera calibration.

    Science.gov (United States)

    Ergun, B; Kavzoglu, T; Colkesen, I; Sahin, C

    2010-02-01

    The use of non-metric digital cameras in close-range photogrammetric applications and machine vision has become a popular research agenda. Being an essential component of photogrammetric evaluation, camera calibration is a crucial stage for non-metric cameras. Therefore, accurate camera calibration and orientation procedures have become prerequisites for the extraction of precise and reliable 3D metric information from images. The lack of accurate inner orientation parameters can lead to unreliable results in the photogrammetric process. A camera can be well defined with its principal distance, principal point offset and lens distortion parameters. Different camera models have been formulated and used in close-range photogrammetry, but generally sensor orientation and calibration is performed with a perspective geometrical model by means of the bundle adjustment. In this study, support vector machines (SVMs) using radial basis function kernel is employed to model the distortions measured for Olympus Aspherical Zoom lens Olympus E10 camera system that are later used in the geometric calibration process. It is intended to introduce an alternative approach for the on-the-job photogrammetric calibration stage. Experimental results for DSLR camera with three focal length settings (9, 18 and 36 mm) were estimated using bundle adjustment with additional parameters, and analyses were conducted based on object point discrepancies and standard errors. Results show the robustness of the SVMs approach on the correction of image coordinates by modelling total distortions on-the-job calibration process using limited number of images.

  2. Rapid Global Calibration Technology for Hybrid Visual Inspection System.

    Science.gov (United States)

    Liu, Tao; Yin, Shibin; Guo, Yin; Zhu, Jigui

    2017-06-19

    Vision-based methods for product quality inspection are playing an increasingly important role in modern industries for their good performance and high efficiency. A hybrid visual inspection system, which consists of an industrial robot with a flexible sensor and several stationary sensors, has been widely applied in mass production, especially in automobile manufacturing. In this paper, a rapid global calibration method for the hybrid visual inspection system is proposed. Global calibration of a flexible sensor is performed first based on the robot kinematic. Then, with the aid of the calibrated flexible sensor, stationary sensors are calibrated globally one by one based on homography. Only a standard sphere and an auxiliary target with a 2D planar pattern are applied during the system global calibration, and the calibration process can be easily re-performed during the system's periodical maintenance. An error compensation method is proposed for the hybrid inspection system, and the final accuracy of the hybrid system is evaluated with the deviation and correlation coefficient between the measured results of the hybrid system and Coordinate Measuring Machine (CMM). An accuracy verification experiment shows that deviation of over 95% of featured points are less than ±0.3 mm, and the correlation coefficients of over 85% of points are larger than 0.7.

  3. Neutron multiplication error in TRU waste measurements

    Energy Technology Data Exchange (ETDEWEB)

    Veilleux, John [Los Alamos National Laboratory; Stanfield, Sean B [CCP; Wachter, Joe [CCP; Ceo, Bob [CCP

    2009-01-01

    Total Measurement Uncertainty (TMU) in neutron assays of transuranic waste (TRU) are comprised of several components including counting statistics, matrix and source distribution, calibration inaccuracy, background effects, and neutron multiplication error. While a minor component for low plutonium masses, neutron multiplication error is often the major contributor to the TMU for items containing more than 140 g of weapons grade plutonium. Neutron multiplication arises when neutrons from spontaneous fission and other nuclear events induce fissions in other fissile isotopes in the waste, thereby multiplying the overall coincidence neutron response in passive neutron measurements. Since passive neutron counters cannot differentiate between spontaneous and induced fission neutrons, multiplication can lead to positive bias in the measurements. Although neutron multiplication can only result in a positive bias, it has, for the purpose of mathematical simplicity, generally been treated as an error that can lead to either a positive or negative result in the TMU. While the factors that contribute to neutron multiplication include the total mass of fissile nuclides, the presence of moderating material in the matrix, the concentration and geometry of the fissile sources, and other factors; measurement uncertainty is generally determined as a function of the fissile mass in most TMU software calculations because this is the only quantity determined by the passive neutron measurement. Neutron multiplication error has a particularly pernicious consequence for TRU waste analysis because the measured Fissile Gram Equivalent (FGE) plus twice the TMU error must be less than 200 for TRU waste packaged in 55-gal drums and less than 325 for boxed waste. For this reason, large errors due to neutron multiplication can lead to increased rejections of TRU waste containers. This report will attempt to better define the error term due to neutron multiplication and arrive at values that are

  4. A fast combination calibration of foreground and background for pipelined ADCs

    Institute of Scientific and Technical Information of China (English)

    Sun Kexu; He Lenian

    2012-01-01

    This paper describes a fast digital calibration scheme for pipelined analog-to-digital converters (ADCs).The proposed method corrects the nonlinearity caused by finite opamp gain and capacitor mismatch in multiplying digital-to-analog converters (MDACs).The considered calibration technique takes the advantages of both foreground and background calibration schemes.In this combination calibration algorithm,a novel parallel background calibration with signal-shifted correlation is proposed,and its calibration cycle is very short.The details of this technique are described in the example of a 14-bit 100 Msample/s pipelined ADC.The high convergence speed of this background calibration is achieved by three means.First,a modified 1.5-bit stage is proposed in order to allow the injection of a large pseudo-random dithering without missing code.Second,before correlating the signal,it is shifted according to the input signal so that the correlation error converges quickly.Finally,the front pipeline stages are calibrated simultaneously rather than stage by stage to reduce the calibration tracking constants.Simulation results confirm that the combination calibration has a fast startup process and a short background calibration cycle of 2×221 conversions.

  5. A fast combination calibration of foreground and background for pipelined ADCs

    Science.gov (United States)

    Kexu, Sun; Lenian, He

    2012-06-01

    This paper describes a fast digital calibration scheme for pipelined analog-to-digital converters (ADCs). The proposed method corrects the nonlinearity caused by finite opamp gain and capacitor mismatch in multiplying digital-to-analog converters (MDACs). The considered calibration technique takes the advantages of both foreground and background calibration schemes. In this combination calibration algorithm, a novel parallel background calibration with signal-shifted correlation is proposed, and its calibration cycle is very short. The details of this technique are described in the example of a 14-bit 100 Msample/s pipelined ADC. The high convergence speed of this background calibration is achieved by three means. First, a modified 1.5-bit stage is proposed in order to allow the injection of a large pseudo-random dithering without missing code. Second, before correlating the signal, it is shifted according to the input signal so that the correlation error converges quickly. Finally, the front pipeline stages are calibrated simultaneously rather than stage by stage to reduce the calibration tracking constants. Simulation results confirm that the combination calibration has a fast startup process and a short background calibration cycle of 2 × 221 conversions.

  6. Quasi-Static Calibration Method of a High-g Accelerometer.

    Science.gov (United States)

    Wang, Yan; Fan, Jinbiao; Zu, Jing; Xu, Peng

    2017-02-20

    To solve the problem of resonance during quasi-static calibration of high-g accelerometers, we deduce the relationship between the minimum excitation pulse width and the resonant frequency of the calibrated accelerometer according to the second-order mathematical model of the accelerometer, and improve the quasi-static calibration theory. We establish a quasi-static calibration testing system, which uses a gas gun to generate high-g acceleration signals, and apply a laser interferometer to reproduce the impact acceleration. These signals are used to drive the calibrated accelerometer. By comparing the excitation acceleration signal and the output responses of the calibrated accelerometer to the excitation signals, the impact sensitivity of the calibrated accelerometer is obtained. As indicated by the calibration test results, this calibration system produces excitation acceleration signals with a pulse width of less than 1000 μs, and realize the quasi-static calibration of high-g accelerometers with a resonant frequency above 20 kHz when the calibration error was 3%.

  7. Correction of placement error in EBL using model based method

    Science.gov (United States)

    Babin, Sergey; Borisov, Sergey; Militsin, Vladimir; Komagata, Tadashi; Wakatsuki, Tetsuro

    2016-10-01

    The main source of placement error in maskmaking using electron beam is charging. DISPLACE software provides a method to correct placement errors for any layout, based on a physical model. The charge of a photomask and multiple discharge mechanisms are simulated to find the charge distribution over the mask. The beam deflection is calculated for each location on the mask, creating data for the placement correction. The software considers the mask layout, EBL system setup, resist, and writing order, as well as other factors such as fogging and proximity effects correction. The output of the software is the data for placement correction. Unknown physical parameters such as fogging can be found from calibration experiments. A test layout on a single calibration mask was used to calibrate physical parameters used in the correction model. The extracted model parameters were used to verify the correction. As an ultimate test for the correction, a sophisticated layout was used for verification that was very different from the calibration mask. The placement correction results were predicted by DISPLACE, and the mask was fabricated and measured. A good correlation of the measured and predicted values of the correction all over the mask with the complex pattern confirmed the high accuracy of the charging placement error correction.

  8. Contouring error compensation on a micro coordinate measuring machine

    Science.gov (United States)

    Fan, Kuang-Chao; Wang, Hung-Yu; Ye, Jyun-Kuan

    2011-12-01

    In recent years, three-dimensional measurements of nano-technology researches have received a great attention in the world. Based on the high accuracy demand, the error compensation of measurement machine is very important. In this study, a high precision Micro-CMM (coordinate measuring machine) has been developed which is composed of a coplanar stage for reducing the Abbé error in the vertical direction, the linear diffraction grating interferometer (LDGI) as the position feedback sensor in nanometer resolution, and ultrasonic motors for position control. This paper presents the error compensation strategy including "Home accuracy" and "Position accuracy" in both axes. For the home error compensation, we utilize a commercial DVD pick-up head and its S-curve principle to accurately search the origin of each axis. For the positioning error compensation, the absolute positions relative to the home are calibrated by laser interferometer and the error budget table is stored for feed forward error compensation. Contouring error can thus be compensated if both the compensation of both X and Y positioning errors are applied. Experiments show the contouring accuracy can be controlled to within 50nm after compensation.

  9. Error Analysis for the Airborne Direct Georeferincing Technique

    Science.gov (United States)

    Elsharkawy, Ahmed S.; Habib, Ayman F.

    2016-10-01

    Direct Georeferencing was shown to be an important alternative to standard indirect image orientation using classical or GPS-supported aerial triangulation. Since direct Georeferencing without ground control relies on an extrapolation process only, particular focus has to be laid on the overall system calibration procedure. The accuracy performance of integrated GPS/inertial systems for direct Georeferencing in airborne photogrammetric environments has been tested extensively in the last years. In this approach, the limiting factor is a correct overall system calibration including the GPS/inertial component as well as the imaging sensor itself. Therefore remaining errors in the system calibration will significantly decrease the quality of object point determination. This research paper presents an error analysis for the airborne direct Georeferencing technique, where integrated GPS/IMU positioning and navigation systems are used, in conjunction with aerial cameras for airborne mapping compared with GPS/INS supported AT through the implementation of certain amount of error on the EOP and Boresight parameters and study the effect of these errors on the final ground coordinates. The data set is a block of images consists of 32 images distributed over six flight lines, the interior orientation parameters, IOP, are known through careful camera calibration procedure, also 37 ground control points are known through terrestrial surveying procedure. The exact location of camera station at time of exposure, exterior orientation parameters, EOP, is known through GPS/INS integration process. The preliminary results show that firstly, the DG and GPS-supported AT have similar accuracy and comparing with the conventional aerial photography method, the two technologies reduces the dependence on ground control (used only for quality control purposes). Secondly, In the DG Correcting overall system calibration including the GPS/inertial component as well as the imaging sensor itself

  10. Orwell's Instructive Errors

    Science.gov (United States)

    Julian, Liam

    2009-01-01

    In this article, the author talks about George Orwell, his instructive errors, and the manner in which Orwell pierced worthless theory, faced facts and defended decency (with fluctuating success), and largely ignored the tradition of accumulated wisdom that has rendered him a timeless teacher--one whose inadvertent lessons, while infrequently…

  11. Development and calibration of an air-floating six-axis force measurement platform using self-calibration

    Science.gov (United States)

    Huang, Bin; Wang, Xiaomeng; Li, Chengwei; Yi, Jiajing; Lu, Rongsheng; Tao, Jiayue

    2016-09-01

    This paper describes the design, working principle, as well as calibration of an air-floating six-axis force measurement platform, where the floating plate and nozzles were connected without contact, preventing inter-dimensional coupling and increasing precision significantly. The measurement repeatability error of the force size in the platform is less than 0.2% full scale (FS), which is significantly better than the precision of 1% FS in the six-axis force sensors on the current market. We overcame the difficulties of weight loading device in high-precision calibration by proposing a self-calibration method based on the floating plate gravity and met the calibration precision requirement of 0.02% FS. This study has general implications for the development and calibration of high-precision multi-axis force sensors. In particular, the air-floating six-axis force measurement platform could be applied to the calibration of some special sensors such as flexible tactile sensors and may be used as a micro-nano mechanical assembly platform for real-time assembly force testing.

  12. Challenge and Error: Critical Events and Attention-Related Errors

    Science.gov (United States)

    Cheyne, James Allan; Carriere, Jonathan S. A.; Solman, Grayden J. F.; Smilek, Daniel

    2011-01-01

    Attention lapses resulting from reactivity to task challenges and their consequences constitute a pervasive factor affecting everyday performance errors and accidents. A bidirectional model of attention lapses (error [image omitted] attention-lapse: Cheyne, Solman, Carriere, & Smilek, 2009) argues that errors beget errors by generating attention…

  13. System for Measuring Elevator Guide Rail Quality and Its Calibration

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    A system for measuring the quality parameters of elevator guide rails is developed. The quality parameters the system can measure include straightness, flatness, squareness, width and height of the rail. The system consists of six parts:main guideway, auxiliary guideway, reference rail, saddle, control casing and measured rail. The guide rail to be measured is mounted on a bed.The straightness errors of surfaces are checked by five linear displacement sensors mounted on the saddle. The deviation of readings from the sensor, which is in contact with top guiding surface,gives the straightness error of the surface and height of the rail. The other four sensors are used to measure side guiding surfaces respectively and give other parameters including flatness on the surfaces, squareness, width and height of the rail. A novel calibration method is also developed to calibrate the straightness motion error of the system in horizontal and vertical directions. The deflection deformation of the measured rail is fitted by using a fourth-order polynomial. Experimental results show that the uncertainty of the system on the side surfaces after compensating the straightness motion error is less than 0.01 mm, and the uncertainty of the system on the top surface after compensating the straightness motion error and the deflection deformation of the rail is less than 0.03 mm.

  14. Camera calibration method of binocular stereo vision based on OpenCV

    Science.gov (United States)

    Zhong, Wanzhen; Dong, Xiaona

    2015-10-01

    Camera calibration, an important part of the binocular stereo vision research, is the essential foundation of 3D reconstruction of the spatial object. In this paper, the camera calibration method based on OpenCV (open source computer vision library) is submitted to make the process better as a result of obtaining higher precision and efficiency. First, the camera model in OpenCV and an algorithm of camera calibration are presented, especially considering the influence of camera lens radial distortion and decentering distortion. Then, camera calibration procedure is designed to compute those parameters of camera and calculate calibration errors. High-accurate profile extraction algorithm and a checkboard with 48 corners have also been used in this part. Finally, results of calibration program are presented, demonstrating the high efficiency and accuracy of the proposed approach. The results can reach the requirement of robot binocular stereo vision.

  15. Calibration of the Microwave Limb Sounder on the Upper Atmosphere Research Satellite

    Science.gov (United States)

    Jarnot, R. F.; Cofield, R. E.; Waters, J. W.; Flower, D. A.; Peckham, G. E.

    1996-01-01

    The Microwave Limb Sounder (MLS) is a three-radiometer, passive, limb emission instrument onboard the Upper Atmosphere Research Satellite (UARS). Radiometric, spectral and field-of-view calibrations of the MLS instrument are described in this paper. In-orbit noise performance, gain stability, spectral baseline and dynamic range are described, as well as use of in-flight data for validation and refinement of prelaunch calibrations. Estimated systematic scaling uncertainties (3 sigma) on calibrated limb radiances from prelaunch calibrations are 2.6% in bands 1 through 3, 3.4% in band 4, and 6% in band 5. The observed systematic errors in band 6 are about 15%, consistent with prelaunch calibration uncertainties. Random uncertainties on individual limb radiance measurements are very close to the levels predicted from measured radiometer noise temperature, with negligible contribution from noise and drifts on the regular in-flight gain calibration measurements.

  16. Enhancing the quality of hydrologic model calibrations and their transfer to operational flood forecasters

    Science.gov (United States)

    Aggett, Graeme; Spies, Ryan; Szfranski, Bill; Hahn, Claudia; Weil, Page

    2016-04-01

    An adequate forecasting model may not perform well if it is inadequately calibrated. Model calibration is often constrained by the lack of adequate calibration data, especially for small river basins with high spatial rainfall variability. Rainfall/snow station networks may not be dense enough to accurately estimate the catchment rainfall/SWE. High discharges during flood events are subject to significant error due to flow gauging difficulty. Dynamic changes in catchment conditions (e.g., urbanization; losses in karstic systems) invariably introduce non-homogeneity in the water level and flow data. This presentation will highlight some of the challenges in reliable calibration of National Weather Service (i.e. US) operational flood forecast models, emphasizing the various challenges in different physiographic/climatic domains. It will also highlight the benefit of using various data visualization techniques to transfer information about model calibration to operational forecasters so they may understand the influence of the calibration on model performance under various conditions.

  17. Tectonic calibrations in molecular dating

    Institute of Scientific and Technical Information of China (English)

    Ullasa KODANDARAMAIAH

    2011-01-01

    Molecular dating techniques require the use of calibrations, which are usually fossil or geological vicariance-based.Fossil calibrations have been criticised because they result only in minimum age estimates. Based on a historical biogeographic perspective, Ⅰ suggest that vicariance-based calibrations are more dangerous. Almost all analytical methods in historical biogeography are strongly biased towards inferring vicariance, hence vicariance identified through such methods is unreliable. Other studies, especially of groups found on Gondwanan fragments, have simply assumed vicariance. Although it was previously believed that vicariance was the predominant mode of speciation, mounting evidence now indicates that speciation by dispersal is common, dominating vicariance in several groups. Moreover, the possibility of speciation having occurred before the said geological event cannot be precluded. Thus, geological calibrations can under- or overestimate times, whereas fossil calibrations always result in minimum estimates. Another major drawback of vicariant calibrations is the problem of circular reasoning when the resulting estimates are used to infer ages of biogeographic events. Ⅰ argue that fossil-based dating is a superior alternative to vicariance, primarily because the strongest assumption in the latter, that speciation was caused by the said geological process, is more often than not the most tenuous. When authors prefer to use a combination of fossil and vicariant calibrations, one suggestion is to report results both with and without inclusion of the geological constraints. Relying solely on vicariant calibrations should be strictly avoided.

  18. UVIS G280 Wavelength Calibration

    Science.gov (United States)

    Bushouse, Howard

    2009-07-01

    Wavelength calibration of the UVIS G280 grism will be established using observations of the Wolf Rayet star WR14. Accompanying direct exposures will provide wavelength zeropoints for dispersed exposures. The calibrations will be obtained at the central position of each CCD chip and at the center of the UVIS field. No additional field-dependent variations will be obtained.

  19. Forward Global Photometric Calibration of the Dark Energy Survey

    Energy Technology Data Exchange (ETDEWEB)

    Burke, D.L.; et al.

    2017-06-05

    Many scientific goals for the Dark Energy Survey (DES) require calibration of optical/NIR broadband $b = grizY$ photometry that is stable in time and uniform over the celestial sky to one percent or better. It is also necessary to limit to similar accuracy systematic uncertainty in the calibrated broadband magnitudes due to uncertainty in the spectrum of the source. Here we present a "Forward Global Calibration Method (FGCM)" for photometric calibration of the DES, and we present results of its application to the first three years of the survey (Y3A1). The FGCM combines data taken with auxiliary instrumentation at the observatory with data from the broad-band survey imaging itself and models of the instrument and atmosphere to estimate the spatial- and time-dependence of the passbands of individual DES survey exposures. "Standard" passbands are chosen that are typical of the passbands encountered during the survey. The passband of any individual observation is combined with an estimate of the source spectral shape to yield a magnitude $m_b^{\\mathrm{std}}$ in the standard system. This "chromatic correction" to the standard system is necessary to achieve sub-percent calibrations. The FGCM achieves reproducible and stable photometric calibration of standard magnitudes $m_b^{\\mathrm{std}}$ of stellar sources over the multi-year Y3A1 data sample with residual random calibration errors of $\\sigma=5-6\\,\\mathrm{mmag}$ per exposure. The accuracy of the calibration is uniform across the $5000\\,\\mathrm{deg}^2$ DES footprint to within $\\sigma=7\\,\\mathrm{mmag}$. The systematic uncertainties of magnitudes in the standard system due to the spectra of sources are less than $5\\,\\mathrm{mmag}$ for main sequence stars with $0.5

  20. Post launch calibration and testing of the Geostationary Lightning Mapper on GOES-R satellite

    Science.gov (United States)

    Rafal, Marc; Clarke, Jared T.; Cholvibul, Ruth W.

    2016-05-01

    The Geostationary Operational Environmental Satellite R (GOES-R) series is the planned next generation of operational weather satellites for the United States National Oceanic and Atmospheric Administration (NOAA). The National Aeronautics and Space Administration (NASA) is procuring the GOES-R spacecraft and instruments with the first launch of the GOES-R series planned for October 2016. Included in the GOES-R Instrument suite is the Geostationary Lightning Mapper (GLM). GLM is a single-channel, near-infrared optical detector that can sense extremely brief (800 μs) transient changes in the atmosphere, indicating the presence of lightning. GLM will measure total lightning activity continuously over the Americas and adjacent ocean regions with near-uniform spatial resolution of approximately 10 km. Due to its large CCD (1372x1300 pixels), high frame rate, sensitivity and onboard event filtering, GLM will require extensive post launch characterization and calibration. Daytime and nighttime images will be used to characterize both image quality criteria inherent to GLM as a space-based optic system (focus, stray light, crosstalk, solar glint) and programmable image processing criteria (dark offsets, gain, noise, linearity, dynamic range). In addition ground data filtering will be adjusted based on lightning-specific phenomenology (coherence) to isolate real from false transients with their own characteristics. These parameters will be updated, as needed, on orbit in an iterative process guided by pre-launch testing. This paper discusses the planned tests to be performed on GLM over the six-month Post Launch Test period to optimize and demonstrate GLM performance.

  1. Cobalt source calibration

    Energy Technology Data Exchange (ETDEWEB)

    Rizvi, H.M.

    1999-12-03

    The data obtained from these tests determine the dose rate of the two cobalt sources in SRTC. Building 774-A houses one of these sources while the other resides in room C-067 of Building 773-A. The data from this experiment shows the following: (1) The dose rate of the No.2 cobalt source in Building 774-A measured 1.073 x 10{sup 5} rad/h (June 17, 1999). The dose rate of the Shepherd Model 109 Gamma cobalt source in Building 773-A measured 9.27 x 10{sup 5} rad/h (June 25, 1999). These rates come from placing the graduated cylinder containing the dosimeter solution in the center of the irradiation chamber. (2) Two calibration tests in the 774-A source placed the graduated cylinder with the dosimeter solution approximately 1.5 inches off center in the axial direction. This movement of the sample reduced the measured dose rate 0.92% from 1.083 x 10{sup 5} rad/h to 1.073 x 10{sup 5} rad/h. and (3) A similar test in the cobalt source in 773-A placed the graduated cylinder approximately 2.0 inches off center in the axial direction. This change in position reduced the measured dose rate by 10.34% from 1.036 x 10{sup 6} to 9.27 x 10{sup 5}. This testing used chemical dosimetry to measure the dose rate of a radioactive source. In this method, one determines the dose by the chemical change that takes place in the dosimeter. For this calibration experiment, the author used a Fricke (ferrous ammonium sulfate) dosimeter. This solution works well for dose rates to 10{sup 7} rad/h. During irradiation of the Fricke dosimeter solution the Fe{sup 2+} ions ionize to Fe{sup 3+}. When this occurs, the solution acquires a slightly darker tint (not visible to the human eye). To determine the magnitude of the change in Fe ions, one places the solution in an UV-VIS Spectrophotometer. The UV-VIS Spectrophotometer measures the absorbency of the solution. Dividing the absorbency by the total time (in minutes) of exposure yields the dose rate.

  2. Dynamic Beam Based Calibration of Beam Position Monitors

    CERN Document Server

    Dehning, Bernd; Galbraith, Peter; Mugnai, G; Placidi, Massimo; Sonnemann, F; Tecker, F A; Wenninger, J

    1998-01-01

    The degree of spin polarization at LEP is strongly dependent on the knowledge of the vertical orbit. Quadrupole magnet alignment and beam position monitor (BPM) offsets are the main source of the orbi t uncertainty. The error of the orbit monitor readings can be largely reduced by calibrating the monitor relative to the adjacent quadrupole. At LEP, 16 BPM offsets can be determined in parallel durin g 40 minutes. The error of the measure offset is about 30mm. During the LEP run 1997, more than 500 measurements were made and used for the optimisation of polarization. The method of dynamic beam bas ed calibration will be explained and the results will be shown.

  3. Dual-channel and multifrequency radar system calibration

    Science.gov (United States)

    Stjernman, Anders; Vivekanandan, J.; Nystrom, Anders

    1995-03-01

    Uncertainty in absolute gain and crosstalk factors are the primary sources of error in dual-channel radar measurements. A full two-port calibration technique compensates for the errors introduced due to an imperfect antenna system and improves the isolation between orthogonal polarization channels as long as the observed cross section is above the equivalent system noise cross section. A novel technique for calibrating a dual-polarized network analyzer-based scatterometer system is discussed. Rigorous two-port S-parameter representation is used to describe absolute gain and crosstalk characteristics. Validity of the crosstalk correction is demonstrated by measuring the point target scattering matrix. Correction factors are obtained by measuring the S-parameters of trihedral and dihedral corner reflectors of known sizes. Results of absolute gain of the antenna system are verified using independent test target cross section measurements.

  4. Estimates of Identification Result Disturbances in Parallel Mechanism Calibration

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    General QR decomposition of the observation matrix is used to solve identification functions to evaluate identification results of every parameter in parallel mechanism calibrations. A relationship between measured information and identification results is obtained by analyzing numerous matrix transforms and QR decompositions. When distributions of measurement error are determined, random distributions of identification result disturbances (IRDs) can be obtained from this relationship as a function of measurement errors. Then the ranges of the IRDs can be effectively estimated, even if true parameter values are unknown. An optimization index based on IRD estimate is presented to select measurement configurations to achieve smaller IRDs. Two simulation examples were carried out with different modes and calibration methods. The results show that the method is effective and that the optimization index is useful. Some regular parameter identification problems can be explained by the IRD estimates.

  5. Technical note: Bayesian calibration of dynamic ruminant nutrition models.

    Science.gov (United States)

    Reed, K F; Arhonditsis, G B; France, J; Kebreab, E

    2016-08-01

    Mechanistic models of ruminant digestion and metabolism have advanced our understanding of the processes underlying ruminant animal physiology. Deterministic modeling practices ignore the inherent variation within and among individual animals and thus have no way to assess how sources of error influence model outputs. We introduce Bayesian calibration of mathematical models to address the need for robust mechanistic modeling tools that can accommodate error analysis by remaining within the bounds of data-based parameter estimation. For the purpose of prediction, the Bayesian approach generates a posterior predictive distribution that represents the current estimate of the value of the response variable, taking into account both the uncertainty about the parameters and model residual variability. Predictions are expressed as probability distributions, thereby conveying significantly more information than point estimates in regard to uncertainty. Our study illustrates some of the technical advantages of Bayesian calibration and discusses the future perspectives in the context of animal nutrition modeling.

  6. Optimised Calibration Method for Six-Port Junction

    Institute of Scientific and Technical Information of China (English)

    XIONG Xiang-zheng; LIAO Cheng; XIAO Hua-qing

    2008-01-01

    A dual-tone technique is used to produce multi-samples in optimising calibration of six-port junction. More accurate results are achieved by using the least-square method and excluding those samples which may cause bigger errors. A 0.80 1.10 GHz microwave integrated circuit (MIC) six-port reflectometer is constructed. Nine test samples are used in the measurement. With Engens calibration procedure, the difference between the HP8510 and the six-port reflectrometer is in the order of 0.20 dB/1.5° for most cases, above 0.50 dB/5.0° at boundary frequency . With the optimised method, the difference is less than 0.10 dB/1.0° for most cases, and the biggest error is 0.42 dB/2.1° for boundary frequencies.

  7. Automated calibration of multistatic arrays

    Energy Technology Data Exchange (ETDEWEB)

    Henderer, Bruce

    2017-03-14

    A method is disclosed for calibrating a multistatic array having a plurality of transmitter and receiver pairs spaced from one another along a predetermined path and relative to a plurality of bin locations, and further being spaced at a fixed distance from a stationary calibration implement. A clock reference pulse may be generated, and each of the transmitters and receivers of each said transmitter/receiver pair turned on at a monotonically increasing time delay interval relative to the clock reference pulse. Ones of the transmitters and receivers may be used such that a previously calibrated transmitter or receiver of a given one of the transmitter/receiver pairs is paired with a subsequently un-calibrated one of the transmitters or receivers of an immediately subsequently positioned transmitter/receiver pair, to calibrate the transmitter or receiver of the immediately subsequent transmitter/receiver pair.

  8. Liquid Krypton Calorimeter Calibration Software

    CERN Document Server

    Hughes, Christina Lindsay

    2013-01-01

    Calibration of the liquid krypton calorimeter (LKr) of the NA62 experiment is managed by a set of standalone programs, or an online calibration driver. These programs are similar to those used by NA48, but have been updated to utilize classes and translated to C++ while maintaining a common functionality. A set of classes developed to handle communication with hardware was used to develop the three standalone programs as well as the main driver program for online calibration between bursts. The main calibration driver has been designed to respond to run control commands and receive burst data, both transmitted via DIM. In order to facilitate the process of reading in calibration parameters, a serializable class has been introduced, allowing the replacement of standard text files with XML configuration files.

  9. TIME CALIBRATED OSCILLOSCOPE SWEEP CIRCUIT

    Science.gov (United States)

    Smith, V.L.; Carstensen, H.K.

    1959-11-24

    An improved time calibrated sweep circuit is presented, which extends the range of usefulness of conventional oscilloscopes as utilized for time calibrated display applications in accordance with U. S. Patent No. 2,832,002. Principal novelty resides in the provision of a pair of separate signal paths, each of which is phase and amplitude adjustable, to connect a high-frequency calibration oscillator to the output of a sawtooth generator also connected to the respective horizontal deflection plates of an oscilloscope cathode ray tube. The amplitude and phase of the calibration oscillator signals in the two signal paths are adjusted to balance out feedthrough currents capacitively coupled at high frequencies of the calibration oscillator from each horizontal deflection plate to the vertical plates of the cathode ray tube.

  10. The Advanced LIGO Photon Calibrators

    CERN Document Server

    Karki, S; Kandhasamy, S; Abbott, B P; Abbott, T D; Anders, E H; Berliner, J; Betzwieser, J; Daveloza, H P; Cahillane, C; Canete, L; Conley, C; Gleason, J R; Goetz, E; Kissel, J S; Izumi, K; Mendell, G; Quetschke, V; Rodruck, M; Sachdev, S; Sadecki, T; Schwinberg, P B; Sottile, A; Wade, M; Weinstein, A J; West, M; Savage, R L

    2016-01-01

    The two interferometers of the Laser Interferometry Gravitaional-wave Observatory (LIGO) recently detected gravitational waves from the mergers of binary black hole systems. Accurate calibration of the output of these detectors was crucial for the observation of these events, and the extraction of parameters of the sources. The principal tools used to calibrate the responses of the second-generation (Advanced) LIGO detectors to gravitational waves are systems based on radiation pressure and referred to as Photon Calibrators. These systems, which were completely redesigned for Advanced LIGO, include several significant upgrades that enable them to meet the calibration requirements of second-generation gravitational wave detectors in the new era of gravitational-wave astronomy. We report on the design, implementation, and operation of these Advanced LIGO Photon Calibrators that are currently providing fiducial displacements on the order of $10^{-18}$ m/$\\sqrt{\\textrm{Hz}}$ with accuracy and precision of better ...

  11. The Advanced LIGO photon calibrators

    Science.gov (United States)

    Karki, S.; Tuyenbayev, D.; Kandhasamy, S.; Abbott, B. P.; Abbott, T. D.; Anders, E. H.; Berliner, J.; Betzwieser, J.; Cahillane, C.; Canete, L.; Conley, C.; Daveloza, H. P.; De Lillo, N.; Gleason, J. R.; Goetz, E.; Izumi, K.; Kissel, J. S.; Mendell, G.; Quetschke, V.; Rodruck, M.; Sachdev, S.; Sadecki, T.; Schwinberg, P. B.; Sottile, A.; Wade, M.; Weinstein, A. J.; West, M.; Savage, R. L.

    2016-11-01

    The two interferometers of the Laser Interferometry Gravitational-wave Observatory (LIGO) recently detected gravitational waves from the mergers of binary black hole systems. Accurate calibration of the output of these detectors was crucial for the observation of these events and the extraction of parameters of the sources. The principal tools used to calibrate the responses of the second-generation (Advanced) LIGO detectors to gravitational waves are systems based on radiation pressure and referred to as photon calibrators. These systems, which were completely redesigned for Advanced LIGO, include several significant upgrades that enable them to meet the calibration requirements of second-generation gravitational wave detectors in the new era of gravitational-wave astronomy. We report on the design, implementation, and operation of these Advanced LIGO photon calibrators that are currently providing fiducial displacements on the order of 1 0-18m /√{Hz } with accuracy and precision of better than 1%.

  12. Antenna Calibration and Measurement Equipment

    Science.gov (United States)

    Rochblatt, David J.; Cortes, Manuel Vazquez

    2012-01-01

    A document describes the Antenna Calibration & Measurement Equipment (ACME) system that will provide the Deep Space Network (DSN) with instrumentation enabling a trained RF engineer at each complex to perform antenna calibration measurements and to generate antenna calibration data. This data includes continuous-scan auto-bore-based data acquisition with all-sky data gathering in support of 4th order pointing model generation requirements. Other data includes antenna subreflector focus, system noise temperature and tipping curves, antenna efficiency, reports system linearity, and instrument calibration. The ACME system design is based on the on-the-fly (OTF) mapping technique and architecture. ACME has contributed to the improved RF performance of the DSN by approximately a factor of two. It improved the pointing performances of the DSN antennas and productivity of its personnel and calibration engineers.

  13. A New Full Pose Measurement Method for Robot Calibration

    Directory of Open Access Journals (Sweden)

    Hee-Jun Kang

    2013-07-01

    Full Text Available Identification of robot kinematic errors during the calibration process often requires accurate full pose measurements (position and orientation of robot end-effectors in Cartesian space. This paper proposes a new method of full pose measurement of robot end-effectors for calibration. This method is based on an analysis of the features of a set of target points (placed on a rotating end-effector on a circular trajectory. The accurate measurement is validated by computational simulation results from the Puma robot. Moreover, experimental calibration and validation results for the Hyundai HA-06 robot prove the effectiveness, correctness, and reliability of the proposed method. This method can be applied to robots that have entirely revolute joints or to robots for which only the last joint is revolute.

  14. Fuzzy Interpolation and Other Interpolation Methods Used in Robot Calibrations

    Directory of Open Access Journals (Sweden)

    Ying Bai

    2012-01-01

    Full Text Available A novel interpolation algorithm, fuzzy interpolation, is presented and compared with other popular interpolation methods widely implemented in industrial robots calibrations and manufacturing applications. Different interpolation algorithms have been developed, reported, and implemented in many industrial robot calibrations and manufacturing processes in recent years. Most of them are based on looking for the optimal interpolation trajectories based on some known values on given points around a workspace. However, it is rare to build an optimal interpolation results based on some random noises, and this is one of the most popular topics in industrial testing and measurement applications. The fuzzy interpolation algorithm (FIA reported in this paper provides a convenient and simple way to solve this problem and offers more accurate interpolation results based on given position or orientation errors that are randomly distributed in real time. This method can be implemented in many industrial applications, such as manipulators measurements and calibrations, industrial automations, and semiconductor manufacturing processes.

  15. Improving Planck calibration by including frequency-dependent relativistic corrections

    CERN Document Server

    Quartin, Miguel

    2015-01-01

    The Planck satellite detectors are calibrated in the 2015 release using the "orbital dipole", which is the time-dependent dipole generated by the Doppler effect due to the motion of the satellite around the Sun. Such an effect has also relativistic time-dependent corrections of relative magnitude 10^(-3), due to coupling with the "solar dipole" (the motion of the Sun compared to the CMB rest frame), which are included in the data calibration by the Planck collaboration. We point out that such corrections are subject to a frequency-dependent multiplicative factor. This factor differs from unity especially at the highest frequencies, relevant for the HFI instrument. Since currently Planck calibration errors are dominated by systematics, to the point that polarization data is currently unreliable at large scales, such a correction can in principle be highly relevant for future data releases.

  16. Improving Planck calibration by including frequency-dependent relativistic corrections

    Science.gov (United States)

    Quartin, Miguel; Notari, Alessio

    2015-09-01

    The Planck satellite detectors are calibrated in the 2015 release using the "orbital dipole", which is the time-dependent dipole generated by the Doppler effect due to the motion of the satellite around the Sun. Such an effect has also relativistic time-dependent corrections of relative magnitude 10-3, due to coupling with the "solar dipole" (the motion of the Sun compared to the CMB rest frame), which are included in the data calibration by the Planck collaboration. We point out that such corrections are subject to a frequency-dependent multiplicative factor. This factor differs from unity especially at the highest frequencies, relevant for the HFI instrument. Since currently Planck calibration errors are dominated by systematics, to the point that polarization data is currently unreliable at large scales, such a correction can in principle be highly relevant for future data releases.

  17. Light field camera self-calibration and registration

    Science.gov (United States)

    Ji, Zhe; Zhang, Chunping; Wang, Qing

    2016-10-01

    The multi-view light fields (MVLF) provide new solutions to the existing problems in monocular light field, such as the limited field of view. However as key steps in MVLF, the calibration and registration have been limited studied. In this paper, we propose a method to calibrate the camera and register different LFs without the checkboard at the same time, which we call the self-calibrating method. We model the LF structure as a 5-parameter two-parallel-plane (2PP) model, then represent the associations between rays and reconstructed points as a 3D projective transformation. With the constraints of ray-ray correspondences in different LFs, the parameters can be solved with a linear initialization and a nonlinear refinement. The result in real scene and 3D point clouds registration error of MVLF in simulated data verify the high performance of the proposed model.

  18. Flexible Calibration Method for 3D Laser Scanner System

    Institute of Scientific and Technical Information of China (English)

    杨中东; 王鹏; 李晓慧; 孙长库

    2014-01-01

    In this paper, a flexible high-precision calibration method suitable for industrial field was proposed. The complexity of the coordinate transformation was simplified by choosing the camera coordinate system as the unified reference coordinate system. A flexible planar calibration pattern was introduced to the calibration process, which can be arbitrarily placed and from which the known feature points can be extracted to construct other unknown feature points. With the known intrinsic parameters, the laser projector plane equation was fitted by the multi-noncollinear points, which were acquired through the principle of triangulation and the projective invariance of cross ratio. With this method, the strict alignment and multiple times of coordinate transformation can be avoided. Experimental results showed that the arithmetic mean of the root mean square (RMS) error of distance was 0.000 7 mm.

  19. Band extension in digital methods of transfer function determination – signal conditioners asymmetry error corrections

    Directory of Open Access Journals (Sweden)

    Zbigniew Staroszczyk

    2014-12-01

    Full Text Available [b]Abstract[/b]. In the paper, the calibrating method for error correction in transfer function determination with the use of DSP has been proposed. The correction limits/eliminates influence of transfer function input/output signal conditioners on the estimated transfer functions in the investigated object. The method exploits frequency domain conditioning paths descriptor found during training observation made on the known reference object.[b]Keywords[/b]: transfer function, band extension, error correction, phase errors

  20. A robust and simple two-mode digital calibration technique for pipelined ADC

    Institute of Scientific and Technical Information of China (English)

    Yin Xiumei; Zhao Nan; Sekedi Bomeh Kobenge; Yang Huazhong

    2011-01-01

    This paper presents a two-mode digital calibration technique for pipelined analog-to-digital converters (ADC).The proposed calibration eliminates the errors of residual difference voltage induced by capacitor mismatch of pseudorandom (PN) sequence injection capacitors at the ADC initialization,while applies digital background calibration to continuously compensate the interstage gain errors in ADC normal operation.The presented technique not only reduces the complexity of analog circuit by eliminating the implementation of PN sequence with accurate amplitude in analog domain,but also improves the performance of digital background calibration by minimizing the sensitivity of calibration accuracy to sub-ADC errors.The use ofopamps with low DC gains in normal operation makes the proposed design more compatible with future nanometer CMOS technology.The prototype of a 12-bit 40-MS/s pipelined ADC with the two-mode digital calibration is implemented in 0.18-μm CMOS process.Adopting a simple telescopic opamp with a DC gain of 58-dB in the first stage,the measured SFDR and SNDR within the first Nyquist zone reach 80-dB and 66-dB,respectively.With the calibration,the maximum integral nonlinearity (INL) of the ADC reduces from 4.75-LSB to 0.65-LSB,while the ADC core consumes 82-mW at 3.3-V power supply.