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Sample records for models dems digital

  1. Digital Elevation Model (DEM) 24K

    Data.gov (United States)

    Kansas Data Access and Support Center — Digital Elevation Model (DEM) is the terminology adopted by the USGS to describe terrain elevation data sets in a digital raster form. The standard DEM consists of a...

  2. Coastal Digital Elevation Models (DEMs)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Digital elevation models (DEMs) of U.S. and other coasts that typically integrate ocean bathymetry and land topography. The DEMs support NOAA's mission to understand...

  3. ASTER Orthorectified Digital Elevation Model (DEM) V003

    Data.gov (United States)

    National Aeronautics and Space Administration — The ASTER L3 DEM and Orthorectified Images form a multi-file product that contains both the Digital Elevation Model (DEM), and the Orthorectified Image products....

  4. Estimating Coastal Digital Elevation Model (DEM) Uncertainty

    Science.gov (United States)

    Amante, C.; Mesick, S.

    2017-12-01

    Integrated bathymetric-topographic digital elevation models (DEMs) are representations of the Earth's solid surface and are fundamental to the modeling of coastal processes, including tsunami, storm surge, and sea-level rise inundation. Deviations in elevation values from the actual seabed or land surface constitute errors in DEMs, which originate from numerous sources, including: (i) the source elevation measurements (e.g., multibeam sonar, lidar), (ii) the interpolative gridding technique (e.g., spline, kriging) used to estimate elevations in areas unconstrained by source measurements, and (iii) the datum transformation used to convert bathymetric and topographic data to common vertical reference systems. The magnitude and spatial distribution of the errors from these sources are typically unknown, and the lack of knowledge regarding these errors represents the vertical uncertainty in the DEM. The National Oceanic and Atmospheric Administration (NOAA) National Centers for Environmental Information (NCEI) has developed DEMs for more than 200 coastal communities. This study presents a methodology developed at NOAA NCEI to derive accompanying uncertainty surfaces that estimate DEM errors at the individual cell-level. The development of high-resolution (1/9th arc-second), integrated bathymetric-topographic DEMs along the southwest coast of Florida serves as the case study for deriving uncertainty surfaces. The estimated uncertainty can then be propagated into the modeling of coastal processes that utilize DEMs. Incorporating the uncertainty produces more reliable modeling results, and in turn, better-informed coastal management decisions.

  5. The Importance of Precise Digital Elevation Models (DEM) in Modelling Floods

    Science.gov (United States)

    Demir, Gokben; Akyurek, Zuhal

    2016-04-01

    Digital elevation Models (DEM) are important inputs for topography for the accurate modelling of floodplain hydrodynamics. Floodplains have a key role as natural retarding pools which attenuate flood waves and suppress flood peaks. GPS, LIDAR and bathymetric surveys are well known surveying methods to acquire topographic data. It is not only time consuming and expensive to obtain topographic data through surveying but also sometimes impossible for remote areas. In this study it is aimed to present the importance of accurate modelling of topography for flood modelling. The flood modelling for Samsun-Terme in Blacksea region of Turkey is done. One of the DEM is obtained from the point observations retrieved from 1/5000 scaled orthophotos and 1/1000 scaled point elevation data from field surveys at x-sections. The river banks are corrected by using the orthophotos and elevation values. This DEM is named as scaled DEM. The other DEM is obtained from bathymetric surveys. 296 538 number of points and the left/right bank slopes were used to construct the DEM having 1 m spatial resolution and this DEM is named as base DEM. Two DEMs were compared by using 27 x-sections. The maximum difference at thalweg of the river bed is 2m and the minimum difference is 20 cm between two DEMs. The channel conveyance capacity in base DEM is larger than the one in scaled DEM and floodplain is modelled in detail in base DEM. MIKE21 with flexible grid is used in 2- dimensional shallow water flow modelling. The model by using two DEMs were calibrated for a flood event (July 9, 2012). The roughness is considered as the calibration parameter. From comparison of input hydrograph at the upstream of the river and output hydrograph at the downstream of the river, the attenuation is obtained as 91% and 84% for the base DEM and scaled DEM, respectively. The time lag in hydrographs does not show any difference for two DEMs and it is obtained as 3 hours. Maximum flood extents differ for the two DEMs

  6. Digital Elevation Models (DEMs) for the main 8 Hawaiian Islands

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Digital elevation model (DEM) data are arrays of regularly spaced elevation values referenced horizontally either to a Universal Transverse Mercator (UTM) projection...

  7. OPEN-SOURCE DIGITAL ELEVATION MODEL (DEMs EVALUATION WITH GPS AND LiDAR DATA

    Directory of Open Access Journals (Sweden)

    N. F. Khalid

    2016-09-01

    Full Text Available Advanced Spaceborne Thermal Emission and Reflection Radiometer-Global Digital Elevation Model (ASTER GDEM, Shuttle Radar Topography Mission (SRTM, and Global Multi-resolution Terrain Elevation Data 2010 (GMTED2010 are freely available Digital Elevation Model (DEM datasets for environmental modeling and studies. The quality of spatial resolution and vertical accuracy of the DEM data source has a great influence particularly on the accuracy specifically for inundation mapping. Most of the coastal inundation risk studies used the publicly available DEM to estimated the coastal inundation and associated damaged especially to human population based on the increment of sea level. In this study, the comparison between ground truth data from Global Positioning System (GPS observation and DEM is done to evaluate the accuracy of each DEM. The vertical accuracy of SRTM shows better result against ASTER and GMTED10 with an RMSE of 6.054 m. On top of the accuracy, the correlation of DEM is identified with the high determination of coefficient of 0.912 for SRTM. For coastal zone area, DEMs based on airborne light detection and ranging (LiDAR dataset was used as ground truth data relating to terrain height. In this case, the LiDAR DEM is compared against the new SRTM DEM after applying the scale factor. From the findings, the accuracy of the new DEM model from SRTM can be improved by applying scale factor. The result clearly shows that the value of RMSE exhibit slightly different when it reached 0.503 m. Hence, this new model is the most suitable and meets the accuracy requirement for coastal inundation risk assessment using open source data. The suitability of these datasets for further analysis on coastal management studies is vital to assess the potentially vulnerable areas caused by coastal inundation.

  8. Digitial Elevation Model (DEM) 100K

    Data.gov (United States)

    Kansas Data Access and Support Center — Digital Elevation Model (DEM) is the terminology adopted by the USG to describe terrain elevation data sets in a digital raster form. The standard DEM consists of a...

  9. Digtial Elevation Model (DEM) 250K

    Data.gov (United States)

    Kansas Data Access and Support Center — Digital Elevation Model (DEM) is the terminology adopted by the USGS to describe terrain elevation data sets in a digital raster form. The standard DEM consists of a...

  10. Analysis the Accuracy of Digital Elevation Model (DEM) for Flood Modelling on Lowland Area

    Science.gov (United States)

    Zainol Abidin, Ku Hasna Zainurin Ku; Razi, Mohd Adib Mohammad; Bukari, Saifullizan Mohd

    2018-04-01

    Flood is one type of natural disaster that occurs almost every year in Malaysia. Commonly the lowland areas are the worst affected areas. This kind of disaster is controllable by using an accurate data for proposing any kinds of solutions. Elevation data is one of the data used to produce solutions for flooding. Currently, the research about the application of Digital Elevation Model (DEM) in hydrology was increased where this kind of model will identify the elevation for required areas. University of Tun Hussein Onn Malaysia is one of the lowland areas which facing flood problems on 2006. Therefore, this area was chosen in order to produce DEM which focussed on University Health Centre (PKU) and drainage area around Civil and Environment Faculty (FKAAS). Unmanned Aerial Vehicle used to collect aerial photos data then undergoes a process of generating DEM according to three types of accuracy and quality from Agisoft PhotoScan software. The higher the level of accuracy and quality of DEM produced, the longer time taken to generate a DEM. The reading of the errors created while producing the DEM shows almost 0.01 different. Therefore, it has been identified there are some important parameters which influenced the accuracy of DEM.

  11. Optimizing digital elevation models (DEMs) accuracy for planning and design of mobile communication networks

    Science.gov (United States)

    Hassan, Mahmoud A.

    2004-02-01

    Digital elevation models (DEMs) are important tools in the planning, design and maintenance of mobile communication networks. This research paper proposes a method for generating high accuracy DEMs based on SPOT satellite 1A stereo pair images, ground control points (GCP) and Erdas OrthoBASE Pro image processing software. DEMs with 0.2911 m mean error were achieved for the hilly and heavily populated city of Amman. The generated DEM was used to design a mobile communication network resulted in a minimum number of radio base transceiver stations, maximum number of covered regions and less than 2% of dead zones.

  12. Antarctic 1 km Digital Elevation Model (DEM) from Combined ERS-1 Radar and ICESat Laser Satellite Altimetry

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set provides a 1 km resolution Digital Elevation Model (DEM) of Antarctica. The DEM combines measurements from the European Remote Sensing Satellite-1...

  13. Original Product Resolution (OPR) Source Digital Elevation Models (DEMs) - USGS National Map 3DEP Downloadable Data Collection

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This data collection is the Original Product Resolution (OPR) Digital Elevation Model (DEM) as provided to the USGS. This DEM is delivered in the original...

  14. Generation and performance assessment of the global TanDEM-X digital elevation model

    Science.gov (United States)

    Rizzoli, Paola; Martone, Michele; Gonzalez, Carolina; Wecklich, Christopher; Borla Tridon, Daniela; Bräutigam, Benjamin; Bachmann, Markus; Schulze, Daniel; Fritz, Thomas; Huber, Martin; Wessel, Birgit; Krieger, Gerhard; Zink, Manfred; Moreira, Alberto

    2017-10-01

    The primary objective of the TanDEM-X mission is the generation of a global, consistent, and high-resolution digital elevation model (DEM) with unprecedented global accuracy. The goal is achieved by exploiting the interferometric capabilities of the two twin SAR satellites TerraSAR-X and TanDEM-X, which fly in a close orbit formation, acting as an X-band single-pass interferometer. Between December 2010 and early 2015 all land surfaces have been acquired at least twice, difficult terrain up to seven or eight times. The acquisition strategy, data processing, and DEM calibration and mosaicking have been systematically monitored and optimized throughout the entire mission duration, in order to fulfill the specification. The processing of all data has finally been completed in September 2016 and this paper reports on the final performance of the TanDEM-X global DEM and presents the acquisition and processing strategy which allowed to obtain the final DEM quality. The results confirm the outstanding global accuracy of the delivered product, which can be now utilized for both scientific and commercial applications.

  15. Uncertainty modelling and analysis of volume calculations based on a regular grid digital elevation model (DEM)

    Science.gov (United States)

    Li, Chang; Wang, Qing; Shi, Wenzhong; Zhao, Sisi

    2018-05-01

    The accuracy of earthwork calculations that compute terrain volume is critical to digital terrain analysis (DTA). The uncertainties in volume calculations (VCs) based on a DEM are primarily related to three factors: 1) model error (ME), which is caused by an adopted algorithm for a VC model, 2) discrete error (DE), which is usually caused by DEM resolution and terrain complexity, and 3) propagation error (PE), which is caused by the variables' error. Based on these factors, the uncertainty modelling and analysis of VCs based on a regular grid DEM are investigated in this paper. Especially, how to quantify the uncertainty of VCs is proposed by a confidence interval based on truncation error (TE). In the experiments, the trapezoidal double rule (TDR) and Simpson's double rule (SDR) were used to calculate volume, where the TE is the major ME, and six simulated regular grid DEMs with different terrain complexity and resolution (i.e. DE) were generated by a Gauss synthetic surface to easily obtain the theoretical true value and eliminate the interference of data errors. For PE, Monte-Carlo simulation techniques and spatial autocorrelation were used to represent DEM uncertainty. This study can enrich uncertainty modelling and analysis-related theories of geographic information science.

  16. 5 Meter Alaska Digital Elevation Models (DEMs) - USGS National Map 3DEP Downloadable Data Collection

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This dataset is comprised of 5-meter ifsar-derived Digital Elevation Models (DEMs) over Alaska only. It is distributed as one-degree blocks with overedge. Horizontal...

  17. Development of a LiDAR derived digital elevation model (DEM) as Input to a METRANS geographic information system (GIS).

    Science.gov (United States)

    2011-05-01

    This report describes an assessment of digital elevation models (DEMs) derived from : LiDAR data for a subset of the Ports of Los Angeles and Long Beach. A methodology : based on Monte Carlo simulation was applied to investigate the accuracy of DEMs ...

  18. Coastal Digital Elevation Models (DEMs) for tsunami hazard assessment on the French coasts

    Science.gov (United States)

    Maspataud, Aurélie; Biscara, Laurie; Hébert, Hélène; Schmitt, Thierry; Créach, Ronan

    2015-04-01

    Building precise and up-to-date coastal DEMs is a prerequisite for accurate modeling and forecasting of hydrodynamic processes at local scale. Marine flooding, originating from tsunamis, storm surges or waves, is one of them. Some high resolution DEMs are being generated for multiple coast configurations (gulf, embayment, strait, estuary, harbor approaches, low-lying areas…) along French Atlantic and Channel coasts. This work is undertaken within the framework of the TANDEM project (Tsunamis in the Atlantic and the English ChaNnel: Definition of the Effects through numerical Modeling) (2014-2017). DEMs boundaries were defined considering the vicinity of French civil nuclear facilities, site effects considerations and potential tsunamigenic sources. Those were identified from available historical observations. Seamless integrated topographic and bathymetric coastal DEMs will be used by institutions taking part in the study to simulate expected wave height at regional and local scale on the French coasts, for a set of defined scenarii. The main tasks were (1) the development of a new capacity of production of DEM, (2) aiming at the release of high resolution and precision digital field models referred to vertical reference frameworks, that require (3) horizontal and vertical datum conversions (all source elevation data need to be transformed to a common datum), on the basis of (4) the building of (national and/or local) conversion grids of datum relationships based on known measurements. Challenges in coastal DEMs development deal with good practices throughout model development that can help minimizing uncertainties. This is particularly true as scattered elevation data with variable density, from multiple sources (national hydrographic services, state and local government agencies, research organizations and private engineering companies) and from many different types (paper fieldsheets to be digitized, single beam echo sounder, multibeam sonar, airborne laser

  19. High-Accuracy Tidal Flat Digital Elevation Model Construction Using TanDEM-X Science Phase Data

    Science.gov (United States)

    Lee, Seung-Kuk; Ryu, Joo-Hyung

    2017-01-01

    This study explored the feasibility of using TanDEM-X (TDX) interferometric observations of tidal flats for digital elevation model (DEM) construction. Our goal was to generate high-precision DEMs in tidal flat areas, because accurate intertidal zone data are essential for monitoring coastal environment sand erosion processes. To monitor dynamic coastal changes caused by waves, currents, and tides, very accurate DEMs with high spatial resolution are required. The bi- and monostatic modes of the TDX interferometer employed during the TDX science phase provided a great opportunity for highly accurate intertidal DEM construction using radar interferometry with no time lag (bistatic mode) or an approximately 10-s temporal baseline (monostatic mode) between the master and slave synthetic aperture radar image acquisitions. In this study, DEM construction in tidal flat areas was first optimized based on the TDX system parameters used in various TDX modes. We successfully generated intertidal zone DEMs with 57-m spatial resolutions and interferometric height accuracies better than 0.15 m for three representative tidal flats on the west coast of the Korean Peninsula. Finally, we validated these TDX DEMs against real-time kinematic-GPS measurements acquired in two tidal flat areas; the correlation coefficient was 0.97 with a root mean square error of 0.20 m.

  20. Landform classification using a sub-pixel spatial attraction model to increase spatial resolution of digital elevation model (DEM

    Directory of Open Access Journals (Sweden)

    Marzieh Mokarrama

    2018-04-01

    Full Text Available The purpose of the present study is preparing a landform classification by using digital elevation model (DEM which has a high spatial resolution. To reach the mentioned aim, a sub-pixel spatial attraction model was used as a novel method for preparing DEM with a high spatial resolution in the north of Darab, Fars province, Iran. The sub-pixel attraction models convert the pixel into sub-pixels based on the neighboring pixels fraction values, which can only be attracted by a central pixel. Based on this approach, a mere maximum of eight neighboring pixels can be selected for calculating of the attraction value. In the mentioned model, other pixels are supposed to be far from the central pixel to receive any attraction. In the present study by using a sub-pixel attraction model, the spatial resolution of a DEM was increased. The design of the algorithm is accomplished by using a DEM with a spatial resolution of 30 m (the Advanced Space borne Thermal Emission and Reflection Radiometer; (ASTER and a 90 m (the Shuttle Radar Topography Mission; (SRTM. In the attraction model, scale factors of (S = 2, S = 3, and S = 4 with two neighboring methods of touching (T = 1 and quadrant (T = 2 are applied to the DEMs by using MATLAB software. The algorithm is evaluated by taking the best advantages of 487 sample points, which are measured by surveyors. The spatial attraction model with scale factor of (S = 2 gives better results compared to those scale factors which are greater than 2. Besides, the touching neighborhood method is turned to be more accurate than the quadrant method. In fact, dividing each pixel into more than two sub-pixels decreases the accuracy of the resulted DEM. On the other hand, in these cases DEM, is itself in charge of increasing the value of root-mean-square error (RMSE and shows that attraction models could not be used for S which is greater than 2. Thus considering results, the proposed model is highly capable of

  1. TecDEM: A MATLAB Based Toolbox for understanding Tectonics from Digital Elevation Models

    Science.gov (United States)

    Shahzad, F.; Mahmood, S. A.; Gloaguen, R.

    2009-04-01

    TecDEM is a MATLAB based tool box for understanding the tectonics from digital elevation models (DEMs) of any area. These DEMs can be derived from data of any spatial resolution (Low, medium and High). In the first step we extract drainage network from the DEMs using flow grid approach. Drainage network is a group of streams having elevation and catchment area information as a function of spatial locations. We implement an array of stream structure to study this drainage network. Knickpoints can be identified on each stream of the drainage network by a graphical user interface and are helpful for understanding stream morphology. Stream profile analysis in steady state condition is applied on all streams to calculate geomorphic parameters and regional uplift rates. Hack index is calculated for all the profiles at a certain interval and over the change of knickpoints. Reports menu of this tool box generates detailed statistics report, complete tabulated report, graphical output of each analyzed stream profile and Hack index profile. All the calculated values are part of stream structure and is saved as .mat file for later use with this tool box. The spatial distribution of geomorphic parameters, uplift rates and knickpoints are exported as a shape files for visualization in professional GIS software. We test this tool box on DEMs from different tectonic settings worldwide and received verifiable results with other studies.

  2. Digital Elevation Model (DEM), The county-wide DEM is published with a 20-foot grid size, though we have a more detailed DEM/DTM for some parts of the county, particularly the Green Bay Metro area, Published in 2000, 1:4800 (1in=400ft) scale, Brown County Government.

    Data.gov (United States)

    NSGIC Local Govt | GIS Inventory — Digital Elevation Model (DEM) dataset current as of 2000. The county-wide DEM is published with a 20-foot grid size, though we have a more detailed DEM/DTM for some...

  3. Accuracy assessment of the global TanDEM-X Digital Elevation Model with GPS data

    Science.gov (United States)

    Wessel, Birgit; Huber, Martin; Wohlfart, Christian; Marschalk, Ursula; Kosmann, Detlev; Roth, Achim

    2018-05-01

    The primary goal of the German TanDEM-X mission is the generation of a highly accurate and global Digital Elevation Model (DEM) with global accuracies of at least 10 m absolute height error (linear 90% error). The global TanDEM-X DEM acquired with single-pass SAR interferometry was finished in September 2016. This paper provides a unique accuracy assessment of the final TanDEM-X global DEM using two different GPS point reference data sets, which are distributed across all continents, to fully characterize the absolute height error. Firstly, the absolute vertical accuracy is examined by about three million globally distributed kinematic GPS (KGPS) points derived from 19 KGPS tracks covering a total length of about 66,000 km. Secondly, a comparison is performed with more than 23,000 "GPS on Bench Marks" (GPS-on-BM) points provided by the US National Geodetic Survey (NGS) scattered across 14 different land cover types of the US National Land Cover Data base (NLCD). Both GPS comparisons prove an absolute vertical mean error of TanDEM-X DEM smaller than ±0.20 m, a Root Means Square Error (RMSE) smaller than 1.4 m and an excellent absolute 90% linear height error below 2 m. The RMSE values are sensitive to land cover types. For low vegetation the RMSE is ±1.1 m, whereas it is slightly higher for developed areas (±1.4 m) and for forests (±1.8 m). This validation confirms an outstanding absolute height error at 90% confidence level of the global TanDEM-X DEM outperforming the requirement by a factor of five. Due to its extensive and globally distributed reference data sets, this study is of considerable interests for scientific and commercial applications.

  4. Digital Elevation Model (DEM), DEM data are useful for terrain analysis and modeling including slope and aspect calculations. They may be used to produced shaded relief maps and contour maps., Published in 2001, 1:24000 (1in=2000ft) scale, Louisiana State University (LSU).

    Data.gov (United States)

    NSGIC Education | GIS Inventory — Digital Elevation Model (DEM) dataset current as of 2001. DEM data are useful for terrain analysis and modeling including slope and aspect calculations. They may be...

  5. An automated, open-source pipeline for mass production of digital elevation models (DEMs) from very-high-resolution commercial stereo satellite imagery

    Science.gov (United States)

    Shean, David E.; Alexandrov, Oleg; Moratto, Zachary M.; Smith, Benjamin E.; Joughin, Ian R.; Porter, Claire; Morin, Paul

    2016-06-01

    We adapted the automated, open source NASA Ames Stereo Pipeline (ASP) to generate digital elevation models (DEMs) and orthoimages from very-high-resolution (VHR) commercial imagery of the Earth. These modifications include support for rigorous and rational polynomial coefficient (RPC) sensor models, sensor geometry correction, bundle adjustment, point cloud co-registration, and significant improvements to the ASP code base. We outline a processing workflow for ˜0.5 m ground sample distance (GSD) DigitalGlobe WorldView-1 and WorldView-2 along-track stereo image data, with an overview of ASP capabilities, an evaluation of ASP correlator options, benchmark test results, and two case studies of DEM accuracy. Output DEM products are posted at ˜2 m with direct geolocation accuracy of process individual stereo pairs on a local workstation, the methods presented here were developed for large-scale batch processing in a high-performance computing environment. We are leveraging these resources to produce dense time series and regional mosaics for the Earth's polar regions.

  6. A new 100-m Digital Elevation Model of the Antarctic Peninsula derived from ASTER Global DEM: methods and accuracy assessment

    Directory of Open Access Journals (Sweden)

    A. J. Cook

    2012-10-01

    Full Text Available A high resolution surface topography Digital Elevation Model (DEM is required to underpin studies of the complex glacier system on the Antarctic Peninsula. A complete DEM with better than 200 m pixel size and high positional and vertical accuracy would enable mapping of all significant glacial basins and provide a dataset for glacier morphology analyses. No currently available DEM meets these specifications. We present a new 100-m DEM of the Antarctic Peninsula (63–70° S, based on ASTER Global Digital Elevation Model (GDEM data. The raw GDEM products are of high-quality on the rugged terrain and coastal-regions of the Antarctic Peninsula and have good geospatial accuracy, but they also contain large errors on ice-covered terrain and we seek to minimise these artefacts. Conventional data correction techniques do not work so we have developed a method that significantly improves the dataset, smoothing the erroneous regions and hence creating a DEM with a pixel size of 100 m that will be suitable for many glaciological applications. We evaluate the new DEM using ICESat-derived elevations, and perform horizontal and vertical accuracy assessments based on GPS positions, SPOT-5 DEMs and the Landsat Image Mosaic of Antarctica (LIMA imagery. The new DEM has a mean elevation difference of −4 m (± 25 m RMSE from ICESat (compared to −13 m mean and ±97 m RMSE for the original ASTER GDEM, and a horizontal error of less than 2 pixels, although elevation accuracies are lower on mountain peaks and steep-sided slopes. The correction method significantly reduces errors on low relief slopes and therefore the DEM can be regarded as suitable for topographical studies such as measuring the geometry and ice flow properties of glaciers on the Antarctic Peninsula. The DEM is available for download from the NSIDC website: http://nsidc.org/data/nsidc-0516.html (Coastal DEMs with Cross-Track Interferometry

    NARCIS (Netherlands)

    Greidanus, H.S.F.; Huising, E.J.; Platschorre, Y.; Bree, R.J.P. van; Halsema, D. van; Vaessen, E.M.J.

    1999-01-01

    Digital elevation models (DEMs) are produced from airborne radar cross-track interferometric measurements. Radar DEMs recorded from perpendicular orientations are intercompared, and compared to DEMs derived from airborne laser altimetry

  7. Creating high-resolution bare-earth digital elevation models (DEMs) from stereo imagery in an area of densely vegetated deciduous forest using combinations of procedures designed for lidar point cloud filtering

    Science.gov (United States)

    DeWitt, Jessica D.; Warner, Timothy A.; Chirico, Peter G.; Bergstresser, Sarah E.

    2017-01-01

    For areas of the world that do not have access to lidar, fine-scale digital elevation models (DEMs) can be photogrammetrically created using globally available high-spatial resolution stereo satellite imagery. The resultant DEM is best termed a digital surface model (DSM) because it includes heights of surface features. In densely vegetated conditions, this inclusion can limit its usefulness in applications requiring a bare-earth DEM. This study explores the use of techniques designed for filtering lidar point clouds to mitigate the elevation artifacts caused by above ground features, within the context of a case study of Prince William Forest Park, Virginia, USA. The influences of land cover and leaf-on vs. leaf-off conditions are investigated, and the accuracy of the raw photogrammetric DSM extracted from leaf-on imagery was between that of a lidar bare-earth DEM and the Shuttle Radar Topography Mission DEM. Although the filtered leaf-on photogrammetric DEM retains some artifacts of the vegetation canopy and may not be useful for some applications, filtering procedures significantly improved the accuracy of the modeled terrain. The accuracy of the DSM extracted in leaf-off conditions was comparable in most areas to the lidar bare-earth DEM and filtering procedures resulted in accuracy comparable of that to the lidar DEM.

  8. External Validation of the ASTER GDEM2, GMTED2010 and CGIAR-CSI- SRTM v4.1 Free Access Digital Elevation Models (DEMs in Tunisia and Algeria

    Directory of Open Access Journals (Sweden)

    Djamel Athmania

    2014-05-01

    Full Text Available Digital Elevation Models (DEMs including Advanced Spaceborne Thermal Emission and Reflection Radiometer-Global Digital Elevation Model (ASTER GDEM, Shuttle Radar Topography Mission (SRTM, and Global Multi-resolution Terrain Elevation Data 2010 (GMTED2010 are freely available for nearly the entire earth’s surface. DEMs that are usually subject to errors need to be evaluated using reference elevation data of higher accuracy. This work was performed to assess the vertical accuracy of the ASTER GDEM version 2, (ASTER GDEM2, the Consultative Group on International Agriculture Research-Consortium for Spatial Information (CGIAR-CSI SRTM version 4.1 (SRTM v4.1 and the systematic subsample GMTED2010, at their original spatial resolution, using Global Navigation Satellite Systems (GNSS validation points. Two test sites, the Anaguid Saharan platform in southern Tunisia and the Tebessa basin in north eastern Algeria, were chosen for accuracy assessment of the above mentioned DEMs, based on geostatistical and statistical measurements. Within the geostatistical approach, empirical variograms of each DEM were compared with those of the GPS validation points. Statistical measures were computed from the elevation differences between the DEM pixel value and the corresponding GPS point. For each DEM, a Root Mean Square Error (RMSE was determined for model validation. In addition, statistical tools such as frequency histograms and Q-Q plots were used to evaluate error distributions in each DEM. The results indicate that the vertical accuracy of SRTM model is much higher than ASTER GDEM2 and GMTED2010 for both sites. In Anaguid test site, the vertical accuracy of SRTM is estimated 3.6 m (in terms of RMSE 5.3 m and 4.5 m for the ASTERGDEM2 and GMTED2010 DEMs, respectively. In Tebessa test site, the overall vertical accuracy shows a RMSE of 9.8 m, 8.3 m and 9.6 m for ASTER GDEM 2, SRTM and GMTED2010 DEM, respectively. This work is the first study to report the

  9. Revealing topographic lineaments through IHS enhancement of DEM data. [Digital Elevation Model

    Science.gov (United States)

    Murdock, Gary

    1990-01-01

    Intensity-hue-saturation (IHS) processing of slope (dip), aspect (dip direction), and elevation to reveal subtle topographic lineaments which may not be obvious in the unprocessed data are used to enhance digital elevation model (DEM) data from northwestern Nevada. This IHS method of lineament identification was applied to a mosiac of 12 square degrees using a Cray Y-MP8/864. Square arrays from 3 x 3 to 31 x 31 points were tested as well as several different slope enhancements. When relatively few points are used to fit the plane, lineaments of various lengths are observed and a mechanism for lineament classification is described. An area encompassing the gold deposits of the Carlin trend and including the Rain in the southeast to Midas in the northwest is investigated in greater detail. The orientation and density of lineaments may be determined on the gently sloping pediment surface as well as in the more steeply sloping ranges.

  10. Evaluating the Quality and Accuracy of TanDEM-X Digital Elevation Models at Archaeological Sites in the Cilician Plain, Turkey

    Directory of Open Access Journals (Sweden)

    Stefan Erasmi

    2014-10-01

    Full Text Available Satellite remote sensing provides a powerful instrument for mapping and monitoring traces of historical settlements and infrastructure, not only in distant areas and crisis regions. It helps archaeologists to embed their findings from field surveys into the broader context of the landscape. With the start of the TanDEM-X mission, spatially explicit 3D-information is available to researchers at an unprecedented resolution worldwide. We examined different experimental TanDEM-X digital elevation models (DEM that were processed from two different imaging modes (Stripmap/High Resolution Spotlight using the operational alternating bistatic acquisition mode. The quality and accuracy of the experimental DEM products was compared to other available DEM products and a high precision archaeological field survey. The results indicate the potential of TanDEM-X Stripmap (SM data for mapping surface elements at regional scale. For the alluvial plain of Cilicia, a suspected palaeochannel could be reconstructed. At the local scale, DEM products from TanDEM-X High Resolution Spotlight (HS mode were processed at 2 m spatial resolution using a merge of two monostatic/bistatic interferograms. The absolute and relative vertical accuracy of the outcome meet the specification of high resolution elevation data (HRE standards from the National System for Geospatial Intelligence (NSG at the HRE20 level.

  11. kawaihae_dem.grd

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NGDC builds and distributes high-resolution, coastal digital elevation models (DEMs) that integrate ocean bathymetry and land topography to support NOAA's mission to...

  12. Comparison of digital elevation models for aquatic data development.

    Science.gov (United States)

    Sharon Clarke; Kelly. Burnett

    2003-01-01

    Thirty-meter digital elevation models (DEMs) produced by the U.S. Geological Survey (USGS) are widely available and commonly used in analyzing aquatic systems. However, these DEMs are of relatively coarse resolution, were inconsistently produced (i.e., Level 1 versus Level 2 DEMs), and lack drainage enforcement. Such issues may hamper efforts to accurately model...

  13. Uncertainty of soil erosion modelling using open source high resolution and aggregated DEMs

    Directory of Open Access Journals (Sweden)

    Arun Mondal

    2017-05-01

    Full Text Available Digital Elevation Model (DEM is one of the important parameters for soil erosion assessment. Notable uncertainties are observed in this study while using three high resolution open source DEMs. The Revised Universal Soil Loss Equation (RUSLE model has been applied to analysis the assessment of soil erosion uncertainty using open source DEMs (SRTM, ASTER and CARTOSAT and their increasing grid space (pixel size from the actual. The study area is a part of the Narmada river basin in Madhya Pradesh state, which is located in the central part of India and the area covered 20,558 km2. The actual resolution of DEMs is 30 m and their increasing grid spaces are taken as 90, 150, 210, 270 and 330 m for this study. Vertical accuracy of DEMs has been assessed using actual heights of the sample points that have been taken considering planimetric survey based map (toposheet. Elevations of DEMs are converted to the same vertical datum from WGS 84 to MSL (Mean Sea Level, before the accuracy assessment and modelling. Results indicate that the accuracy of the SRTM DEM with the RMSE of 13.31, 14.51, and 18.19 m in 30, 150 and 330 m resolution respectively, is better than the ASTER and the CARTOSAT DEMs. When the grid space of the DEMs increases, the accuracy of the elevation and calculated soil erosion decreases. This study presents a potential uncertainty introduced by open source high resolution DEMs in the accuracy of the soil erosion assessment models. The research provides an analysis of errors in selecting DEMs using the original and increased grid space for soil erosion modelling.

  14. Hydraulic correction method (HCM) to enhance the efficiency of SRTM DEM in flood modeling

    Science.gov (United States)

    Chen, Huili; Liang, Qiuhua; Liu, Yong; Xie, Shuguang

    2018-04-01

    Digital Elevation Model (DEM) is one of the most important controlling factors determining the simulation accuracy of hydraulic models. However, the currently available global topographic data is confronted with limitations for application in 2-D hydraulic modeling, mainly due to the existence of vegetation bias, random errors and insufficient spatial resolution. A hydraulic correction method (HCM) for the SRTM DEM is proposed in this study to improve modeling accuracy. Firstly, we employ the global vegetation corrected DEM (i.e. Bare-Earth DEM), developed from the SRTM DEM to include both vegetation height and SRTM vegetation signal. Then, a newly released DEM, removing both vegetation bias and random errors (i.e. Multi-Error Removed DEM), is employed to overcome the limitation of height errors. Last, an approach to correct the Multi-Error Removed DEM is presented to account for the insufficiency of spatial resolution, ensuring flow connectivity of the river networks. The approach involves: (a) extracting river networks from the Multi-Error Removed DEM using an automated algorithm in ArcGIS; (b) correcting the location and layout of extracted streams with the aid of Google Earth platform and Remote Sensing imagery; and (c) removing the positive biases of the raised segment in the river networks based on bed slope to generate the hydraulically corrected DEM. The proposed HCM utilizes easily available data and tools to improve the flow connectivity of river networks without manual adjustment. To demonstrate the advantages of HCM, an extreme flood event in Huifa River Basin (China) is simulated on the original DEM, Bare-Earth DEM, Multi-Error removed DEM, and hydraulically corrected DEM using an integrated hydrologic-hydraulic model. A comparative analysis is subsequently performed to assess the simulation accuracy and performance of four different DEMs and favorable results have been obtained on the corrected DEM.

  15. Automated Quality Control for Ortholmages and DEMs

    DEFF Research Database (Denmark)

    Höhle, Joachim; Potucková, Marketa

    2005-01-01

    The checking of geometric accurancy of orthoimages and digital elevation models (DEMs) is discussed. As a reference, an existing orthoimage and a second orthoimage derived from an overlapping aerial image, are used. The proposed automated procedures for checking the orthoimages and DEMs are based...

  16. IceBridge DMS L3 Photogrammetric DEM

    Data.gov (United States)

    National Aeronautics and Space Administration — The IceBridge DMS L3 Photogrammetric DEM (IODMS3) data set contains gridded digital elevation models and orthorectified images of Greenland derived from the Digital...

  17. Automatic relative RPC image model bias compensation through hierarchical image matching for improving DEM quality

    Science.gov (United States)

    Noh, Myoung-Jong; Howat, Ian M.

    2018-02-01

    The quality and efficiency of automated Digital Elevation Model (DEM) extraction from stereoscopic satellite imagery is critically dependent on the accuracy of the sensor model used for co-locating pixels between stereo-pair images. In the absence of ground control or manual tie point selection, errors in the sensor models must be compensated with increased matching search-spaces, increasing both the computation time and the likelihood of spurious matches. Here we present an algorithm for automatically determining and compensating the relative bias in Rational Polynomial Coefficients (RPCs) between stereo-pairs utilizing hierarchical, sub-pixel image matching in object space. We demonstrate the algorithm using a suite of image stereo-pairs from multiple satellites over a range stereo-photogrammetrically challenging polar terrains. Besides providing a validation of the effectiveness of the algorithm for improving DEM quality, experiments with prescribed sensor model errors yield insight into the dependence of DEM characteristics and quality on relative sensor model bias. This algorithm is included in the Surface Extraction through TIN-based Search-space Minimization (SETSM) DEM extraction software package, which is the primary software used for the U.S. National Science Foundation ArcticDEM and Reference Elevation Model of Antarctica (REMA) products.

  18. Uncertainty of SWAT model at different DEM resolutions in a large mountainous watershed.

    Science.gov (United States)

    Zhang, Peipei; Liu, Ruimin; Bao, Yimeng; Wang, Jiawei; Yu, Wenwen; Shen, Zhenyao

    2014-04-15

    The objective of this study was to enhance understanding of the sensitivity of the SWAT model to the resolutions of Digital Elevation Models (DEMs) based on the analysis of multiple evaluation indicators. The Xiangxi River, a large tributary of Three Gorges Reservoir in China, was selected as the study area. A range of 17 DEM spatial resolutions, from 30 to 1000 m, was examined, and the annual and monthly model outputs based on each resolution were compared. The following results were obtained: (i) sediment yield was greatly affected by DEM resolution; (ii) the prediction of dissolved oxygen load was significantly affected by DEM resolutions coarser than 500 m; (iii) Total Nitrogen (TN) load was not greatly affected by the DEM resolution; (iv) Nitrate Nitrogen (NO₃-N) and Total Phosphorus (TP) loads were slightly affected by the DEM resolution; and (v) flow and Ammonia Nitrogen (NH₄-N) load were essentially unaffected by the DEM resolution. The flow and dissolved oxygen load decreased more significantly in the dry season than in the wet and normal seasons. Excluding flow and dissolved oxygen, the uncertainties of the other Hydrology/Non-point Source (H/NPS) pollution indicators were greater in the wet season than in the dry and normal seasons. Considering the temporal distribution uncertainties, the optimal DEM resolutions for flow was 30-200 m, for sediment and TP was 30-100 m, for dissolved oxygen and NO₃-N was 30-300 m, for NH₄-N was 30 to 70 m and for TN was 30-150 m. Copyright © 2014 Elsevier Ltd. All rights reserved.

  19. Urban DEM generation, analysis and enhancements using TanDEM-X

    Science.gov (United States)

    Rossi, Cristian; Gernhardt, Stefan

    2013-11-01

    This paper analyzes the potential of the TanDEM-X mission for the generation of urban Digital Elevation Models (DEMs). The high resolution of the sensors and the absence of temporal decorrelation are exploited. The interferometric chain and the problems encountered for correct mapping of urban areas are analyzed first. The operational Integrated TanDEM-X Processor (ITP) algorithms are taken as reference. The ITP main product is called the raw DEM. Whereas the ITP coregistration stage is demonstrated to be robust enough, large improvements in the raw DEM such as fewer percentages of phase unwrapping errors, can be obtained by using adaptive fringe filters instead of the conventional ones in the interferogram generation stage. The shape of the raw DEM in the layover area is also shown and determined to be regular for buildings with vertical walls. Generally, in the presence of layover, the raw DEM exhibits a height ramp, resulting in a height underestimation for the affected structure. Examples provided confirm the theoretical background. The focus is centered on high resolution DEMs produced using spotlight acquisitions. In particular, a raw DEM over Berlin (Germany) with a 2.5 m raster is generated and validated. For this purpose, ITP is modified in its interferogram generation stage by adopting the Intensity Driven Adaptive Neighbourhood (IDAN) algorithm. The height Root Mean Square Error (RMSE) between the raw DEM and a reference is about 8 m for the two classes defining the urban DEM: structures and non-structures. The result can be further improved for the structure class using a DEM generated with Persistent Scatterer Interferometry. A DEM fusion is thus proposed and a drop of about 20% in the RMSE is reported.

  1. Galveston, Texas Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  2. Savannah, Georgia Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  3. Biloxi, Mississippi Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  4. Puerto Rico Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  5. Hilo, Hawaii Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  6. Hanalei, Hawaii Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  7. Taholah, Washington Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  8. Chignik, Alaska Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  9. Monterey, California Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  10. Garibaldi, Oregon Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  11. Keauhou, Hawaii Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  12. Atka, Alaska Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  13. Lahaina, Hawaii Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  14. Kawaihae, Hawaii Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  15. Nikolski, Alaska Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  16. Shemya, Alaska Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  17. Portland, Maine Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  18. Craig, Alaska Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  19. Midway Atoll Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  20. Adak, Alaska Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  1. Cordova, Alaska Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  2. Nantucket, Massachusetts Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  3. Oahu, Hawaii Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  4. Central Oregon Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  5. Southeast Alaska Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) to support individual coastal States as part of the...

  6. Tatitlek, Alaska Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) to support individual coastal States as part of the...

  7. Hoonah, Alaska Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) to support individual coastal States as part of the...

  8. Whittier, Alaska Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) to support individual coastal States as part of the...

  9. Gustavus, Alaska Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) to support individual coastal States as part of the...

  10. Chenega, Alaska Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) to support individual coastal States as part of the...

  11. Juneau, Alaska Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) to support individual coastal States as part of the...

  12. Mariana Trench Bathymetric Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) created a bathymetric digital elevation model (DEM) for the Mariana Trench and adjacent seafloor in the Western...

  13. Unalaska, Alaska Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) to support individual coastal States as part of the...

  14. Pembuatan Digital Elevation Model Resolusi 10m dari Peta RBI dan Survei GPS dengan Algoritma Anudem

    Directory of Open Access Journals (Sweden)

    Indarto

    2014-04-01

    Full Text Available This study proposes the generation of Digital Elevation Model (DEM with spatial resolution of 10m x 10m by re-interpolation of elevation data. Data input for this study includes: (1 digitized datum coordinate from RBI map, (2 sample points surveyed by GPS, (3 digitized contour data fromSRTM DEM and ASTER GDEM2, and (4 digitized stream-network layer from RBI. All collected data were converted to mass point coordinats. On the top of Topogrid-ArcGIS, all points data were interpolated to produce DEM. After that the produced DEM were compared and evaluated to the SRTM and ASTER DEMvisually. The result shows that produced DEM are more accurate to represent the detailed topography of the study areas.

  15. ASTER Digital Elevation Model V003

    Data.gov (United States)

    National Aeronautics and Space Administration — The ASTER Digital Elevation Model (DEM) product is generated using bands 3N (nadir-viewing) and 3B (backward-viewing) of an ASTER Level-1A image acquired by the...

  16. Kachemak Bay, Alaska Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  17. Virginia Beach, Virginia Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  18. Santa Barbara, California Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  19. Ocean City, Maryland Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  20. King Cove, Alaska Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  1. Panama City, Florida Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  2. Montauk, New York Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  3. Sand Point, Alaska Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  4. La Push, Washington Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  5. Arena Cove, California Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  6. Port Orford, Oregon Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  7. Arecibo, Puerto Rico Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  8. Grenada Digital Elevation Model - 1 arc-second

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Centers for Environmental Information is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  9. Guayama, Puerto Rico Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  10. Fajardo, Puerto Rico Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  11. Corpus Christi, Texas Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  12. Dutch Harbor, Alaska Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  13. Ponce, Puerto Rico Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  14. Daytona Beach, Florida Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  15. Small catchments DEM creation using Unmanned Aerial Vehicles

    Science.gov (United States)

    Gafurov, A. M.

    2018-01-01

    Digital elevation models (DEM) are an important source of information on the terrain, allowing researchers to evaluate various exogenous processes. The higher the accuracy of DEM the better the level of the work possible. An important source of data for the construction of DEMs are point clouds obtained with terrestrial laser scanning (TLS) and unmanned aerial vehicles (UAV). In this paper, we present the results of constructing a DEM on small catchments using UAVs. Estimation of the UAV DEM showed comparable accuracy with the TLS if real time kinematic Global Positioning System (RTK-GPS) ground control points (GCPs) and check points (CPs) were used. In this case, the main source of errors in the construction of DEMs are the errors in the referencing of survey results.

  16. NOAA Coastal Services Center Coastal Inundation Digital Elevation Model: Philadelphia WFO - Pennsylvania

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This digital elevation model (DEM) is a part of a series of DEMs produced for the National Oceanic and Atmospheric Administration Coastal Services Center's Sea Level...

  17. Port Alexander Alaska Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) to support individual coastal States as part of the...

  18. Envolving the Operations of the TerraSAR-X/TanDEM-X Mission Planning System during the TanDEM-X Science Phase

    OpenAIRE

    Stathopoulos, Fotios; Guillermin, Guillaume; Garcia Acero, Carlos; Reich, Karin; Mrowka, Falk

    2016-01-01

    After the successful Global Coverage of the Digital Elevation Model, the TanDEM-X Science phase was initiated in September of 2014, dedicated to the demonstration of innovative techniques and experiments. The TanDEM-X Science phase had a large impact on the TerraSAR-X/TanDEM-X Mission Planning System. The two main challenges were the formation flying changes and the activation of a new acquisition mode, the so called Dual Receive Antenna (DRA) acquisition mode. This paper describes all action...

  19. New Orleans, Louisiana Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions in the Gulf of Mexico....

  20. 2016 USGS Lidar DEM: Maine QL2

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Product: These are Digital Elevation Model (DEM) data for Franklin, Oxford, Piscataquis, and Somerset Counties, Maine as part of the required deliverables for the...

  1. NOAA Office for Coastal Management Coastal Inundation Digital Elevation Model: Charleston WFO (Georgia)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This digital elevation model (DEM) is a part of a series of DEMs produced for the National Oceanic and Atmospheric Administration Office for Coastal Management's Sea...

  2. San Juan Islands, Washington Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  3. San Juan, Puerto Rico Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  4. U.S. Virgin Islands Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  5. Cape Hatteras, North Carolina Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  6. Sand Point, Alaska MHW Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  7. Port San Luis, California Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  8. Rarotonga 1 arc-second Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Centers for Environmental Information is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  9. Eastern Canada Digital Elevation Model - 3 arc-second

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Centers for Environmental Information is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  10. Central Oregon Coastal Digital Elevation Model NAVD 88

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  11. Atlantic City, New Jersey Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  12. Galapagos Islands, Ecuador 1 sec Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Centers for Environmental Information is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  13. Galapagos Islands, Ecuador 3 sec Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Centers for Environmental Information is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  14. 2014 USACE NCMP Topobathy Lidar DEM: Oregon

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — These Digital Elevation Model (DEM) files contain rasterized topobathy lidar elevations at a 1 m grid size, generated from data collected by the Coastal Zone Mapping...

  15. An Optimal DEM Reconstruction Method for Linear Array Synthetic Aperture Radar Based on Variational Model

    Directory of Open Access Journals (Sweden)

    Shi Jun

    2015-02-01

    Full Text Available Downward-looking Linear Array Synthetic Aperture Radar (LASAR has many potential applications in the topographic mapping, disaster monitoring and reconnaissance applications, especially in the mountainous area. However, limited by the sizes of platforms, its resolution in the linear array direction is always far lower than those in the range and azimuth directions. This disadvantage leads to the blurring of Three-Dimensional (3D images in the linear array direction, and restricts the application of LASAR. To date, the research on 3D SAR image enhancement has focused on the sparse recovery technique. In this case, the one-to-one mapping of Digital Elevation Model (DEM brakes down. To overcome this, an optimal DEM reconstruction method for LASAR based on the variational model is discussed in an effort to optimize the DEM and the associated scattering coefficient map, and to minimize the Mean Square Error (MSE. Using simulation experiments, it is found that the variational model is more suitable for DEM enhancement applications to all kinds of terrains compared with the Orthogonal Matching Pursuit (OMPand Least Absolute Shrinkage and Selection Operator (LASSO methods.

  16. Contours, This Layer was derived from the USGS National Elevation Dataset (NED) based on 7.5 minute Digital Elevation Model (DEM) image files., Published in 1999, 1:24000 (1in=2000ft) scale, Atlanta Regional Commission.

    Data.gov (United States)

    NSGIC Regional | GIS Inventory — Contours dataset current as of 1999. This Layer was derived from the USGS National Elevation Dataset (NED) based on 7.5 minute Digital Elevation Model (DEM) image...

  17. Application of Digital Elevation Model (DEM for description of soil microtopography changes in laboratory experiments

    Directory of Open Access Journals (Sweden)

    Stańczyk Tomasz

    2016-12-01

    Full Text Available In the study we evaluated spatial and quantitative changes in soil surface microtopography to describe water erosion process under simulated rain with use of a non-contact optical 3D scanner. The experiment was conducted in two variants: with and without drainage layer. Two clay soils collected from farmlands from the catchment of lake Zgorzała (Warsaw were investigated. Six tests of simulated rain were applied, with 55 mm·h−1. The surface roughness and microrelief were determined immediately after every 10 min of rainfall simulation by 3D scanner. The volume of surface and underground runoff as well as soil moisture were measured. The surface points coordinates obtained while scanning were interpolated using natural neighbour method and GIS software to generate Digital Elevation Models (DEM with a 0.5 mm resolution. Two DEM-derived surface roughness indices: Random Roughness (RR and Terrain Ruggedness Index (TRI were used for microrelief description. Calculated values of both roughness factors have decreased with time under the influence of rainfall in all analyzed variants. During the sprinkling the moisture of all samples had been growing rapidly from air-dry state reaching values close to the maximum water capacity (37–48% vol. in 20–30 min. Simultaneously the intensity of surface runoff was increasing and cumulative runoff value was: 17–35% for variants with drainage and 72–83% for the variants without drainage, relative to cumulative rainfall. The observed soil surface elevation changes were associated with aggregates decomposition, erosion and sedimentation, and above all, with a compaction of the soil, which was considered to be a dominant factor hindering the assessment of the erosion intensity of the of the scanned surface.

  18. Minnesota Digital Elevation Model - Tiled 93 Meter Resolution

    Data.gov (United States)

    Minnesota Department of Natural Resources — Digital Elevation Model (DEM) at a resolution of 93 meters. Original data resolution was 3 arc seconds which corresponds (approximately) to a matrix of points at a...

  19. NOAA Office for Coastal Management Coastal Inundation Digital Elevation Model: San Diego (CA) WFO

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This digital elevation model (DEM) is a part of a series of DEMs produced for the National Oceanic and Atmospheric Administration Office for Coastal Management's Sea...

  20. Radarsat Antarctic Mapping Project Digital Elevation Model, Version 2

    Data.gov (United States)

    National Aeronautics and Space Administration — The high-resolution Radarsat Antarctic Mapping Project (RAMP) Digital Elevation Model (DEM) combines topographic data from a variety of sources to provide consistent...

  1. Easter Island, Chile Digital Elevation Model 3 arc-second

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Centers for Environmental Information is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  2. Optimizing landslide susceptibility zonation: Effects of DEM spatial resolution and slope unit delineation on logistic regression models

    Science.gov (United States)

    Schlögel, R.; Marchesini, I.; Alvioli, M.; Reichenbach, P.; Rossi, M.; Malet, J.-P.

    2018-01-01

    We perform landslide susceptibility zonation with slope units using three digital elevation models (DEMs) of varying spatial resolution of the Ubaye Valley (South French Alps). In so doing, we applied a recently developed algorithm automating slope unit delineation, given a number of parameters, in order to optimize simultaneously the partitioning of the terrain and the performance of a logistic regression susceptibility model. The method allowed us to obtain optimal slope units for each available DEM spatial resolution. For each resolution, we studied the susceptibility model performance by analyzing in detail the relevance of the conditioning variables. The analysis is based on landslide morphology data, considering either the whole landslide or only the source area outline as inputs. The procedure allowed us to select the most useful information, in terms of DEM spatial resolution, thematic variables and landslide inventory, in order to obtain the most reliable slope unit-based landslide susceptibility assessment.

  3. 2015 USACE NCMP Topobathy Lidar DEM: Avalon (NJ)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — These Digital Elevation Model (DEM) files contain rasterized topobathy lidar elevations at a 1 m grid size, generated from data collected by the Coastal Zone Mapping...

  4. 2013 USACE NCMP Topobathy Lidar DEM: Niihau (HI)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — These Digital Elevation Model (DEM) files contain rasterized topobathy lidar elevations at a 1 m grid size, generated from data collected by the Coastal Zone Mapping...

  5. Chignik, Alaska 1 arc-second Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) to support individual coastal States as part of the...

  6. Akutan, Alaska 8 Arc-second Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) to support individual coastal States as part of the...

  7. Mobile, Alabama 1/3 MHW Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions in the Gulf of Mexico....

  8. THE GLOBAL TANDEM-X DEM: PRODUCTION STATUS AND FIRST VALIDATION RESULTS

    Directory of Open Access Journals (Sweden)

    M. Huber

    2012-07-01

    Full Text Available The TanDEM-X mission will derive a global digital elevation model (DEM with satellite SAR interferometry. Two radar satellites (TerraSAR-X and TanDEM-X will map the Earth in a resolution and accuracy with an absolute height error of 10m and a relative height error of 2m for 90% of the data. In order to fulfill the height requirements in general two global coverages are acquired and processed. Besides the final TanDEM-X DEM, an intermediate DEM with reduced accuracy is produced after the first coverage is completed. The last step in the whole workflow for generating the TanDEM-X DEM is the calibration of remaining systematic height errors and the merge of single acquisitions to 1°x1° DEM tiles. In this paper the current status of generating the intermediate DEM and first validation results based on GPS tracks, laser scanning DEMs, SRTM data and ICESat points are shown for different test sites.

  9. 2016 NOAA Topobathy Lidar DEM: Upper Lake Michigan Islands

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This digital elevation model (DEM) was created from data collected by Leading Edge Geomatics using a Leica Chiroptera II Bathymetric & Topographic Sensor. The...

  10. Digital elevation model and orthophotographs of Greenland based on aerial photographs from 1978–1987

    Science.gov (United States)

    Korsgaard, Niels J.; Nuth, Christopher; Khan, Shfaqat A.; Kjeldsen, Kristian K.; Bjørk, Anders A.; Schomacker, Anders; Kjær, Kurt H.

    2016-01-01

    Digital Elevation Models (DEMs) play a prominent role in glaciological studies for the mass balance of glaciers and ice sheets. By providing a time snapshot of glacier geometry, DEMs are crucial for most glacier evolution modelling studies, but are also important for cryospheric modelling in general. We present a historical medium-resolution DEM and orthophotographs that consistently cover the entire surroundings and margins of the Greenland Ice Sheet 1978–1987. About 3,500 aerial photographs of Greenland are combined with field surveyed geodetic ground control to produce a 25 m gridded DEM and a 2 m black-and-white digital orthophotograph. Supporting data consist of a reliability mask and a photo footprint coverage with recording dates. Through one internal and two external validation tests, this DEM shows an accuracy better than 10 m horizontally and 6 m vertically while the precision is better than 4 m. This dataset proved successful for topographical mapping and geodetic mass balance. Other uses include control and calibration of remotely sensed data such as imagery or InSAR velocity maps. PMID:27164457

  11. 2015 USACE NCMP Topobathy Lidar DEM: Egmont Key (FL)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — These 1 m gridded bare earth Digital Elevation Model (DEM) files contain rasterized topobathy lidar elevations generated from data collected by the Coastal Zone...

  12. TanDEM-X the Earth surface observation project from space level - basis and mission status

    Directory of Open Access Journals (Sweden)

    Jerzy Wiśniowski

    2015-03-01

    Full Text Available TanDEM-X is DLR (Deutsches Zentrum für Luft- und Raumfahrt the Earth surface observation project using high-resolution SAR interferometry. It opens a new era in space borne radar remote sensing. The system is based on two satellites: TerraSAR-X (TSX and TanDEM-X (TDX flying on the very close, strictly controlled orbits. This paper gives an overview of the radar technology and overview of the TanDEM-X mission concept which is based on several innovative technologies. The primary objective of the mission is to deliver a global digital elevation model (DEM with an unprecedented accuracy, which is equal to or surpass the HRTI-3 specifications (12 m posting, relative height accuracy ±2 m for slope < 20% and ±4 m for slope > 20% [8]. Beyond that, TanDEM-X provides a highly reconfigurable platform for the demonstration of new radar imaging techniques and applications.[b]Keywords[/b]: remote sensing, Bistatic SAR, digital elevation model (DEM, Helix formation, SAR interferomery, HRTI-3, synchronization

  13. St. Croix, U.S. Virgin Islands Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  14. Wake Island 3 Arc-second MHW Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  15. Barkley Sound, Canada 1 arc-second Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Centers for Environmental Information is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  16. Miami 1/3 arc-second MHW Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  17. Midway Atoll 3 Arc-second MHW Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  18. Society Islands, French Polynesia Digital Elevation Model - 3 arc-second

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Centers for Environmental Information is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  19. Sitka, Alaska 3 Arc-second MHW Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  20. Kodiak, Alaska 1/3 arc-second Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  1. Central California 1 Arc-second MWH Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  2. 2016 USACE NCMP Topobathy Lidar DEM: Gulf Coast (TX)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — These bare earth Digital Elevation Model (DEM) files contain rasterized topobathy lidar elevations at a 1 meter grid size, generated from data collected by the...

  3. Digital elevation modeling via curvature interpolation for lidar data

    Science.gov (United States)

    Digital elevation model (DEM) is a three-dimensional (3D) representation of a terrain's surface - for a planet (including Earth), moon, or asteroid - created from point cloud data which measure terrain elevation. Its modeling requires surface reconstruction for the scattered data, which is an ill-p...

  4. Akutan, Alaska 8/3 Arc-second Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) to support individual coastal States as part of the...

  5. Nikolski, Alaska 1 arc-second MHHW Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) to support individual coastal States as part of the...

  6. Yakutat, Alaska 8 Arc-second MHHW Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) to support individual coastal States as part of the...

  7. King Cove, Alaska 8 arc-second Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) to support individual coastal States as part of the...

  8. Akutan, Alaska 8/15 Arc-second Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) to support individual coastal States as part of the...

  9. Chiniak, Alaska 8/15 arc-second Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Centers for Environmental Information is building high-resolution digital elevation models (DEMs) to support individual coastal States as part of the...

  10. Cold Bay, Alaska 8 arc-second Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) to support individual coastal States as part of the...

  11. Chignik, Alaska 1/3 arc-second Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) to support individual coastal States as part of the...

  12. 2015 USACE NCMP Topobathy Lidar DEM: Sand Island (WA)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — These Digital Elevation Model (DEM) files contain rasterized topobathy lidar elevations at a 1 m grid size, generated from data collected by the Coastal Zone Mapping...

  13. Estimating Horizontal Displacement between DEMs by Means of Particle Image Velocimetry Techniques

    Directory of Open Access Journals (Sweden)

    Juan F. Reinoso

    2015-12-01

    Full Text Available To date, digital terrain model (DTM accuracy has been studied almost exclusively by computing its height variable. However, the largely ignored horizontal component bears a great influence on the positional accuracy of certain linear features, e.g., in hydrological features. In an effort to fill this gap, we propose a means of measurement different from the geomatic approach, involving fluid mechanics (water and air flows or aerodynamics. The particle image velocimetry (PIV algorithm is proposed as an estimator of horizontal differences between digital elevation models (DEM in grid format. After applying a scale factor to the displacement estimated by the PIV algorithm, the mean error predicted is around one-seventh of the cell size of the DEM with the greatest spatial resolution, and around one-nineteenth of the cell size of the DEM with the least spatial resolution. Our methodology allows all kinds of DTMs to be compared once they are transformed into DEM format, while also allowing comparison of data from diverse capture methods, i.e., LiDAR versus photogrammetric data sources.

  14. ArcticDEM Validation and Accuracy Assessment

    Science.gov (United States)

    Candela, S. G.; Howat, I.; Noh, M. J.; Porter, C. C.; Morin, P. J.

    2017-12-01

    ArcticDEM comprises a growing inventory Digital Elevation Models (DEMs) covering all land above 60°N. As of August, 2017, ArcticDEM had openly released 2-m resolution, individual DEM covering over 51 million km2, which includes areas of repeat coverage for change detection, as well as over 15 million km2 of 5-m resolution seamless mosaics. By the end of the project, over 80 million km2 of 2-m DEMs will be produced, averaging four repeats of the 20 million km2 Arctic landmass. ArcticDEM is produced from sub-meter resolution, stereoscopic imagery using open source software (SETSM) on the NCSA Blue Waters supercomputer. These DEMs have known biases of several meters due to errors in the sensor models generated from satellite positioning. These systematic errors are removed through three-dimensional registration to high-precision Lidar or other control datasets. ArcticDEM is registered to seasonally-subsetted ICESat elevations due its global coverage and high report accuracy ( 10 cm). The vertical accuracy of ArcticDEM is then obtained from the statistics of the fit to the ICESat point cloud, which averages -0.01 m ± 0.07 m. ICESat, however, has a relatively coarse measurement footprint ( 70 m) which may impact the precision of the registration. Further, the ICESat data predates the ArcticDEM imagery by a decade, so that temporal changes in the surface may also impact the registration. Finally, biases may exist between different the different sensors in the ArcticDEM constellation. Here we assess the accuracy of ArcticDEM and the ICESat registration through comparison to multiple high-resolution airborne lidar datasets that were acquired within one year of the imagery used in ArcticDEM. We find the ICESat dataset is performing as anticipated, introducing no systematic bias during the coregistration process, and reducing vertical errors to within the uncertainty of the airborne Lidars. Preliminary sensor comparisons show no significant difference post coregistration

  15. Northern Gulf 1 Arc-second MHW Coast Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions in the Gulf of Mexico....

  16. Mobile, Alabama 1/3 NAVD 88 Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions in the Gulf of Mexico....

  17. NOAA Office for Coastal Management Coastal Inundation Digital Elevation Model: Melbourne (FL) WFO - Brevard and Volusia Counties

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This digital elevation model (DEM) is a part of a series of DEMs produced for the National Oceanic and Atmospheric Administration Office for Coastal Management's Sea...

  18. Accuracy assessment of TanDEM-X IDEM using airborne LiDAR on the area of Poland

    Directory of Open Access Journals (Sweden)

    Woroszkiewicz Małgorzata

    2017-06-01

    Full Text Available The TerraSAR-X add-on for Digital Elevation Measurement (TanDEM-X mission launched in 2010 is another programme – after the Shuttle Radar Topography Mission (SRTM in 2000 – that uses space-borne radar interferometry to build a global digital surface model. This article presents the accuracy assessment of the TanDEM-X intermediate Digital Elevation Model (IDEM provided by the German Aerospace Center (DLR under the project “Accuracy assessment of a Digital Elevation Model based on TanDEM-X data” for the southwestern territory of Poland. The study area included: open terrain, urban terrain and forested terrain. Based on a set of 17,498 reference points acquired by airborne laser scanning, the mean errors of average heights and standard deviations were calculated for areas with a terrain slope below 2 degrees, between 2 and 6 degrees and above 6 degrees. The absolute accuracy of the IDEM data for the analysed area, expressed as a root mean square error (Total RMSE, was 0.77 m.

  19. Radar and Lidar Radar DEM

    Science.gov (United States)

    Liskovich, Diana; Simard, Marc

    2011-01-01

    Using radar and lidar data, the aim is to improve 3D rendering of terrain, including digital elevation models (DEM) and estimates of vegetation height and biomass in a variety of forest types and terrains. The 3D mapping of vegetation structure and the analysis are useful to determine the role of forest in climate change (carbon cycle), in providing habitat and as a provider of socio-economic services. This in turn will lead to potential for development of more effective land-use management. The first part of the project was to characterize the Shuttle Radar Topography Mission DEM error with respect to ICESat/GLAS point estimates of elevation. We investigated potential trends with latitude, canopy height, signal to noise ratio (SNR), number of LiDAR waveform peaks, and maximum peak width. Scatter plots were produced for each variable and were fitted with 1st and 2nd degree polynomials. Higher order trends were visually inspected through filtering with a mean and median filter. We also assessed trends in the DEM error variance. Finally, a map showing how DEM error was geographically distributed globally was created.

  20. The influence of digital elevation model resolution on overland flow networks for modelling urban pluvial flooding.

    Science.gov (United States)

    Leitão, J P; Boonya-Aroonnet, S; Prodanović, D; Maksimović, C

    2009-01-01

    This paper presents the developments towards the next generation of overland flow modelling of urban pluvial flooding. Using a detailed analysis of the Digital Elevation Model (DEM) the developed GIS tools can automatically generate surface drainage networks which consist of temporary ponds (floodable areas) and flow paths and link them with the underground network through inlets. For different commercially-available Rainfall-Runoff simulation models, the tool will generate the overland flow network needed to model the surface runoff and pluvial flooding accurately. In this paper the emphasis is placed on a sensitivity analysis of ponds and preferential overland flow paths creation. Different DEMs for three areas were considered in order to compare the results obtained. The DEMs considered were generated using different acquisition techniques and hence represent terrain with varying levels of resolution and accuracy. The results show that DEMs can be used to generate surface flow networks reliably. As expected, the quality of the surface network generated is highly dependent on the quality and resolution of the DEMs and successful representation of buildings and streets.

  1. Greenland 5 km DEM, Ice Thickness, and Bedrock Elevation Grids

    Data.gov (United States)

    National Aeronautics and Space Administration — A Digital Elevation Model (DEM), ice thickness grid, and bedrock elevation grid of Greenland acquired as part of the PARCA program are available in ASCII text format...

  2. Estimating River Surface Elevation From ArcticDEM

    Science.gov (United States)

    Dai, Chunli; Durand, Michael; Howat, Ian M.; Altenau, Elizabeth H.; Pavelsky, Tamlin M.

    2018-04-01

    ArcticDEM is a collection of 2-m resolution, repeat digital surface models created from stereoscopic satellite imagery. To demonstrate the potential of ArcticDEM for measuring river stages and discharges, we estimate river surface heights along a reach of Tanana River near Fairbanks, Alaska, by the precise detection of river shorelines and mapping of shorelines to land surface elevation. The river height profiles over a 15-km reach agree with in situ measurements to a standard deviation less than 30 cm. The time series of ArcticDEM-derived river heights agree with the U.S. Geological Survey gage measurements with a standard deviation of 32 cm. Using the rating curve for that gage, we obtain discharges with a validation accuracy (root-mean-square error) of 234 m3/s (23% of the mean discharge). Our results demonstrate that ArcticDEM can accurately measure spatial and temporal variations of river surfaces, providing a new and powerful data set for hydrologic analysis.

  3. Marquesas Islands, French Polynesia 3 arc-second Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Centers for Environmental Information is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  4. Port Alberni, Canada 1/3 arc-second Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Centers for Environmental Information is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  5. Digital Elevation Model of Kauai, Hawaii, Integrating Bathymetric and Topographic Datasets

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  6. Crescent City, California 1/3 Arc-second Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  7. Cordova, Alaska 1/3 Arc-second MHW Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  8. Tutuila, American Samoa 1/3 arc-second Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  9. Eureka, California 1/3 Arc-second MHW Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  10. Central Florida 1/3 arc-second MHW Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  11. Puget Sound 1/3 arc-second MHW Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  12. Society Islands (Leeward), French Polynesia Digital Elevation Model - 1 arc-second

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Centers for Environmental Information is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  13. Midway Atoll 1/3 Arc-second MHW Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  14. Society Islands (Windward), French Polynesia Digital Elevation Model - 1 arc-second

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Centers for Environmental Information is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  15. Miami 1/3 arc-second NAVD 88 Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  16. Central California 1 Arc-second NAVD 88 Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  17. Wake Island 1/3 Arc-second MHW Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  18. Monterey, California 1/3 Arc-second MHW Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  19. Tampa Bay 1/3 arc-second MHW Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  20. Garibaldi, Oregon 1/3 Arc-second MHW Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  1. Sitka, Alaska 1/3 Arc-second MHW Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  2. Parabolic Equation Modeling of Propagation over Terrain Using Digital Elevation Model

    Directory of Open Access Journals (Sweden)

    Xiao-Wei Guan

    2018-01-01

    Full Text Available The parabolic equation method based on digital elevation model (DEM is applied on propagation predictions over irregular terrains. Starting from a parabolic approximation to the Helmholtz equation, a wide-angle parabolic equation is deduced under the assumption of forward propagation and the split-step Fourier transform algorithm is used to solve it. The application of DEM is extended to the Cartesian coordinate system and expected to provide a precise representation of a three-dimensional surface with high efficiency. In order to validate the accuracy, a perfectly conducting Gaussian terrain profile is simulated and the results are compared with the shift map. As a consequence, a good agreement is observed. Besides, another example is given to provide a theoretical basis and reference for DEM selection. The simulation results demonstrate that the prediction errors will be obvious only when the resolution of the DEM used is much larger than the range step in the PE method.

  3. False Pass, Alaska 8/15 arc-second Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Centers for Environmental Information is building high-resolution digital elevation models (DEMs) to support individual coastal States as part of the...

  4. Yakutat, Alaska 8/15 Arc-second MHHW Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) to support individual coastal States as part of the...

  5. Elfin Cove Alaska 1/3 Arc-second Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) to support individual coastal States as part of the...

  6. Cordova, Alaska 8/15 Arc-second MHHW Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) to support individual coastal States as part of the...

  7. King Cove, Alaska 8/3 arc-second Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) to support individual coastal States as part of the...

  8. King Cove, Alaska 8/15 arc-second Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) to support individual coastal States as part of the...

  9. Nikolski, Alaska 1/3 arc-second MHHW Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) to support individual coastal States as part of the...

  10. Port Lions, Alaska 8/15 arc-second Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Centers for Environmental Information is building high-resolution digital elevation models (DEMs) to support individual coastal States as part of the...

  11. Yakutat, Alaska 8/3 Arc-second MHHW Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) to support individual coastal States as part of the...

  12. Digital Elevation Model of Southeast Alaska, Integrating Bathymetric and Topographic Datasets

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) to support individual coastal States as part of the...

  13. Cold Bay, Alaska 8/15 arc-second Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) to support individual coastal States as part of the...

  14. MEaSUREs Greenland Ice Mapping Project (GIMP) Digital Elevation Model from GeoEye and WorldView Imagery, Version 1

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set consists of an enhanced resolution digital elevation model (DEM) for the Greenland Ice Sheet. The DEM is derived from sub-meter resolution,...

  15. VERTICAL ACCURACY COMPARISON OF DIGITAL ELEVATION MODEL FROM LIDAR AND MULTITEMPORAL SATELLITE IMAGERY

    Directory of Open Access Journals (Sweden)

    J. Octariady

    2017-05-01

    Full Text Available Digital elevation model serves to illustrate the appearance of the earth's surface. DEM can be produced from a wide variety of data sources including from radar data, LiDAR data, and stereo satellite imagery. Making the LiDAR DEM conducted using point cloud data from LiDAR sensor. Making a DEM from stereo satellite imagery can be done using same temporal or multitemporal stereo satellite imagery. How much the accuracy of DEM generated from multitemporal stereo stellite imagery and LiDAR data is not known with certainty. The study was conducted using LiDAR DEM data and multitemporal stereo satellite imagery DEM. Multitemporal stereo satellite imagery generated semi-automatically by using 3 scene stereo satellite imagery with acquisition 2013–2014. The high value given each of DEM serve as the basis for calculating high accuracy DEM respectively. The results showed the high value differences in the fraction of the meter between LiDAR DEM and multitemporal stereo satellite imagery DEM.

  16. NOAA Office for Coastal Management Coastal Inundation Digital Elevation Model: Portland (OR) WFO - Tillamook, Lincoln, and Lane Counties

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This digital elevation model (DEM) is a part of a series of DEMs produced for the National Oceanic and Atmospheric Administration Office for Coastal Management's Sea...

  17. NOAA Office for Coastal Management Coastal Inundation Digital Elevation Model: Jacksonville (FL) WFO - Duval, Clay, and Nassau Counties

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This digital elevation model (DEM) is a part of a series of DEMs produced for the National Oceanic and Atmospheric Administration Office for Coastal Management's Sea...

  18. NOAA Office for Coastal Management Coastal Inundation Digital Elevation Model: Eureka (CA) WFO - Humboldt and Del Norte Counties

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This digital elevation model (DEM) is a part of a series of DEMs produced for the National Oceanic and Atmospheric Administration Office for Coastal Management's Sea...

  19. Digital elevation model and orthophotographs of Greenland based on aerial photographs from 1978-1987

    DEFF Research Database (Denmark)

    Korsgaard, Niels J.; Nuth, Christopher; Khan, Shfaqat Abbas

    2016-01-01

    Digital Elevation Models (DEMs) play a prominent role in glaciological studies for the mass balance of glaciers and ice sheets. By providing a time snapshot of glacier geometry, DEMs are crucial for most glacier evolution modelling studies, but are also important for cryospheric modelling...... in general. We present a historical medium-resolution DEM and orthophotographs that consistently cover the entire surroundings and margins of the Greenland Ice Sheet 1978-1987. About 3,500 aerial photographs of Greenland are combined with field surveyed geodetic ground control to produce a 25 m gridded DEM...... is better than 4 m. This dataset proved successful for topographical mapping and geodetic mass balance. Other uses include control and calibration of remotely sensed data such as imagery or InSAR velocity maps....

  20. Creating high-resolution digital elevation model using thin plate spline interpolation and Monte Carlo simulation

    International Nuclear Information System (INIS)

    Pohjola, J.; Turunen, J.; Lipping, T.

    2009-07-01

    In this report creation of the digital elevation model of Olkiluoto area incorporating a large area of seabed is described. The modeled area covers 960 square kilometers and the apparent resolution of the created elevation model was specified to be 2.5 x 2.5 meters. Various elevation data like contour lines and irregular elevation measurements were used as source data in the process. The precision and reliability of the available source data varied largely. Digital elevation model (DEM) comprises a representation of the elevation of the surface of the earth in particular area in digital format. DEM is an essential component of geographic information systems designed for the analysis and visualization of the location-related data. DEM is most often represented either in raster or Triangulated Irregular Network (TIN) format. After testing several methods the thin plate spline interpolation was found to be best suited for the creation of the elevation model. The thin plate spline method gave the smallest error in the test where certain amount of points was removed from the data and the resulting model looked most natural. In addition to the elevation data the confidence interval at each point of the new model was required. The Monte Carlo simulation method was selected for this purpose. The source data points were assigned probability distributions according to what was known about their measurement procedure and from these distributions 1 000 (20 000 in the first version) values were drawn for each data point. Each point of the newly created DEM had thus as many realizations. The resulting high resolution DEM will be used in modeling the effects of land uplift and evolution of the landscape in the time range of 10 000 years from the present. This time range comes from the requirements set for the spent nuclear fuel repository site. (orig.)

  1. Northern Gulf 1 Arc-second NAVD 88 Coast Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions in the Gulf of Mexico....

  2. Digital elevation model production from scanned topographic contour maps via thin plate spline interpolation

    International Nuclear Information System (INIS)

    Soycan, Arzu; Soycan, Metin

    2009-01-01

    GIS (Geographical Information System) is one of the most striking innovation for mapping applications supplied by the developing computer and software technology to users. GIS is a very effective tool which can show visually combination of the geographical and non-geographical data by recording these to allow interpretations and analysis. DEM (Digital Elevation Model) is an inalienable component of the GIS. The existing TM (Topographic Map) can be used as the main data source for generating DEM by amanual digitizing or vectorization process for the contours polylines. The aim of this study is to examine the DEM accuracies, which were obtained by TMs, as depending on the number of sampling points and grid size. For these purposes, the contours of the several 1/1000 scaled scanned topographical maps were vectorized. The different DEMs of relevant area have been created by using several datasets with different numbers of sampling points. We focused on the DEM creation from contour lines using gridding with RBF (Radial Basis Function) interpolation techniques, namely TPS as the surface fitting model. The solution algorithm and a short review of the mathematical model of TPS (Thin Plate Spline) interpolation techniques are given. In the test study, results of the application and the obtained accuracies are drawn and discussed. The initial object of this research is to discuss the requirement of DEM in GIS, urban planning, surveying engineering and the other applications with high accuracy (a few deci meters). (author)

  3. CREATING DIGITAL ELEVATION MODEL USING A MOBILE DEVICE

    Directory of Open Access Journals (Sweden)

    A. İ. Durmaz

    2017-11-01

    Full Text Available DEM (Digital Elevation Models is the best way to interpret topography on the ground. In recent years, lidar technology allows to create more accurate elevation models. However, the problem is this technology is not common all over the world. Also if Lidar data are not provided by government agencies freely, people have to pay lots of money to reach these point clouds. In this article, we will discuss how we can create digital elevation model from less accurate mobile devices’ GPS data. Moreover, we will evaluate these data on the same mobile device which we collected data to reduce cost of this modeling.

  4. VT Lidar Hydro-flattened DEM (0.7 meter) - 2015 - Windham County

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) This metadata applies to the following collection area(s): Windham County 2015 0.7m and Digital Elevation Model (DEM) dataset of the following...

  5. Eureka, California 1/3 Arc-second NAVD 88 Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  6. Myrtle Beach, South Carolina 1/ Arc-second MWH Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  7. Bar Harbor, Maine 1/3 Arc-second MWH Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  8. Santa Monica, California 1/3 Arc-second MHW Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  9. San Diego, California 1/3 Arc-second MHW Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  10. Pago Pago, American Samoa 3 Arc-second MWH Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  11. Central Florida 1/3 arc-second NAVD 88 Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  12. Fort Bragg, California 1/3 Arc-second MHW Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  13. Port Townsend, Washington 1/3 Arc-second MWH Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  14. Tampa Bay 1/3 arc-second NAVD 88 Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  15. Puget Sound 1/3 arc-second NAVD 88 Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  16. Key West, Florida 1/3 Arc-second MHW Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  17. Pensacola, Florida 1/3 arc-second NAVD 88 Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Centers for Environmental Information (NCEI) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These...

  18. Palm Beach, Florida 1/3 Arc-second MWH Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  19. Garibaldi, Oregon 1/3 Arc-second NAVD 88 Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  20. Monterey, California 1/3 Arc-second NAVD 88 Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  1. Central Washington Coast 1/3 arc-second NAVD 88 Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  2. DEM-based research on the landform features of China

    Science.gov (United States)

    Tang, Guoan; Liu, Aili; Li, Fayuan; Zhou, Jieyu

    2006-10-01

    Landforms can be described and identified by parameterization of digital elevation model (DEM). This paper discusses the large-scale geomorphological characteristics of China based on numerical analysis of terrain parameters and develop a methodology for characterizing landforms from DEMs. The methodology is implemented as a two-step process. First, terrain variables are derived from a 1-km DEM in a given statistical unit including local relief, the earth's surface incision, elevation variance coefficient, roughness, mean slope and mean elevation. Second, every parameter regarded as a single-band image is combined into a multi-band image. Then ISODATA unsupervised classification and the Bayesian technique of Maximum Likelihood supervised classification are applied for landform classification. The resulting landforms are evaluated by the means of Stratified Sampling with respect to an existing map and the overall classification accuracy reaches to rather high value. It's shown that the derived parameters carry sufficient physiographic information and can be used for landform classification. Since the classification method integrates manifold terrain indexes, conquers the limitation of the subjective cognition, as well as a low cost, apparently it could represent an applied foreground in the classification of macroscopic relief forms. Furthermore, it exhibits significance in consummating the theory and the methodology of DEMs on digital terrain analysis.

  3. NOAA Office for Coastal Management Coastal Inundation Digital Elevation Model: Tampa (FL) WFO - Manatee, Sarasota, Charlotte, and Lee Counties

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This digital elevation model (DEM) is a part of a series of DEMs produced for the National Oceanic and Atmospheric Administration Office for Coastal Management's Sea...

  4. NOAA Office for Coastal Management Coastal Inundation Digital Elevation Model: Jacksonville (FL) WFO - St. Johns, Flagler and Putnam Counties

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This digital elevation model (DEM) is a part of a series of DEMs produced for the National Oceanic and Atmospheric Administration Office for Coastal Management's Sea...

  5. Digital elevation model generation from satellite interferometric synthetic aperture radar: Chapter 5

    Science.gov (United States)

    Lu, Zhong; Dzurisin, Daniel; Jung, Hyung-Sup; Zhang, Lei; Lee, Wonjin; Lee, Chang-Wook

    2012-01-01

    An accurate digital elevation model (DEM) is a critical data set for characterizing the natural landscape, monitoring natural hazards, and georeferencing satellite imagery. The ideal interferometric synthetic aperture radar (InSAR) configuration for DEM production is a single-pass two-antenna system. Repeat-pass single-antenna satellite InSAR imagery, however, also can be used to produce useful DEMs. DEM generation from InSAR is advantageous in remote areas where the photogrammetric approach to DEM generation is hindered by inclement weather conditions. There are many sources of errors in DEM generation from repeat-pass InSAR imagery, for example, inaccurate determination of the InSAR baseline, atmospheric delay anomalies, and possible surface deformation because of tectonic, volcanic, or other sources during the time interval spanned by the images. This chapter presents practical solutions to identify and remove various artifacts in repeat-pass satellite InSAR images to generate a high-quality DEM.

  6. Destin, Florida 1/3 arc-second NAVD88 Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Centers for Environmental Information is building high-resolution digital elevation models (DEMs) to support individual coastal States as part of the...

  7. Elfin Cove Alaska 1/3 Arc-second MHHW Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) to support individual coastal States as part of the...

  8. Prince William Sound, Alaska 8 Arc-second MHHW Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) to support individual coastal States as part of the...

  9. Uncertainty aspects of the digital elevation model for the Forsmark area

    Energy Technology Data Exchange (ETDEWEB)

    Stroemgren, Maarten; Brydsten, Lars (Umeaa Univ., Umeaa (Sweden))

    2009-10-15

    A digital elevation model (DEM) describes the terrain relief. A proper DEM is an important data source for many of the different site description models conducted in the Forsmark region. Input data for the Forsmark DEM is elevation data for both land and sea areas of different origin and quality. No statistical analysis of the error in the Forsmark DEM is so far carried out. However, the Forsmark DEM is part of the quality assessment of the regolith depth model for the Forsmark area since it represents the upper surface of the regolith depth model. The aim of this project was to calculate the errors in different areas in the Forsmark DEM and present them in terms of general descriptive statistics. Measurements have confirmed the knowledge that the 0.25-metre DEM produced from the laser scanning measurements in the Laxemar-Simpevarp area is of very high quality. The 0.25-metre DEM was used to calculate the errors of the 10 and 50-metre DEMs, and the errors for different sea shoreline sources. These error distributions were placed randomly among points for the same data sources in the Forsmark area and used for correction of the original elevation levels. Using the corrected input data for the 10 and 50-metre DEMs and for the sea shoreline, a new DEM was produced. All other input data remained unchanged. The error for the Forsmark DEM was calculated for areas within the data sources corrected from the 0.25-metre DEM. The 0.25-metre DEM from the Laxemar-Simpevarp area was also used for a calculation of how density of input data points used in interpolation affects quality in a 20-metre DEM. Part of the input data was removed in the sea area, new DEMs were produced and compared to the existing Forsmark DEM within the areas of the removed data, to get a measure of the error in these areas of the DEM. In areas of input data for the sea shoreline, the quality of the Forsmark DEM is high. The errors within the SKB 10-metre DEM are slightly less than within the extension

  10. Uncertainty aspects of the digital elevation model for the Forsmark area

    International Nuclear Information System (INIS)

    Stroemgren, Maarten; Brydsten, Lars

    2009-10-01

    A digital elevation model (DEM) describes the terrain relief. A proper DEM is an important data source for many of the different site description models conducted in the Forsmark region. Input data for the Forsmark DEM is elevation data for both land and sea areas of different origin and quality. No statistical analysis of the error in the Forsmark DEM is so far carried out. However, the Forsmark DEM is part of the quality assessment of the regolith depth model for the Forsmark area since it represents the upper surface of the regolith depth model. The aim of this project was to calculate the errors in different areas in the Forsmark DEM and present them in terms of general descriptive statistics. Measurements have confirmed the knowledge that the 0.25-metre DEM produced from the laser scanning measurements in the Laxemar-Simpevarp area is of very high quality. The 0.25-metre DEM was used to calculate the errors of the 10 and 50-metre DEMs, and the errors for different sea shoreline sources. These error distributions were placed randomly among points for the same data sources in the Forsmark area and used for correction of the original elevation levels. Using the corrected input data for the 10 and 50-metre DEMs and for the sea shoreline, a new DEM was produced. All other input data remained unchanged. The error for the Forsmark DEM was calculated for areas within the data sources corrected from the 0.25-metre DEM. The 0.25-metre DEM from the Laxemar-Simpevarp area was also used for a calculation of how density of input data points used in interpolation affects quality in a 20-metre DEM. Part of the input data was removed in the sea area, new DEMs were produced and compared to the existing Forsmark DEM within the areas of the removed data, to get a measure of the error in these areas of the DEM. In areas of input data for the sea shoreline, the quality of the Forsmark DEM is high. The errors within the SKB 10-metre DEM are slightly less than within the extension

  11. New Orleans, Louisiana 1/3 Arc-second MLLW Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions in the Gulf of Mexico....

  12. New Orleans, Louisiana 1/3 Arc-second MHW Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions in the Gulf of Mexico....

  13. Panama City, Florida 1/3 Arc-second MHW Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions in the Gulf of Mexico....

  14. NOAA Office for Coastal Management Coastal Inundation Digital Elevation Model: Tampa (FL) WFO - Citrus, Hernando, Pasco, Pinellas, and Hillsborough Counties

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This digital elevation model (DEM) is a part of a series of DEMs produced for the National Oceanic and Atmospheric Administration Office for Coastal Management's Sea...

  15. NOAA Office for Coastal Management Coastal Inundation Digital Elevation Model: Melbourne (FL) WFO - Indian River, St. Lucie, and Martin Counties

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This digital elevation model (DEM) is a part of a series of DEMs produced for the National Oceanic and Atmospheric Administration Office for Coastal Management's Sea...

  16. NOAA Office for Coastal Management Coastal Inundation Digital Elevation Model: Los Angeles/Oxnard (CA) WFO - Los Angeles and Ventura Counties

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This digital elevation model (DEM) is a part of a series of DEMs produced for the National Oceanic and Atmospheric Administration Office for Coastal Management's Sea...

  17. MAPPING OF THE RUSSIAN NORTHERN SEAS BOTTOM RELIEF USING DIGITAL ELEVATION MODELS

    Directory of Open Access Journals (Sweden)

    S. M. Koshel

    2014-01-01

    Full Text Available The task of the project is the design of the digital elevation models (DEM of the bottoms of Barents Sea, Pechora Sea, and the White Sea. Accuracy (resolution of DEMs allows for adequate delineation of morphological structures and peculiarities of the sea bottoms and the design of bathymetrical and derivative maps. DEMs of the sea bottom were compiled using data from navigation charts of different scales, where additional isobaths were drawn manually taking into account the classification features of the bottom topography forms. Next procedures were carried out: scanning of these charts, processing of scanned images, isobaths vectorization and creation of attribute tables, vector layers transformation to geographical coordinates as well editing, merging and joining of the map sheets, correction of geometry and attributes. For generation of digital model of bottom topography it is important to choose algorithm which allows for representation all of the sea bottom features expressed by isobaths in most details. The original algorithm based on fast calculation of distances to the two different nearest isobaths was used. Interpretation of isolines as vector linear objects is the main peculiarity of this algorithm. The resulted DEMs were used to design bathymetrical maps of Barents Sea of 1:2 500 000 scale, Pechora Sea of 1:1 000 000 scale, and White Sea of 1:750 000 scale. Different derivative maps were compiled based on DEM of the White Sea.

  18. International Digital Elevation Model Service (IDEMS): A Revived IAG Service

    Science.gov (United States)

    Kelly, K. M.; Hirt, C., , Dr; Kuhn, M.; Barzaghi, R.

    2017-12-01

    A newly developed International Digital Elevation Model Service (IDEMS) is now available under the umbrella of the International Gravity Field Service of the International Association of Geodesy. Hosted and operated by Environmental Systems Research Institute (Esri) (http://www.esri.com/), the new IDEMS website is available at: https://idems.maps.arcgis.com/home/index.html. IDEMS provides a focus for distribution of data and information about various digital elevation models, including spherical-harmonic models of Earth's global topography and lunar and planetary DEM. Related datasets, such as representation of inland water within DEMs, and relevant software which are available in the public domain are also provided. Currently, IDEMS serves as repository of links to providers of global terrain and bathymetry, terrain related Earth models and datasets such as digital elevation data services managed and maintained by Esri (Terrain and TopoBathy), Bedmap2-Ice thickness and subglacial topographic model of Antarctica and Ice, Cloud, and Land Elevation ICESat/GLAS Data, as well as planetary terrain data provided by PDS Geosciences Node at Washington University, St. Louis. These services provide online access to a collection of multi-resolution and multi-source elevation and bathymetry data, including metadata and source information. In addition to IDEMS current holdings of terrestrial and planetary DEMs, some topography related products IDEMS may include in future are: dynamic ocean topography, 3D crustal density models, Earth's dynamic topography, etc. IDEMS may also consider terrain related products such as quality assessments, global terrain corrections, global height anomaly-to-geoid height corrections and other geodesy-relevant studies and products. IDEMS encourages contributions to the site from the geodetic community in any of the product types listed above. Please contact the authors if you would like to contribute or recommend content you think appropriate for

  19. Towards the optimal fusion of high-resolution Digital Elevation Models for detailed urban flood assessment

    Science.gov (United States)

    Leitão, J. P.; de Sousa, L. M.

    2018-06-01

    Newly available, more detailed and accurate elevation data sets, such as Digital Elevation Models (DEMs) generated on the basis of imagery from terrestrial LiDAR (Light Detection and Ranging) systems or Unmanned Aerial Vehicles (UAVs), can be used to improve flood-model input data and consequently increase the accuracy of the flood modelling results. This paper presents the first application of the MBlend merging method and assesses the impact of combining different DEMs on flood modelling results. It was demonstrated that different raster merging methods can have different and substantial impacts on these results. In addition to the influence associated with the method used to merge the original DEMs, the magnitude of the impact also depends on (i) the systematic horizontal and vertical differences of the DEMs, and (ii) the orientation between the DEM boundary and the terrain slope. The greater water depth and flow velocity differences between the flood modelling results obtained using the reference DEM and the merged DEMs ranged from -9.845 to 0.002 m, and from 0.003 to 0.024 m s-1 respectively; these differences can have a significant impact on flood hazard estimates. In most of the cases investigated in this study, the differences from the reference DEM results were smaller for the MBlend method than for the results of the two conventional methods. This study highlighted the importance of DEM merging when conducting flood modelling and provided hints on the best DEM merging methods to use.

  20. San Francisco Bay, California 1/3 Arc-second MHW Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  1. Palm Beach, Florida 1/3 Arc-second NAVD 88 Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  2. Key West, Florida 1/3 Arc-second NAVD 88 Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  3. Orange County, California 1/3 arc-second NAVD 88 Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Centers for Environmental Information (NCEI) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These...

  4. Pago Pago, American Samoa 1/3 Arc-second MWH Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  5. Astoria, Oregon 1/3 arc-second MHW Coastal Digital Elevation Model Vers.3

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Centers for Environmental Information (NCEI) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These...

  6. Port Townsend, Washington 1/3 Arc-second NAVD 88 Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  7. Santa Monica, California 1/3 Arc-second NAVD 88 Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  8. Mayaguez, Puerto Rico 2006 1/3 Arc-second MWH Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  9. Fort Bragg, California 1/3 Arc-second NAVD 88 Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  10. Myrtle Beach, South Carolina 1/3 Arc-second MWH Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  11. South Padre Island, Texas 1/3 Arc-second MHW Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  12. Crescent City, California 1/3 Arc-second NAVD 88 Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  13. San Juan, Puerto Rico 1/9 arc-second PRVD Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Centers for Environmental Information (NCEI) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These...

  14. San Diego, California 1/3 Arc-second NAVD 88 Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  15. St. Thomas and St. John, U.S. Virgin Islands Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  16. Mayaguez, Puerto Rico 2007 1/3 Arc-second MWH Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  17. Morehead City, North Carolina 1/3 Arc-second MHW Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  18. Port San Luis, California 1/3 Arc-second MWH Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  19. Bar Harbor, Maine 1/3 Arc-second NAVD 88 Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  20. DEM Development from Ground-Based LiDAR Data: A Method to Remove Non-Surface Objects

    Directory of Open Access Journals (Sweden)

    Maneesh Sharma

    2010-11-01

    Full Text Available Topography and land cover characteristics can have significant effects on infiltration, runoff, and erosion processes on watersheds. The ability to model the timing and routing of surface water and erosion is affected by the resolution of the digital elevation model (DEM. High resolution ground-based Light Detecting and Ranging (LiDAR technology can be used to collect detailed topographic and land cover characteristic data. In this study, a method was developed to remove vegetation from ground-based LiDAR data to create high resolution DEMs. Research was conducted on intensively studied rainfall–runoff plots on the USDA-ARS Walnut Gulch Experimental Watershed in Southeast Arizona. LiDAR data were used to generate 1 cm resolution digital surface models (DSM for 5 plots. DSMs created directly from LiDAR data contain non-surface objects such as vegetation cover. A vegetation removal method was developed which used a slope threshold and a focal mean filter method to remove vegetation and create bare earth DEMs. The method was validated on a synthetic plot, where rocks and vegetation were added incrementally. Results of the validation showed a vertical error of ±7.5 mm in the final DEM.

  1. Prince William Sound, Alaska 8/3 Arc-second MHHW Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) to support individual coastal States as part of the...

  2. Perryville and Ivanof Bay, Alaska 1/3 arc-second Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) to support individual coastal States as part of the...

  3. A comparative appraisal of hydrological behavior of SRTM DEM at catchment level

    Science.gov (United States)

    Sharma, Arabinda; Tiwari, K. N.

    2014-11-01

    The Shuttle Radar Topography Mission (SRTM) data has emerged as a global elevation data in the past one decade because of its free availability, homogeneity and consistent accuracy compared to other global elevation dataset. The present study explores the consistency in hydrological behavior of the SRTM digital elevation model (DEM) with reference to easily available regional 20 m contour interpolated DEM (TOPO DEM). Analysis ranging from simple vertical accuracy assessment to hydrological simulation of the studied Maithon catchment, using empirical USLE model and semidistributed, physical SWAT model, were carried out. Moreover, terrain analysis involving hydrological indices was performed for comparative assessment of the SRTM DEM with respect to TOPO DEM. Results reveal that the vertical accuracy of SRTM DEM (±27.58 m) in the region is less than the specified standard (±16 m). Statistical analysis of hydrological indices such as topographic wetness index (TWI), stream power index (SPI), slope length factor (SLF) and geometry number (GN) shows a significant differences in hydrological properties of the two studied DEMs. Estimation of soil erosion potentials of the catchment and conservation priorities of microwatersheds of the catchment using SRTM DEM and TOPO DEM produce considerably different results. Prediction of soil erosion potential using SRTM DEM is far higher than that obtained using TOPO DEM. Similarly, conservation priorities determined using the two DEMs are found to be agreed for only 34% of microwatersheds of the catchment. ArcSWAT simulation reveals that runoff predictions are less sensitive to selection of the two DEMs as compared to sediment yield prediction. The results obtained in the present study are vital to hydrological analysis as it helps understanding the hydrological behavior of the DEM without being influenced by the model structural as well as parameter uncertainty. It also reemphasized that SRTM DEM can be a valuable dataset for

  4. NOAA Office for Coastal Management Coastal Inundation Digital Elevation Model: San Francisco Bay/Monterey (CA) WFO - Santa Cruz and Monterey Counties

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This digital elevation model (DEM) is a part of a series of DEMs produced for the National Oceanic and Atmospheric Administration Office for Coastal Management's Sea...

  5. NOAA Office for Coastal Management Coastal Inundation Digital Elevation Model: Seattle (WA) WFO - Clallam, Jefferson, Kitsap, Mason, Pierce, and Thurston Counties

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This digital elevation model (DEM) is a part of a series of DEMs produced for the National Oceanic and Atmospheric Administration Office for Coastal Management's Sea...

  6. DEM Resolution Impact on the Estimation of the Physical Characteristics of Watersheds by Using SWAT

    Directory of Open Access Journals (Sweden)

    Waranyu Buakhao

    2016-01-01

    Full Text Available A digital elevation model (DEM is an important spatial input for automatic extraction of topographic parameters for the soil and water assessment tool (SWAT. The objective of this study was to investigate the impact of DEM resolution (from 5 to 90 m on the delineation process of a SWAT model with two types of watershed characteristics (flat area and mountain area and three sizes of watershed area (about 20,000, 200,000, and 1,500,000 hectares. The results showed that the total lengths of the streamline, main channel slope, watershed area, and area slope were significantly different when using the DEM datasets to delineate. Delineation using the SRTM DEM (90 m, ASTER DEM (30 m, and LDD DEM (5 m for all watershed characteristics showed that the watershed sizes and shapes obtained were only slightly different, whereas the area slopes obtained were significantly different. The total lengths of the generated streams increased when the resolution of the DEM used was higher. The stream slopes obtained using the small area sizes were insignificant, whereas the slopes obtained using the large area sizes were significantly different. This suggests that water resource model users should use the ASTER DEM as opposed to a finer resolution DEM for model input to save time for the model calibration and validation.

  7. Assessing the quality of digital elevation models obtained from mini unmanned aerial vehicles for overland flow modelling in urban areas

    Science.gov (United States)

    Leitão, João P.; Moy de Vitry, Matthew; Scheidegger, Andreas; Rieckermann, Jörg

    2016-04-01

    Precise and detailed digital elevation models (DEMs) are essential to accurately predict overland flow in urban areas. Unfortunately, traditional sources of DEM, such as airplane light detection and ranging (lidar) DEMs and point and contour maps, remain a bottleneck for detailed and reliable overland flow models, because the resulting DEMs are too coarse to provide DEMs of sufficient detail to inform urban overland flows. Interestingly, technological developments of unmanned aerial vehicles (UAVs) suggest that they have matured enough to be a competitive alternative to satellites or airplanes. However, this has not been tested so far. In this study we therefore evaluated whether DEMs generated from UAV imagery are suitable for urban drainage overland flow modelling. Specifically, 14 UAV flights were conducted to assess the influence of four different flight parameters on the quality of generated DEMs: (i) flight altitude, (ii) image overlapping, (iii) camera pitch, and (iv) weather conditions. In addition, we compared the best-quality UAV DEM to a conventional lidar-based DEM. To evaluate both the quality of the UAV DEMs and the comparison to lidar-based DEMs, we performed regression analysis on several qualitative and quantitative metrics, such as elevation accuracy, quality of object representation (e.g. buildings, walls and trees) in the DEM, which were specifically tailored to assess overland flow modelling performance, using the flight parameters as explanatory variables. Our results suggested that, first, as expected, flight altitude influenced the DEM quality most, where lower flights produce better DEMs; in a similar fashion, overcast weather conditions are preferable, but weather conditions and other factors influence DEM quality much less. Second, we found that for urban overland flow modelling, the UAV DEMs performed competitively in comparison to a traditional lidar-based DEM. An important advantage of using UAVs to generate DEMs in urban areas is

  8. Panama City, Florida 1/3 Arc-second NAVD 88 Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions in the Gulf of Mexico....

  9. RADAR INTERFEROMETRY APPLICATION FOR DIGITAL ELEVATION MODEL IN MOUNT BROMO, INDONESIA

    Directory of Open Access Journals (Sweden)

    Noorlaila Hayati

    2015-06-01

    Full Text Available This paper reviewed the result and processing of digital elevation model (DEM using L-Band ALOS PALSAR data and two-pass radar interferometry method in Bromo Mountain region. Synthetic Aperture Radar is an advanced technology that has been used to monitor deformation, land cover change, image detection and especially topographic information such as DEM.  We used two scenes of SAR imageries to generate DEM extraction which assumed there is no deformation effect between two acquisitions. We could derive topographic information using phase difference by combining two single looks complex (SLC images called focusing process. The next steps were doing interferogram generation, phase unwrapping and geocoding. DEM-InSAR was compared to SRTM 90m that there were significant elevation differences between two DEMs such as smoothing surface and detail topographic. Particularly for hilly areas, DEM-InSAR showed better quality than SRTM 90 m where the elevation could have 25.94 m maximum gap. Although the processing involved adaptive filter to amplify the phase signal, we concluded that InSAR DEM result still had error noise because of signal wavelength, incidence angle, SAR image relationship, and only using ascending orbit direction.

  10. Combined Usage of TanDEM-X and CryoSat-2 for Generating a High Resolution Digital Elevation Model of Fast Moving Ice Stream and Its Application in Grounding Line Estimation

    Directory of Open Access Journals (Sweden)

    Seung Hee Kim

    2017-02-01

    Full Text Available Definite surface topography of ice provides fundamental information for most glaciologists to study climate change. However, the topography at the marginal region of ice sheets exhibits noticeable dynamical changes from fast flow velocity and large thinning rates; thus, it is difficult to determine instantaneous topography. In this study, the surface topography of the marginal region of Thwaites Glacier in the Amundsen Sector of West Antarctica, where ice melting and thinning are prevailing, is extracted using TanDEM-X interferometry in combination with data from the near-coincident CryoSat-2 radar altimeter. The absolute height offset, which has been a persistent problem in applying the interferometry technique for generating DEMs, is determined by linear least-squares fitting between the uncorrected TanDEM-X heights and reliable reference heights from CryoSat-2. The reliable heights are rigorously selected at locations of high normalized cross-correlation and low RMS heights between segments of data points. The generated digital elevation model with the resolved absolute height offset is assessed with airborne laser altimeter data from the Operation IceBridge that were acquired five months after TanDEM-X and show high correlation with biases of 3.19 m and −4.31 m at the grounding zone and over the ice sheet surface, respectively. For practical application of the generated DEM, grounding line estimation assuming hydrostatic equilibrium was carried out, and the feasibility was seen through comparison with the previous grounding line. Finally, it is expected that the combination of interferometry and altimetery with similar datasets can be applied at regions even with a lack of ground control points.

  11. South Padre Island, Texas 1/3 Arc-second NAVD 88 Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  12. Port San Luis, California 1/3 Arc-second NAVD 88 Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  13. San Francisco Bay, California 1/3 Arc-second NAVD 88 Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  14. Morehead City, North Carolina 1/3 Arc-second NAVD 88 Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — NOAA's National Geophysical Data Center (NGDC) is building high-resolution digital elevation models (DEMs) for select U.S. coastal regions. These integrated...

  15. NOAA Office for Coastal Management Coastal Inundation Digital Elevation Model: Los Angeles/Oxnard (CA) WFO - Santa Barbara and San Luis Obispo Counties

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This digital elevation model (DEM) is a part of a series of DEMs produced for the National Oceanic and Atmospheric Administration Office for Coastal Management's Sea...

  16. NOAA Office for Coastal Management Coastal Inundation Digital Elevation Model: Seattle (WA) WFO - Whatcom, San Juan, Skagit, Island, Snohomish, and King Counties

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This digital elevation model (DEM) is a part of a series of DEMs produced for the National Oceanic and Atmospheric Administration Office for Coastal Management's Sea...

  17. NOAA Office for Coastal Management Coastal Inundation Digital Elevation Model: Miami (FL) WFO - Palm Beach, Broward, Miami-Dade, and Monroe (Keys) Counties

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This digital elevation model (DEM) is a part of a series of DEMs produced for the National Oceanic and Atmospheric Administration Office for Coastal Management's Sea...

  18. Assessment of the most recent satellite based digital elevation models of Egypt

    Science.gov (United States)

    Rabah, Mostafa; El-Hattab, Ahmed; Abdallah, Mohamed

    2017-12-01

    Digital Elevation Model (DEM) is crucial to a wide range of surveying and civil engineering applications worldwide. Some of the DEMs such as ASTER, SRTM1 and SRTM3 are freely available open source products. In order to evaluate the three DEMs, the contribution of EGM96 are removed and all DEMs heights are becoming ellipsoidal height. This step was done to avoid the errors occurred due to EGM96. 601 points of observed ellipsoidal heights compared with the three DEMs, the results show that the SRTM1 is the most accurate one, that produces mean height difference and standard deviations equal 2.89 and ±8.65 m respectively. In order to increase the accuracy of SRTM1 in EGYPT, a precise Global Geopotential Model (GGM) is needed to convert the SRTM1 ellipsoidal height to orthometric height, so that, we quantify the precision of most-recent released GGM (five models). The results show that, the GECO model is the best fit global models over Egypt, which produces a standard deviation of geoid undulation differences equals ±0.42 m over observed 17 HARN GPS/leveling stations. To confirm an enhanced DEM in EGYPT, the two orthometric height models (SRTM1 ellipsoidal height + EGM96) and (SRTM1 ellipsoidal height + GECO) are assessment with 17 GPS/leveling stations and 112 orthometric height stations, the results show that the estimated height differences between the SRTM1 before improvements and the enhanced model are at rate of 0.44 m and 0.06 m respectively.

  19. Comparison of elevation derived from insar data with dem from topography map in Son Dong, Bac Giang, Viet Nam

    Science.gov (United States)

    Nguyen, Duy

    2012-07-01

    Digital Elevation Models (DEMs) are used in many applications in the context of earth sciences such as in topographic mapping, environmental modeling, rainfall-runoff studies, landslide hazard zonation, seismic source modeling, etc. During the last years multitude of scientific applications of Synthetic Aperture Radar Interferometry (InSAR) techniques have evolved. It has been shown that InSAR is an established technique of generating high quality DEMs from space borne and airborne data, and that it has advantages over other methods for the generation of large area DEM. However, the processing of InSAR data is still a challenging task. This paper describes InSAR operational steps and processing chain for DEM generation from Single Look Complex (SLC) SAR data and compare a satellite SAR estimate of surface elevation with a digital elevation model (DEM) from Topography map. The operational steps are performed in three major stages: Data Search, Data Processing, and product Validation. The Data processing stage is further divided into five steps of Data Pre-Processing, Co-registration, Interferogram generation, Phase unwrapping, and Geocoding. The Data processing steps have been tested with ERS 1/2 data using Delft Object-oriented Interferometric (DORIS) InSAR processing software. Results of the outcome of the application of the described processing steps to real data set are presented.

  20. 2012 Oregon Department of Geology and Mineral Industries (DOGAMI) Lidar DEM: Rogue River Oregon

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The dataset encompasses portions of Coos, Curry, Douglas, Jackson, and Josephine Counties.The bare earth digital elevation model (DEM) represents the earth's surface...

  1. VT Lidar Hydro-flattened DEM (0.7 meter) - 2014 - Chittenden, Lamoille, Orleans, & Washington Counties

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) This metadata applies to the following collection area(s): Eastern VT 2014 0.7m and Digital Elevation Model (DEM) dataset of the following...

  2. Identification and delineation of areas flood hazard using high accuracy of DEM data

    Science.gov (United States)

    Riadi, B.; Barus, B.; Widiatmaka; Yanuar, M. J. P.; Pramudya, B.

    2018-05-01

    Flood incidents that often occur in Karawang regency need to be mitigated. These expectations exist on technologies that can predict, anticipate and reduce disaster risks. Flood modeling techniques using Digital Elevation Model (DEM) data can be applied in mitigation activities. High accuracy DEM data used in modeling, will result in better flooding flood models. The result of high accuracy DEM data processing will yield information about surface morphology which can be used to identify indication of flood hazard area. The purpose of this study was to identify and describe flood hazard areas by identifying wetland areas using DEM data and Landsat-8 images. TerraSAR-X high-resolution data is used to detect wetlands from landscapes, while land cover is identified by Landsat image data. The Topography Wetness Index (TWI) method is used to detect and identify wetland areas with basic DEM data, while for land cover analysis using Tasseled Cap Transformation (TCT) method. The result of TWI modeling yields information about potential land of flood. Overlay TWI map with land cover map that produces information that in Karawang regency the most vulnerable areas occur flooding in rice fields. The spatial accuracy of the flood hazard area in this study was 87%.

  3. Impact of mesh and DEM resolutions in SEM simulation of 3D seismic response

    NARCIS (Netherlands)

    Khan, Saad; van der Meijde, M.; van der Werff, H.M.A.; Shafique, Muhammad

    2017-01-01

    This study shows that the resolution of a digital elevation model (DEM) and model mesh strongly influences 3D simulations of seismic response. Topographic heterogeneity scatters seismic waves and causes variation in seismic response (am-plification and deamplification of seismic amplitudes) at the

  4. An evaluation of onshore digital elevation models for tsunami inundation modelling

    Science.gov (United States)

    Griffin, J.; Latief, H.; Kongko, W.; Harig, S.; Horspool, N.; Hanung, R.; Rojali, A.; Maher, N.; Fountain, L.; Fuchs, A.; Hossen, J.; Upi, S.; Dewanto, S. E.; Cummins, P. R.

    2012-12-01

    Tsunami inundation models provide fundamental information about coastal areas that may be inundated in the event of a tsunami along with additional parameters such as flow depth and velocity. This can inform disaster management activities including evacuation planning, impact and risk assessment and coastal engineering. A fundamental input to tsunami inundation models is adigital elevation model (DEM). Onshore DEMs vary widely in resolution, accuracy, availability and cost. A proper assessment of how the accuracy and resolution of DEMs translates into uncertainties in modelled inundation is needed to ensure results are appropriately interpreted and used. This assessment can in turn informdata acquisition strategies depending on the purpose of the inundation model. For example, lower accuracy elevation data may give inundation results that are sufficiently accurate to plan a community's evacuation route but not sufficient to inform engineering of a vertical evacuation shelters. A sensitivity study is undertaken to assess the utility of different available onshore digital elevation models for tsunami inundation modelling. We compare airborne interferometric synthetic aperture radar (IFSAR), ASTER and SRTM against high resolution (historical tsunami run-up data. Large vertical errors (> 10 m) and poor resolution of the coastline in the ASTER and SRTM elevation models cause modelled inundation to be much less compared with models using better data and with observations. Therefore we recommend that ASTER and SRTM should not be used for modelling tsunami inundation in order to determine tsunami extent or any other measure of onshore tsunami hazard. We suggest that for certain disaster management applications where the important factor is the extent of inundation, such as evacuation planning, airborne IFSAR provides a good compromise between cost and accuracy; however the representation of flow parameters such as depth and velocity is not sufficient to inform detailed

  5. Comparison Between Topographic Expression of RADARSAT and DEM in Simpang Pulai to Pos Selim, Malaysia

    Directory of Open Access Journals (Sweden)

    M.F.Ramli

    2010-01-01

    Full Text Available Radar and digital elevation model had been utilised in many structural studies. The main objective of this study is to compare the RADARSAT and digital elevation model for lineament interpretation which probably represent the main joints or faults along the Simpang Pulai to Pos Selim highway, Malaysia. These joints and faults may influence the instability along the highway. Manual comparison in terms of topographical aspect was undertaken between RADARSAT with 25 m spatial resolution and digital elevation model derived from 20 m contour interval of the topographical map. The previously interpreted lineaments of more than 2 km in the study area was draped over the RADARSAT and digital elevation model to compared whether the lineament concurred with the topographical representation. The interpreted lineaments were derived from Landsat TM of 1990 and 2002, where the DEM had been utilised in the negative lineament determination. It is concluded that the application RADARSAT is not very useful in terms of topographical expression in the structural geological interpretation for the study area compared to DEM derived from contour data. Further work is suggested before any conclusion can be confidently derived.

  6. Uplift mechanism for a shallow-buried structure in liquefiable sand subjected to seismic load: centrifuge model test and DEM modeling

    Science.gov (United States)

    Zhou, Jian; Wang, Zihan; Chen, Xiaoliang; Zhang, Jiao

    2014-06-01

    Based on a centrifuge model test and distinct element method (DEM), this study provides new insights into the uplift response of a shallow-buried structure and the liquefaction mechanism for saturated sand around the structure under seismic action. In the centrifuge test, a high-speed microscopic camera was installed in the structure model, by which the movements of particles around the structure were monitored. Then, a two-dimensional digital image processing technology was used to analyze the microstructure of saturated sand during the shaking event. Herein, a numerical simulation of the centrifuge experiment was conducted using a two-phase (solid and fluid) fully coupled distinct element code. This code incorporates a particle-fluid coupling model by means of a "fixed coarse-grid" fluid scheme in PFC3D (Particle Flow Code in Three Dimensions), with the modeling parameters partially calibrated based on earlier studies. The physical and numerical models both indicate the uplifts of the shallow-buried structure and the sharp rise in excess pore pressure. The corresponding micro-scale responses and explanations are provided. Overall, the uplift response of an underground structure and the occurrence of liquefaction in saturated sand are predicted successfully by DEM modeling. However, the dynamic responses during the shaking cannot be modeled accurately due to the restricted computer power.

  7. Research on a dem Coregistration Method Based on the SAR Imaging Geometry

    Science.gov (United States)

    Niu, Y.; Zhao, C.; Zhang, J.; Wang, L.; Li, B.; Fan, L.

    2018-04-01

    Due to the systematic error, especially the horizontal deviation that exists in the multi-source, multi-temporal DEMs (Digital Elevation Models), a method for high precision coregistration is needed. This paper presents a new fast DEM coregistration method based on a given SAR (Synthetic Aperture Radar) imaging geometry to overcome the divergence and time-consuming problem of the conventional DEM coregistration method. First, intensity images are simulated for two DEMs under the given SAR imaging geometry. 2D (Two-dimensional) offsets are estimated in the frequency domain using the intensity cross-correlation operation in the FFT (Fast Fourier Transform) tool, which can greatly accelerate the calculation process. Next, the transformation function between two DEMs is achieved via the robust least-square fitting of 2D polynomial operation. Accordingly, two DEMs can be precisely coregistered. Last, two DEMs, i.e., one high-resolution LiDAR (Light Detection and Ranging) DEM and one low-resolution SRTM (Shutter Radar Topography Mission) DEM, covering the Yangjiao landslide region of Chongqing are taken as an example to test the new method. The results indicate that, in most cases, this new method can achieve not only a result as much as 80 times faster than the minimum elevation difference (Least Z-difference, LZD) DEM registration method, but also more accurate and more reliable results.

  8. Hydrography-driven coarsening of grid digital elevation models

    Science.gov (United States)

    Moretti, G.; Orlandini, S.

    2017-12-01

    A new grid coarsening strategy, denoted as hydrography-driven (HD) coarsening, is developed in the present study. The HD coarsening strategy is designed to retain the essential hydrographic features of surface flow paths observed in high-resolution digital elevation models (DEMs): (1) depressions are filled in the considered high-resolution DEM, (2) the obtained topographic data are used to extract a reference grid network composed of all surface flow paths, (3) the Horton order is assigned to each link of the reference grid network, and (4) within each coarse grid cell, the elevation of the point lying along the highest-order path of the reference grid network and displaying the minimum distance to the cell center is assigned to this coarse grid cell center. The capabilities of the HD coarsening strategy to provide consistent surface flow paths with respect to those observed in high-resolution DEMs are evaluated over a synthetic valley and two real drainage basins located in the Italian Alps and in the Italian Apennines. The HD coarsening is found to yield significantly more accurate surface flow path profiles than the standard nearest neighbor (NN) coarsening. In addition, the proposed strategy is found to reduce drastically the impact of depression-filling procedures in coarsened topographic data. The HD coarsening strategy is therefore advocated for all those cases in which the relief of the extracted drainage network is an important hydrographic feature. The figure below reports DEMs of a synthetic valley and extracted surface flow paths. (a) 10-m grid DEM displaying no depressions and extracted surface flow path (gray line). (b) 1-km grid DEM obtained from NN coarsening. (c) 1-km grid DEM obtained from NN coarsening plus depression-filling and extracted surface flow path (light blue line). (d) 1-km grid DEM obtained from HD coarsening and extracted surface flow path (magenta line).

  9. How processing digital elevation models can affect simulated water budgets

    Science.gov (United States)

    Kuniansky, E.L.; Lowery, M.A.; Campbell, B.G.

    2009-01-01

    For regional models, the shallow water table surface is often used as a source/sink boundary condition, as model grid scale precludes simulation of the water table aquifer. This approach is appropriate when the water table surface is relatively stationary. Since water table surface maps are not readily available, the elevation of the water table used in model cells is estimated via a two-step process. First, a regression equation is developed using existing land and water table elevations from wells in the area. This equation is then used to predict the water table surface for each model cell using land surface elevation available from digital elevation models (DEM). Two methods of processing DEM for estimating the land surface for each cell are commonly used (value nearest the cell centroid or mean value in the cell). This article demonstrates how these two methods of DEM processing can affect the simulated water budget. For the example presented, approximately 20% more total flow through the aquifer system is simulated if the centroid value rather than the mean value is used. This is due to the one-third greater average ground water gradients associated with the centroid value than the mean value. The results will vary depending on the particular model area topography and cell size. The use of the mean DEM value in each model cell will result in a more conservative water budget and is more appropriate because the model cell water table value should be representative of the entire cell area, not the centroid of the model cell.

  10. Cross Validation on the Equality of Uav-Based and Contour-Based Dems

    Science.gov (United States)

    Ma, R.; Xu, Z.; Wu, L.; Liu, S.

    2018-04-01

    Unmanned Aerial Vehicles (UAV) have been widely used for Digital Elevation Model (DEM) generation in geographic applications. This paper proposes a novel framework of generating DEM from UAV images. It starts with the generation of the point clouds by image matching, where the flight control data are used as reference for searching for the corresponding images, leading to a significant time saving. Besides, a set of ground control points (GCP) obtained from field surveying are used to transform the point clouds to the user's coordinate system. Following that, we use a multi-feature based supervised classification method for discriminating non-ground points from ground ones. In the end, we generate DEM by constructing triangular irregular networks and rasterization. The experiments are conducted in the east of Jilin province in China, which has been suffered from soil erosion for several years. The quality of UAV based DEM (UAV-DEM) is compared with that generated from contour interpolation (Contour-DEM). The comparison shows a higher resolution, as well as higher accuracy of UAV-DEMs, which contains more geographic information. In addition, the RMSE errors of the UAV-DEMs generated from point clouds with and without GCPs are ±0.5 m and ±20 m, respectively.

  11. Dem Generation from Close-Range Photogrammetry Using Extended Python Photogrammetry Toolbox

    Science.gov (United States)

    Belmonte, A. A.; Biong, M. M. P.; Macatulad, E. G.

    2017-10-01

    Digital elevation models (DEMs) are widely used raster data for different applications concerning terrain, such as for flood modelling, viewshed analysis, mining, land development, engineering design projects, to name a few. DEMs can be obtained through various methods, including topographic survey, LiDAR or photogrammetry, and internet sources. Terrestrial close-range photogrammetry is one of the alternative methods to produce DEMs through the processing of images using photogrammetry software. There are already powerful photogrammetry software that are commercially-available and can produce high-accuracy DEMs. However, this entails corresponding cost. Although, some of these software have free or demo trials, these trials have limits in their usable features and usage time. One alternative is the use of free and open-source software (FOSS), such as the Python Photogrammetry Toolbox (PPT), which provides an interface for performing photogrammetric processes implemented through python script. For relatively small areas such as in mining or construction excavation, a relatively inexpensive, fast and accurate method would be advantageous. In this study, PPT was used to generate 3D point cloud data from images of an open pit excavation. The PPT was extended to add an algorithm converting the generated point cloud data into a usable DEM.

  12. Novel application of DEM to modelling comminution processes

    International Nuclear Information System (INIS)

    Delaney, Gary W; Cleary, Paul W; Sinnott, Matt D; Morrison, Rob D

    2010-01-01

    Comminution processes in which grains are broken down into smaller and smaller sizes represent a critical component in many industries including mineral processing, cement production, food processing and pharmaceuticals. We present a novel DEM implementation capable of realistically modelling such comminution processes. This extends on a previous implementation of DEM particle breakage that utilized spherical particles. Our new extension uses super-quadric particles, where daughter fragments with realistic size and shape distributions are packed inside a bounding parent super-quadric. We demonstrate the flexibility of our approach in different particle breakage scenarios and examine the effect of the chosen minimum resolved particle size. This incorporation of the effect of particle shape in the breakage process allows for more realistic DEM simulations to be performed, that can provide additional fundamental insights into comminution processes and into the behaviour of individual pieces of industrial machinery.

  13. Modelling above Ground Biomass in Tanzanian Miombo Woodlands Using TanDEM-X WorldDEM and Field Data

    Directory of Open Access Journals (Sweden)

    Stefano Puliti

    2017-09-01

    Full Text Available The use of Interferometric Synthetic Aperture Radar (InSAR data has great potential for monitoring large scale forest above ground biomass (AGB in the tropics due to the increased ability to retrieve 3D information even under cloud cover. To date; results in tropical forests have been inconsistent and further knowledge on the accuracy of models linking AGB and InSAR height data is crucial for the development of large scale forest monitoring programs. This study provides an example of the use of TanDEM-X WorldDEM data to model AGB in Tanzanian woodlands. The primary objective was to assess the accuracy of a model linking AGB with InSAR height from WorldDEM after the subtraction of ground heights. The secondary objective was to assess the possibility of obtaining InSAR height for field plots when the terrain heights were derived from global navigation satellite systems (GNSS; i.e., as an alternative to using airborne laser scanning (ALS. The results revealed that the AGB model using InSAR height had a predictive accuracy of R M S E = 24.1 t·ha−1; or 38.8% of the mean AGB when terrain heights were derived from ALS. The results were similar when using terrain heights from GNSS. The accuracy of the predicted AGB was improved when compared to a previous study using TanDEM-X for a sub-area of the area of interest and was of similar magnitude to what was achieved in the same sub-area using ALS data. Overall; this study sheds new light on the opportunities that arise from the use of InSAR data for large scale AGB modelling in tropical woodlands.

  14. 2012 NOAA Office for Coastal Management Coastal Inundation Digital Elevation Model: Mobile/Tallahassee (AL/FL) WFO - Wakulla (portion), Franklin (portion), Jefferson, Taylor, Dixie, and Levy Counties

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This digital elevation model (DEM) is a part of a series of DEMs produced for the National Oceanic and Atmospheric Administration Office for Coastal Management's Sea...

  15. EVALUATING THE ACCURACY OF DEM GENERATION ALGORITHMS FROM UAV IMAGERY

    Directory of Open Access Journals (Sweden)

    J. J. Ruiz

    2013-08-01

    Full Text Available In this work we evaluated how the use of different positioning systems affects the accuracy of Digital Elevation Models (DEMs generated from aerial imagery obtained with Unmanned Aerial Vehicles (UAVs. In this domain, state-of-the-art DEM generation algorithms suffer from typical errors obtained by GPS/INS devices in the position measurements associated with each picture obtained. The deviations from these measurements to real world positions are about meters. The experiments have been carried out using a small quadrotor in the indoor testbed at the Center for Advanced Aerospace Technologies (CATEC. This testbed houses a system that is able to track small markers mounted on the UAV and along the scenario with millimeter precision. This provides very precise position measurements, to which we can add random noise to simulate errors in different GPS receivers. The results showed that final DEM accuracy clearly depends on the positioning information.

  16. ANALYSIS AND VALIDATION OF GRID DEM GENERATION BASED ON GAUSSIAN MARKOV RANDOM FIELD

    Directory of Open Access Journals (Sweden)

    F. J. Aguilar

    2016-06-01

    Full Text Available Digital Elevation Models (DEMs are considered as one of the most relevant geospatial data to carry out land-cover and land-use classification. This work deals with the application of a mathematical framework based on a Gaussian Markov Random Field (GMRF to interpolate grid DEMs from scattered elevation data. The performance of the GMRF interpolation model was tested on a set of LiDAR data (0.87 points/m2 provided by the Spanish Government (PNOA Programme over a complex working area mainly covered by greenhouses in Almería, Spain. The original LiDAR data was decimated by randomly removing different fractions of the original points (from 10% to up to 99% of points removed. In every case, the remaining points (scattered observed points were used to obtain a 1 m grid spacing GMRF-interpolated Digital Surface Model (DSM whose accuracy was assessed by means of the set of previously extracted checkpoints. The GMRF accuracy results were compared with those provided by the widely known Triangulation with Linear Interpolation (TLI. Finally, the GMRF method was applied to a real-world case consisting of filling the LiDAR-derived DSM gaps after manually filtering out non-ground points to obtain a Digital Terrain Model (DTM. Regarding accuracy, both GMRF and TLI produced visually pleasing and similar results in terms of vertical accuracy. As an added bonus, the GMRF mathematical framework makes possible to both retrieve the estimated uncertainty for every interpolated elevation point (the DEM uncertainty and include break lines or terrain discontinuities between adjacent cells to produce higher quality DTMs.

  17. 3D Fractal reconstruction of terrain profile data based on digital elevation model

    International Nuclear Information System (INIS)

    Huang, Y.M.; Chen, C.-J.

    2009-01-01

    Digital Elevation Model (DEM) often makes it difficult for terrain reconstruction and data storage due to the failure in acquisition of details with higher resolution. If original terrain of DEM can be simulated, resulting in geographical details can be represented precisely while reducing the data size, then an effective reconstruction scheme is essential. This paper adopts two sets of real-world 3D terrain profile data to proceed data reducing, i.e. data sampling randomly, then reconstruct them through 3D fractal reconstruction. Meanwhile, the quantitative and qualitative difference generated from different reduction rates were evaluated statistically. The research results show that, if 3D fractal interpolation method is applied to DEM reconstruction, the higher reduction rate can be obtained for DEM of larger data size with respect to that of smaller data size under the assumption that the entire terrain structure is still maintained.

  18. Mapping boreal forest biomass from a SRTM and TanDEM-X based on canopy height model and Landsat spectral indices

    Science.gov (United States)

    Sadeghi, Yaser; St-Onge, Benoît; Leblon, Brigitte; Prieur, Jean-François; Simard, Marc

    2018-06-01

    We propose a method for mapping above-ground biomass (AGB) (Mg ha-1) in boreal forests based predominantly on Landsat 8 images and on canopy height models (CHM) generated using interferometric synthetic aperture radar (InSAR) from the Shuttle Radar Topographic Mission (SRTM) and the TanDEM-X mission. The original SRTM digital elevation model (DEM) was corrected by modelling the respective effects of landform and land cover on its errors and then subtracted from a TanDEM-X DSM to produce a SAR CHM. Among all the landform factors, the terrain curvature had the largest effect on SRTM elevation errors, with a r2 of 0.29. The NDSI was the best predictor of the residual SRTM land cover error, with a r2 of 0.30. The final SAR CHM had a RMSE of 2.45 m, with a bias of 0.07 m, compared to a lidar-based CHM. An AGB prediction model was developed based on a combination of the SAR CHM, TanDEM-X coherence, Landsat 8 NDVI, and other vegetation indices of RVI, DVI, GRVI, EVI, LAI, GNDVI, SAVI, GVI, Brightness, Greenness, and Wetness. The best results were obtained using a Random forest regression algorithm, at the stand level, yielding a RMSE of 26 Mg ha-1 (34% of average biomass), with a r2 of 0.62. This method has the potential of creating spatially continuous biomass maps over entire biomes using only spaceborne sensors and requiring only low-intensity calibration.

  19. A coupled DEM-CFD method for impulse wave modelling

    Science.gov (United States)

    Zhao, Tao; Utili, Stefano; Crosta, GiovanBattista

    2015-04-01

    Rockslides can be characterized by a rapid evolution, up to a possible transition into a rock avalanche, which can be associated with an almost instantaneous collapse and spreading. Different examples are available in the literature, but the Vajont rockslide is quite unique for its morphological and geological characteristics, as well as for the type of evolution and the availability of long term monitoring data. This study advocates the use of a DEM-CFD framework for the modelling of the generation of hydrodynamic waves due to the impact of a rapid moving rockslide or rock-debris avalanche. 3D DEM analyses in plane strain by a coupled DEM-CFD code were performed to simulate the rockslide from its onset to the impact with still water and the subsequent wave generation (Zhao et al., 2014). The physical response predicted is in broad agreement with the available observations. The numerical results are compared to those published in the literature and especially to Crosta et al. (2014). According to our results, the maximum computed run up amounts to ca. 120 m and 170 m for the eastern and western lobe cross sections, respectively. These values are reasonably similar to those recorded during the event (i.e. ca. 130 m and 190 m respectively). In these simulations, the slope mass is considered permeable, such that the toe region of the slope can move submerged in the reservoir and the impulse water wave can also flow back into the slope mass. However, the upscaling of the grains size in the DEM model leads to an unrealistically high hydraulic conductivity of the model, such that only a small amount of water is splashed onto the northern bank of the Vajont valley. The use of high fluid viscosity and coarse grain model has shown the possibility to model more realistically both the slope and wave motions. However, more detailed slope and fluid properties, and the need for computational efficiency should be considered in future research work. This aspect has also been

  20. NOAA Office for Coastal Management Coastal Inundation Digital Elevation Model: San Francisco Bay/Monterey (CA) WFO - Contra Costa, San Francisco, Alameda, San Mateo, and Santa Clara Counties

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This digital elevation model (DEM) is a part of a series of DEMs produced for the National Oceanic and Atmospheric Administration Office for Coastal Management's Sea...

  1. VT Data - Lidar Hydro-flattened DEM (0.7m) 2016, Essex, Caledonia, Orange, and Windsor Counties

    Data.gov (United States)

    Vermont Center for Geographic Information — (Link to Metadata) This metadata applies to the following collection area(s): Middle CT River subbasin 2016 0.7m and Digital Elevation Model (DEM) dataset of the...

  2. Accuracy Assessment of Different Digital Surface Models

    Directory of Open Access Journals (Sweden)

    Ugur Alganci

    2018-03-01

    Full Text Available Digital elevation models (DEMs, which can occur in the form of digital surface models (DSMs or digital terrain models (DTMs, are widely used as important geospatial information sources for various remote sensing applications, including the precise orthorectification of high-resolution satellite images, 3D spatial analyses, multi-criteria decision support systems, and deformation monitoring. The accuracy of DEMs has direct impacts on specific calculations and process chains; therefore, it is important to select the most appropriate DEM by considering the aim, accuracy requirement, and scale of each study. In this research, DSMs obtained from a variety of satellite sensors were compared to analyze their accuracy and performance. For this purpose, freely available Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER 30 m, Shuttle Radar Topography Mission (SRTM 30 m, and Advanced Land Observing Satellite (ALOS 30 m resolution DSM data were obtained. Additionally, 3 m and 1 m resolution DSMs were produced from tri-stereo images from the SPOT 6 and Pleiades high-resolution (PHR 1A satellites, respectively. Elevation reference data provided by the General Command of Mapping, the national mapping agency of Turkey—produced from 30 cm spatial resolution stereo aerial photos, with a 5 m grid spacing and ±3 m or better overall vertical accuracy at the 90% confidence interval (CI—were used to perform accuracy assessments. Gross errors and water surfaces were removed from the reference DSM. The relative accuracies of the different DSMs were tested using a different number of checkpoints determined by different methods. In the first method, 25 checkpoints were selected from bare lands to evaluate the accuracies of the DSMs on terrain surfaces. In the second method, 1000 randomly selected checkpoints were used to evaluate the methods’ accuracies for the whole study area. In addition to the control point approach, vertical cross

  3. Google Earth's derived digital elevation model: A comparative assessment with Aster and SRTM data

    International Nuclear Information System (INIS)

    Rusli, N; Majid, M R; Din, A H M

    2014-01-01

    This paper presents a statistical analysis showing additional evidence that Digital Elevation Model (DEM) derived from Google Earth is commendable and has a good correlation with ASTER (Advanced Space-borne Thermal Emission and Reflection Radiometer) and SRTM (Shuttle Radar Topography Mission) elevation data. The accuracy of DEM elevation points from Google Earth was compared against that of DEMs from ASTER and SRTM for flat, hilly and mountainous sections of a pre-selected rural watershed. For each section, a total of 5,000 DEM elevation points were extracted as samples from each type of DEM data. The DEM data from Google Earth and SRTM for flat and hilly sections are strongly correlated with the R 2 of 0.791 and 0.891 respectively. Even stronger correlation is shown for the mountainous section where the R 2 values between Google Earth's DEM and ASTER's and between Google Earth's DEM and SRTM's DEMs are respectively 0.917 and 0.865. Further accuracy testing was carried out by utilising the DEM dataset to delineate Muar River's watershed boundary using ArcSWAT2009, a hydrological modelling software. The result shows that the percentage differences of the watershed size delineated from Google Earth's DEM compared to those derived from Department of Irrigation and Drainage's data (using 20m-contour topographic map), ASTER and SRTM data are 9.6%, 10.6%, and 7.6% respectively. It is therefore justified to conclude that the DEM derived from Google Earth is relatively as acceptable as DEMs from other sources

  4. Combined DEM Extration Method from StereoSAR and InSAR

    Science.gov (United States)

    Zhao, Z.; Zhang, J. X.; Duan, M. Y.; Huang, G. M.; Yang, S. C.

    2015-06-01

    A pair of SAR images acquired from different positions can be used to generate digital elevation model (DEM). Two techniques exploiting this characteristic have been introduced: stereo SAR and interferometric SAR. They permit to recover the third dimension (topography) and, at the same time, to identify the absolute position (geolocation) of pixels included in the imaged area, thus allowing the generation of DEMs. In this paper, StereoSAR and InSAR combined adjustment model are constructed, and unify DEM extraction from InSAR and StereoSAR into the same coordinate system, and then improve three dimensional positioning accuracy of the target. We assume that there are four images 1, 2, 3 and 4. One pair of SAR images 1,2 meet the required conditions for InSAR technology, while the other pair of SAR images 3,4 can form stereo image pairs. The phase model is based on InSAR rigorous imaging geometric model. The master image 1 and the slave image 2 will be used in InSAR processing, but the slave image 2 is only used in the course of establishment, and the pixels of the slave image 2 are relevant to the corresponding pixels of the master image 1 through image coregistration coefficient, and it calculates the corresponding phase. It doesn't require the slave image in the construction of the phase model. In Range-Doppler (RD) model, the range equation and Doppler equation are a function of target geolocation, while in the phase equation, the phase is also a function of target geolocation. We exploit combined adjustment model to deviation of target geolocation, thus the problem of target solution is changed to solve three unkonwns through seven equations. The model was tested for DEM extraction under spaceborne InSAR and StereoSAR data and compared with InSAR and StereoSAR methods respectively. The results showed that the model delivered a better performance on experimental imagery and can be used for DEM extraction applications.

  5. Object-oriented classification of drumlins from digital elevation models

    Science.gov (United States)

    Saha, Kakoli

    Drumlins are common elements of glaciated landscapes which are easily identified by their distinct morphometric characteristics including shape, length/width ratio, elongation ratio, and uniform direction. To date, most researchers have mapped drumlins by tracing contours on maps, or through on-screen digitization directly on top of hillshaded digital elevation models (DEMs). This paper seeks to utilize the unique morphometric characteristics of drumlins and investigates automated extraction of the landforms as objects from DEMs by Definiens Developer software (V.7), using the 30 m United States Geological Survey National Elevation Dataset DEM as input. The Chautauqua drumlin field in Pennsylvania and upstate New York, USA was chosen as a study area. As the study area is huge (approximately covers 2500 sq.km. of area), small test areas were selected for initial testing of the method. Individual polygons representing the drumlins were extracted from the elevation data set by automated recognition, using Definiens' Multiresolution Segmentation tool, followed by rule-based classification. Subsequently parameters such as length, width and length-width ratio, perimeter and area were measured automatically. To test the accuracy of the method, a second base map was produced by manual on-screen digitization of drumlins from topographic maps and the same morphometric parameters were extracted from the mapped landforms using Definiens Developer. Statistical comparison showed a high agreement between the two methods confirming that object-oriented classification for extraction of drumlins can be used for mapping these landforms. The proposed method represents an attempt to solve the problem by providing a generalized rule-set for mass extraction of drumlins. To check that the automated extraction process was next applied to a larger area. Results showed that the proposed method is as successful for the bigger area as it was for the smaller test areas.

  6. Digital Elevation Model (DEM), LiDAR acquired and processed over the entire county to support the generation of 1"=100' scale orthophotos & 2' contours. The Lidar LAS data has been classified to bare-earth as well as first-return points., Published in 2009, 1:1200 (1in=100ft) scale, Maryland National Capital Park and Planning Commission.

    Data.gov (United States)

    NSGIC Non-Profit | GIS Inventory — Digital Elevation Model (DEM) dataset current as of 2009. LiDAR acquired and processed over the entire county to support the generation of 1"=100' scale orthophotos...

  7. Spatial Characterization of Landscapes through Multifractal Analysis of DEM

    Directory of Open Access Journals (Sweden)

    P. L. Aguado

    2014-01-01

    Full Text Available Landscape evolution is driven by abiotic, biotic, and anthropic factors. The interactions among these factors and their influence at different scales create a complex dynamic. Landscapes have been shown to exhibit numerous scaling laws, from Horton’s laws to more sophisticated scaling of heights in topography and river network topology. This scaling and multiscaling analysis has the potential to characterise the landscape in terms of the statistical signature of the measure selected. The study zone is a matrix obtained from a digital elevation model (DEM (map 10 × 10 m, and height 1 m that corresponds to homogeneous region with respect to soil characteristics and climatology known as “Monte El Pardo” although the water level of a reservoir and the topography play a main role on its organization and evolution. We have investigated whether the multifractal analysis of a DEM shows common features that can be used to reveal the underlying patterns and information associated with the landscape of the DEM mapping and studied the influence of the water level of the reservoir on the applied analysis. The results show that the use of the multifractal approach with mean absolute gradient data is a useful tool for analysing the topography represented by the DEM.

  8. A new digital elevation model of Antarctica derived from CryoSat-2 altimetry

    Science.gov (United States)

    Slater, Thomas; Shepherd, Andrew; McMillan, Malcolm; Muir, Alan; Gilbert, Lin; Hogg, Anna E.; Konrad, Hannes; Parrinello, Tommaso

    2018-05-01

    We present a new digital elevation model (DEM) of the Antarctic ice sheet and ice shelves based on 2.5 × 108 observations recorded by the CryoSat-2 satellite radar altimeter between July 2010 and July 2016. The DEM is formed from spatio-temporal fits to elevation measurements accumulated within 1, 2, and 5 km grid cells, and is posted at the modal resolution of 1 km. Altogether, 94 % of the grounded ice sheet and 98 % of the floating ice shelves are observed, and the remaining grid cells north of 88° S are interpolated using ordinary kriging. The median and root mean square difference between the DEM and 2.3 × 107 airborne laser altimeter measurements acquired during NASA Operation IceBridge campaigns are -0.30 and 13.50 m, respectively. The DEM uncertainty rises in regions of high slope, especially where elevation measurements were acquired in low-resolution mode; taking this into account, we estimate the average accuracy to be 9.5 m - a value that is comparable to or better than that of other models derived from satellite radar and laser altimetry.

  9. 2012 NOAA Office for Coastal Management Coastal Inundation Digital Elevation Model: Mobile/Tallahassee (AL/FL) WFO - Mobile County in Alabama and Escambia, Santa Rosa, and Okaloosa (portion) Counties in Florida

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This digital elevation model (DEM) is a part of a series of DEMs produced for the National Oceanic and Atmospheric Administration Office for Coastal Management's Sea...

  10. COMPARISON AND CO-REGISTRATION OF DEMS GENERATED FROM HiRISE AND CTX IMAGES

    Directory of Open Access Journals (Sweden)

    Y. Wang

    2016-06-01

    Full Text Available Images from two sensors, the High-Resolution Imaging Science Experiment (HiRISE and the Context Camera (CTX, both on-board the Mars Reconnaissance Orbiter (MRO, were used to generate high-quality DEMs (Digital Elevation Models of the Martian surface. However, there were discrepancies between the DEMs generated from the images acquired by these two sensors due to various reasons, such as variations in boresight alignment between the two sensors during the flight in the complex environment. This paper presents a systematic investigation of the discrepancies between the DEMs generated from the HiRISE and CTX images. A combined adjustment algorithm is presented for the co-registration of HiRISE and CTX DEMs. Experimental analysis was carried out using the HiRISE and CTX images collected at the Mars Rover landing site and several other typical regions. The results indicated that there were systematic offsets between the HiRISE and CTX DEMs in the longitude and latitude directions. However, the offset in the altitude was less obvious. After combined adjustment, the offsets were eliminated and the HiRISE and CTX DEMs were co-registered to each other. The presented research is of significance for the synergistic use of HiRISE and CTX images for precision Mars topographic mapping.

  11. High-resolution DEMs for High-mountain Asia: A systematic, region-wide assessment of geodetic glacier mass balance and dynamics

    Science.gov (United States)

    Shean, D. E.; Arendt, A. A.; Osmanoglu, B.; Montesano, P.

    2017-12-01

    High Mountain Asia (HMA) constitutes the largest glacierized region outside of the Earth's polar regions. Although available observations are limited, long-term records indicate sustained regional glacier mass loss since 1850, with increased loss in recent decades. Recent satellite data (e.g., GRACE, ICESat-1) show spatially variable glacier mass balance, with significant mass loss in the Himalaya and Hindu Kush and slight mass gain in the Karakoram. We generated 4000 high-resolution digital elevation models (DEMs) from sub-meter commercial stereo imagery (DigitalGlobe WorldView/GeoEye) acquired over glaciers in High-mountain Asia from 2002-present (mostly 2013-present). We produced a regional 8-m DEM mosaic for 2015 and estimated 15-year geodetic mass balance for 40000 glaciers larger than 0.1 km2. We are combining with other regional DEM sources to systematically document the spatiotemporal evolution of glacier mass balance for the entire HMA region. We also generated monthly to interannual DEM and velocity time series for high-priority sites distributed across the region, with >15-20 DEMs available for some locations from 2010-present. These records document glacier dynamics, seasonal snow accumulation/redistribution, and processes that affect glacier mass balance (e.g., ice-cliff retreat, debris cover evolution). These efforts will provide basin-scale assessments of snow/ice melt runoff contributions for model cal/val and downstream water resources applications. We will continue processing all archived and newly available commercial stereo imagery for HMA, and will release all DEMs through the HiMAT DAAC.

  12. Estuarine Bathymetric Digital Elevation Models (30 meter and 3 arc second resolution) Derived From Source Hydrographic Survey Soundings Collected by NOAA

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — These Bathymetric Digital Elevation Models (DEM) were generated from original point soundings collected during hydrographic surveys conducted by the National Ocean...

  13. A new digital elevation model of Antarctica derived from CryoSat-2 altimetry

    Directory of Open Access Journals (Sweden)

    T. Slater

    2018-05-01

    Full Text Available We present a new digital elevation model (DEM of the Antarctic ice sheet and ice shelves based on 2.5 × 108 observations recorded by the CryoSat-2 satellite radar altimeter between July 2010 and July 2016. The DEM is formed from spatio-temporal fits to elevation measurements accumulated within 1, 2, and 5 km grid cells, and is posted at the modal resolution of 1 km. Altogether, 94 % of the grounded ice sheet and 98 % of the floating ice shelves are observed, and the remaining grid cells north of 88° S are interpolated using ordinary kriging. The median and root mean square difference between the DEM and 2.3 × 107 airborne laser altimeter measurements acquired during NASA Operation IceBridge campaigns are −0.30 and 13.50 m, respectively. The DEM uncertainty rises in regions of high slope, especially where elevation measurements were acquired in low-resolution mode; taking this into account, we estimate the average accuracy to be 9.5 m – a value that is comparable to or better than that of other models derived from satellite radar and laser altimetry.

  14. A new seamless, high-resolution digital elevation model of the San Francisco Bay-Delta Estuary, California

    Science.gov (United States)

    Fregoso, Theresa A.; Wang, Rueen-Fang; Ateljevich, Eli; Jaffe, Bruce E.

    2017-06-14

    Climate change, sea-level rise, and human development have contributed to the changing geomorphology of the San Francisco Bay - Delta (Bay-Delta) Estuary system. The need to predict scenarios of change led to the development of a new seamless, high-resolution digital elevation model (DEM) of the Bay – Delta that can be used by modelers attempting to understand potential future changes to the estuary system. This report details the three phases of the creation of this DEM. The first phase took a bathymetric-only DEM created in 2005 by the U.S. Geological Survey (USGS), refined it with additional data, and identified areas that would benefit from new surveys. The second phase began a USGS collaboration with the California Department of Water Resources (DWR) that updated a 2012 DWR seamless bathymetric/topographic DEM of the Bay-Delta with input from the USGS and modifications to fit the specific needs of USGS modelers. The third phase took the work from phase 2 and expanded the coverage area in the north to include the Yolo Bypass up to the Fremont Weir, the Sacramento River up to Knights Landing, and the American River up to the Nimbus Dam, and added back in the elevations for interior islands. The constant evolution of the Bay-Delta will require continuous updates to the DEM of the Delta, and there still are areas with older data that would benefit from modern surveys. As a result, DWR plans to continue updating the DEM.

  15. Parallelizing flow-accumulation calculations on graphics processing units—From iterative DEM preprocessing algorithm to recursive multiple-flow-direction algorithm

    Science.gov (United States)

    Qin, Cheng-Zhi; Zhan, Lijun

    2012-06-01

    As one of the important tasks in digital terrain analysis, the calculation of flow accumulations from gridded digital elevation models (DEMs) usually involves two steps in a real application: (1) using an iterative DEM preprocessing algorithm to remove the depressions and flat areas commonly contained in real DEMs, and (2) using a recursive flow-direction algorithm to calculate the flow accumulation for every cell in the DEM. Because both algorithms are computationally intensive, quick calculation of the flow accumulations from a DEM (especially for a large area) presents a practical challenge to personal computer (PC) users. In recent years, rapid increases in hardware capacity of the graphics processing units (GPUs) provided in modern PCs have made it possible to meet this challenge in a PC environment. Parallel computing on GPUs using a compute-unified-device-architecture (CUDA) programming model has been explored to speed up the execution of the single-flow-direction algorithm (SFD). However, the parallel implementation on a GPU of the multiple-flow-direction (MFD) algorithm, which generally performs better than the SFD algorithm, has not been reported. Moreover, GPU-based parallelization of the DEM preprocessing step in the flow-accumulation calculations has not been addressed. This paper proposes a parallel approach to calculate flow accumulations (including both iterative DEM preprocessing and a recursive MFD algorithm) on a CUDA-compatible GPU. For the parallelization of an MFD algorithm (MFD-md), two different parallelization strategies using a GPU are explored. The first parallelization strategy, which has been used in the existing parallel SFD algorithm on GPU, has the problem of computing redundancy. Therefore, we designed a parallelization strategy based on graph theory. The application results show that the proposed parallel approach to calculate flow accumulations on a GPU performs much faster than either sequential algorithms or other parallel GPU

  16. Extraction and Validation of Geomorphological Features from EU-DEM in The Vicinity of the Mygdonia Basin, Northern Greece

    Science.gov (United States)

    Mouratidis, Antonios; Karadimou, Georgia; Ampatzidis, Dimitrios

    2017-12-01

    The European Union Digital Elevation Model (EU-DEM) is a relatively new, hybrid elevation product, principally based on SRTM DEM and ASTER GDEM data, but also on publically available Russian topographic maps for regions north of 60° N. More specifically, EU-DEM is a Digital Surface Model (DSM) over Europe from the Global Monitoring for Environment and Security (GMES) Reference Data Access (RDA) project - a realisation of the Copernicus (former GMES) programme, managed by the European Commission/DG Enterprise and Industry. Even if EU-DEM is indeed more reliable in terms of elevation accuracy than its constituents, it ought to be noted that it is not representative of the original elevation measurements, but is rather a secondary (mathematical) product. Therefore, for specific applications, such as those of geomorphological interest, artefacts may be induced. To this end, the purpose of this paper is to investigate the performance of EU-DEM for geomorphological applications and compare it against other available datasets, i.e. topographic maps and (almost) global DEMs such as SRTM, ASTER-GDEM and WorldDEM™. This initial investigation is carried out in Central Macedonia, Northern Greece, in the vicinity of the Mygdonia basin, which corresponds to an area of particular interest for several geoscience applications. This area has also been serving as a test site for the systematic validation of DEMs for more than a decade. Consequently, extensive elevation datasets and experience have been accumulated over the years, rendering the evaluation of new elevation products a coherent and useful exercise on a local to regional scale. In this context, relief classification, drainage basin delineation, slope and slope aspect, as well as extraction and classification of drainage network are performed and validated among the aforementioned elevation sources. The achieved results focus on qualitative and quantitative aspects of automatic geomorphological feature extraction from

  17. DEM investigation of weathered rocks using a novel bond contact model

    Directory of Open Access Journals (Sweden)

    Zhenming Shi

    2015-06-01

    Full Text Available The distinct element method (DEM incorporated with a novel bond contact model was applied in this paper to shed light on the microscopic physical origin of macroscopic behaviors of weathered rock, and to achieve the changing laws of microscopic parameters from observed decaying properties of rocks during weathering. The changing laws of macroscopic mechanical properties of typical rocks were summarized based on the existing research achievements. Parametric simulations were then conducted to analyze the relationships between macroscopic and microscopic parameters, and to derive the changing laws of microscopic parameters for the DEM model. Equipped with the microscopic weathering laws, a series of DEM simulations of basic laboratory tests on weathered rock samples was performed in comparison with analytical solutions. The results reveal that the relationships between macroscopic and microscopic parameters of rocks against the weathering period can be successfully attained by parametric simulations. In addition, weathering has a significant impact on both stress–strain relationship and failure pattern of rocks.

  18. BOREAS HYP-8 DEM Data Over The NSA-MSA and SSA-MSA in The AEAC Projection

    Science.gov (United States)

    Knapp, David E.; Hall, Forrest G. (Editor); Wang, Xue-Wen; Band, L. E.; Smith, David E. (Technical Monitor)

    2000-01-01

    These data were derived from the original Digital Elevation Models (DEMs) produced by the Boreal Ecosystem-Atmosphere Study (BOREAS) Hydrology (HYD)-8 team. The original DEMs were in the Universal Transverse Mercator (UTM) projection, while this product is projected in the Albers Equal-Area Conic (AEAC) projection. The pixel size of the data is 100 meters, which is appropriate for the 1:50,000-scale contours from which the DEMs were made. The original data were compiled from information available in the 1970s and 1980s. This data set covers the two Modeling Sub-Areas (MSAs) that are contained within the Southern Study Area (SSA) and the Northern Study Area (NSA). The data are stored in binary, image format files. The DEM data over the NSA-MSA and SSA-MSA in the AEAC projection are available from the Earth Observing System Data and Information System (EOSDIS) Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC). The data files are available on a CD-ROM (see document number 20010000884).

  19. An algorithm for treating flat areas and depressions in digital elevation models using linear interpolation

    Science.gov (United States)

    F. Pan; M. Stieglitz; R.B. McKane

    2012-01-01

    Digital elevation model (DEM) data are essential to hydrological applications and have been widely used to calculate a variety of useful topographic characteristics, e.g., slope, flow direction, flow accumulation area, stream channel network, topographic index, and others. Except for slope, none of the other topographic characteristics can be calculated until the flow...

  20. Methodological application so as to obtain digital elevation models DEM in wetland areas

    International Nuclear Information System (INIS)

    Quintero, Deiby A; Montoya V, Diana M; Betancur, Teresita

    2009-01-01

    In order to understand hydrological systems and the description of flow processes that occur among its components it is essential to have a physiographic description that morphometric and relief characteristics. When local studies are performed, the basic cartography available, in the best case 1:25,000 scale, tends not to obey the needs required to represent the water dynamics that characterize the interactions between streams, aquifers and lenticular water bodies in flat zones particularly in those where there are wetlands localized in ancient F100D plains of rivers. A lack of financial resources is the principal obstacle to acquiring; information that is current and sufficient for the scale of the project. Geomorphologic conditions of flat relief zones are a good alternative for the construction of the new data. Using the basic cartography available and the new data, it is possible to obtain DEMs that are improved and consistent with the dynamics of surface and groundwater flows in the hydrological system. To accomplish this one must use spatial modeling tools coupled with Geographic Information System - GIS. This article present a methodological application for the region surrounding the catchment of wetland Cienaga Colombia in the Bajo Cauca region of Antioquia.

  1. Comparison of Multi-Scale Digital Elevation Models for Defining Waterways and Catchments Over Large Areas

    Science.gov (United States)

    Harris, B.; McDougall, K.; Barry, M.

    2012-07-01

    Digital Elevation Models (DEMs) allow for the efficient and consistent creation of waterways and catchment boundaries over large areas. Studies of waterway delineation from DEMs are usually undertaken over small or single catchment areas due to the nature of the problems being investigated. Improvements in Geographic Information Systems (GIS) techniques, software, hardware and data allow for analysis of larger data sets and also facilitate a consistent tool for the creation and analysis of waterways over extensive areas. However, rarely are they developed over large regional areas because of the lack of available raw data sets and the amount of work required to create the underlying DEMs. This paper examines definition of waterways and catchments over an area of approximately 25,000 km2 to establish the optimal DEM scale required for waterway delineation over large regional projects. The comparative study analysed multi-scale DEMs over two test areas (Wivenhoe catchment, 543 km2 and a detailed 13 km2 within the Wivenhoe catchment) including various data types, scales, quality, and variable catchment input parameters. Historic and available DEM data was compared to high resolution Lidar based DEMs to assess variations in the formation of stream networks. The results identified that, particularly in areas of high elevation change, DEMs at 20 m cell size created from broad scale 1:25,000 data (combined with more detailed data or manual delineation in flat areas) are adequate for the creation of waterways and catchments at a regional scale.

  2. Soil-landscape modelling using fuzzy c-means clustering of attribute data derived from a Digital Elevation Model (DEM).

    NARCIS (Netherlands)

    Bruin, de S.; Stein, A.

    1998-01-01

    This study explores the use of fuzzy c-means clustering of attribute data derived from a digital elevation model to represent transition zones in the soil-landscape. The conventional geographic model used for soil-landscape description is not able to properly deal with these. Fuzzy c-means

  3. Precise baseline determination for the TanDEM-X mission

    Science.gov (United States)

    Koenig, Rolf; Moon, Yongjin; Neumayer, Hans; Wermuth, Martin; Montenbruck, Oliver; Jäggi, Adrian

    The TanDEM-X mission will strive for generating a global precise Digital Elevation Model (DEM) by way of bi-static SAR in a close formation of the TerraSAR-X satellite, already launched on June 15, 2007, and the TanDEM-X satellite to be launched in May 2010. Both satellites carry the Tracking, Occultation and Ranging (TOR) payload supplied by the GFZ German Research Centre for Geosciences. The TOR consists of a high-precision dual-frequency GPS receiver, called Integrated GPS Occultation Receiver (IGOR), and a Laser retro-reflector (LRR) for precise orbit determination (POD) and atmospheric sounding. The IGOR is of vital importance for the TanDEM-X mission objectives as the millimeter level determination of the baseline or distance between the two spacecrafts is needed to derive meter level accurate DEMs. Within the TanDEM-X ground segment GFZ is responsible for the operational provision of precise baselines. For this GFZ uses two software chains, first its Earth Parameter and Orbit System (EPOS) software and second the BERNESE software, for backup purposes and quality control. In a concerted effort also the German Aerospace Center (DLR) generates precise baselines independently with a dedicated Kalman filter approach realized in its FRNS software. By the example of GRACE the generation of baselines with millimeter accuracy from on-board GPS data can be validated directly by way of comparing them to the intersatellite K-band range measurements. The K-band ranges are accurate down to the micrometer-level and therefore may be considered as truth. Both TanDEM-X baseline providers are able to generate GRACE baselines with sub-millimeter accuracy. By merging the independent baselines by GFZ and DLR, the accuracy can even be increased. The K-band validation however covers solely the along-track component as the K-band data measure just the distance between the two GRACE satellites. In addition they inhibit an un-known bias which must be modelled in the comparison, so the

  4. Use of DEMs Derived from TLS and HRSI Data for Landslide Feature Recognition

    Directory of Open Access Journals (Sweden)

    Maurizio Barbarella

    2018-04-01

    Full Text Available This paper addresses the problems arising from the use of data acquired with two different remote sensing techniques—high-resolution satellite imagery (HRSI and terrestrial laser scanning (TLS—for the extraction of digital elevation models (DEMs used in the geomorphological analysis and recognition of landslides, taking into account the uncertainties associated with DEM production. In order to obtain a georeferenced and edited point cloud, the two data sets require quite different processes, which are more complex for satellite images than for TLS data. The differences between the two processes are highlighted. The point clouds are interpolated on a DEM with a 1 m grid size using kriging. Starting from these DEMs, a number of contour, slope, and aspect maps are extracted, together with their associated uncertainty maps. Comparative analysis of selected landslide features drawn from the two data sources allows recognition and classification of hierarchical and multiscale landslide components. Taking into account the uncertainty related to the map enables areas to be located for which one data source was able to give more reliable results than another. Our case study is located in Southern Italy, in an area known for active landslides.

  5. Influence of Terraced area DEM Resolution on RUSLE LS Factor

    Science.gov (United States)

    Zhang, Hongming; Baartman, Jantiene E. M.; Yang, Xiaomei; Gai, Lingtong; Geissen, Viollette

    2017-04-01

    Topography has a large impact on the erosion of soil by water. Slope steepness and slope length are combined (the LS factor) in the universal soil-loss equation (USLE) and its revised version (RUSLE) for predicting soil erosion. The LS factor is usually extracted from a digital elevation model (DEM). The grid size of the DEM will thus influence the LS factor and the subsequent calculation of soil loss. Terracing is considered as a support practice factor (P) in the USLE/RUSLE equations, which is multiplied with the other USLE/RUSLE factors. However, as terraces change the slope length and steepness, they also affect the LS factor. The effect of DEM grid size on the LS factor has not been investigated for a terraced area. We obtained a high-resolution DEM by unmanned aerial vehicles (UAVs) photogrammetry, from which the slope steepness, slope length, and LS factor were extracted. The changes in these parameters at various DEM resolutions were then analysed. The DEM produced detailed LS-factor maps, particularly for low LS factors. High (small valleys, gullies, and terrace ridges) and low (flats and terrace fields) spatial frequencies were both sensitive to changes in resolution, so the areas of higher and lower slope steepness both decreased with increasing grid size. Average slope steepness decreased and average slope length increased with grid size. Slope length, however, had a larger effect than slope steepness on the LS factor as the grid size varied. The LS factor increased when the grid size increased from 0.5 to 30-m and increased significantly at grid sizes >5-m. The LS factor was increasingly overestimated as grid size decreased. The LS factor decreased from grid sizes of 30 to 100-m, because the details of the terraced terrain were gradually lost, but the factor was still overestimated.

  6. Constructing Palaeo-DEMs in landscape evolution: example of the Geren catchment, Turkey

    Science.gov (United States)

    van Gorp, Wouter; Schoorl, Jeroen M.; Veldkamp, Tom; Maddy, Darrel; Demir, Tuncer; Aytac, Serdar

    2017-04-01

    How to reconstruct the past landscape and how does this influence your modelling results? This is an important paradigma in the soilscape and landscape evolution modelling community. Here an example of Turkey will be presented where a 300 ka LEM simulation requested to the thoroughly think about the initial landscape as an important input. What information can be used to know the morphology of a landscape 300 ka ago? The Geren catchment, a tributary of the upstream Gediz river near Kula, Turkey, has been influenced by base level changes during the Late Pleistocene and Holocene. Different lavaflows have blocked the Gediz and Geren river several times over in the timespan of the last 300 ka -200 Ka and in the recent Holocene. The heavily dissected Geren catchment shows a landscape evolution which is more complex than just a reaction on these base level changes. The steps and inputs of the palaeo DEM reconstruction will be presented and the modelling results will be presented. Keywords: Digital Elevation Model, Palaeo DEMs, Numerical modelling

  7. Micromechanics of non-active clays in saturated state and DEM modelling

    Directory of Open Access Journals (Sweden)

    Pagano Arianna Gea

    2017-01-01

    Full Text Available The paper presents a conceptual micromechanical model for 1-D compression behaviour of non-active clays in saturated state. An experimental investigation was carried out on kaolin clay samples saturated with fluids of different pH and dielectric permittivity. The effect of pore fluid characteristics on one-dimensional compressibility behaviour of kaolin was investigated. A three dimensional Discrete Element Method (DEM was implemented in order to simulate the response of saturated kaolin observed during the experiments. A complex contact model was introduced, considering both the mechanical and physico-chemical microscopic interactions between clay particles. A simple analysis with spherical particles only was performed as a preliminary step in the DEM study in the elastic regime.

  8. Discrete Element Modeling (DEM) of Triboelectrically Charged Particles: Revised Experiments

    Science.gov (United States)

    Hogue, Michael D.; Calle, Carlos I.; Curry, D. R.; Weitzman, P. S.

    2008-01-01

    In a previous work, the addition of basic screened Coulombic electrostatic forces to an existing commercial discrete element modeling (DEM) software was reported. Triboelectric experiments were performed to charge glass spheres rolling on inclined planes of various materials. Charge generation constants and the Q/m ratios for the test materials were calculated from the experimental data and compared to the simulation output of the DEM software. In this paper, we will discuss new values of the charge generation constants calculated from improved experimental procedures and data. Also, planned work to include dielectrophoretic, Van der Waals forces, and advanced mechanical forces into the software will be discussed.

  9. COMPARISON OF MULTI-SCALE DIGITAL ELEVATION MODELS FOR DEFINING WATERWAYS AND CATCHMENTS OVER LARGE AREAS

    Directory of Open Access Journals (Sweden)

    B. Harris

    2012-07-01

    Full Text Available Digital Elevation Models (DEMs allow for the efficient and consistent creation of waterways and catchment boundaries over large areas. Studies of waterway delineation from DEMs are usually undertaken over small or single catchment areas due to the nature of the problems being investigated. Improvements in Geographic Information Systems (GIS techniques, software, hardware and data allow for analysis of larger data sets and also facilitate a consistent tool for the creation and analysis of waterways over extensive areas. However, rarely are they developed over large regional areas because of the lack of available raw data sets and the amount of work required to create the underlying DEMs. This paper examines definition of waterways and catchments over an area of approximately 25,000 km2 to establish the optimal DEM scale required for waterway delineation over large regional projects. The comparative study analysed multi-scale DEMs over two test areas (Wivenhoe catchment, 543 km2 and a detailed 13 km2 within the Wivenhoe catchment including various data types, scales, quality, and variable catchment input parameters. Historic and available DEM data was compared to high resolution Lidar based DEMs to assess variations in the formation of stream networks. The results identified that, particularly in areas of high elevation change, DEMs at 20 m cell size created from broad scale 1:25,000 data (combined with more detailed data or manual delineation in flat areas are adequate for the creation of waterways and catchments at a regional scale.

  10. 1 Arc-second Digital Elevation Models (DEMs) - USGS National Map 3DEP Downloadable Data Collection

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This is a tiled collection of the 3D Elevation Program (3DEP) and is 1 arc-second (approximately 30 m) resolution.The elevations in this Digital Elevation Model...

  11. The Influence of DEM Quality on Mapping Accuracy of Coniferous- and Deciduous-Dominated Forest Using TerraSAR‑X Images

    Directory of Open Access Journals (Sweden)

    Gerald Kändler

    2012-03-01

    Full Text Available Climate change is a factor that largely contributes to the increase of forest areas affected by natural damages. Therefore, the development of methodologies for forest monitoring and rapid assessment of affected areas is required. Space-borne synthetic aperture radar (SAR imagery with high resolution is now available for large-scale forest mapping and forest monitoring applications. However, a correct interpretation of SAR images requires an adequate preprocessing of the data consisting of orthorectification and radiometric calibration. The resolution and quality of the digital elevation model (DEM used as reference is crucial for this purpose. Therefore, the primary aim of this study was to analyze the influence of the DEM quality used in the preprocessing of the SAR data on the mapping accuracy of forest types. In order to examine TerraSAR-X images to map forest dominated by deciduous and coniferous trees, High Resolution SpotLight images were acquired for two study sites in southern Germany. The SAR images were preprocessed with a Shuttle Radar Topography Mission (SRTM DEM (resolution approximately 90 m, an airborne laser scanning (ALS digital terrain model (DTM (5 m resolution, and an ALS digital surface model (DSM (5 m resolution. The orthorectification of the SAR images using high resolution ALS DEMs was found to be important for the reduction of errors in pixel location and to increase the classification accuracy of forest types. SAR images preprocessed with ALS DTMs resulted in the highest classification accuracies, with kappa coefficients of 0.49 and 0.41, respectively. SAR images preprocessed with ALS DTMs resulted in greater accuracy than those preprocessed with ALS DSMs in most cases. The classification accuracy of forest types using SAR images preprocessed with the SRTM DEM was fair, with kappa coefficients of 0.23 and 0.32, respectively.Analysis of the radar backscatter indicated that sample plots dominated by coniferous trees

  12. Klasifikasi Bentuk Wilayah yang Diturunkan dari Digital Elevation Models: Kasus DAS Citarum, Sub DAS Cilalawi, Jawa Barat

    Directory of Open Access Journals (Sweden)

    Salwati

    2008-05-01

    Full Text Available Application of GIS technology (Geographic Information System, that is Digital Elevation Models (DEMs for the analysis of landform or slope have been conducted in the Citarum watershed, Purwakarta West Java Province from August until November 2003. Research aim to make landform classification of DEMs use classification of ISODATA and to evaluate the quality of landform classification which alighted from DEMs. To reach the target have been made DEMs, is later then degraded to become map set of regional form. DEMS made from contour map scale 1 : 25.000 with inteval of 12.5 m use Arcview version 2.65 with resolution of 25 m, and slope classification made software of ER Mapper. Field observation conducted for validation result of classification. Result of research indicate that wave landform (slope 8-15% and hilly (slope 15-30% in sub watershed of Cilalawi is DEMs have lower level class of fact in the field. While set of regional form level of (slope 30% in sub of DAS Cilalawi have bevel class which almost is equal to fact in the field. Result of the research indicated that map of landform or alighted from slope is DEMs not entirely as according to situation in fact of the field. Interconnected the mentioned sliver with quality map of used contour. Thereby verification in field is absolutely needed.

  13. Landslide Detection in the Carlyon Beach, WA Peninsula: Analysis Of High Resolution DEMs

    Science.gov (United States)

    Fayne, J.; Tran, C.; Mora, O. E.

    2017-12-01

    Landslides are geological events caused by slope instability and degradation, leading to the sliding of large masses of rock and soil down a mountain or hillside. These events are influenced by topography, geology, weather and human activity, and can cause extensive damage to the environment and infrastructure, such as the destruction of transportation networks, homes, and businesses. It is therefore imperative to detect early-warning signs of landslide hazards as a means of mitigation and disaster prevention. Traditional landslide surveillance consists of field mapping, but the process is expensive and time consuming. This study uses Light Detection and Ranging (LiDAR) derived Digital Elevation Models (DEMs) and k-means clustering and Gaussian Mixture Model (GMM) to analyze surface roughness and extract spatial features and patterns of landslides and landslide-prone areas. The methodology based on several feature extractors employs an unsupervised classifier on the Carlyon Beach Peninsula in the state of Washington to attempt to identify slide potential terrain. When compared with the independently compiled landslide inventory map, the proposed algorithm correctly classifies up to 87% of the terrain. These results suggest that the proposed methods and LiDAR-derived DEMs can provide important surface information and be used as efficient tools for digital terrain analysis to create accurate landslide maps.

  14. Interpolation Routines Assessment in ALS-Derived Digital Elevation Models for Forestry Applications

    Directory of Open Access Journals (Sweden)

    Antonio Luis Montealegre

    2015-07-01

    Full Text Available Airborne Laser Scanning (ALS is capable of estimating a variety of forest parameters using different metrics extracted from the normalized heights of the point cloud using a Digital Elevation Model (DEM. In this study, six interpolation routines were tested over a range of land cover and terrain roughness in order to generate a collection of DEMs with spatial resolution of 1 and 2 m. The accuracy of the DEMs was assessed twice, first using a test sample extracted from the ALS point cloud, second using a set of 55 ground control points collected with a high precision Global Positioning System (GPS. The effects of terrain slope, land cover, ground point density and pulse penetration on the interpolation error were examined stratifying the study area with these variables. In addition, a Classification and Regression Tree (CART analysis allowed the development of a prediction uncertainty map to identify in which areas DEMs and Airborne Light Detection and Ranging (LiDAR derived products may be of low quality. The Triangulated Irregular Network (TIN to raster interpolation method produced the best result in the validation process with the training data set while the Inverse Distance Weighted (IDW routine was the best in the validation with GPS (RMSE of 2.68 cm and RMSE of 37.10 cm, respectively.

  15. Large-baseline InSAR for precise topographic mapping: a framework for TanDEM-X large-baseline data

    Directory of Open Access Journals (Sweden)

    M. Pinheiro

    2017-09-01

    Full Text Available The global Digital Elevation Model (DEM resulting from the TanDEM-X mission provides information about the world topography with outstanding precision. In fact, performance analysis carried out with the already available data have shown that the global product is well within the requirements of 10 m absolute vertical accuracy and 2 m relative vertical accuracy for flat to moderate terrain. The mission's science phase took place from October 2014 to December 2015. During this phase, bistatic acquisitions with across-track separation between the two satellites up to 3.6 km at the equator were commanded. Since the relative vertical accuracy of InSAR derived elevation models is, in principle, inversely proportional to the system baseline, the TanDEM-X science phase opened the doors for the generation of elevation models with improved quality with respect to the standard product. However, the interferometric processing of the large-baseline data is troublesome due to the increased volume decorrelation and very high frequency of the phase variations. Hence, in order to fully profit from the increased baseline, sophisticated algorithms for the interferometric processing, and, in particular, for the phase unwrapping have to be considered. This paper proposes a novel dual-baseline region-growing framework for the phase unwrapping of the large-baseline interferograms. Results from two experiments with data from the TanDEM-X science phase are discussed, corroborating the expected increased level of detail of the large-baseline DEMs.

  16. To the question on accuracy of forest heights’ measurements by the TanDEM-X radar interferometry data

    Directory of Open Access Journals (Sweden)

    T. N. Chimitdorzhiev

    2016-08-01

    Full Text Available The paper presents the validation results of the InSAR method for determining the forest canopy height, based on TanDEM-X and ALOS PALSAR data. The research conducted on the territory of the Baikal-Kudara forest area of the Republic of Buryatia (52°10'N, 106°48'E. Forest vegetation is represented mainly by conifers – pine, and spruce, with a small admixture of deciduous trees – aspen, birch, etc. The forest vegetation height was determined by subtracting the digital elevation model (DEM of the digital terrain model (DTM. DEM is built according to the L-band (wavelength of 23.5 cm ALOS PALSAR satellite with horizontal co-polarization mode. In the investigation it was assumed that a radar signal of ALOS PALSAR passes all forest thickness and reflected from the underlying surface, made it possible to recover terrain under forest canopy. DTM has been built using the TanDEM-X data (wavelength 3 cm. In this case, it was assumed that the radar echoes scattered from a some virtual phase centers of scattering surface, which characterizes the upper limit of the continuous forest canopy. To check the accuracy of satellite definitions of forest height in study area were made high-precision geodetic measurement of trees heights using electronic total station and the coordinates of geographic control points using differential GPS receivers. The discrepancy between the satellite and ground-based measurements at 11 test sites did not exceed 2 m, which is mainly due to the difference in measurement techniques: height of individual trees by ground methods and continuous forest canopy height using radar interferometry.

  17. Drainage network extraction from a high-resolution DEM using parallel programming in the .NET Framework

    Science.gov (United States)

    Du, Chao; Ye, Aizhong; Gan, Yanjun; You, Jinjun; Duan, Qinyun; Ma, Feng; Hou, Jingwen

    2017-12-01

    High-resolution Digital Elevation Models (DEMs) can be used to extract high-accuracy prerequisite drainage networks. A higher resolution represents a larger number of grids. With an increase in the number of grids, the flow direction determination will require substantial computer resources and computing time. Parallel computing is a feasible method with which to resolve this problem. In this paper, we proposed a parallel programming method within the .NET Framework with a C# Compiler in a Windows environment. The basin is divided into sub-basins, and subsequently the different sub-basins operate on multiple threads concurrently to calculate flow directions. The method was applied to calculate the flow direction of the Yellow River basin from 3 arc-second resolution SRTM DEM. Drainage networks were extracted and compared with HydroSHEDS river network to assess their accuracy. The results demonstrate that this method can calculate the flow direction from high-resolution DEMs efficiently and extract high-precision continuous drainage networks.

  18. ASTER-Derived 30-Meter-Resolution Digital Elevation Models of Afghanistan

    Science.gov (United States)

    Chirico, Peter G.; Warner, Michael B.

    2007-01-01

    INTRODUCTION The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is an imaging instrument aboard the Terra satellite, launched on December 19, 1999, as part of the National Aeronautics and Space Administration's (NASA) Earth Observing System (EOS). The ASTER sensor consists of three subsystems: the visible and near infrared (VNIR), the shortwave infrared (SWIR), and the thermal infrared (TIR), each with a different spatial resolution (VNIR, 15 meters; SWIR, 30 meters, TIR 90 meters). The VNIR system has the capability to generate along-track stereo images that can be used to create digital elevation models (DEMs) at 30-meter resolution. Currently, the only available DEM dataset for Afghanistan is the 90-meter-resolution Shuttle Radar Topography Mission (SRTM) data. This dataset is appropriate for macroscale DEM analysis and mapping. However, ASTER provides a low cost opportunity to generate higher resolution data. For this publication, study areas were identified around populated areas and areas where higher resolution elevation data were desired to assist in natural resource assessments. The higher resolution fidelity of these DEMs can also be used for other terrain analysis including landform classification and geologic structure analysis. For this publication, ASTER scenes were processed and mosaicked to generate 36 DEMs which were created and extracted using PCI Geomatics' OrthoEngine 3D Stereo software. The ASTER images were geographically registered to Landsat data with at least 15 accurate and well distributed ground control points with a root mean square error (RMSE) of less that one pixel (15 meters). An elevation value was then assigned to each ground control point by extracting the elevation from the 90-meter SRTM data. The 36 derived DEMs demonstrate that the software correlated on nearly flat surfaces and smooth slopes accurately. Larger errors occur in cloudy and snow-covered areas, lakes, areas with steep slopes, and

  19. A new DEM of the Austfonna ice cap by combining differential SAR interferometry with ICESat laser altimetry

    Directory of Open Access Journals (Sweden)

    Geir Moholdt

    2012-05-01

    Full Text Available We present a new digital elevation model (DEM of the Austfonna ice cap in the Svalbard Archipelago, Norwegian Arctic. Previous DEMs derived from synthetic aperture radar (SAR and optical shape-from-shading have been tied to airborne radio echo-sounding surface profiles from 1983 which contain an elevation-dependent bias of up to several tens of metres compared with recent elevation data. The new and freely available DEM is constructed purely from spaceborne remote sensing data using differential SAR interferometry (DInSAR in combination with ICESat laser altimetry. Interferograms were generated from pairs of SAR scenes from the one-day repeat tandem phase of the European Remote Sensing Satellites 1/2 (ERS-1/2 in 1996. ICESat elevations from winter 2006–08 were used as ground control points to refine the interferometric baseline. The resulting DEM is validated against the same ground control points and independent surface elevation profiles from Global Navigation Satellite Systems (GNSS and airborne laser altimetry, yielding root mean square (RMS errors of about 10 m in all cases. This quality is sufficient for most glaciological applications, and the new DEM will be a baseline data set for ongoing and future research at Austfonna. The technique of combining satellite DInSAR with high-resolution satellite altimetry for DEM generation might also be a good solution in other glacier regions with similar characteristics, especially when data from TanDEM-X and CryoSat-2 become available.

  20. Automated identification of stream-channel geomorphic features from high‑resolution digital elevation models in West Tennessee watersheds

    Science.gov (United States)

    Cartwright, Jennifer M.; Diehl, Timothy H.

    2017-01-17

    High-resolution digital elevation models (DEMs) derived from light detection and ranging (lidar) enable investigations of stream-channel geomorphology with much greater precision than previously possible. The U.S. Geological Survey has developed the DEM Geomorphology Toolbox, containing seven tools to automate the identification of sites of geomorphic instability that may represent sediment sources and sinks in stream-channel networks. These tools can be used to modify input DEMs on the basis of known locations of stormwater infrastructure, derive flow networks at user-specified resolutions, and identify possible sites of geomorphic instability including steep banks, abrupt changes in channel slope, or areas of rough terrain. Field verification of tool outputs identified several tool limitations but also demonstrated their overall usefulness in highlighting likely sediment sources and sinks within channel networks. In particular, spatial clusters of outputs from multiple tools can be used to prioritize field efforts to assess and restore eroding stream reaches.

  1. Rockslide and Impulse Wave Modelling in the Vajont Reservoir by DEM-CFD Analyses

    Science.gov (United States)

    Zhao, T.; Utili, S.; Crosta, G. B.

    2016-06-01

    This paper investigates the generation of hydrodynamic water waves due to rockslides plunging into a water reservoir. Quasi-3D DEM analyses in plane strain by a coupled DEM-CFD code are adopted to simulate the rockslide from its onset to the impact with the still water and the subsequent generation of the wave. The employed numerical tools and upscaling of hydraulic properties allow predicting a physical response in broad agreement with the observations notwithstanding the assumptions and characteristics of the adopted methods. The results obtained by the DEM-CFD coupled approach are compared to those published in the literature and those presented by Crosta et al. (Landslide spreading, impulse waves and modelling of the Vajont rockslide. Rock mechanics, 2014) in a companion paper obtained through an ALE-FEM method. Analyses performed along two cross sections are representative of the limit conditions of the eastern and western slope sectors. The max rockslide average velocity and the water wave velocity reach ca. 22 and 20 m/s, respectively. The maximum computed run up amounts to ca. 120 and 170 m for the eastern and western lobe cross sections, respectively. These values are reasonably similar to those recorded during the event (i.e. ca. 130 and 190 m, respectively). Therefore, the overall study lays out a possible DEM-CFD framework for the modelling of the generation of the hydrodynamic wave due to the impact of a rapid moving rockslide or rock-debris avalanche.

  2. Landscape unit based digital elevation model development for the freshwater wetlands within the Arthur C. Marshall Loxahatchee National Wildlife Refuge, Southeastern Florida

    Science.gov (United States)

    Xie, Zhixiao; Liu, Zhongwei; Jones, John W.; Higer, Aaron L.; Telis, Pamela A.

    2011-01-01

    The hydrologic regime is a critical limiting factor in the delicate ecosystem of the greater Everglades freshwater wetlands in south Florida that has been severely altered by management activities in the past several decades. "Getting the water right" is regarded as the key to successful restoration of this unique wetland ecosystem. An essential component to represent and model its hydrologic regime, specifically water depth, is an accurate ground Digital Elevation Model (DEM). The Everglades Depth Estimation Network (EDEN) supplies important hydrologic data, and its products (including a ground DEM) have been well received by scientists and resource managers involved in Everglades restoration. This study improves the EDEN DEMs of the Loxahatchee National Wildlife Refuge, also known as Water Conservation Area 1 (WCA1), by adopting a landscape unit (LU) based interpolation approach. The study first filtered the input elevation data based on newly available vegetation data, and then created a separate geostatistical model (universal kriging) for each LU. The resultant DEMs have encouraging cross-validation and validation results, especially since the validation is based on an independent elevation dataset (derived by subtracting water depth measurements from EDEN water surface elevations). The DEM product of this study will directly benefit hydrologic and ecological studies as well as restoration efforts. The study will also be valuable for a broad range of wetland studies.

  3. Artificial terraced field extraction based on high resolution DEMs

    Science.gov (United States)

    Na, Jiaming; Yang, Xin; Xiong, Liyang; Tang, Guoan

    2017-04-01

    With the increase of human activities, artificial landforms become one of the main terrain features with special geographical and hydrological value. Terraced field, as the most important artificial landscapes of the loess plateau, plays an important role in conserving soil and water. With the development of digital terrain analysis (DTA), there is a current and future need in developing a robust, repeatable and cost-effective research methodology for terraced fields. In this paper, a novel method using bidirectional DEM shaded relief is proposed for terraced field identification based on high resolution DEM, taking Zhifanggou watershed, Shannxi province as the study area. Firstly, 1m DEM is obtained by low altitude aerial photogrammetry using Unmanned Aerial Vehicle (UAV), and 0.1m DOM is also obtained as the test data. Then, the positive and negative terrain segmentation is done to acquire the area of terraced field. Finally, a bidirectional DEM shaded relief is simulated to extract the ridges of each terraced field stages. The method in this paper can get not only polygon feature of the terraced field areas but also line feature of terraced field ridges. The accuracy is 89.7% compared with the artificial interpretation result from DOM. And additional experiment shows that this method has a strong robustness as well as high accuracy.

  4. U.S. Virgin Islands Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The 1 arc-second Virgin Islands DEM will be used to support NOAA's tsunami forecast system and for tsunami inundation modeling. This DEM encompasses the Virgin...

  5. Inundation Analysis of Reservoir Flood Based on Computer Aided Design (CAD and Digital Elevation Model (DEM

    Directory of Open Access Journals (Sweden)

    Jiqing Li

    2018-04-01

    Full Text Available GIS (Geographic Information System can be used to combine multiple hydrologic data and geographic data for FIA (Flood Impact Assessment. For a developing country like China, a lot of geographic data is in the CAD (Computer Aided Design format. The commonly used method for converting CAD into DEM may result in data loss. This paper introduces a solution for the conversion between CAD data and DEM data. The method has been applied to the FIA based on the topographic map of CAD in Hanjiang River. When compared with the other method, the new method solves the data loss problem. Besides, the paper use GIS to simulate the inundation range, area, and the depth distribution of flood backwater. Based on the analysis, the author concludes: (1 the differences of the inundation areas between the flood of HQ100 and the flood of HQ50 are small. (2 The inundation depth shows a decreasing trend along the upstream of the river. (3 The inundation area less than 4 m in flood of HQ50 is larger than that in flood of HQ100, the result is opposite when the inundation depth is greater than 4 m. (4 The flood loss is 392.32 million RMB for flood of HQ50 and 610.02 million RMB for flood of HQ100. The method can be applied to FIA.

  6. How large is the Upper Indus Basin? The pitfalls of auto-delineation using DEMs

    Science.gov (United States)

    Khan, Asif; Richards, Keith S.; Parker, Geoffrey T.; McRobie, Allan; Mukhopadhyay, Biswajit

    2014-02-01

    Extraction of watershed areas from Digital Elevation Models (DEMs) is increasingly required in a variety of environmental analyses. It is facilitated by the availability of DEMs based on remotely sensed data, and by Geographical Information System (GIS) software. However, accurate delineation depends on the quality of the DEM and the methodology adopted. This paper considers automated and supervised delineation in a case study of the Upper Indus Basin (UIB), Pakistan, for which published estimates of the basin area show significant disagreement, ranging from 166,000 to 266,000 km2. Automated delineation used ArcGIS Archydro and hydrology tools applied to three good quality DEMs (two from SRTM data with 90m resolution, and one from 30m resolution ASTER data). Automatic delineation defined a basin area of c.440,000 km2 for the UIB, but included a large area of internal drainage in the western Tibetan Plateau. It is shown that discrepancies between different estimates reflect differences in the initial extent of the DEM used for watershed delineation, and the unchecked effect of iterative pit-filling of the DEM (going beyond the filling of erroneous pixels to filling entire closed basins). For the UIB we have identified critical points where spurious addition of catchment area has arisen, and use Google Earth to examine the geomorphology adjacent to these points, and also examine the basin boundary data provided by the HydroSHEDS database. We show that the Pangong Tso watershed and some other areas in the western Tibetan plateau are not part of the UIB, but are areas of internal drainage. Our best estimate of the area of the Upper Indus Basin (at Besham Qila) is 164,867 km2 based on the SRTM DEM, and 164,853 km2 using the ASTER DEM). This matches the catchment area measured by WAPDA SWHP. An important lesson from this investigation is that one should not rely on automated delineation, as iterative pit-filling can produce spurious drainage networks and basins, when

  7. Bermuda 3 arc-second Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The 3 arc-second Bermuda DEM will be used to support NOAA's tsunami forecast system and for tsunami inundation modeling. This DEM encompasses the islands of Bermuda...

  8. Bermuda 1 arc-second Coastal Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The 1 arc-second Bermuda DEM will be used to support NOAA's tsunami forecast system and for tsunami inundation modeling. This DEM encompasses the islands of Bermuda...

  9. Construction of a digital elevation model: methods and parallelization

    International Nuclear Information System (INIS)

    Mazzoni, Christophe

    1995-01-01

    The aim of this work is to reduce the computation time needed to produce the Digital Elevation Models (DEM) by using a parallel machine. It is made in collaboration between the French 'Institut Geographique National' (IGN) and the Laboratoire d'Electronique de Technologie et d'Instrumentation (LETI) of the French Atomic Energy Commission (CEA). The IGN has developed a system which provides DEM that is used to produce topographic maps. The kernel of this system is the correlator, a software which automatically matches pairs of homologous points of a stereo-pair of photographs. Nevertheless the correlator is expensive In computing time. In order to reduce computation time and to produce the DEM with same accuracy that the actual system, we have parallelized the IGN's correlator on the OPENVISION system. This hardware solution uses a SIMD (Single Instruction Multiple Data) parallel machine SYMPATI-2, developed by the LETI that is involved in parallel architecture and image processing. Our analysis of the implementation has demonstrated the difficulty of efficient coupling between scalar and parallel structure. So we propose solutions to reinforce this coupling. In order to accelerate more the processing we evaluate SYMPHONIE, a SIMD calculator, successor of SYMPATI-2. On an other hand, we developed a multi-agent approach for what a MIMD (Multiple Instruction, Multiple Data) architecture is available. At last, we describe a Multi-SIMD architecture that conciliates our two approaches. This architecture offers a capacity to apprehend efficiently multi-level treatment image. It is flexible by its modularity, and its communication network supplies reliability that interest sensible systems. (author) [fr

  10. EFFECT OF DIGITAL ELEVATION MODEL MESH SIZE ON GEOMORPHIC INDICES: A CASE STUDY OF THE IVAÍ RIVER WATERSHED - STATE OF PARANÁ, BRAZIL

    Directory of Open Access Journals (Sweden)

    Vanessa Cristina Dos Santos

    Full Text Available Abstract: Geomorphometry is the science of quantitative description of land surface morphology by the mean of geomorphic indices extracted from Digital Elevation Models (DEMs. The analysis of these indices is the first and most common procedure performed in several geoscience-related subjects. This study aims to assess the impact of mesh size degradation on different local and regional geomorphic indices extracted for GDEM and TOPODATA DEMs. Thus, these DEMs, having a mesh size of 30 m, were subsampled to 60, 120 and 240 m and then geomorphic indices were calculated using the full resolution DEM and the subsampled ones. Depending on their behavior, these indices are then classified into stable and unstable. The results show that the most affected indices are slope and hydrographic indices such as Strahler order, stream sinuosity and fractal dimension and watershed perimeter, whereas elevation remains stable. It also shows that the effect depends on the presence of the canopy and geological structures in the studied area.

  11. ASTER Global Digital Elevation Model Version 2 - summary of validation results

    Science.gov (United States)

    Tachikawa, Tetushi; Kaku, Manabu; Iwasaki, Akira; Gesch, Dean B.; Oimoen, Michael J.; Zhang, Z.; Danielson, Jeffrey J.; Krieger, Tabatha; Curtis, Bill; Haase, Jeff; Abrams, Michael; Carabajal, C.; Meyer, Dave

    2011-01-01

    On June 29, 2009, NASA and the Ministry of Economy, Trade and Industry (METI) of Japan released a Global Digital Elevation Model (GDEM) to users worldwide at no charge as a contribution to the Global Earth Observing System of Systems (GEOSS). This “version 1” ASTER GDEM (GDEM1) was compiled from over 1.2 million scenebased DEMs covering land surfaces between 83°N and 83°S latitudes. A joint U.S.-Japan validation team assessed the accuracy of the GDEM1, augmented by a team of 20 cooperators. The GDEM1 was found to have an overall accuracy of around 20 meters at the 95% confidence level. The team also noted several artifacts associated with poor stereo coverage at high latitudes, cloud contamination, water masking issues and the stacking process used to produce the GDEM1 from individual scene-based DEMs (ASTER GDEM Validation Team, 2009). Two independent horizontal resolution studies estimated the effective spatial resolution of the GDEM1 to be on the order of 120 meters.

  12. Estimating Vegetation Height from WorldView-02 and ArcticDEM Data for Broad Ecological Applications

    Science.gov (United States)

    Meddens, A. J.; Vierling, L. A.; Eitel, J.; Jennewein, J. S.; White, J. C.; Wulder, M.

    2017-12-01

    Boreal and arctic regions are warming at an unprecedented rate, and at a rate higher than in other regions across the globe. Ecological processes are highly responsive to temperature and therefore substantial changes in these northern ecosystems are expected. Recently, NASA initiated the Arctic-Boreal Vulnerability Experiment (ABoVE), which is a large-scale field campaign that aims to gain a better understanding of how the arctic responds to environmental change. High-resolution data products that quantify vegetation structure and function will improve efforts to assess these environmental change impacts. Our objective was to develop and test an approach that allows for mapping vegetation height at a 5m grid cell resolution across the ABoVE domain. To accomplish this, we selected three study areas across a north-south gradient in Alaska, representing an area of approximately 130 km2. We developed a RandomForest modeling approach for predicting vegetation height using the ArcticDEM (a digital surface model produced across the Arctic by the Polar Geospatial Center) and high-resolution multispectral satellite data (WorldView-2) in conjunction with aerial lidar data for calibration and validation. Vegetation height was successfully predicted across the three study areas and evaluated using an independent dataset, with R2 ranging from 0.58 to 0.76 and RMSEs ranging from 1.8 to 2.4 m. This predicted vegetation height dataset also led to the development of a digital terrain model using the ArcticDEM digital surface model by removing canopy heights from the surface heights. Our results show potential to establish a high resolution pan-arctic vegetation height map, which will provide useful information to a broad range of ongoing and future ecological research in high northern latitudes.

  13. High Resolution Digital Elevation Models of Pristine Explosion Craters

    Science.gov (United States)

    Farr, T. G.; Krabill, W.; Garvin, J. B.

    2004-01-01

    In order to effectively capture a realistic terrain applicable to studies of cratering processes and landing hazards on Mars, we have obtained high resolution digital elevation models of several pristine explosion craters at the Nevada Test Site. We used the Airborne Terrain Mapper (ATM), operated by NASA's Wallops Flight Facility to obtain DEMs with 1 m spacing and 10 cm vertical errors of 4 main craters and many other craters and collapse pits. The main craters that were mapped are Sedan, Scooter, Schooner, and Danny Boy. The 370 m diameter Sedan crater, located on Yucca Flat, is the largest and freshest explosion crater on Earth that was formed under conditions similar to hypervelocity impact cratering. As such, it is effectively pristine, having been formed in 1962 as a result of a controlled detonation of a 100 kiloton thermonuclear device, buried at the appropriate equivalent depth of burst required to make a simple crater. Sedan was formed in alluvium of mixed lithology and subsequently studied using a variety of field-based methods. Nearby secondary craters were also formed at the time and were also mapped by ATM. Adjacent to Sedan and also in alluvium is Scooter, about 90 m in diameter and formed by a high-explosive event. Schooner (240 m) and Danny Boy (80 m) craters were also important targets for ATM as they were excavated in hard basalt and therefore have much rougher ejecta. This will allow study of ejecta patterns in hard rock as well as engineering tests of crater and rock avoidance and rover trafficability. In addition to the high resolution DEMs, crater geometric characteristics, RMS roughness maps, and other higher-order derived data products will be generated using these data. These will provide constraints for models of landing hazards on Mars and for rover trafficability. Other planned studies will include ejecta size-frequency distribution at the resolution of the DEM and at finer resolution through air photography and field measurements

  14. Effects of External Digital Elevation Model Inaccuracy on StaMPS-PS Processing: A Case Study in Shenzhen, China

    Directory of Open Access Journals (Sweden)

    Yanan Du

    2017-11-01

    Full Text Available External Digital Elevation Models (DEMs with different resolutions and accuracies cause different topographic residuals in differential interferograms of Multi-temporal InSAR (MTInSAR, especially for the phase-based StaMPS-PS. The PS selection and deformation parameter estimation of StaMPS-PS are closely related to the spatially uncorrected error, which is directly affected by external DEMs. However, it is still far from clear how the high resolution and accurate external DEM affects the results of the StaMPS-PS (e.g., PS selection and deformation parameter calculation on different platforms (X band TerraSAR, C band ENVISAT ASAR and L band ALOS/PALSAR1. In this study, abundant synthetic tests are performed to assess the influences of external DEMs on parameter estimations, such as the mean deformation rate and the deformation time-series. Real SAR images, covering Shenzhen city in China, are also selected to analyze the PS selection and distribution as well as to validate the results of synthetic tests. The results show that the PS points selected by the 5 m TanDEM-X DEM are 10.32%, 4.25% and 0.34% more than those selected by the 30 m SRTM DEM at X, C and L bands SAR platforms, respectively, when a multi-look geocoding operation is adopted for X band in the SRTM DEM case. We also find that the influences of external DEMs on the mean deformation rate are not significant and are inversely proportional to the wavelength of the satellite platforms. The standard deviations of the mean deformation rate difference for the X, C and L bands are 0.54, 0.30 and 0.10 mm/year, respectively. Similarly, the influences of external DEMs on the deformation time-series estimation for the three platforms are also slight, except for local artifacts whose root-mean-square error (RMSE ≥ 6 mm. Based on these analyses, some implications and suggestions for external DEMs on StaMPS-PS processing are discussed and provided.

  15. Landsat 5 TM images and DEM in lithologic mapping of Payen Volcanic Field (Mendoza Province, Argentina)

    International Nuclear Information System (INIS)

    Fornaciai, A.; Bisson, M.; Mazzarini, F.; Del Carlo, P.; Pasquare, G.

    2009-01-01

    Satellite image such as Landsat 5 TM scene provides excellent representation of Earth and synoptic view of large geographic areas in different band combination. Landsat TM images allow automatic and semi-automatic classification of land cover, nevertheless the software frequently may some difficulties in distinguishing between similar radiometric surfaces. In this case, the use of Digital Elevation Model (DEM) can be an important tool to identify different surface covers. In this study, several False Color Composite (FCC) of Landsat 5 TM Image, DEM and the respective draped image of them, were used to delineate lithological boundaries and tectonic features of regional significance of the Paven Volcanic Field (PVF). PFV is a Quaternary fissural structure belonging to the black-arc extensional areas of the Andes in the Mendoza Province (Argentina) characterized by many composite basaltic lava flow fields. The necessity to identify different lava flows with the same composition, and then with same spectral features, allows to highlight the improvement of synergic use of TM images and shaded DEM in the visual interpretation. Information obtained from Satellite data and DEM have been compared with previous geological maps and transferred into a topographical base map. Based on these data a new lithological map at 1:100.000 scale has been presented [it

  16. Improving low-relief coastal LiDAR DEMs with hydro-conditioning of fine-scale and artificial drainages

    Directory of Open Access Journals (Sweden)

    Thomas Richard Allen

    2015-11-01

    Full Text Available Improvements in Light Detection and Ranging (LiDAR technology and spatial analysis of high-resolution digital elevation models (DEMs have advanced the accuracy and diversity of applications for coastal hazards and natural resources management. This article presents a concise synthesis of LiDAR analysis for coastal flooding and management applications in low-relief coastal plains and a case study demonstration of a new, efficient drainage mapping algorithm. The impetus for these LiDAR applications follows historic flooding from Hurricane Floyd in 1999, after which the State of North Carolina and the Federal Emergency Management Agency undertook extensive LiDAR data acquisition and technological developments for high-resolution floodplain mapping. An efficient algorithm is outlined for hydro-conditioning bare earth LiDAR DEMs using available US Geological Survey National Hydrography Dataset canal and ditch vectors. The methodology is illustrated in Moyock, North Carolina, for refinement of hydro-conditioning by combines pre-existing bare earth DEMs with spatial analysis of LiDAR point clouds in segmented and buffered ditch and canal networks. The methodology produces improved maps of fine-scale drainage, reduced omission of areal flood inundation, and subwatershed delineations that typify heavily ditched and canalled drainage areas. These preliminary results illustrate the capability of the technique to improve the representation of ditches in DEMs as well as subsequent flow and inundation modeling that could spur further research on low-relief coastal LiDAR applications.

  17. Volcanic activity at Etna volcano, Sicily, Italy between June 2011 and March 2017 studied with TanDEM-X SAR interferometry

    Science.gov (United States)

    Kubanek, J.; Raible, B.; Westerhaus, M.; Heck, B.

    2017-12-01

    High-resolution and up-to-date topographic data are of high value in volcanology and can be used in a variety of applications such as volcanic flow modeling or hazard assessment. Furthermore, time-series of topographic data can provide valuable insights into the dynamics of an ongoing eruption. Differencing topographic data acquired at different times enables to derive areal coverage of lava, flow volumes, and lava extrusion rates, the most important parameters during ongoing eruptions for estimating hazard potential, yet most difficult to determine. Anyhow, topographic data acquisition and provision is a challenge. Very often, high-resolution data only exists within a small spatial extension, or the available data is already outdated when the final product is provided. This is especially true for very dynamic landscapes, such as volcanoes. The bistatic TanDEM-X radar satellite mission enables for the first time to generate up-to-date and high-resolution digital elevation models (DEMs) repeatedly using the interferometric phase. The repeated acquisition of TanDEM-X data facilitates the generation of a time-series of DEMs. Differencing DEMs generated from bistatic TanDEM-X data over time can contribute to monitor topographic changes at active volcanoes, and can help to estimate magmatic ascent rates. Here, we use the bistatic TanDEM-X data to investigate the activity of Etna volcano in Sicily, Italy. Etna's activity is characterized by lava fountains and lava flows with ash plumes from four major summit crater areas. Especially the newest crater, the New South East Crater (NSEC) that was formed in 2011 has been highly active in recent years. Over one hundred bistatic TanDEM-X data pairs were acquired between January 2011 and March 2017 in StripMap mode, covering episodes of lava fountaining and lava flow emplacement at Etna's NSEC and its surrounding area. Generating DEMs of every bistatic data pair enables us to assess areal extension of the lava flows, to

  18. Digital Elevation Model Correction for the thalweg values of Obion River system, TN

    Science.gov (United States)

    Dullo, T. T.; Bhuyian, M. N. M.; Hawkins, S. A.; Kalyanapu, A. J.

    2016-12-01

    Obion River system is located in North-West Tennessee and discharges into the Mississippi River. To facilitate US Department of Agriculture (USDA) to estimate water availability for agricultural consumption a one-dimensional HEC-RAS model has been proposed. The model incorporates the major tributaries (north and south), main stem of Obion River along with a segment of the Mississippi River. A one-meter spatial resolution Light Detection and Ranging (LiDAR) derived Digital Elevation Model (DEM) was used as the primary source of topographic data. LiDAR provides fine-resolution terrain data over given extent. However, it lacks in accurate representation of river bathymetry due to limited penetration beyond a certain water depth. This reduces the conveyance along river channel as represented by the DEM and affects the hydrodynamic modeling performance. This research focused on proposing a method to overcome this issue and test the qualitative improvement by the proposed method over an existing technique. Therefore, objective of this research is to compare effectiveness of a HEC-RAS based bathymetry optimization method with an existing hydraulic based DEM correction technique (Bhuyian et al., 2014) for Obion River system in Tennessee. Accuracy of hydrodynamic simulations (upon employing bathymetry from respective sources) would be regarded as the indicator of performance. The aforementioned river system includes nine major reaches with a total river length of 310 km. The bathymetry of the river was represented via 315 cross sections equally spaced at about one km. This study targeted to selecting best practice for treating LiDAR based terrain data over complex river system at a sub-watershed scale.

  19. Forest operations planning by using RTK-GPS based digital elevation model

    Directory of Open Access Journals (Sweden)

    Neşe Gülci

    2015-07-01

    Full Text Available Having large proportion of forests in mountainous terrain in Turkey, the logging methods that not only minimize operational costs but also minimize environmental damages should be determined in forest operations planning. In a case where necessary logging equipment and machines are available, ground slope is the most important factor in determining the logging method. For this reason, accurate, up to date, and precise ground slope data is very crucial in the success of forest operations planning. In recent years, high-resolution Digital Elevation Models (DEM can be generated for forested areas by using Real Time Kinematic (RTK GPS method and these DEMs can be used to develop precise slope maps. In this study, high-resolution DEM was developed by RTK-GPS method to generate precise slope map in a sample area. Then, the slope map was classified into slope classes specified by IUFRO in order to assist forest operations planning. According to the results, logging methods that are suitable for very steep and steep terrain conditions (i.e. skyline logging, cable pulling, and chute systems should be preferred in 48.1% of the study area. It was also found that logging methods that are suitable for terrain with medium slope (i.e. skidding and cable pulling and gentle slope (i.e. skidding and mobile winch should be preferred in 34.1% and 17.8% of the study area, respectively.

  20. Statistical correction of lidar-derived digital elevation models with multispectral airborne imagery in tidal marshes

    Science.gov (United States)

    Buffington, Kevin J.; Dugger, Bruce D.; Thorne, Karen M.; Takekawa, John Y.

    2016-01-01

    Airborne light detection and ranging (lidar) is a valuable tool for collecting large amounts of elevation data across large areas; however, the limited ability to penetrate dense vegetation with lidar hinders its usefulness for measuring tidal marsh platforms. Methods to correct lidar elevation data are available, but a reliable method that requires limited field work and maintains spatial resolution is lacking. We present a novel method, the Lidar Elevation Adjustment with NDVI (LEAN), to correct lidar digital elevation models (DEMs) with vegetation indices from readily available multispectral airborne imagery (NAIP) and RTK-GPS surveys. Using 17 study sites along the Pacific coast of the U.S., we achieved an average root mean squared error (RMSE) of 0.072 m, with a 40–75% improvement in accuracy from the lidar bare earth DEM. Results from our method compared favorably with results from three other methods (minimum-bin gridding, mean error correction, and vegetation correction factors), and a power analysis applying our extensive RTK-GPS dataset showed that on average 118 points were necessary to calibrate a site-specific correction model for tidal marshes along the Pacific coast. By using available imagery and with minimal field surveys, we showed that lidar-derived DEMs can be adjusted for greater accuracy while maintaining high (1 m) resolution.

  1. British Columbia 3 arc-second Bathymetric Digital Elevation Model

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The 3 arc-second British Columbia DEM will be used to support NOAA's tsunami forecast system and for tsunami inundation modeling. This DEM covers the coastal area...

  2. Detection of seasonal cycles of erosion processes in a black marl gully from a time series of high-resolution digital elevation models (DEMs

    Directory of Open Access Journals (Sweden)

    J. Bechet

    2016-10-01

    Full Text Available The Roubine catchment located in the experimental research station of Draix-Bléone (south French Alps is situated in Callovo-Oxfordian black marls, a lithology particularly prone to erosion and weathering processes. For 30 years, this small watershed (0.13 ha has been monitored for analysing hillslope processes on the scale of elementary gullies. Since 2007, surface changes have been monitored by comparing high-resolution digital elevation models (HRDEMs produced from terrestrial laser scanner (TLS. The objectives are (1 to detect and (2 to quantify the sediment production and the evolution of the gully morphology in terms of sediment availability/transport capacity vs. rainfall and runoff generation. Time series of TLS observations have been acquired periodically based on the seasonal runoff activity with a very high point cloud density ensuring a resolution of the digital elevation model (DEM on the centimetre scale. The topographic changes over a time span of 2 years are analysed. Quantitative analyses of the seasonal erosion activity and of the sediment fluxes show and confirm that during winter, loose regolith is created by mechanical weathering, and it is eroded and accumulates in the rills and gullies. Because of limited rainfall intensity in spring, part of the material is transported in the main gullies, which are assumed to be a transport-limited erosion system. In the late spring and summer the rainfall intensities increase, allowing the regolith, weathered and accumulated in the gullies and rills during the earlier seasons, to be washed out. Later in the year the catchment acts as a sediment-limited system because no more loose regolith is available. One interesting result is the fact that in the gullies the erosion–deposition processes are more active around the slope angle value of 35°, which probably indicates a behaviour close to dry granular material. It is also observed that there exist thresholds for the rainfall

  3. Modelling of Singapore's topographic transformation based on DEMs

    Science.gov (United States)

    Wang, Tao; Belle, Iris; Hassler, Uta

    2015-02-01

    Singapore's topography has been heavily transformed by industrialization and urbanization processes. To investigate topographic changes and evaluate soil mass flows, historical topographic maps of 1924 and 2012 were employed, and basic topographic features were vectorized. Digital elevation models (DEMs) for the two years were reconstructed based on vector features. Corresponding slope maps, a surface difference map and a scatter plot of elevation changes were generated and used to quantify and categorize the nature of the topographic transformation. The surface difference map is aggregated into five main categories of changes: (1) areas without significant height changes, (2) lowered-down areas where hill ranges were cut down, (3) raised-up areas where valleys and swamps were filled in, (4) reclaimed areas from the sea, and (5) new water-covered areas. Considering spatial proximity and configurations of different types of changes, topographic transformation can be differentiated as either creating inland flat areas or reclaiming new land from the sea. Typical topographic changes are discussed in the context of Singapore's urbanization processes. The two slope maps and elevation histograms show that generally, the topographic surface of Singapore has become flatter and lower since 1924. More than 89% of height changes have happened within a range of 20 m and 95% have been below 40 m. Because of differences in land surveying and map drawing methods, uncertainties and inaccuracies inherent in the 1924 topographic maps are discussed in detail. In this work, a modified version of a traditional scatter plot is used to present height transformation patterns intuitively. This method of deriving categorical maps of topographical changes from a surface difference map can be used in similar studies to qualitatively interpret transformation. Slope maps and histograms were also used jointly to reveal additional patterns of topographic change.

  4. Optimization of the resolution of remotely sensed digital elevation model to facilitate the simulation and spatial propagation of flood events in flat areas

    Science.gov (United States)

    Karapetsas, Nikolaos; Skoulikaris, Charalampos; Katsogiannos, Fotis; Zalidis, George; Alexandridis, Thomas

    2013-04-01

    The use of satellite remote sensing products, such as Digital Elevation Models (DEMs), under specific computational interfaces of Geographic Information Systems (GIS) has fostered and facilitated the acquisition of data on specific hydrologic features, such as slope, flow direction and flow accumulation, which are crucial inputs to hydrology or hydraulic models at the river basin scale. However, even though DEMs of different resolution varying from a few km up to 20m are freely available for the European continent, these remotely sensed elevation data are rather coarse in cases where large flat areas are dominant inside a watershed, resulting in an unsatisfactory representation of the terrain characteristics. This scientific work aims at implementing a combing interpolation technique for the amelioration of the analysis of a DEM in order to be used as the input ground model to a hydraulic model for the assessment of potential flood events propagation in plains. More specifically, the second version of the ASTER Global Digital Elevation Model (GDEM2), which has an overall accuracy of around 20 meters, was interpolated with a vast number of aerial control points available from the Hellenic Mapping and Cadastral Organization (HMCO). The uncertainty that was inherent in both the available datasets (ASTER & HMCO) and the appearance of uncorrelated errors and artifacts was minimized by incorporating geostatistical filtering. The resolution of the produced DEM was approximately 10 meters and its validation was conducted with the use of an external dataset of 220 geodetic survey points. The derived DEM was then used as an input to the hydraulic model InfoWorks RS, whose operation is based on the relief characteristics contained in the ground model, for defining, in an automated way, the cross section parameters and simulating the flood spatial distribution. The plain of Serres, which is located in the downstream part of the Struma/Strymon transboundary river basin shared

  5. MORPHOLOGICAL FILLING OF DIGITAL ELEVATION MODELS

    Directory of Open Access Journals (Sweden)

    T. Krauß

    2012-09-01

    Full Text Available In this paper a new approach for a more detailed post processing and filling of digital elevation models (DEMs in urban areas is presented. To reach the required specifications in a first step the errors in digital surface models (DSMs generated by dense stereo algorithms are analyzed and methods for detection and classification of the different types of errors are implemented. Subsequently the classified erroneous areas are handled in separate manner to eliminate outliers and fill the DSM properly. The errors which can be detected in DSMs range from outliers – single pixels or small areas containing extremely high or low values – over noise from mismatches, single small holes to occlusions, where large areas are not visible in one of the images of the stereo pair. To validate the presented method artificial DSMs are generated and superimposed with all different kinds of described errors like noise (small holes cut in, outliers (small areas moved up/down, occlusions (larger areas beneath steep walls and so on. The method is subsequently applied to the artificial DSMs and the resulting filled DSMs are compared to the original artificial DSMs without the introduced errors. Also the method is applied to stereo satellite generated DSMs from the ISPRS Comission 1 WG4 benchmark dataset and the results are checked with the also provided first pulse laser DSM data. Finally the results are discussed, strengths and weaknesses of the approach are shown and suggestions for application and optimization are given.

  6. Multiscale geomorphometric modeling of Mercury

    Science.gov (United States)

    Florinsky, I. V.

    2018-02-01

    Topography is one of the key characteristics of a planetary body. Geomorphometry deals with quantitative modeling and analysis of the topographic surface and relationships between topography and other natural components of landscapes. The surface of Mercury is systematically studied by interpretation of images acquired during the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission. However, the Mercurian surface is still little explored by methods of geomorphometry. In this paper, we evaluate the Mercury MESSENGER Global DEM MSGR_DEM_USG_SC_I_V02 - a global digital elevation model (DEM) of Mercury with the resolution of 0.015625° - as a source for geomorphometric modeling of this planet. The study was performed at three spatial scales: the global, regional (the Caloris basin), and local (the Pantheon Fossae area) ones. As the initial data, we used three DEMs of these areas with resolutions of 0.25°, 0.0625°, and 0.015625°, correspondingly. The DEMs were extracted from the MESSENGER Global DEM. From the DEMs, we derived digital models of several fundamental morphometric variables, such as: slope gradient, horizontal curvature, vertical curvature, minimal curvature, maximal curvature, catchment area, and dispersive area. The morphometric maps obtained represent peculiarities of the Mercurian topography in different ways, according to the physical and mathematical sense of a particular variable. Geomorphometric models are a rich source of information on the Mercurian surface. These data can be utilized to study evolution and internal structure of the planet, for example, to visualize and quantify regional topographic differences as well as to refine geological boundaries.

  7. A guide for the use of digital elevation model data for making soil surveys

    Science.gov (United States)

    Klingebiel, A.A.; Horvath, Emil H.; Reybold, William U.; Moore, D.G.; Fosnight, E.A.; Loveland, Thomas R.

    1988-01-01

    The intent of this publication is twofold: (1) to serve as a user guide for soil scientists and others interested in learning about the value and use of digital elevation model (DEM) data in making soil surveys and (2) to provide documentation of the Soil Landscape Analysis Project (SLAP). This publication provides a step-by-step guide on how digital slope-class maps are adjusted to topographic maps and orthophotoquads to obtain accurate slope-class maps, and how these derivative maps can be used as a base for soil survey premaps. In addition, guidance is given on the use of aspect-class maps and other resource data in making pre-maps. The value and use of tabular summaries are discussed. Examples of the use of DEM products by the authors and by selected field soil scientists are also given. Additional information on SLAP procedures may be obtained from USDA, Soil Conservation Service, Soil Survey Division, P.O. Box 2890, Washington, D.C. 20013, and from references (Horvath and others, 1987; Horvath and others, 1983; Klingebiel and others, 1987; and Young, 1987) listed in this publication. The slope and aspect products and the procedures for using these products have evolved during 5 years of cooperative research with the USDA, Soil Conservation Service and Forest Service, and the USDI, Bureau of Land Management.

  8. Suitability of digital elevation models generated by uav photogrammetry for slope stability assessment (case study of landslide in Svätý Anton, Slovakia

    Directory of Open Access Journals (Sweden)

    Rusnák Miloš

    2016-12-01

    Full Text Available Assessing the accuracy of photogrammetrically-derived digital elevation models (DEMs from UAV is essential in many geoscience disciplines. The suitability of different DEM devised for slope stability assessment was evaluated in the example of the landslide in Svätý Anton village in Slovakia. Aerial data was acquired during a one-day field campaign in autumn 2014. The point cloud from 218 images (54,607,748 points was manually classified into 7 different classes for filtering vegetation cover and buildings. Assessment of vertical differences between the UAV derived elevation model and real terrain surface was based on comparison of control points targeted by GPS (337 points and unclassified and ground classified point cloud for raster elevation models with 1, 5, 10, 20 and 50 cm pixel resolution.

  9. Ground target geolocation based on digital elevation model for airborne wide-area reconnaissance system

    Science.gov (United States)

    Qiao, Chuan; Ding, Yalin; Xu, Yongsen; Xiu, Jihong

    2018-01-01

    To obtain the geographical position of the ground target accurately, a geolocation algorithm based on the digital elevation model (DEM) is developed for an airborne wide-area reconnaissance system. According to the platform position and attitude information measured by the airborne position and orientation system and the gimbal angles information from the encoder, the line-of-sight pointing vector in the Earth-centered Earth-fixed coordinate frame is solved by the homogeneous coordinate transformation. The target longitude and latitude can be solved with the elliptical Earth model and the global DEM. The influences of the systematic error and measurement error on ground target geolocation calculation accuracy are analyzed by the Monte Carlo method. The simulation results show that this algorithm can improve the geolocation accuracy of ground target in rough terrain area obviously. The geolocation accuracy of moving ground target can be improved by moving average filtering (MAF). The validity of the geolocation algorithm is verified by the flight test in which the plane flies at a geodetic height of 15,000 m and the outer gimbal angle is <47°. The geolocation root mean square error of the target trajectory is <45 and <7 m after MAF.

  10. Landslide-susceptibility analysis using light detection and ranging-derived digital elevation models and logistic regression models: a case study in Mizunami City, Japan

    Science.gov (United States)

    Wang, Liang-Jie; Sawada, Kazuhide; Moriguchi, Shuji

    2013-01-01

    To mitigate the damage caused by landslide disasters, different mathematical models have been applied to predict landslide spatial distribution characteristics. Although some researchers have achieved excellent results around the world, few studies take the spatial resolution of the database into account. Four types of digital elevation model (DEM) ranging from 2 to 20 m derived from light detection and ranging technology to analyze landslide susceptibility in Mizunami City, Gifu Prefecture, Japan, are presented. Fifteen landslide-causative factors are considered using a logistic-regression approach to create models for landslide potential analysis. Pre-existing landslide bodies are used to evaluate the performance of the four models. The results revealed that the 20-m model had the highest classification accuracy (71.9%), whereas the 2-m model had the lowest value (68.7%). In the 2-m model, 89.4% of the landslide bodies fit in the medium to very high categories. For the 20-m model, only 83.3% of the landslide bodies were concentrated in the medium to very high classes. When the cell size decreases from 20 to 2 m, the area under the relative operative characteristic increases from 0.68 to 0.77. Therefore, higher-resolution DEMs would provide better results for landslide-susceptibility mapping.

  11. Historic Low Wall Detection via Topographic Parameter Images Derived from Fine-Resolution DEM

    Directory of Open Access Journals (Sweden)

    Hone-Jay Chu

    2017-11-01

    Full Text Available Coral walls protect vegetation gardens from strong winds that sweep across Xiji Island, Taiwan Strait for half the year. Topographic parameters based on light detection and ranging (LiDAR-based high-resolution digital elevation model (DEM provide obvious correspondence with the expected form of landscape features. The information on slope, curvature, and openness can help identify the location of landscape features. This study applied the automatic landscape line detection to extract historic vegetable garden wall lines from a LiDAR-derived DEM. The three rapid processes used in this study included the derivation of topographic parameters, line extraction, and aggregation. The rules were extracted from a decision tree to check the line detection from multiple topographic parameters. Results show that wall line detection with multiple topographic parameter images is an alternative means of obtaining essential historic wall feature information. Multiple topographic parameters are highly related to low wall feature identification. Furthermore, the accuracy of wall feature detection is 74% compared with manual interpretation. Thus, this study provides rapid wall detection systems with multiple topographic parameters for further historic landscape management.

  12. The effects of digital elevation model resolution on the calculation and predictions of topographic wetness indices.

    Energy Technology Data Exchange (ETDEWEB)

    Drover, Damion, Ryan

    2011-12-01

    One of the largest exports in the Southeast U.S. is forest products. Interest in biofuels using forest biomass has increased recently, leading to more research into better forest management BMPs. The USDA Forest Service, along with the Oak Ridge National Laboratory, University of Georgia and Oregon State University are researching the impacts of intensive forest management for biofuels on water quality and quantity at the Savannah River Site in South Carolina. Surface runoff of saturated areas, transporting excess nutrients and contaminants, is a potential water quality issue under investigation. Detailed maps of variable source areas and soil characteristics would therefore be helpful prior to treatment. The availability of remotely sensed and computed digital elevation models (DEMs) and spatial analysis tools make it easy to calculate terrain attributes. These terrain attributes can be used in models to predict saturated areas or other attributes in the landscape. With laser altimetry, an area can be flown to produce very high resolution data, and the resulting data can be resampled into any resolution of DEM desired. Additionally, there exist many maps that are in various resolutions of DEM, such as those acquired from the U.S. Geological Survey. Problems arise when using maps derived from different resolution DEMs. For example, saturated areas can be under or overestimated depending on the resolution used. The purpose of this study was to examine the effects of DEM resolution on the calculation of topographic wetness indices used to predict variable source areas of saturation, and to find the best resolutions to produce prediction maps of soil attributes like nitrogen, carbon, bulk density and soil texture for low-relief, humid-temperate forested hillslopes. Topographic wetness indices were calculated based on the derived terrain attributes, slope and specific catchment area, from five different DEM resolutions. The DEMs were resampled from LiDAR, which is a

  13. DEM modeling of failure mechanisms induced by excavations on the Moon

    Science.gov (United States)

    jiang, mingjing; shen, zhifu; Utili, Stefano

    2013-04-01

    2D Discrete Element Method (DEM) analyses were performed for excavations supported by retaining walls in lunar environment. The lunar terrain is made of a layer of sand (regolith) which differs from terrestrial sands for two main features: the presence of adhesive attractive forces due to van der Waals interactions and grains being very irregular in shape leading to high interlocking. A simplified contact model based on linear elasticity and perfect plasticity was employed. The contact model includes a moment - relative rotation law to account for high interlocking among grains and a normal adhesion law to account for the van der Waals interactions. Analyses of the excavations were run under both lunar and terrestrial environments. Under lunar environment, gravity is approximately one sixth than the value on Earth and adhesion forces between grains of lunar regolith due to van der Waals interactions are not negligible. From the DEM simulations it emerged that van der Waals interactions may significantly increase the bending moment and deflection of the retaining wall, and the ground displacements. Hence this study indicates that an unsafe estimate of the wall response to an excavation on the Moon would be obtained from physical experiments performed in a terrestrial environment, i.e., considering the effect of gravity but neglecting the van der Waals interactions.

  14. Bathymetric survey and digital elevation model of Little Holland Tract, Sacramento-San Joaquin Delta, California

    Science.gov (United States)

    Snyder, Alexander G.; Lacy, Jessica R.; Stevens, Andrew W.; Carlson, Emily M.

    2016-06-10

    The U.S. Geological Survey conducted a bathymetric survey in Little Holland Tract, a flooded agricultural tract, in the northern Sacramento-San Joaquin Delta (the “Delta”) during the summer of 2015. The new bathymetric data were combined with existing data to generate a digital elevation model (DEM) at 1-meter resolution. Little Holland Tract (LHT) was historically diked off for agricultural uses and has been tidally inundated since an accidental levee breach in 1983. Shallow tidal regions such as LHT have the potential to improve habitat quality in the Delta. The DEM of LHT was developed to support ongoing studies of habitat quality in the area and to provide a baseline for evaluating future geomorphic change. The new data comprise 138,407 linear meters of real-time-kinematic (RTK) Global Positioning System (GPS) elevation data, including both bathymetric data collected from personal watercraft and topographic elevations collected on foot at low tide. A benchmark (LHT15_b1) was established for geodetic control of the survey. Data quality was evaluated both by comparing results among surveying platforms, which showed systematic offsets of 1.6 centimeters (cm) or less, and by error propagation, which yielded a mean vertical uncertainty of 6.7 cm. Based on the DEM and time-series measurements of water depth, the mean tidal prism of LHT was determined to be 2,826,000 cubic meters. The bathymetric data and DEM are available at http://dx.doi.org/10.5066/F7RX9954. 

  15. Developmental Eye Movement (DEM Test Norms for Mandarin Chinese-Speaking Chinese Children.

    Directory of Open Access Journals (Sweden)

    Yachun Xie

    Full Text Available The Developmental Eye Movement (DEM test is commonly used as a clinical visual-verbal ocular motor assessment tool to screen and diagnose reading problems at the onset. No established norm exists for using the DEM test with Mandarin Chinese-speaking Chinese children. This study aims to establish the normative values of the DEM test for the Mandarin Chinese-speaking population in China; it also aims to compare the values with three other published norms for English-, Spanish-, and Cantonese-speaking Chinese children. A random stratified sampling method was used to recruit children from eight kindergartens and eight primary schools in the main urban and suburban areas of Nanjing. A total of 1,425 Mandarin Chinese-speaking children aged 5 to 12 years took the DEM test in Mandarin Chinese. A digital recorder was used to record the process. All of the subjects completed a symptomatology survey, and their DEM scores were determined by a trained tester. The scores were computed using the formula in the DEM manual, except that the "vertical scores" were adjusted by taking the vertical errors into consideration. The results were compared with the three other published norms. In our subjects, a general decrease with age was observed for the four eye movement indexes: vertical score, adjusted horizontal score, ratio, and total error. For both the vertical and adjusted horizontal scores, the Mandarin Chinese-speaking children completed the tests much more quickly than the norms for English- and Spanish-speaking children. However, the same group completed the test slightly more slowly than the norms for Cantonese-speaking children. The differences in the means were significant (P0.05; compared with Spanish-speaking children, the scores were statistically significant (P0.05. DEM norms may be affected by differences in language, cultural, and educational systems among various ethnicities. The norms of the DEM test are proposed for use with Mandarin Chinese

  16. Adjustment of Measurements with Multiplicative Errors: Error Analysis, Estimates of the Variance of Unit Weight, and Effect on Volume Estimation from LiDAR-Type Digital Elevation Models

    Directory of Open Access Journals (Sweden)

    Yun Shi

    2014-01-01

    Full Text Available Modern observation technology has verified that measurement errors can be proportional to the true values of measurements such as GPS, VLBI baselines and LiDAR. Observational models of this type are called multiplicative error models. This paper is to extend the work of Xu and Shimada published in 2000 on multiplicative error models to analytical error analysis of quantities of practical interest and estimates of the variance of unit weight. We analytically derive the variance-covariance matrices of the three least squares (LS adjustments, the adjusted measurements and the corrections of measurements in multiplicative error models. For quality evaluation, we construct five estimators for the variance of unit weight in association of the three LS adjustment methods. Although LiDAR measurements are contaminated with multiplicative random errors, LiDAR-based digital elevation models (DEM have been constructed as if they were of additive random errors. We will simulate a model landslide, which is assumed to be surveyed with LiDAR, and investigate the effect of LiDAR-type multiplicative error measurements on DEM construction and its effect on the estimate of landslide mass volume from the constructed DEM.

  17. Direct regional quasi-geoid determination using EGM2008 and DEM: A case study for Mainland China and its vicinity areas

    Directory of Open Access Journals (Sweden)

    Jin Li

    2015-11-01

    Full Text Available Earth's gravity model (EGM helps people better determine the figure of Earth, which is generally represented by a global geoid. For a considerable amount of practical applications, people use quasi-geoid to approximate the geoid, thus the quasi-geoid is also treated as an important height datum. In this study we revisit the method to directly determine regional quasi-geoid using EGM and digital elevation model (DEM, on the basis of Molodensky theory. According to the method we obtain a 5′ × 5′ quasi-geoid for Mainland China and its vicinity areas, based on the EGM2008 gravitational potential model and the Shuttle Radar Topography Mission (SRTM DEM model. By comparing height anomalies derived from EGM2008 with observations at 70 GPS/leveling points in areas including northwest, mid-west, mid-east and southeast of China, we find that the 5′ × 5′ EGM2008 quasi-geoid well fits the GPS/leveling results, with average deviations less than 10 cm for the selected areas in east China (with mainly plain topography and ∼20 cm for the selected areas in west China (highland or mountainous areas. We also discuss a few technical issues for directly determining height anomalies based on EGM and DEM, under the frame of Molodensky theory.

  18. Avaliação de modelos digitais de elevação para aplicação em um mapeamento digital de solos Evaluation of digital elevation models for application in a digital soil mapping

    Directory of Open Access Journals (Sweden)

    César S. Chagas

    2010-02-01

    Full Text Available No Brasil, normalmente os modelos digitais de elevação (MDEs são produzidos pelos próprios usuários e pouca atenção tem sido dada às suas limitações, como fonte de informação espacial. Este estudo propôs avaliar diferentes MDEs para subsidiar a escolha do modelo apropriado para derivar atributos topográficos utilizados em um mapeamento digital de solos, por redes neurais artificiais. A avaliação constou da determinação da raiz quadrada do erro médio quadrático da elevação (RMSE; análise das depressões espúrias; comparação entre drenagem mapeada e drenagem numérica, curvas de nível derivadas e curvas de nível originais, e análise das bacias de contribuição derivadas. Os resultados obtidos demonstraram que apenas o RMSE não foi suficiente para avaliar a qualidade desses modelos. O MDE, derivado de curvas de nível (CARTA, obtido com a utilização do módulo TOPOGRID apresentou qualidade superior aos MDEs derivados de sensores remotos (ASTER e SRTM. A análise qualitativa também identificou que o MDE CARTA é superior aos demais, pois estes apresentaram grande quantidade de erros que podem comprometer o estabelecimento das relações entre atributos do terreno e as condições locais de solos.In Brazil, the digital elevation models (DEMs are usually produced by users themselves and little attention has been given to their limitations as source of spatial information. The objective of this study was to evaluate different DEMs to help in choosing an appropriate model to derive topographical attributes used in a digital soil mapping based on a neural networks approach. The evaluation consisted of the following analysis: determination of root mean square error (RMSE of elevation; analysis of the spurious depressions; comparison between mapped drainage and numeric drainage and between derived contour lines and original contour lines; and analysis of the derived contribution basins. The results demonstrated that RMSE

  19. An Automated Processing Algorithm for Flat Areas Resulting from DEM Filling and Interpolation

    Directory of Open Access Journals (Sweden)

    Xingwei Liu

    2017-11-01

    Full Text Available Correction of digital elevation models (DEMs for flat areas is a critical process for hydrological analyses and modeling, such as the determination of flow directions and accumulations, and the delineation of drainage networks and sub-basins. In this study, a new algorithm is proposed for flat correction/removal. It uses the puddle delineation (PD program to identify depressions (including their centers and overflow/spilling thresholds, compute topographic characteristics, and further fill the depressions. Three different levels of elevation increments are used for flat correction. The first and second level of increments create flows toward the thresholds and centers of the filled depressions or flats, while the third level of small random increments is introduced to cope with multiple threshold conditions. A set of artificial surfaces and two real-world landscapes were selected to test the new algorithm. The results showed that the proposed method was not limited by the shapes, the number of thresholds, and the surrounding topographic conditions of flat areas. Compared with the traditional methods, the new algorithm simplified the flat correction procedure and reduced the final elevation increments by 5.71–33.33%. This can be used to effectively remove/correct topographic flats and create flat-free DEMs.

  20. DEM ASSESSMENT DERIVED FROM CLOSE RANGE PHOTOGRAMMETRY: A CASE STUDY FROM KADAVUR AREA, KARUR DISTRICT, TAMIL NADU, INDIA

    Directory of Open Access Journals (Sweden)

    S. Anbarasan

    2012-07-01

    Full Text Available Close-Range Photogrammetry is an accurate, cost effective technique of collecting measurements of real world objects and conditions, directly from photographs. Photogrammetry utilizes digital images to obtain accurate measurements and geometric data of the object or area of interest, in order to provide spatial information for Engineering design, spatial surveys or 3D modeling. The benefits of close-range Photogrammetry over other field procedures are purported to be: Increased accuracy; complete as-built information; reduced costs; reduced on-site time; and effective for small and large projects. The same basic principle of traditional Aerial Photogrammetry can be applied to stereoscopic pictures taken from lower altitudes or from the ground. Terrestrial, ground-based, and close-range are all descriptive terms that refer to photos taken with an object-to-camera distance less than 300m (1000 feet. (Matthews, N.A, 2008. Close range Photogrammetry is a technique for obtaining the geometric information (e.g. position, distance, size and shape of any object in 3D space that was imaged on the two dimensional (2D photos, (Wolf, P.R, et.al, 2000 DEM Generation requires many processing and computation, such as camera calibration, stereo matching, editing, and interpolation. All the mentioned steps contribute to the quality of DEM. Image on close range Photogrammetry can be captured using three kind of camera: metric camera, semi-metric camera, and non-metric camera (Hanke, K., et.al, 2002. In this paper DEM quality assessed at Kadavur area, Karur district, Tamil Naudu, India using Close Range Photogrammetry technique, Commercial Digital Camera and Leica Photogrammetry Suite.

  1. Toward the modeling of combustion reactions through discrete element method (DEM) simulations

    Science.gov (United States)

    Reis, Martina Costa; Alobaid, Falah; Wang, Yongqi

    2018-03-01

    In this work, the process of combustion of coal particles under turbulent regime in a high-temperature reaction chamber is modeled through 3D discrete element method (DEM) simulations. By assuming the occurrence of interfacial transport phenomena between the gas and solid phases, one investigates the influence of the physicochemical properties of particles on the rates of heterogeneous chemical reactions, as well as the influence of eddies present in the gas phase on the mass transport of reactants toward the coal particles surface. Moreover, by considering a simplistic chemical mechanism for the combustion process, thermochemical and kinetic parameters obtained from the simulations are employed to discuss some phenomenological aspects of the combustion process. In particular, the observed changes in the mass and volume of coal particles during the gasification and combustion steps are discussed by emphasizing the changes in the chemical structure of the coal. In addition to illustrate how DEM simulations can be used in the modeling of consecutive and parallel chemical reactions, this work also shows how heterogeneous and homogeneous chemical reactions become a source of mass and energy for the gas phase.

  2. Comparing Digital Flood Insurance Rate Maps (DFIRMs) to Interferometric Synthetic Aperture Radar (IFSAR) Products

    National Research Council Canada - National Science Library

    Damron, James J

    2000-01-01

    .... IFSAR Digital Elevation Model (DEM) and Ortho-Rectified Image (ORI), referred to as a magnitude image, were used to compare the data accuracy and content of the DFIRMs. This study will provide timely information needed for future DFIRM production.

  3. The geomorphological evidences of subsidence in the Nile Delta: Analysis of high resolution topographic DEM and multi-temporal satellite images

    Science.gov (United States)

    El Bastawesy, M.; Cherif, O. H.; Sultan, M.

    2017-12-01

    This paper investigates the relevance of landforms to the subsidence of the Nile Delta using a high resolution topographic digital elevation model (DEM) and sets of multi-temporal Landsat satellite images. 195 topographic map sheets produced in 1946 at 1:25,000 scale were digitized, and the DEM was interpolated. The undertaken processing techniques have distinguished all the natural low-lying closed depressions from the artificial errors induced by the interpolation of the DEM. The local subsidence of these depressions from their surroundings reaches a maximum depth of 2.5 m. The regional subsidence of the Nile Delta has developed inverted topography, where the tracts occupied by the contemporary distributary channels are standing at higher elevations than the areas in between. This inversion could be related to the differences in the hydrological and sedimentological properties of underlying sediments, as the channels are underlain by water-saturated sands while the successions of clay and silt on flood plains are prone to compaction. Furthermore, the analysis of remote sensing and topographic data clearly show significant changes in the land cover and land use, particularly in the northern lagoons and adjacent sabkhas, which are dominated by numerous low subsiding depressions. The areas covered by water logging and ponds are increasing on the expense of agricultural areas, and aquaculture have been practiced instead. The precise estimation of subsidence rates and distribution should be worked out to evaluate probable changes in land cover and land use.

  4. Insight From the Statistics of Nothing: Estimating Limits of Change Detection Using Inferred No-Change Areas in DEM Difference Maps and Application to Landslide Hazard Studies

    Science.gov (United States)

    Haneberg, W. C.

    2017-12-01

    Remote characterization of new landslides or areas of ongoing movement using differences in high resolution digital elevation models (DEMs) created through time, for example before and after major rains or earthquakes, is an attractive proposition. In the case of large catastrophic landslides, changes may be apparent enough that simple subtraction suffices. In other cases, statistical noise can obscure landslide signatures and place practical limits on detection. In ideal cases on land, GPS surveys of representative areas at the time of DEM creation can quantify the inherent errors. In less-than-ideal terrestrial cases and virtually all submarine cases, it may be impractical or impossible to independently estimate the DEM errors. Examining DEM difference statistics for areas reasonably inferred to have no change, however, can provide insight into the limits of detectability. Data from inferred no-change areas of airborne LiDAR DEM difference maps of the 2014 Oso, Washington landslide and landslide-prone colluvium slopes along the Ohio River valley in northern Kentucky, show that DEM difference maps can have non-zero mean and slope dependent error components consistent with published studies of DEM errors. Statistical thresholds derived from DEM difference error and slope data can help to distinguish between DEM differences that are likely real—and which may indicate landsliding—from those that are likely spurious or irrelevant. This presentation describes and compares two different approaches, one based upon a heuristic assumption about the proportion of the study area likely covered by new landslides and another based upon the amount of change necessary to ensure difference at a specified level of probability.

  5. Implications of different digital elevation models and preprocessing techniques to delineate debris flow inundation hazard zones in El Salvador

    Science.gov (United States)

    Anderson, E. R.; Griffin, R.; Irwin, D.

    2013-12-01

    Heavy rains and steep, volcanic slopes in El Salvador cause numerous landslides every year, posing a persistent threat to the population, economy and environment. Although potential debris inundation hazard zones have been delineated using digital elevation models (DEMs), some disparities exist between the simulated zones and actual affected areas. Moreover, these hazard zones have only been identified for volcanic lahars and not the shallow landslides that occur nearly every year. This is despite the availability of tools to delineate a variety of landslide types (e.g., the USGS-developed LAHARZ software). Limitations in DEM spatial resolution, age of the data, and hydrological preprocessing techniques can contribute to inaccurate hazard zone definitions. This study investigates the impacts of using different elevation models and pit filling techniques in the final debris hazard zone delineations, in an effort to determine which combination of methods most closely agrees with observed landslide events. In particular, a national DEM digitized from topographic sheets from the 1970s and 1980s provide an elevation product at a 10 meter resolution. Both natural and anthropogenic modifications of the terrain limit the accuracy of current landslide hazard assessments derived from this source. Global products from the Shuttle Radar Topography Mission (SRTM) and the Advanced Spaceborne Thermal Emission and Reflection Radiometer Global DEM (ASTER GDEM) offer more recent data but at the cost of spatial resolution. New data derived from the NASA Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) in 2013 provides the opportunity to update hazard zones at a higher spatial resolution (approximately 6 meters). Hydrological filling of sinks or pits for current hazard zone simulation has previously been achieved through ArcInfo spatial analyst. Such hydrological processing typically only fills pits and can lead to drastic modifications of original elevation values

  6. INFLUENCE OF DEM IN WATERSHED MANAGEMENT AS FLOOD ZONATION MAPPING

    Directory of Open Access Journals (Sweden)

    M. Alrajhi

    2016-06-01

    Full Text Available Despite of valuable efforts from working groups and research organizations towards flood hazard reduction through its program, still minimal diminution from these hazards has been realized. This is mainly due to the fact that with rapid increase in population and urbanization coupled with climate change, flood hazards are becoming increasingly catastrophic. Therefore there is a need to understand and access flood hazards and develop means to deal with it through proper preparations, and preventive measures. To achieve this aim, Geographical Information System (GIS, geospatial and hydrological models were used as tools to tackle with influence of flash floods in the Kingdom of Saudi Arabia due to existence of large valleys (Wadis which is a matter of great concern. In this research paper, Digital Elevation Models (DEMs of different resolution (30m, 20m,10m and 5m have been used, which have proven to be valuable tool for the topographic parameterization of hydrological models which are the basis for any flood modelling process. The DEM was used as input for performing spatial analysis and obtaining derivative products and delineate watershed characteristics of the study area using ArcGIS desktop and its Arc Hydro extension tools to check comparability of different elevation models for flood Zonation mapping. The derived drainage patterns have been overlaid over aerial imagery of study area, to check influence of greater amount of precipitation which can turn into massive destructions. The flow accumulation maps derived provide zones of highest accumulation and possible flow directions. This approach provide simplified means of predicting extent of inundation during flood events for emergency action especially for large areas because of large coverage area of the remotely sensed data.

  7. Method for Measuring the Information Content of Terrain from Digital Elevation Models

    Directory of Open Access Journals (Sweden)

    Lujin Hu

    2015-10-01

    Full Text Available As digital terrain models are indispensable for visualizing and modeling geographic processes, terrain information content is useful for terrain generalization and representation. For terrain generalization, if the terrain information is considered, the generalized terrain may be of higher fidelity. In other words, the richer the terrain information at the terrain surface, the smaller the degree of terrain simplification. Terrain information content is also important for evaluating the quality of the rendered terrain, e.g., the rendered web terrain tile service in Google Maps (Google Inc., Mountain View, CA, USA. However, a unified definition and measures for terrain information content have not been established. Therefore, in this paper, a definition and measures for terrain information content from Digital Elevation Model (DEM, i.e., a digital model or 3D representation of a terrain’s surface data are proposed and are based on the theory of map information content, remote sensing image information content and other geospatial information content. The information entropy was taken as the information measuring method for the terrain information content. Two experiments were carried out to verify the measurement methods of the terrain information content. One is the analysis of terrain information content in different geomorphic types, and the results showed that the more complex the geomorphic type, the richer the terrain information content. The other is the analysis of terrain information content with different resolutions, and the results showed that the finer the resolution, the richer the terrain information. Both experiments verified the reliability of the measurements of the terrain information content proposed in this paper.

  8. A global digital elevation model - GTOP030

    Science.gov (United States)

    1999-01-01

    GTOP030, the U.S. Geological Survey's (USGS) digital elevation model (DEM) of the Earth, provides the flrst global coverage of moderate resolution elevation data.  The original GTOP30 data set, which was developed over a 3-year period through a collaborative effort led by the USGS, was completed in 1996 at the USGS EROS Data Center in Sioux Falls, South Dakota.  The collaboration involved contributions of staffing, funding, or source data from cooperators including the National Aeronautics and Space Administration (NASA), the United Nations Environment Programme Global Resource Information Database (UNEP/GRID), the U.S. Agency for International Development (USAID), the Instituto Nacional de Estadistica Geografia e Informatica (INEGI) of Mexico, the Geographical Survey Institute (GSI) of Japan, Manaaki Whenua Landcare Research of New Zealand, and the Scientific Committee on Antarctic Research (SCAR). In 1999, work was begun on an update to the GTOP030 data set. Additional data sources are being incorporated into GTOP030 with an enhanced and improved data set planned for release in 2000.

  9. Converting Topographic Maps into Digital Form to Aid in Archeological Research in the Peten, Guatemala

    Science.gov (United States)

    Aldrich, Serena R.

    1999-01-01

    The purpose of my project was to convert a topographical map into digital form so that the data can be manipulated and easily accessed in the field. With the data in this particular format, Dr. Sever and his colleagues can highlight the specific features of the landscape that they require for their research of the ancient Mayan civilization. Digital elevation models (DEMs) can also be created from the digitized contour features adding another dimension to their research.

  10. Modelling topographic potential for erosion and deposition using GIS

    Science.gov (United States)

    Helena Mitasova; Louis R. Iverson

    1996-01-01

    Modelling of erosion and deposition in complex terrain within a geographical information system (GIS) requires a high resolution digital elevation model (DEM), reliable estimation of topographic parameters, and formulation of erosion models adequate for digital representation of spatially distributed parameters. Regularized spline with tension was integrated within a...

  11. On the COSMO-SkyMed Exploitation for Interferometric DEM Generation

    Science.gov (United States)

    Teresa, C. M.; Raffaele, N.; Oscar, N. D.; Fabio, B.

    2011-12-01

    Work supported by ASI (Agenzia Spaziale Italiana) in the framework of the project "AO-COSMO Project ID-1462 - Feasibility of possible use of COSMO/SkyMed in bistatic SAR Earth observation - ASI Contract I/063/09/0". References [1] B. Rabus, M. Eineder, A. Roth, and R. Bamler, "The Shuttle Radar Topography Mission-A new class of digital elevation models acquired by spaceborne radar," ISPRS J. Photogramm. Remote Sens., vol. 57, no. 4, pp. 241-262, Feb. 2003. [2] F. BOVENGA, D. O. NITTI, R. NUTRICATO, M. T. CHIARADIA, "C- and X-band multi-pass InSAR analysis over Alpine and Apennine regions". In Proceedings of the European Space Agency Living Planet Symposium, June 28 - July 2, 2010, Bergen, Norway. [3] D. REALE, D. O. NITTI, D. PEDUTO, R. NUTRICATO, F. BOVENGA, G. FORNARO, "Postseismic Deformation Monitoring With The COSMO/SKYMED Constellation". IEEE Geoscience Remote Sensing Letters, 2011. DOI: 10.1109/LGRS.2010.2100364 [4] Nitti, D.O., Nutricato, R., Bovenga, F., Conte, D., Guerriero, L. & Milillo, G., "Quantitative Analysis of Stripmap And Spotlight SAR Interferometry with CosmoSkyMed constellation.", Proceedings if IEEE IGARSS 2009, July 13-17, 2009. Cape Town, South Africa.

  12. DEM GENERATION FROM HIGH RESOLUTION SATELLITE IMAGES THROUGH A NEW 3D LEAST SQUARES MATCHING ALGORITHM

    Directory of Open Access Journals (Sweden)

    T. Kim

    2012-09-01

    Full Text Available Automated generation of digital elevation models (DEMs from high resolution satellite images (HRSIs has been an active research topic for many years. However, stereo matching of HRSIs, in particular based on image-space search, is still difficult due to occlusions and building facades within them. Object-space matching schemes, proposed to overcome these problem, often are very time consuming and critical to the dimensions of voxels. In this paper, we tried a new least square matching (LSM algorithm that works in a 3D object space. The algorithm starts with an initial height value on one location of the object space. From this 3D point, the left and right image points are projected. The true height is calculated by iterative least squares estimation based on the grey level differences between the left and right patches centred on the projected left and right points. We tested the 3D LSM to the Worldview images over 'Terrassa Sud' provided by the ISPRS WG I/4. We also compared the performance of the 3D LSM with the correlation matching based on 2D image space and the correlation matching based on 3D object space. The accuracy of the DEM from each method was analysed against the ground truth. Test results showed that 3D LSM offers more accurate DEMs over the conventional matching algorithms. Results also showed that 3D LSM is sensitive to the accuracy of initial height value to start the estimation. We combined the 3D COM and 3D LSM for accurate and robust DEM generation from HRSIs. The major contribution of this paper is that we proposed and validated that LSM can be applied to object space and that the combination of 3D correlation and 3D LSM can be a good solution for automated DEM generation from HRSIs.

  13. Research on Digital Product Modeling Key Technologies of Digital Manufacturing

    Institute of Scientific and Technical Information of China (English)

    DING Guoping; ZHOU Zude; HU Yefa; ZHAO Liang

    2006-01-01

    With the globalization and diversification of the market and the rapid development of Information Technology (IT) and Artificial Intelligence (AI), the digital revolution of manufacturing is coming. One of the key technologies in digital manufacturing is product digital modeling. This paper firstly analyzes the information and features of the product digital model during each stage in the product whole lifecycle, then researches on the three critical technologies of digital modeling in digital manufacturing-product modeling, standard for the exchange of product model data and digital product data management. And the potential signification of the product digital model during the process of digital manufacturing is concluded-product digital model integrates primary features of each stage during the product whole lifecycle based on graphic features, applies STEP as data exchange mechanism, and establishes PDM system to manage the large amount, complicated and dynamic product data to implement the product digital model data exchange, sharing and integration.

  14. Eine Analyse des Zusammenhangs zwischen dem Konsum von Alkopops und dem Problemverhalten von Jugendlichen

    OpenAIRE

    Metzner, Cornelia Beate Isabel

    2007-01-01

    Zielsetzung: In dieser Arbeit wird untersucht, ob bei Jugendlichen ein Zusammenhang zwischen dem Konsum von Alkopops einerseits und dem sonstigen Alkoholtrinkverhalten, dem Konsum von Zigaretten und illegalen Drogen sowie weiteren Risikoverhaltensweisen andererseits besteht, ferner ob sich Unterschiede im Verhalten von Jungen und Mädchen ergeben. Theoretischer und empirischer Hintergrund: �Alkopops�, d. h. Mischgetränke diverser Hersteller aus Likör bzw. Schnaps und Limonade sowie wein- ...

  15. Time-averaged discharge rate of subaerial lava at Kīlauea Volcano, Hawai‘i, measured from TanDEM-X interferometry: Implications for magma supply and storage during 2011-2013

    Science.gov (United States)

    Poland, Michael P.

    2014-01-01

    Differencing digital elevation models (DEMs) derived from TerraSAR add-on for Digital Elevation Measurements (TanDEM-X) synthetic aperture radar imagery provides a measurement of elevation change over time. On the East Rift Zone (EZR) of Kīlauea Volcano, Hawai‘i, the effusion of lava causes changes in topography. When these elevation changes are summed over the area of an active lava flow, it is possible to quantify the volume of lava emplaced at the surface during the time spanned by the TanDEM-X data—a parameter that can be difficult to measure across the entirety of an ~100 km2 lava flow field using ground-based techniques or optical remote sensing data. Based on the differences between multiple TanDEM-X-derived DEMs collected days to weeks apart, the mean dense-rock equivalent time-averaged discharge rate of lava at Kīlauea between mid-2011 and mid-2013 was approximately 2 m3/s, which is about half the long-term average rate over the course of Kīlauea's 1983–present ERZ eruption. This result implies that there was an increase in the proportion of lava stored versus erupted, a decrease in the rate of magma supply to the volcano, or some combination of both during this time period. In addition to constraining the time-averaged discharge rate of lava and the rates of magma supply and storage, topographic change maps derived from space-based TanDEM-X data provide insights into the four-dimensional evolution of Kīlauea's ERZ lava flow field. TanDEM-X data are a valuable complement to other space-, air-, and ground-based observations of eruptive activity at Kīlauea and offer great promise at locations around the world for aiding with monitoring not just volcanic eruptions but any hazardous activity that results in surface change, including landslides, floods, earthquakes, and other natural and anthropogenic processes.

  16. An automated, open-source (NASA Ames Stereo Pipeline) workflow for mass production of high-resolution DEMs from commercial stereo satellite imagery: Application to mountain glacies in the contiguous US

    Science.gov (United States)

    Shean, D. E.; Arendt, A. A.; Whorton, E.; Riedel, J. L.; O'Neel, S.; Fountain, A. G.; Joughin, I. R.

    2016-12-01

    We adapted the open source NASA Ames Stereo Pipeline (ASP) to generate digital elevation models (DEMs) and orthoimages from very-high-resolution (VHR) commercial imagery of the Earth. These modifications include support for rigorous and rational polynomial coefficient (RPC) sensor models, sensor geometry correction, bundle adjustment, point cloud co-registration, and significant improvements to the ASP code base. We outline an automated processing workflow for 0.5 m GSD DigitalGlobe WorldView-1/2/3 and GeoEye-1 along-track and cross-track stereo image data. Output DEM products are posted at 2, 8, and 32 m with direct geolocation accuracy of process individual stereo pairs on a local workstation, the methods presented here were developed for large-scale batch processing in a high-performance computing environment. We have leveraged these resources to produce dense time series and regional mosaics for the Earth's ice sheets. We are now processing and analyzing all available 2008-2016 commercial stereo DEMs over glaciers and perennial snowfields in the contiguous US. We are using these records to study long-term, interannual, and seasonal volume change and glacier mass balance. This analysis will provide a new assessment of regional climate change, and will offer basin-scale analyses of snowpack evolution and snow/ice melt runoff for water resource applications.

  17. Near instantaneous production of digital terrain models in the field using smartphone and Structure-from-Motion photogrammetry

    Science.gov (United States)

    Micheletti, Natan; Chandler, Jim; Lane, Stuart

    2013-04-01

    Whilst high-resolution topographic and terrain data is essential in many geoscience applications, its acquisition has traditionally required either specific expertise (e.g. applications of photogrammetry) or expensive equipment (e.g. ground-based laser altimetric systems). Recent work in geomorphology (e.g. James and Robson, 2012; Carbonneau et al., 2012) has demonstrated the potential of Structure-from-Motion photogrammetry as a low cost, low expertise alternative for Digital Elevation Model (DEM) generation. These methods have geomorphological appeal because the more sophisticated image matching approaches remove many of the geometrical constraints associated with image acquisition: traditionally, vertical and "normal" image pairs acquired with a metric camera. This increases both the number of potential applications and the efficacy of image acquisition in the field. It also allows for genuine 3D (where the same (x,y) can have multiple z values) rather than 2.5D (where each (x,y) must have a unique z value) representation of the terrain surface. In this paper, we progress this technology further, by testing what can be acquired using hand-held smartphone technology, where the acquired images can be uploaded in the field to Open Source technology freely available to the research community. This is achieved by evaluating the quality of DEMs generated with a fully automated, open-source, Structure-from-Motion package and a smartphone (Apple Iphone 4) integrated camera (5 megapixels) using terrestrial laser scanning (TLS) data as benchmark. To allow a more objective assessment, it is necessary to compare both device and package with traditional approaches. Accordingly, we compare the error in the smartphone DEMs with the errors associated with data derived using a 16.2 megapixel digital camera and processed using the more traditional, commercial, close-range and semi-automated software PhotoModeler. Results demonstrate that centimeter precision DTMs can be achieved

  18. An Improved dem Construction Method for Mudflats Based on BJ-1 Small Satellite Images: a Case Study on Bohai Bay

    Science.gov (United States)

    Wu, D.; Du, Y.; Su, F.; Huang, W.; Zhang, L.

    2018-04-01

    The topographic measurement of muddy tidal flat is restricted by the difficulty of access to the complex, wide-range and dynamic tidal conditions. Then the waterline detection method (WDM) has the potential to investigate the morph-dynamics quantitatively by utilizing large archives of satellite images. The study explores the potential for using WDM with BJ-1 small satellite images to construct a digital elevation model (DEM) of a wide and grading mudflat. Three major conclusions of the study are as follows: (1) A new intelligent correlating model of waterline detection considering different tidal stages and local geographic conditions was explored. With this correlative algorithm waterline detection model, a series of waterlines were extracted from multi-temporal remotely sensing images collected over the period of a year. The model proved to detect waterlines more efficiently and exactly. (2) The spatial structure of elevation superimposing on the points of waterlines was firstly constructed and a more accurate hydrodynamic ocean tide grid model was used. By the newly constructed abnormal hydrology evaluation model, a more reasonable and reliable set of waterline points was acquired to construct a smoother TIN and GRID DEM. (3) DEM maps of Bohai Bay, with a spatial resolution of about 30 m and height accuracy of about 0.35 m considering LiDAR and 0.19 m considering RTK surveying were constructed over an area of about 266 km2. Results show that remote sensing research in extremely turbid estuaries and tidal areas is possible and is an effective tool for monitoring the tidal flats.

  19. Inferring sediment connectivity from high-resolution DEMs of Difference

    Science.gov (United States)

    Heckmann, Tobias; Vericat, Damià

    2017-04-01

    Topographic changes due to the erosion and deposition of bedrock, sediments and soil can be measured by differencing Digital Elevation Models (DEM) acquired at different points in time. So-called morphological sediment budgets can be computed from such DEMs of Difference (DoD) on an areal rather than a point basis. The advent of high-resolution and highly accurate surveying techniques (e.g. LiDAR, SfM), together with recent advances of survey platforms (e.g. UaVs) provides opportunities to improve the spatial and temporal scale (in terms of extent and resolution), the availability and quality of such measurements. Many studies have used DoD to investigate and interpret the spatial pattern of positive and negative vertical differences in terms of erosion and deposition, or of horizontal movement. Vertical differences can be converted to volumes, and negative (erosion) and positive (deposition) volumetric changes aggregated for spatial units (e.g., landforms, hillslopes, river channels) have been used to compute net balances. We argue that flow routing algorithms common in digital terrain analysis provide a means to enrich DoD-based investigations with some information about (potential) sediment pathways - something that has been widely neglected in previous studies. Where the DoD indicates a positive surface change, flow routing delineates the upslope area where the deposited sediment has potentially been derived from. In the downslope direction, flow routing indicates probable downslope pathways of material eroded/detached/entrained where the DoD shows negative surface change. This material has either been deposited along these pathways or been flushed out of the area of investigation. This is a question of sediment connectivity, a property of a system (i.e. a hillslope, a sub-/catchment) that describes its potential to move sediment through itself. The sediment pathways derived from the DEM are related to structural connectivity, while the spatial pattern of (net

  20. Glacier Volume Change Estimation Using Time Series of Improved Aster Dems

    Science.gov (United States)

    Girod, Luc; Nuth, Christopher; Kääb, Andreas

    2016-06-01

    Volume change data is critical to the understanding of glacier response to climate change. The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) system embarked on the Terra (EOS AM-1) satellite has been a unique source of systematic stereoscopic images covering the whole globe at 15m resolution and at a consistent quality for over 15 years. While satellite stereo sensors with significantly improved radiometric and spatial resolution are available to date, the potential of ASTER data lies in its long consistent time series that is unrivaled, though not fully exploited for change analysis due to lack of data accuracy and precision. Here, we developed an improved method for ASTER DEM generation and implemented it in the open source photogrammetric library and software suite MicMac. The method relies on the computation of a rational polynomial coefficients (RPC) model and the detection and correction of cross-track sensor jitter in order to compute DEMs. ASTER data are strongly affected by attitude jitter, mainly of approximately 4 km and 30 km wavelength, and improving the generation of ASTER DEMs requires removal of this effect. Our sensor modeling does not require ground control points and allows thus potentially for the automatic processing of large data volumes. As a proof of concept, we chose a set of glaciers with reference DEMs available to assess the quality of our measurements. We use time series of ASTER scenes from which we extracted DEMs with a ground sampling distance of 15m. Our method directly measures and accounts for the cross-track component of jitter so that the resulting DEMs are not contaminated by this process. Since the along-track component of jitter has the same direction as the stereo parallaxes, the two cannot be separated and the elevations extracted are thus contaminated by along-track jitter. Initial tests reveal no clear relation between the cross-track and along-track components so that the latter seems not to be

  1. Landbrugets trædemølle

    DEFF Research Database (Denmark)

    Hansen, Henning Otte

    2016-01-01

    Teorien om landbrugets trædemølle siger, at teknologi medfører stigende produktivitet, stigende udbud og dermed faldende priser. Dermed øges behovet for ny teknologi. Det vedvarende teknologipres gavner de innovative landmænd, mens de mere afventende landmænd kun oplever de negative virkninger i...... form af prisfald. I denne artikel beskrives nærmere de enkelte elementer i trædemøllen. Samtidig vurderes trædemøllens betydning og mulige påvirkning. Det konkluderes, at trædemøllen, dens forudsætninger og afledte virkninger stadig er fuldt gældende. Det er ikke muligt for et enkelt land eller region...... af bremse trædemøllen på lang sigt. På lokalt plan kan man løse nogle sociale og økonomiske problemer skabt af trædemøllen gennem nemmere afvandring....

  2. A Novel DEM Approach to Simulate Block Propagation on Forested Slopes

    Science.gov (United States)

    Toe, David; Bourrier, Franck; Dorren, Luuk; Berger, Frédéric

    2018-03-01

    In order to model rockfall on forested slopes, we developed a trajectory rockfall model based on the discrete element method (DEM). This model is able to take the complex mechanical processes at work during an impact into account (large deformations, complex contact conditions) and can explicitly simulate block/soil, block/tree contacts as well as contacts between neighbouring trees. In this paper, we describe the DEM model developed and we use it to assess the protective effect of different types of forest. In addition, we compared it with a more classical rockfall simulation model. The results highlight that forests can significantly reduce rockfall hazard and that the spatial structure of coppice forests has to be taken into account in rockfall simulations in order to avoid overestimating the protective role of these forest structures against rockfall hazard. In addition, the protective role of the forests is mainly influenced by the basal area. Finally, the advantages and limitations of the DEM model were compared with classical rockfall modelling approaches.

  3. Quantification of morphological properties of terrace surface using digital elevation model and its application to stratigraphic correlation of terraces

    International Nuclear Information System (INIS)

    Yamamoto, Shinya; Hataya, Ryuta; Hamada, Takaomi

    2008-01-01

    Uplift estimation during late Quaternary is required for site selection of geological disposal facility of high level radioactive waste (NUMO, 2004). Terrace level and/or difference in elevation of terraces are good indicators of uplift. Therefore, a reliable method of terrace correlation and chronology is a key issues. Air-photograph interpretation is generally carried out in the early stage of a terrace investigation. However, a terrace classification often depends on the observer's qualitative interpretation. In order to improve objectivity of geomorphic investigation with air-photograph interpretation, we examine to quantify the morphological properties of terrace surface by some morphometric variables that are computed from Digital Elevation Model (DEM). In this study, four morphometric variables (average slope, average laplacian, remaining ratio of a terrace surface, and average depth of erosion) were calculated using data sets of terraces of which chronological data are clearly described. The relationship between these variables and terrace ages shows constant tendencies respond to the geomorphological process caused by the erosion. To examine capability of morphometric variables as an index of terrace correlation, regression analyses were carried out. The regression age estimated from morphometric variables allows to classify terraces in correct sequence, and the error with the observed age falls up to 100,000 years. In addition, to discuss appropriate quantities of DEM for terrace correlation, we used three different elevation data to create DEM: 1) aerial photogrammetry data; 2) airborne laser scanner data; 3) 1:25000-scale contour map. By comparing analysis results of each DEMs, we show suitable qualities of elevation data and DEM grid size to represent the degree of erosion correctly. (author)

  4. BOREAS HYD-8 DEM Data Over the NSA-MSA and SSA-MSA in the UTM Projection

    Science.gov (United States)

    Wang, Xue-Wen; Hall, Forrest G. (Editor); Knapp, David E. (Editor); Band, L. E.; Smith, David E. (Technical Monitor)

    2000-01-01

    The BOREAS HYD-8 team focused on describing the scaling behavior of water and carbon flux processes at local and regional scales. These DEMs were produced from digitized contours at a cell resolution of 100 meters. Vector contours of the area were used as input to a software package that interpolates between contours to create a DEM representing the terrain surface. The vector contours had a contour interval of 25 feet. The data cover the BOREAS MSAs of the SSA and NSA and are given in a UTM map projection. Most of the elevation data from which the DEM was produced were collected in the 1970s or 1980s. The data are stored in binary, image format files. The data files are available on a CD-ROM (see document number 20010000884) or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

  5. High Resolution Airborne InSAR DEM of Bagley Ice Valley, South-central Alaska: Geodetic Validation with Airborne Laser Altimeter Data

    Science.gov (United States)

    Muskett, R. R.; Lingle, C. S.; Echelmeyer, K. A.; Valentine, V. B.; Elsberg, D.

    2001-12-01

    Bagley Ice Valley, in the St. Elias and Chugach Mountains of south-central Alaska, is an integral part of the largest connected glacierized terrain on the North American continent. From the flow divide between Mt. Logan and Mt. St. Elias, Bagley Ice Valley flows west-northwest for some 90 km down a slope of less than 1o, at widths up to 15 km, to a saddle-gap where it turns south-west to become Bering Glacier. During 4-13 September 2000, an airborne survey of Bagley Ice Valley was performed by Intermap Technologies, Inc., using their Star-3i X-band SAR interferometer. The resulting digital elevation model (DEM) covers an area of 3243 km2. The DEM elevations are orthometric heights, in meters above the EGM96 geoid. The horizontal locations of the 10-m postings are with respect to the WGS84 ellipsoid. On 26 August 2000, 9 to 18 days prior to the Intermap Star-3i survey, a small-aircraft laser altimeter profile was acquired along the central flow line for validation. The laser altimeter data consists of elevations above the WGS84 ellipsoid and orthometric heights above GEOID99-Alaska. Assessment of the accuracy of the Intermap Star-3i DEM was made by comparison of both the DEM orthometric heights and elevations above the WGS84 ellipsoid with the laser altimeter data. Comparison of the orthometric heights showed an average difference of 5.4 +/- 1.0 m (DEM surface higher). Comparison of elevations above the WGS84 ellipsoid showed an average difference of -0.77 +/- 0.93 m (DEM surface lower). This indicates that the X-band Star-3i interferometer was penetrating the glacier surface by an expected small amount. The WGS84 comparison is well within the 3 m RMS accuracy quoted for GT-3 DEM products. Snow accumulation may have occurred, however, on Bagley Ice Valley between 26 August and 4-13 September 2000. This will be estimated using a mass balance model and used to correct the altimeter-derived surface heights. The new DEM of Bagley Ice Valley will provide a reference

  6. Determination of the hydrological properties of a small-scale catchment area in Northern Greece from ASTER and SRTM DEMs and accuracy assessment with a local DTM

    Science.gov (United States)

    Tzanou, E. A.; Vergos, G. S.

    2012-04-01

    The combined use of Geographic Information Systems and recent high-resolution Digital Elevation Models (DEMs) from Remote Sensing imagery offers a unique opportunity to study the hydrological properties of basin and catchment dynamics and derive the hydrological features of specific regions of various spatial scales. Until recently, the availability of global DEMs was restricted to low-resolution and accuracy models, e.g., ETOPO5, ETOPO2 and GTOPO30, compared to local Digital Terrain Models (DTMs) derived from photogrammetric methods and offered usually in the form of topographic maps of various scales. The advent of the SRTM and ASTER missions, offer some new tools and opportunities in order to use their data within a GIS to study the hydrological properties of basins and consequently validate their performance both amongst each other, as well as in terms of the results derived from a local DTM. The present work focuses on the use of the recent SRTM v2 90 m and ASTER v2 30 m DEMs along with the national 500 m DTM generated by the Hellenic Military Geographic Service (HMGS), within a GIS in order to assess their performance in determining the hydrological properties of basins. To this respect, the ArcHydro extension tool of ArcGIS v9.3 and HEC-GeoRAS v4.3 have been exploited to determine the hydrographic data of the basins under study which are located in Northern Greece. The hydrological characteristics refer to stream geometry, curve number, flooding areas, etc. as well as the topographic characteristics of the basin itself, such as aspect, hillshade, slope e.t.c..

  7. GLACIER VOLUME CHANGE ESTIMATION USING TIME SERIES OF IMPROVED ASTER DEMS

    Directory of Open Access Journals (Sweden)

    L. Girod

    2016-06-01

    Full Text Available Volume change data is critical to the understanding of glacier response to climate change. The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER system embarked on the Terra (EOS AM-1 satellite has been a unique source of systematic stereoscopic images covering the whole globe at 15m resolution and at a consistent quality for over 15 years. While satellite stereo sensors with significantly improved radiometric and spatial resolution are available to date, the potential of ASTER data lies in its long consistent time series that is unrivaled, though not fully exploited for change analysis due to lack of data accuracy and precision. Here, we developed an improved method for ASTER DEM generation and implemented it in the open source photogrammetric library and software suite MicMac. The method relies on the computation of a rational polynomial coefficients (RPC model and the detection and correction of cross-track sensor jitter in order to compute DEMs. ASTER data are strongly affected by attitude jitter, mainly of approximately 4 km and 30 km wavelength, and improving the generation of ASTER DEMs requires removal of this effect. Our sensor modeling does not require ground control points and allows thus potentially for the automatic processing of large data volumes. As a proof of concept, we chose a set of glaciers with reference DEMs available to assess the quality of our measurements. We use time series of ASTER scenes from which we extracted DEMs with a ground sampling distance of 15m. Our method directly measures and accounts for the cross-track component of jitter so that the resulting DEMs are not contaminated by this process. Since the along-track component of jitter has the same direction as the stereo parallaxes, the two cannot be separated and the elevations extracted are thus contaminated by along-track jitter. Initial tests reveal no clear relation between the cross-track and along-track components so that the latter

  8. Comparing the Performance of Commonly Available Digital Elevation Models in GIS-based Flood Simulation

    Science.gov (United States)

    Ybanez, R. L.; Lagmay, A. M. A.; David, C. P.

    2016-12-01

    With climatological hazards increasing globally, the Philippines is listed as one of the most vulnerable countries in the world due to its location in the Western Pacific. Flood hazards mapping and modelling is one of the responses by local government and research institutions to help prepare for and mitigate the effects of flood hazards that constantly threaten towns and cities in floodplains during the 6-month rainy season. Available digital elevation maps, which serve as the most important dataset used in 2D flood modelling, are limited in the Philippines and testing is needed to determine which of the few would work best for flood hazards mapping and modelling. Two-dimensional GIS-based flood modelling with the flood-routing software FLO-2D was conducted using three different available DEMs from the ASTER GDEM, the SRTM GDEM, and the locally available IfSAR DTM. All other parameters kept uniform, such as resolution, soil parameters, rainfall amount, and surface roughness, the three models were run over a 129-sq. kilometer watershed with only the basemap varying. The output flood hazard maps were compared on the basis of their flood distribution, extent, and depth. The ASTER and SRTM GDEMs contained too much error and noise which manifested as dissipated and dissolved hazard areas in the lower watershed where clearly delineated flood hazards should be present. Noise on the two datasets are clearly visible as erratic mounds in the floodplain. The dataset which produced the only feasible flood hazard map is the IfSAR DTM which delineates flood hazard areas clearly and properly. Despite the use of ASTER and SRTM with their published resolution and accuracy, their use in GIS-based flood modelling would be unreliable. Although not as accessible, only IfSAR or better datasets should be used for creating secondary products from these base DEM datasets. For developing countries which are most prone to hazards, but with limited choices for basemaps used in hazards

  9. Comparison of Surface Flow Features from Lidar-Derived Digital Elevation Models with Historical Elevation and Hydrography Data for Minnehaha County, South Dakota

    Science.gov (United States)

    Poppenga, Sandra K.; Worstell, Bruce B.; Stoker, Jason M.; Greenlee, Susan K.

    2009-01-01

    The U.S. Geological Survey (USGS) has taken the lead in the creation of a valuable remote sensing product by incorporating digital elevation models (DEMs) derived from Light Detection and Ranging (lidar) into the National Elevation Dataset (NED), the elevation layer of 'The National Map'. High-resolution lidar-derived DEMs provide the accuracy needed to systematically quantify and fully integrate surface flow including flow direction, flow accumulation, sinks, slope, and a dense drainage network. In 2008, 1-meter resolution lidar data were acquired in Minnehaha County, South Dakota. The acquisition was a collaborative effort between Minnehaha County, the city of Sioux Falls, and the USGS Earth Resources Observation and Science (EROS) Center. With the newly acquired lidar data, USGS scientists generated high-resolution DEMs and surface flow features. This report compares lidar-derived surface flow features in Minnehaha County to 30- and 10-meter elevation data previously incorporated in the NED and ancillary hydrography datasets. Surface flow features generated from lidar-derived DEMs are consistently integrated with elevation and are important in understanding surface-water movement to better detect surface-water runoff, flood inundation, and erosion. Many topographic and hydrologic applications will benefit from the increased availability of accurate, high-quality, and high-resolution surface-water data. The remotely sensed data provide topographic information and data integration capabilities needed for meeting current and future human and environmental needs.

  10. [Constructing 3-dimensional colorized digital dental model assisted by digital photography].

    Science.gov (United States)

    Ye, Hong-qiang; Liu, Yu-shu; Liu, Yun-song; Ning, Jing; Zhao, Yi-jiao; Zhou, Yong-sheng

    2016-02-18

    To explore a method of constructing universal 3-dimensional (3D) colorized digital dental model which can be displayed and edited in common 3D software (such as Geomagic series), in order to improve the visual effect of digital dental model in 3D software. The morphological data of teeth and gingivae were obtained by intra-oral scanning system (3Shape TRIOS), constructing 3D digital dental models. The 3D digital dental models were exported as STL files. Meanwhile, referring to the accredited photography guide of American Academy of Cosmetic Dentistry (AACD), five selected digital photographs of patients'teeth and gingivae were taken by digital single lens reflex camera (DSLR) with the same exposure parameters (except occlusal views) to capture the color data. In Geomagic Studio 2013, after STL file of 3D digital dental model being imported, digital photographs were projected on 3D digital dental model with corresponding position and angle. The junctions of different photos were carefully trimmed to get continuous and natural color transitions. Then the 3D colorized digital dental model was constructed, which was exported as OBJ file or WRP file which was a special file for software of Geomagic series. For the purpose of evaluating the visual effect of the 3D colorized digital model, a rating scale on color simulation effect in views of patients'evaluation was used. Sixteen patients were recruited and their scores on colored and non-colored digital dental models were recorded. The data were analyzed using McNemar-Bowker test in SPSS 20. Universal 3D colorized digital dental model with better color simulation was constructed based on intra-oral scanning and digital photography. For clinical application, the 3D colorized digital dental models, combined with 3D face images, were introduced into 3D smile design of aesthetic rehabilitation, which could improve the patients' cognition for the esthetic digital design and virtual prosthetic effect. Universal 3D colorized

  11. High-resolution digital elevation model of lower Cowlitz and Toutle Rivers, adjacent to Mount St. Helens, Washington, based on an airborne lidar survey of October 2007

    Science.gov (United States)

    Mosbrucker, Adam

    2015-01-01

    The lateral blast, debris avalanche, and lahars of the May 18th, 1980, eruption of Mount St. Helens, Washington, dramatically altered the surrounding landscape. Lava domes were extruded during the subsequent eruptive periods of 1980–1986 and 2004–2008. More than three decades after the emplacement of the 1980 debris avalanche, high sediment production persists in the Toutle River basin, which drains the northern and western flanks of the volcano. Because this sediment increases the risk of flooding to downstream communities on the Toutle and lower Cowlitz Rivers, the U.S. Army Corps of Engineers (USACE), under the direction of Congress to maintain an authorized level of flood protection, continues to monitor and mitigate excess sediment in North and South Fork Toutle River basins to help reduce this risk and to prevent sediment from clogging the shipping channel of the Columbia River. From October 22–27, 2007, Watershed Sciences, Inc., under contract to USACE, collected high-precision airborne lidar (light detection and ranging) data that cover 273 square kilometers (105 square miles) of lower Cowlitz and Toutle River tributaries from the Columbia River at Kelso, Washington, to upper North Fork Toutle River (below the volcano's edifice), including lower South Fork Toutle River. These data provide a digital dataset of the ground surface, including beneath forest cover. Such remotely sensed data can be used to develop sediment budgets and models of sediment erosion, transport, and deposition. The U.S. Geological Survey (USGS) used these lidar data to develop digital elevation models (DEMs) of the study area. DEMs are fundamental to monitoring natural hazards and studying volcanic landforms, fluvial and glacial geomorphology, and surface geology. Watershed Sciences, Inc., provided files in the LASer (LAS) format containing laser returns that had been filtered, classified, and georeferenced. The USGS produced a hydro-flattened DEM from ground-classified points at

  12. Calculation Methods of Topographic Factors Modification Using Data Digital Elevation Model (DEM To Predict Erosion

    Directory of Open Access Journals (Sweden)

    Hengki Simanjuntak

    2018-03-01

    Full Text Available Erosion  is a crucial information for sustainable management of land resources within a particular watershed. The information of erosion is needed for land resource management planning, and is generally counted by USLE (Universal Soil Loss Equation. One of the parameters in USLE is topographic factor (LS. The determinations of LS in erosion estimation model are vary, both in terms of LS factor equation, as well as in terms of the length of the slope (λ and slope (s measurements. There are at least 3 methods used to calculate slope factors in spatial operation, i.e (1 Input of the LS Value from Table (INT, (2 Flow accumulation, and (3 Cell Size. The study was designed to obtain a method of calculation that gives the smallest topographic factor and in order to obtain a LS factors that similar to the slope information. Research location in Kampa Sub watershed, The LS determination in Kampa Sub watershed basically are with (INT and without calculating λ and s. INT method is determination without calculating λ and s, LS value is generate from the contour map and DEM SRTM by giving LS value from table reference of LS value. The Flow Accumulation and Cell Size are determination of LS Value by calculating λ and s. The Flow Accumulation method modifies the determination of λ and s using the middle value of s, λ per land use, and λ and s per cell. Cell Size method determines λ using the amount of cell size. The results showed that the “cell size” and "INT" methods were the best method for topographic factor (LS calculation, because LS value of “cell size” and "INT" methods are smaller than the flow accumulation method and the LS value similar to the slope information. LS value from that methods generated weighted value in average of 0,55−0,58. Keywords: cell size, flow accumulation, flow direction, the length of the slope, USLE

  13. Cost Model for Digital Preservation: Cost of Digital Migration

    DEFF Research Database (Denmark)

    Kejser, Ulla Bøgvad; Nielsen, Anders Bo; Thirifays, Alex

    2011-01-01

    The Danish Ministry of Culture has funded a project to set up a model for costing preservation of digital materials held by national cultural heritage institutions. The overall objective of the project was to increase cost effectiveness of digital preservation activities and to provide a basis...... for comparing and estimating future cost requirements for digital preservation. In this study we describe an activity-based costing methodology for digital preservation based on the Open Archice Information System (OAIS) Reference Model. Within this framework, which we denote the Cost Model for Digital...... Preservation (CMDP), the focus is on costing the functional entity Preservation Planning from the OAIS and digital migration activities. In order to estimate these costs we have identified cost-critical activities by analysing the functions in the OAIS model and the flows between them. The analysis has been...

  14. Accurate Determination of Glacier Surface Velocity Fields with a DEM-Assisted Pixel-Tracking Technique from SAR Imagery

    Directory of Open Access Journals (Sweden)

    Shiyong Yan

    2015-08-01

    Full Text Available We obtained accurate, detailed motion distribution of glaciers in Central Asia by applying digital elevation model (DEM assisted pixel-tracking method to L-band synthetic aperture radar imagery. The paper firstly introduces and analyzes each component of the offset field briefly, and then describes the method used to efficiently and precisely compensate the topography-related offset caused by the large spatial baseline and rugged terrain with the help of DEM. The results indicate that the rugged topography not only forms the complex shapes of glaciers, but also affects the glacier velocity estimation, especially with large spatial baseline. The maximum velocity, 0.85 m∙d−1, was observed in the middle part on the Fedchenko Glacier, which is the world’s longest mountain glacier. The motion fluctuation on its main trunk is apparently influenced by mass flowing in from tributaries, as well as angles between tributaries and the main stream. The approach presented in this paper was proved to be highly appropriate for monitoring glacier motion and will provide valuable sensitive indicators of current and future climate change for environmental analysis.

  15. Application of the PROMETHEE technique to determine depression outlet location and flow direction in DEM

    Science.gov (United States)

    Chou, Tien-Yin; Lin, Wen-Tzu; Lin, Chao-Yuan; Chou, Wen-Chieh; Huang, Pi-Hui

    2004-02-01

    With the fast growing progress of computer technologies, spatial information on watersheds such as flow direction, watershed boundaries and the drainage network can be automatically calculated or extracted from a digital elevation model (DEM). The stubborn problem that depressions exist in DEMs has been frequently encountered while extracting the spatial information of terrain. Several filling-up methods have been proposed for solving depressions. However, their suitability for large-scale flat areas is inadequate. This study proposes a depression watershed method coupled with the Preference Ranking Organization METHod for Enrichment Evaluations (PROMETHEEs) theory to determine the optimal outlet and calculate the flow direction in depressions. Three processing procedures are used to derive the depressionless flow direction: (1) calculating the incipient flow direction; (2) establishing the depression watershed by tracing the upstream drainage area and determining the depression outlet using PROMETHEE theory; (3) calculating the depressionless flow direction. The developed method was used to delineate the Shihmen Reservoir watershed located in Northern Taiwan. The results show that the depression watershed method can effectively solve the shortcomings such as depression outlet differentiating and looped flow direction between depressions. The suitability of the proposed approach was verified.

  16. Effect of DEM resolution on rainfall-triggered landslide modeling within a triangulated network-based model. A case study in the Luquillo Forest, Puerto Rico

    Science.gov (United States)

    Arnone, E.; Dialynas, Y. G.; Noto, L. V.; Bras, R. L.

    2013-12-01

    Catchment slope distribution is one of the topographic characteristics that significantly control rainfall-triggered landslide modeling, in both direct and indirect ways. Slope directly determines the soil volume associated with instability. Indirectly slope also affects the subsurface lateral redistribution of soil moisture across the basin, which in turn determines the water pore pressure conditions that impact slope stability. In this study, we investigate the influence of DEM resolution on slope stability and the slope stability analysis by using a distributed eco-hydrological and landslide model, the tRIBS-VEGGIE (Triangulated Irregular Network (TIN)-based Real-time Integrated Basin Simulator - VEGetation Generator for Interactive Evolution). The model implements a triangulated irregular network to describe the topography, and it is capable of evaluating vegetation dynamics and predicting shallow landslides triggered by rainfall. The impact of DEM resolution on the landslide prediction was studied using five TINs derived from five grid DEMs at different resolutions, i.e. 10, 20, 30, 50 and 70 m respectively. The analysis was carried out on the Mameyes Basin, located in the Luquillo Experimental Forest in Puerto Rico, where previous landslide analyses have been carried out. Results showed that the use of the irregular mesh reduced the loss of accuracy in the derived slope distribution when coarser resolutions were used. The impact of the different resolutions on soil moisture patterns was important only when the lateral redistribution was considerable, depending on hydrological properties and rainfall forcing. In some cases, the use of different DEM resolutions did not significantly affect tRIBS-VEGGIE landslide output, in terms of landslide locations, and values of slope and soil moisture at failure.

  17. Enhanced ASTER DEMs for Decadal Measurements of Glacier Elevation Changes

    Science.gov (United States)

    Girod, L.; Nuth, C.; Kääb, A.

    2016-12-01

    Elevation change data is critical to the understanding of a number of geophysical processes, including glaciers through the measurement their volume change. The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) system on-board the Terra (EOS AM-1) satellite has been a unique source of systematic stereoscopic images covering the whole globe at 15m resolution and at a consistent quality for over 15 years. While satellite stereo sensors with significantly improved radiometric and spatial resolution are available today, the potential of ASTER data lies in its long consistent time series that is unrivaled, though not fully exploited for change analysis due to lack of data accuracy and precision. ASTER data are strongly affected by attitude jitter, mainly of approximately 4 and 30 km wavelength, and improving the generation of ASTER DEMs requires removal of this effect. We developed MMASTER, an improved method for ASTER DEM generation and implemented it in the open source photogrammetric library and software suite MicMac. The method relies on the computation of a rational polynomial coefficients (RPC) model and the detection and correction of cross-track sensor jitter in order to compute DEMs. Our sensor modeling does not require ground control points and thus potentially allows for automatic processing of large data volumes. When compared to ground truth data, we have assessed a ±5m accuracy in DEM differencing when using our processing method, improved from the ±30m when using the AST14DMO DEM product. We demonstrate and discuss this improved ASTER DEM quality for a number of glaciers in Greenland (See figure attached), Alaska, and Svalbard. The quality of our measurements promises to further unlock the underused potential of ASTER DEMs for glacier volume change time series on a global scale. The data produced by our method will thus help to better understand the response of glaciers to climate change and their influence on runoff and sea level.

  18. Granular dynamics, contact mechanics and particle system simulations a DEM study

    CERN Document Server

    Thornton, Colin

    2015-01-01

    This book is devoted to the Discrete Element Method (DEM) technique, a discontinuum modelling approach that takes into account the fact that granular materials are composed of discrete particles which interact with each other at the microscale level. This numerical simulation technique can be used both for dispersed systems in which the particle-particle interactions are collisional and compact systems of particles with multiple enduring contacts. The book provides an extensive and detailed explanation of the theoretical background of DEM. Contact mechanics theories for elastic, elastic-plastic, adhesive elastic and adhesive elastic-plastic particle-particle interactions are presented. Other contact force models are also discussed, including corrections to some of these models as described in the literature, and important areas of further research are identified. A key issue in DEM simulations is whether or not a code can reliably simulate the simplest of systems, namely the single particle oblique impact wit...

  19. High-resolution digital elevation model of Mount St. Helens crater and upper North Fork Toutle River basin, Washington, based on an airborne lidar survey of September 2009

    Science.gov (United States)

    Mosbrucker, Adam

    2014-01-01

    The lateral blast, debris avalanche, and lahars of the May 18th, 1980, eruption of Mount St. Helens, Washington, dramatically altered the surrounding landscape. Lava domes were extruded during the subsequent eruptive periods of 1980–1986 and 2004–2008. More than three decades after the emplacement of the 1980 debris avalanche, high sediment production persists in the North Fork Toutle River basin, which drains the northern flank of the volcano. Because this sediment increases the risk of flooding to downstream communities on the Toutle and Cowlitz Rivers, the U.S. Army Corps of Engineers (USACE), under the direction of Congress to maintain an authorized level of flood protection, built a sediment retention structure on the North Fork Toutle River in 1989 to help reduce this risk and to prevent sediment from clogging the shipping channel of the Columbia River. From September 16–20, 2009, Watershed Sciences, Inc., under contract to USACE, collected high-precision airborne lidar (light detection and ranging) data that cover 214 square kilometers (83 square miles) of Mount St. Helens and the upper North Fork Toutle River basin from the sediment retention structure to the volcano's crater. These data provide a digital dataset of the ground surface, including beneath forest cover. Such remotely sensed data can be used to develop sediment budgets and models of sediment erosion, transport, and deposition. The U.S. Geological Survey (USGS) used these lidar data to develop digital elevation models (DEMs) of the study area. DEMs are fundamental to monitoring natural hazards and studying volcanic landforms, fluvial and glacial geomorphology, and surface geology. Watershed Sciences, Inc., provided files in the LASer (LAS) format containing laser returns that had been filtered, classified, and georeferenced. The USGS produced a hydro-flattened DEM from ground-classified points at Castle, Coldwater, and Spirit Lakes. Final results averaged about five laser last

  20. Karst Depression Detection Using ASTER, ALOS/PRISM and SRTM-Derived Digital Elevation Models in the Bambuí Group, Brazil

    Directory of Open Access Journals (Sweden)

    Osmar Abílio de Carvalho

    2013-12-01

    Full Text Available Remote sensing has been used in karst studies to identify limestone terrain, describe exokarst features, analyze karst depressions, and detect geological structures important to karst development. The aim of this work is to investigate the use of ASTER-, SRTM- and ALOS/PRISM-derived digital elevation models (DEMs to detect and quantify natural karst depressions along the São Francisco River near Barreiras city, northeast Brazil. The study area is a karst landscape characterized by karst depressions (dolines, closed depressions in limestone, many of which contain standing water connected with the ground-water table. The base of dolines is typically sealed with an impermeable clay layer covered by standing water or herbaceous vegetation. We identify dolines by combining the extraction of sink depth from DEMs, morphometric analysis using GIS, and visual interpretation. Our methodology is a semi-automatic approach involving several steps: (a DEM acquisition; (b sink-depth calculation using the difference between the raw DEM and the corresponding DEM with sinks filled; and (c elimination of falsely identified karst depressions using morphometric attributes. The advantages and limitations of the applied methodology using different DEMs are examined by comparison with a sinkhole map generated from traditional geomorphological investigations based on visual interpretation of the high-resolution remote sensing images and field surveys. The threshold values of the depth, area size and circularity index appropriate for distinguishing dolines were identified from the maximum overall accuracy obtained by comparison with a true doline map. Our results indicate that the best performance of the proposed methodology for meso-scale karst feature detection was using ALOS/PRISM data with a threshold depth > 2 m; areas > 13,125 m2 and circularity indexes > 0.3 (overall accuracy of 0.53. The overall correct identification of around half of the true dolines suggests

  1. A new 1 km digital elevation model of the Antarctic derived from combined satellite radar and laser data – Part 1: Data and methods

    Directory of Open Access Journals (Sweden)

    J. L. Bamber

    2009-05-01

    Full Text Available Digital elevation models (DEMs of the whole of Antarctica have been derived, previously, from satellite radar altimetry (SRA and limited terrestrial data. Near the ice sheet margins and in other areas of steep relief the SRA data tend to have relatively poor coverage and accuracy. To remedy this and to extend the coverage beyond the latitudinal limit of the SRA missions (81.5° S we have combined laser altimeter measurements from the Geosciences Laser Altimeter System onboard ICESat with SRA data from the geodetic phase of the ERS-1 satellite mission. The former provide decimetre vertical accuracy but with poor spatial coverage. The latter have excellent spatial coverage but a poorer vertical accuracy. By combining the radar and laser data using an optimal approach we have maximised the vertical accuracy and spatial resolution of the DEM and minimised the number of grid cells with an interpolated elevation estimate. We assessed the optimum resolution for producing a DEM based on a trade-off between resolution and interpolated cells, which was found to be 1 km. This resulted in just under 32% of grid cells having an interpolated value. The accuracy of the final DEM was assessed using a suite of independent airborne altimeter data and used to produce an error map. The RMS error in the new DEM was found to be roughly half that of the best previous 5 km resolution, SRA-derived DEM, with marked improvements in the steeper marginal and mountainous areas and between 81.5 and 86° S. The DEM contains a wealth of information related to ice flow. This is particularly apparent for the two largest ice shelves – the Filchner-Ronne and Ross – where the surface expression of flow of ice streams and outlet glaciers can be traced from the grounding line to the calving front. The surface expression of subglacial lakes and other basal features are also illustrated. We also use the DEM to derive new estimates of balance velocities and ice divide locations.

  2. Cost Model for Digital Curation: Cost of Digital Migration

    DEFF Research Database (Denmark)

    Kejser, Ulla Bøgvad; Nielsen, Anders Bo; Thirifays, Alex

    2009-01-01

    The Danish Ministry of Culture is currently funding a project to set up a model for costing preservation of digital materials held by national cultural heritage institutions. The overall objective of the project is to provide a basis for comparing and estimating future financial requirements...... for digital preservation and to increase cost effectiveness of digital preservation activities. In this study we describe an activity based costing methodology for digital preservation based on the OAIS Reference Model. In order to estimate the cost of digital migrations we have identified cost critical...

  3. 47 CFR 101.503 - Digital Electronic Message Service Nodal Stations.

    Science.gov (United States)

    2010-10-01

    ... Service § 101.503 Digital Electronic Message Service Nodal Stations. 10.6 GHz DEMS Nodal Stations may be... 47 Telecommunication 5 2010-10-01 2010-10-01 false Digital Electronic Message Service Nodal Stations. 101.503 Section 101.503 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) SAFETY...

  4. Drainage Structure Datasets and Effects on LiDAR-Derived Surface Flow Modeling

    Directory of Open Access Journals (Sweden)

    Ruopu Li

    2013-12-01

    Full Text Available With extraordinary resolution and accuracy, Light Detection and Ranging (LiDAR-derived digital elevation models (DEMs have been increasingly used for watershed analyses and modeling by hydrologists, planners and engineers. Such high-accuracy DEMs have demonstrated their effectiveness in delineating watershed and drainage patterns at fine scales in low-relief terrains. However, these high-resolution datasets are usually only available as topographic DEMs rather than hydrologic DEMs, presenting greater land roughness that can affect natural flow accumulation. Specifically, locations of drainage structures such as road culverts and bridges were simulated as barriers to the passage of drainage. This paper proposed a geospatial method for producing LiDAR-derived hydrologic DEMs, which incorporates data collection of drainage structures (i.e., culverts and bridges, data preprocessing and burning of the drainage structures into DEMs. A case study of GIS-based watershed modeling in South Central Nebraska showed improved simulated surface water derivatives after the drainage structures were burned into the LiDAR-derived topographic DEMs. The paper culminates in a proposal and discussion of establishing a national or statewide drainage structure dataset.

  5. Evaluation of the influence of source and spatial resolution of DEMs on derivative products used in landslide mapping

    Directory of Open Access Journals (Sweden)

    Rubini Mahalingam

    2016-11-01

    Full Text Available Landslides are a major geohazard, which result in significant human, infrastructure, and economic losses. Landslide susceptibility mapping can help communities plan and prepare for these damaging events. Digital elevation models (DEMs are one of the most important data-sets used in landslide hazard assessment. Despite their frequent use, limited research has been completed to date on how the DEM source and spatial resolution can influence the accuracy of the produced landslide susceptibility maps. The aim of this paper is to analyse the influence of spatial resolutions and source of DEMs on landslide susceptibility mapping. For this purpose, Advanced Spaceborne Thermal Emission and Reflection (ASTER, National Elevation Dataset (NED, and Light Detection and Ranging (LiDAR DEMs were obtained for two study sections of approximately 140 km2 in north-west Oregon. Each DEM was resampled to 10, 30, and 50 m and slope and aspect grids were derived for each resolution. A set of nine spatial databases was constructed using geoinformation science (GIS for each of the spatial resolution and source. Additional factors such as distance to river and fault maps were included. An analytical hierarchical process (AHP, fuzzy logic model, and likelihood ratio-AHP representing qualitative, quantitative, and hybrid landslide mapping techniques were used for generating landslide susceptibility maps. The results from each of the techniques were verified with the Cohen's kappa index, confusion matrix, and a validation index based on agreement with detailed landslide inventory maps. The spatial resolution of 10 m, derived from the LiDAR data-set showed higher predictive accuracy in all the three techniques used for producing landslide susceptibility maps. At a resolution of 10 m, the output maps based on NED and ASTER had higher misclassification compared to the LiDAR-based outputs. Further, the 30-m LiDAR output showed improved results over the 10-m NED and 10-m

  6. DemQSAR: predicting human volume of distribution and clearance of drugs.

    Science.gov (United States)

    Demir-Kavuk, Ozgur; Bentzien, Jörg; Muegge, Ingo; Knapp, Ernst-Walter

    2011-12-01

    In silico methods characterizing molecular compounds with respect to pharmacologically relevant properties can accelerate the identification of new drugs and reduce their development costs. Quantitative structure-activity/-property relationship (QSAR/QSPR) correlate structure and physico-chemical properties of molecular compounds with a specific functional activity/property under study. Typically a large number of molecular features are generated for the compounds. In many cases the number of generated features exceeds the number of molecular compounds with known property values that are available for learning. Machine learning methods tend to overfit the training data in such situations, i.e. the method adjusts to very specific features of the training data, which are not characteristic for the considered property. This problem can be alleviated by diminishing the influence of unimportant, redundant or even misleading features. A better strategy is to eliminate such features completely. Ideally, a molecular property can be described by a small number of features that are chemically interpretable. The purpose of the present contribution is to provide a predictive modeling approach, which combines feature generation, feature selection, model building and control of overtraining into a single application called DemQSAR. DemQSAR is used to predict human volume of distribution (VD(ss)) and human clearance (CL). To control overtraining, quadratic and linear regularization terms were employed. A recursive feature selection approach is used to reduce the number of descriptors. The prediction performance is as good as the best predictions reported in the recent literature. The example presented here demonstrates that DemQSAR can generate a model that uses very few features while maintaining high predictive power. A standalone DemQSAR Java application for model building of any user defined property as well as a web interface for the prediction of human VD(ss) and CL is

  7. DEM GPU studies of industrial scale particle simulations for granular flow civil engineering applications

    Science.gov (United States)

    Pizette, Patrick; Govender, Nicolin; Wilke, Daniel N.; Abriak, Nor-Edine

    2017-06-01

    The use of the Discrete Element Method (DEM) for industrial civil engineering industrial applications is currently limited due to the computational demands when large numbers of particles are considered. The graphics processing unit (GPU) with its highly parallelized hardware architecture shows potential to enable solution of civil engineering problems using discrete granular approaches. We demonstrate in this study the pratical utility of a validated GPU-enabled DEM modeling environment to simulate industrial scale granular problems. As illustration, the flow discharge of storage silos using 8 and 17 million particles is considered. DEM simulations have been performed to investigate the influence of particle size (equivalent size for the 20/40-mesh gravel) and induced shear stress for two hopper shapes. The preliminary results indicate that the shape of the hopper significantly influences the discharge rates for the same material. Specifically, this work shows that GPU-enabled DEM modeling environments can model industrial scale problems on a single portable computer within a day for 30 seconds of process time.

  8. A semi-automated tool for reducing the creation of false closed depressions from a filled LIDAR-derived digital elevation model

    Science.gov (United States)

    Waller, John S.; Doctor, Daniel H.; Terziotti, Silvia

    2015-01-01

    Closed depressions on the land surface can be identified by ‘filling’ a digital elevation model (DEM) and subtracting the filled model from the original DEM. However, automated methods suffer from artificial ‘dams’ where surface streams cross under bridges and through culverts. Removal of these false depressions from an elevation model is difficult due to the lack of bridge and culvert inventories; thus, another method is needed to breach these artificial dams. Here, we present a semi-automated workflow and toolbox to remove falsely detected closed depressions created by artificial dams in a DEM. The approach finds the intersections between transportation routes (e.g., roads) and streams, and then lowers the elevation surface across the roads to stream level allowing flow to be routed under the road. Once the surface is corrected to match the approximate location of the National Hydrologic Dataset stream lines, the procedure is repeated with sequentially smaller flow accumulation thresholds in order to generate stream lines with less contributing area within the watershed. Through multiple iterations, artificial depressions that may arise due to ephemeral flow paths can also be removed. Preliminary results reveal that this new technique provides significant improvements for flow routing across a DEM and minimizes artifacts within the elevation surface. Slight changes in the stream flow lines generally improve the quality of flow routes; however some artificial dams may persist. Problematic areas include extensive road ditches, particularly along divided highways, and where surface flow crosses beneath road intersections. Limitations do exist, and the results partially depend on the quality of data being input. Of 166 manually identified culverts from a previous study by Doctor and Young in 2013, 125 are within 25 m of culverts identified by this tool. After three iterations, 1,735 culverts were identified and cataloged. The result is a reconditioned

  9. Extraction of multi-scale landslide morphological features based on local Gi* using airborne LiDAR-derived DEM

    Science.gov (United States)

    Shi, Wenzhong; Deng, Susu; Xu, Wenbing

    2018-02-01

    For automatic landslide detection, landslide morphological features should be quantitatively expressed and extracted. High-resolution Digital Elevation Models (DEMs) derived from airborne Light Detection and Ranging (LiDAR) data allow fine-scale morphological features to be extracted, but noise in DEMs influences morphological feature extraction, and the multi-scale nature of landslide features should be considered. This paper proposes a method to extract landslide morphological features characterized by homogeneous spatial patterns. Both profile and tangential curvature are utilized to quantify land surface morphology, and a local Gi* statistic is calculated for each cell to identify significant patterns of clustering of similar morphometric values. The method was tested on both synthetic surfaces simulating natural terrain and airborne LiDAR data acquired over an area dominated by shallow debris slides and flows. The test results of the synthetic data indicate that the concave and convex morphologies of the simulated terrain features at different scales and distinctness could be recognized using the proposed method, even when random noise was added to the synthetic data. In the test area, cells with large local Gi* values were extracted at a specified significance level from the profile and the tangential curvature image generated from the LiDAR-derived 1-m DEM. The morphologies of landslide main scarps, source areas and trails were clearly indicated, and the morphological features were represented by clusters of extracted cells. A comparison with the morphological feature extraction method based on curvature thresholds proved the proposed method's robustness to DEM noise. When verified against a landslide inventory, the morphological features of almost all recent (historical (> 10 years) landslides were extracted. This finding indicates that the proposed method can facilitate landslide detection, although the cell clusters extracted from curvature images should

  10. Sensitivity of drainage morphometry based hydrological response (GIUH) of a river basin to the spatial resolution of DEM data

    Science.gov (United States)

    Sahoo, Ramendra; Jain, Vikrant

    2018-02-01

    Drainage network pattern and its associated morphometric ratios are some of the important plan form attributes of a drainage basin. Extraction of these attributes for any basin is usually done by spatial analysis of the elevation data of that basin. These planform attributes are further used as input data for studying numerous process-response interactions inside the physical premise of the basin. One of the important uses of the morphometric ratios is its usage in the derivation of hydrologic response of a basin using GIUH concept. Hence, accuracy of the basin hydrological response to any storm event depends upon the accuracy with which, the morphometric ratios can be estimated. This in turn, is affected by the spatial resolution of the source data, i.e. the digital elevation model (DEM). We have estimated the sensitivity of the morphometric ratios and the GIUH derived hydrograph parameters, to the resolution of source data using a 30 meter and a 90 meter DEM. The analysis has been carried out for 50 drainage basins in a mountainous catchment. A simple and comprehensive algorithm has been developed for estimation of the morphometric indices from a stream network. We have calculated all the morphometric parameters and the hydrograph parameters for each of these basins extracted from two different DEMs, with different spatial resolutions. Paired t-test and Sign test were used for the comparison. Our results didn't show any statistically significant difference among any of the parameters calculated from the two source data. Along with the comparative study, a first-hand empirical analysis about the frequency distribution of the morphometric and hydrologic response parameters has also been communicated. Further, a comparison with other hydrological models suggests that plan form morphometry based GIUH model is more consistent with resolution variability in comparison to topographic based hydrological model.

  11. Quantifying the performance of automated GIS-based geomorphological approaches for riparian zone delineation using digital elevation models

    Directory of Open Access Journals (Sweden)

    D. Fernández

    2012-10-01

    Full Text Available Riparian zone delineation is a central issue for managing rivers and adjacent areas; however, criteria used to delineate them are still under debate. The area inundated by a 50-yr flood has been indicated as an optimal hydrological descriptor for riparian areas. This detailed hydrological information is usually only available for populated areas at risk of flooding. In this work we created several floodplain surfaces by means of two different GIS-based geomorphological approaches using digital elevation models (DEMs, in an attempt to find hydrologically meaningful potential riparian zones for river networks at the river basin scale. Objective quantification of the performance of the two geomorphologic models is provided by analysing coinciding and exceeding areas with respect to the 50-yr flood surface in different river geomorphological types.

  12. ArcticDEM Year 3; Improving Coverage, Repetition and Resolution

    Science.gov (United States)

    Morin, P. J.; Porter, C. C.; Cloutier, M.; Howat, I.; Noh, M. J.; Willis, M. J.; Candela, S. G.; Bauer, G.; Kramer, W.; Bates, B.; Williamson, C.

    2017-12-01

    Surface topography is among the most fundamental data sets for geosciences, essential for disciplines ranging from glaciology to geodynamics. The ArcticDEM project is using sub-meter, commercial imagery licensed by the National Geospatial-Intelligence Agency, petascale computing, and open source photogrammetry software to produce a time-tagged 2m posting elevation model and a 5m posting mosaic of the entire Arctic region. As ArcticDEM enters its third year, the region has gone from having some of the sparsest and poorest elevation data to some of the most precise and complete data of any region on the globe. To date, we have produced and released over 80,000,000 km2 as 57,000 - 2m posting, time-stamped DEMs. The Arctic, on average, is covered four times though there are hotspots with more than 100 DEMs. In addition, the version 1 release includes a 5m posting mosaic covering the entire 20,000,000 km2 region. All products are publically available through arctidem.org, ESRI web services, and a web viewer. The final year of the project will consist of a complete refiltering of clouds/water and re-mosaicing of all elevation data. Since inception of the project, post-processing techniques have improved significantly, resulting in fewer voids, better registration, sharper coastlines, and fewer inaccuracies due to clouds. All ArcticDEM data will be released in 2018. Data, documentation, web services and web viewer are available at arcticdem.org

  13. Quantification of soil losses from tourist trails - use of Digital Elevation Models

    Science.gov (United States)

    Tomczyk, Aleksandra

    2010-05-01

    Tourism impacts in protected mountain areas are one of the main concerns for land managers. Impact to environment is most visible at locations of highly concentrated activities like tourist trails, campsites etc. The main indicators of the tourist trail degradation are: vegetation loss (trampling of vegetation cover), change of vegetation type and composition, widening of the trails, muddiness and soil erosion. The last one is especially significant, since it can cause serious transformation of the land surface. Such undesirable changes cannot be repaired without high-cost management activities, and, in some cases they can made the trails difficult and unsafe to use. Scientific understanding of soil erosion related to human impact can be useful for more effective management of the natural protected areas. The aim of this study was to use of digital elevation models (DEMs) to precisely quantify of soil losses from tourist trails. In the study precise elevation data were gathered in several test fields of 4 by 5 m spatial dimension. Measurements were taken in 13 test fields, located in two protected natural areas in south Poland: Gorce National Park and Popradzki Landscape Park. The measuring places were located on trails characterized by different slope, type of vegetation and type of use. Each test field was established by four special marks, firmly dug into the ground. Elevation data were measured with the electronic total station. Irregular elevation points were surveying with essential elements of surrounding terrain surface being included. Moreover, surveys in fixed profile lines were done. For each test field a set of 30 measurements in control points has been collected and these data provide the base for verification of digital elevation models. Average density of the surveying was 70 points per square meter (1000 - 1500 elevation points per each test fields). Surveys in each test field were carried out in August and September of 2008, June 2009 and August

  14. Coupled 1D-2D hydrodynamic inundation model for sewer overflow: Influence of modeling parameters

    Directory of Open Access Journals (Sweden)

    Adeniyi Ganiyu Adeogun

    2015-10-01

    Full Text Available This paper presents outcome of our investigation on the influence of modeling parameters on 1D-2D hydrodynamic inundation model for sewer overflow, developed through coupling of an existing 1D sewer network model (SWMM and 2D inundation model (BREZO. The 1D-2D hydrodynamic model was developed for the purpose of examining flood incidence due to surcharged water on overland surface. The investigation was carried out by performing sensitivity analysis on the developed model. For the sensitivity analysis, modeling parameters, such as mesh resolution Digital Elevation Model (DEM resolution and roughness were considered. The outcome of the study shows the model is sensitive to changes in these parameters. The performance of the model is significantly influenced, by the Manning's friction value, the DEM resolution and the area of the triangular mesh. Also, changes in the aforementioned modeling parameters influence the Flood characteristics, such as the inundation extent, the flow depth and the velocity across the model domain. Keywords: Inundation, DEM, Sensitivity analysis, Model coupling, Flooding

  15. Tree-Structured Digital Organisms Model

    Science.gov (United States)

    Suzuki, Teruhiko; Nobesawa, Shiho; Tahara, Ikuo

    Tierra and Avida are well-known models of digital organisms. They describe a life process as a sequence of computation codes. A linear sequence model may not be the only way to describe a digital organism, though it is very simple for a computer-based model. Thus we propose a new digital organism model based on a tree structure, which is rather similar to the generic programming. With our model, a life process is a combination of various functions, as if life in the real world is. This implies that our model can easily describe the hierarchical structure of life, and it can simulate evolutionary computation through mutual interaction of functions. We verified our model by simulations that our model can be regarded as a digital organism model according to its definitions. Our model even succeeded in creating species such as viruses and parasites.

  16. Ice shelf melt rates in Greenland and Antarctica using time-tagged digital imagery from World View and TanDEM-X

    Science.gov (United States)

    Charolais, A.; Rignot, E. J.; Milillo, P.; Scheuchl, B.; Mouginot, J.

    2017-12-01

    The floating extensions of glaciers, or ice shelves, melt vigorously in contact with ocean waters. Melt is non uniform, with the highest melt taking place in the deepest part of the cavity, where thermal forcing is the greatest because of 1) the pressure dependence of the freezing point of the seawater/ice mixture and 2) subglacial water injects fresh, buoyant, cold melt water to fuel stronger ice-ocean interactions. Melt also forms along preferential channels, which are not stationary, and create lines of weakness in the shelf. Ice shelf melt rates have been successfully measured from space over the entire Antarctic continent and on the ice shelves in Greenland using an Eulerian approach that combines ice thickness, ice velocity vectors, surface mass balance data, and measurements of ice thinning rates. The Eulerian approach is limited by the precision of the thickness gradients, typically of a few km, and requires significant spatial averaging to remove advection effects. A Lagrangian approach has been shown to be robust to advection effects and provides higher resolution details. We implemented a Lagrangian methodology for time-tagged World View DEMs by the Polar Geoscience Center (PGS) at the University of Minnesota and time-tagged TanDEM-X DEMs separated by one year. We derive melt rates on a 300-m grid with a precision of a few m/yr. Melt is strongest along grounding lines and along preferred channels. Channels are non-stationary because melt is not the same on opposite sides of the channels. Examining time series of data and comparing with the time-dependent grounding line positions inferred from satellite radar interferometry, we evaluate the magnitude of melt near the grounding line and even within the grounding zone. A non-zero melt rate in the grounding zone has vast implications for ice sheet modeling. This work is funded by a grant from NASA Cryosphere Program.

  17. DEM Calibration Approach: design of experiment

    Science.gov (United States)

    Boikov, A. V.; Savelev, R. V.; Payor, V. A.

    2018-05-01

    The problem of DEM models calibration is considered in the article. It is proposed to divide models input parameters into those that require iterative calibration and those that are recommended to measure directly. A new method for model calibration based on the design of the experiment for iteratively calibrated parameters is proposed. The experiment is conducted using a specially designed stand. The results are processed with technical vision algorithms. Approximating functions are obtained and the error of the implemented software and hardware complex is estimated. The prospects of the obtained results are discussed.

  18. Deep Convolutional Generative Adversarial Network for Procedural 3D Landscape Generation Based on DEM

    OpenAIRE

    Wulff-Jensen, Andreas; Rant, Niclas Nerup; Møller, Tobias Nordvig; Billeskov, Jonas Aksel

    2018-01-01

    This paper proposes a novel framework for improving procedural generation of 3D landscapes using machine learning. We utilized a Deep Convolutional Generative Adversarial Network (DC-GAN) to generate heightmaps. The network was trained on a dataset consisting of Digital Elevation Maps (DEM) of the alps. During map generation, the batch size and learning rate were optimized for the most efficient and satisfying map production. The diversity of the final output was tested against Perlin noise u...

  19. Cost Model for Digital Preservation: Cost of Digital Migration

    Directory of Open Access Journals (Sweden)

    Ulla Bøgvad Kejser

    2011-03-01

    Full Text Available The Danish Ministry of Culture has funded a project to set up a model for costing preservation of digital materials held by national cultural heritage institutions. The overall objective of the project was to increase cost effectiveness of digital preservation activities and to provide a basis for comparing and estimating future cost requirements for digital preservation. In this study we describe an activity-based costing methodology for digital preservation based on the Open Archice Information System (OAIS Reference Model. Within this framework, which we denote the Cost Model for Digital Preservation (CMDP, the focus is on costing the functional entity Preservation Planning from the OAIS and digital migration activities. In order to estimate these costs we have identified cost-critical activities by analysing the functions in the OAIS model and the flows between them. The analysis has been supplemented with findings from the literature, and our own knowledge and experience. The identified cost-critical activities have subsequently been deconstructed into measurable components, cost dependencies have been examined, and the resulting equations expressed in a spreadsheet. Currently the model can calculate the cost of different migration scenarios for a series of preservation formats for text, images, sound, video, geodata, and spreadsheets. In order to verify the model it has been tested on cost data from two different migration projects at the Danish National Archives (DNA. The study found that the OAIS model provides a sound overall framework for the cost breakdown, but that some functions need additional detailing in order to cost activities accurately. Running the two sets of empirical data showed among other things that the model underestimates the cost of manpower-intensive migration projects, while it reinstates an often underestimated cost, which is the cost of developing migration software. The model has proven useful for estimating the

  20. GIS-based debris flow source and runout susceptibility assessment from DEM data – a case study in NW Nicaragua

    Directory of Open Access Journals (Sweden)

    J. M. Vilaplana

    2007-11-01

    Full Text Available In October 1998, Hurricane Mitch triggered numerous landslides (mainly debris flows in Honduras and Nicaragua, resulting in a high death toll and in considerable damage to property. The potential application of relatively simple and affordable spatial prediction models for landslide hazard mapping in developing countries was studied. Our attention was focused on a region in NW Nicaragua, one of the most severely hit places during the Mitch event. A landslide map was obtained at 1:10 000 scale in a Geographic Information System (GIS environment from the interpretation of aerial photographs and detailed field work. In this map the terrain failure zones were distinguished from the areas within the reach of the mobilized materials. A Digital Elevation Model (DEM with 20 m×20 m of pixel size was also employed in the study area. A comparative analysis of the terrain failures caused by Hurricane Mitch and a selection of 4 terrain factors extracted from the DEM which, contributed to the terrain instability, was carried out. Land propensity to failure was determined with the aid of a bivariate analysis and GIS tools in a terrain failure susceptibility map. In order to estimate the areas that could be affected by the path or deposition of the mobilized materials, we considered the fact that under intense rainfall events debris flows tend to travel long distances following the maximum slope and merging with the drainage network. Using the TauDEM extension for ArcGIS software we generated automatically flow lines following the maximum slope in the DEM starting from the areas prone to failure in the terrain failure susceptibility map. The areas crossed by the flow lines from each terrain failure susceptibility class correspond to the runout susceptibility classes represented in a runout susceptibility map. The study of terrain failure and runout susceptibility enabled us to obtain a spatial prediction for landslides, which could contribute to landslide risk

  1. Delineating wetland catchments and modeling hydrologic connectivity using LiDAR data and aerial imagery

    OpenAIRE

    Wu, Qiusheng; Lane, Charles R.

    2017-01-01

    In traditional watershed delineation and topographic modeling, surface depressions are generally treated as spurious features and simply removed from a digital elevation model (DEM) to enforce flow continuity of water across the topographic surface to the watershed outlets. In reality, however, many depressions in the DEM are actual wetland landscape features that are seldom fully filled with water. For instance, wetland depressions in the Prairie Pothole Region (PPR) are seasonally to perman...

  2. Recent glacier mass balance and area changes in the Kangri Karpo Mountains from DEMs and glacier inventories

    Science.gov (United States)

    Wu, Kunpeng; Liu, Shiyin; Jiang, Zongli; Xu, Junli; Wei, Junfeng; Guo, Wanqin

    2018-01-01

    Due to the influence of the Indian monsoon, the Kangri Karpo Mountains in the south-east of the Tibetan Plateau is in the most humid and one of the most important and concentrated regions containing maritime (temperate) glaciers. Glacier mass loss in the Kangri Karpo is an important contributor to global mean sea level rise, and changes run-off distribution, increasing the risk of glacial-lake outburst floods (GLOFs). Because of its inaccessibility and high labour costs, information about the Kangri Karpo glaciers is still limited. Using geodetic methods based on digital elevation models (DEMs) derived from 1980 topographic maps from the Shuttle Radar Topography Mission (SRTM) (2000) and from TerraSAR-X/TanDEM-X (2014), this study has determined glacier elevation changes. Glacier area and length changes between 1980 and 2015 were derived from topographical maps and Landsat TM/ETM+/OLI images. Results show that the Kangri Karpo contained 1166 glaciers with an area of 2048.50 ± 48.65 km2 in 2015. Ice cover diminished by 679.51 ± 59.49 km2 (24.9 ± 2.2 %) or 0.71 ± 0.06 % a-1 from 1980 to 2015, although nine glaciers advanced. A glacierized area of 788.28 km2, derived from DEM differencing, experienced a mean mass loss of 0.46 ± 0.08 m w.e. a-1 from 1980 to 2014. Shrinkage and mass loss accelerated significantly from 2000 to 2015 compared to 1980-2000, consistent with a warming climate.

  3. A Visual Framework for Digital Reconstruction of Topographic Maps

    KAUST Repository

    Thabet, Ali Kassem

    2014-09-30

    We present a framework for reconstructing Digital Elevation Maps (DEM) from scanned topographic maps. We first rectify the images to ensure that maps fit together without distortion. To segment iso-contours, we have developed a novel semi-automated method based on mean-shifts that requires only minimal user interaction. Contour labels are automatically read using an OCR module. To reconstruct the output DEM from scattered data, we generalize natural neighbor interpolation to handle the transfinite case (contours and points). To this end, we use parallel vector propagation to compute a discrete Voronoi diagram of the constraints, and a modified floodfill to compute virtual Voronoi tiles. Our framework is able to handle tens of thousands of contours and points and can generate DEMs comprising more than 100 million samples. We provide quantitative comparison to commercial software and show the benefits of our approach. We furthermore show the robustness of our method on a massive set of old maps predating satellite acquisition. Compared to other methods, our framework is able to accurately and efficiently generate a final DEM despite inconsistencies, sparse or missing contours even for highly complex and cluttered maps. Therefore, this method has broad applicability for digitization and reconstruction of the world\\'s old topographic maps that are often the only record of past landscapess and cultural heritage before their destruction under modern development.

  4. Knowledge discovery from models of soil properties developed through data mining

    NARCIS (Netherlands)

    Bui, E.N.; Henderson, B.L.; Viergever, K.

    2006-01-01

    We modelled the distribution of soil properties across the agricultural zone on the Australian continent using data mining and knowledge discovery from databases (DM&KDD) tools. Piecewise linear tree models were built choosing from 19 climate variables, digital elevation model (DEM) and derived

  5. Alaska 2 Arc-second Digital Elevation Models (DEMs) - USGS National Map 3DEP Downloadable Data Collection

    Data.gov (United States)

    U.S. Geological Survey, Department of the Interior — This is a tiled collection of the 3D Elevation Program (3DEP) and is 2 arc-second (approximately 60 m) resolution covering Alaska. The elevations in this Digital...

  6. Numerical modelling of powder caking at REV scale by using DEM

    Science.gov (United States)

    Guessasma, Mohamed; Silva Tavares, Homayra; Afrassiabian, Zahra; Saleh, Khashayar

    2017-06-01

    This work deals with numerical simulation of powder caking process caused by capillary condensation phenomenon. Caking consists in unwanted agglomeration of powder particles. This process is often irreversible and not easy to predict. To reproduce mechanism involved by caking phenomenon we have used the Discrete Elements Method (DEM). In the present work, we mainly focus on the role of capillary condensation and subsequent liquid bridge formation within a granular medium exposed to fluctuations of ambient relative humidity. Such bridges cause an attractive force between particles, leading to the formation of a cake with intrinsic physicochemical and mechanical properties. By considering a Representative Elementary Volume (REV), the DEM is then performed by means of a MULTICOR-3D software tacking into account the properties of the cake (degree of saturation) in order to establish relationships between the microscopic parameters and the macroscopic behaviour (tensile strength).

  7. Numerical modelling of powder caking at REV scale by using DEM

    Directory of Open Access Journals (Sweden)

    Guessasma Mohamed

    2017-01-01

    Full Text Available This work deals with numerical simulation of powder caking process caused by capillary condensation phenomenon. Caking consists in unwanted agglomeration of powder particles. This process is often irreversible and not easy to predict. To reproduce mechanism involved by caking phenomenon we have used the Discrete Elements Method (DEM. In the present work, we mainly focus on the role of capillary condensation and subsequent liquid bridge formation within a granular medium exposed to fluctuations of ambient relative humidity. Such bridges cause an attractive force between particles, leading to the formation of a cake with intrinsic physicochemical and mechanical properties. By considering a Representative Elementary Volume (REV, the DEM is then performed by means of a MULTICOR-3D software tacking into account the properties of the cake (degree of saturation in order to establish relationships between the microscopic parameters and the macroscopic behaviour (tensile strength.

  8. A NEW HIGH-RESOLUTION ELEVATION MODEL OF GREENLAND DERIVED FROM TANDEM-X

    Directory of Open Access Journals (Sweden)

    B. Wessel

    2016-06-01

    Full Text Available In this paper we present for the first time the new digital elevation model (DEM for Greenland produced by the TanDEM-X (TerraSAR add-on for digital elevation measurement mission. The new, full coverage DEM of Greenland has a resolution of 0.4 arc seconds corresponding to 12 m. It is composed of more than 7.000 interferometric synthetic aperture radar (InSAR DEM scenes. X-Band SAR penetrates the snow and ice pack by several meters depending on the structures within the snow, the acquisition parameters, and the dielectricity constant of the medium. Hence, the resulting SAR measurements do not represent the surface but the elevation of the mean phase center of the backscattered signal. Special adaptations on the nominal TanDEM-X DEM generation are conducted to maintain these characteristics and not to raise or even deform the DEM to surface reference data. For the block adjustment, only on the outer coastal regions ICESat (Ice, Cloud, and land Elevation Satellite elevations as ground control points (GCPs are used where mostly rock and surface scattering predominates. Comparisons with ICESat data and snow facies are performed. In the inner ice and snow pack, the final X-Band InSAR DEM of Greenland lies up to 10 m below the ICESat measurements. At the outer coastal regions it corresponds well with the GCPs. The resulting DEM is outstanding due to its resolution, accuracy and full coverage. It provides a high resolution dataset as basis for research on climate change in the arctic.

  9. Gully incision rates on the bedrock of a large dip-slope landslide revealed by multi-period LiDAR DEMs

    Science.gov (United States)

    Chan, Y. C.; Hsieh, Y. C.

    2017-12-01

    Recent advances in airborne laser scanning (ALS) technology have provided a great opportunity for characterizing surface erosion through developing improved methods in multi-period DEM differencing and geomorphometry. This study uses three periods of ALS digital elevation model (DEM) data to analyze the short-term erosional features of the Tsaoling landslide triggered by the 1999 Chi-Chi earthquake in Taiwan. Two methods for calculating the bedrock incision rate, the equal-interval cross section selection method and the continuous swath profiles selection method, were used in the study after nearly ten years of gully incision following the earthquake-triggered dip-slope landslide. Multi-temporal gully incision rates were obtained using the continuous swath profiles selection method, which is considered a practical and convenient approach in terrain change studies. After error estimation and comparison of the multi-period ALS DEMs, the terrain change in different periods can be directly calculated, reducing time-consuming fieldwork such as installation of erosion pins and measurement of topographic cross sections on site. In this study, the gully bedrock incision rates ranged between 0.23 and 3.98 m/year, remarkably higher than the typical results from the previous studies. By comparing the DEM data, aerial photos, and precipitation records of this area, the effects of erosion could be observed from the retreat of the Chunqiu Cliff outline during August 2011 to September 2012. It was inferred that the change in the topographic elevation during 2011-2012 was mainly due to the torrential rain brought by Typhoon Soula, which occurred on 30 July 2012. The local gully incision rate in the lower part of the landslide surface was remarkably faster than that of the other regions, suggesting that the fast incision of the toe area possibly contributes to the occurrence of repeated landslides in the Tsaoling area.

  10. Can DEM time series produced by UAV be used to quantify diffuse erosion in an agricultural watershed?

    Science.gov (United States)

    Pineux, N.; Lisein, J.; Swerts, G.; Bielders, C. L.; Lejeune, P.; Colinet, G.; Degré, A.

    2017-03-01

    Erosion and deposition modelling should rely on field data. Currently these data are seldom available at large spatial scales and/or at high spatial resolution. In addition, conventional erosion monitoring approaches are labour intensive and costly. This calls for the development of new approaches for field erosion data acquisition. As a result of rapid technological developments and low cost, unmanned aerial vehicles (UAV) have recently become an attractive means of generating high resolution digital elevation models (DEMs). The use of UAV to observe and quantify gully erosion is now widely established. However, in some agro-pedological contexts, soil erosion results from multiple processes, including sheet and rill erosion, tillage erosion and erosion due to harvest of root crops. These diffuse erosion processes often represent a particular challenge because of the limited elevation changes they induce. In this study, we propose to assess the reliability and development perspectives of UAV to locate and quantify erosion and deposition in a context of an agricultural watershed with silt loam soils and a smooth relief. Erosion and deposition rates derived from high resolution DEM time series are compared to field measurements. The UAV technique demonstrates a high level of flexibility and can be used, for instance, after a major erosive event. It delivers a very high resolution DEM (pixel size: 6 cm) which allows us to compute high resolution runoff pathways. This could enable us to precisely locate runoff management practices such as fascines. Furthermore, the DEMs can be used diachronically to extract elevation differences before and after a strongly erosive rainfall and be validated by field measurements. While the analysis for this study was carried out over 2 years, we observed a tendency along the slope from erosion to deposition. Erosion and deposition patterns detected at the watershed scale are also promising. Nevertheless, further development in the

  11. 3D Digital Modelling

    DEFF Research Database (Denmark)

    Hundebøl, Jesper

    wave of new building information modelling tools demands further investigation, not least because of industry representatives' somewhat coarse parlance: Now the word is spreading -3D digital modelling is nothing less than a revolution, a shift of paradigm, a new alphabet... Research qeustions. Based...... on empirical probes (interviews, observations, written inscriptions) within the Danish construction industry this paper explores the organizational and managerial dynamics of 3D Digital Modelling. The paper intends to - Illustrate how the network of (non-)human actors engaged in the promotion (and arrest) of 3...... important to appreciate the analysis. Before turning to the presentation of preliminary findings and a discussion of 3D digital modelling, it begins, however, with an outline of industry specific ICT strategic issues. Paper type. Multi-site field study...

  12. Sensitivity of Particle Size in Discrete Element Method to Particle Gas Method (DEM_PGM) Coupling in Underbody Blast Simulations

    Science.gov (United States)

    2016-06-12

    Particle Size in Discrete Element Method to Particle Gas Method (DEM_PGM) Coupling in Underbody Blast Simulations Venkatesh Babu, Kumar Kulkarni, Sanjay...buried in soil viz., (1) coupled discrete element & particle gas methods (DEM-PGM) and (2) Arbitrary Lagrangian-Eulerian (ALE), are investigated. The...DEM_PGM and identify the limitations/strengths compared to the ALE method. Discrete Element Method (DEM) can model individual particle directly, and

  13. One-meter topobathymetric digital elevation model for Majuro Atoll, Republic of the Marshall Islands, 1944 to 2016

    Science.gov (United States)

    Palaseanu-Lovejoy, Monica; Poppenga, Sandra K.; Danielson, Jeffrey J.; Tyler, Dean J.; Gesch, Dean B.; Kottermair, Maria; Jalandoni, Andrea; Carlson, Edward; Thatcher, Cindy A.; Barbee, Matthew M.

    2018-03-30

    Atoll and island coastal communities are highly exposed to sea-level rise, tsunamis, storm surges, rogue waves, king tides, and the occasional combination of multiple factors, such as high regional sea levels, extreme high local tides, and unusually strong wave set-up. The elevation of most of these atolls averages just under 3 meters (m), with many areas roughly at sea level. The lack of high-resolution topographic data has been identified as a critical data gap for hazard vulnerability and adaptation efforts and for high-resolution inundation modeling for atoll nations. Modern topographic survey equipment and airborne lidar surveys can be very difficult and costly to deploy. Therefore, unmanned aircraft systems (UAS) were investigated for collecting overlapping imagery to generate topographic digital elevation models (DEMs). Medium- and high-resolution satellite imagery (Landsat 8 and WorldView-3) was investigated to derive nearshore bathymetry.The Republic of the Marshall Islands is associated with the United States through a Compact of Free Association, and Majuro Atoll is home to the capital city of Majuro and the largest population of the Republic of the Marshall Islands. The only elevation datasets currently available for the entire Majuro Atoll are the Shuttle Radar Topography Mission and the Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Model Version 2 elevation data, which have a 30-m grid-cell spacing and a 8-m vertical root mean square error (RMSE). Both these datasets have inadequate spatial resolution and vertical accuracy for inundation modeling.The final topobathymetric DEM (TBDEM) developed for Majuro Atoll is derived from various data sources including charts, soundings, acoustic sonar, and UAS and satellite imagery spanning over 70 years of data collection (1944 to 2016) on different sections of the atoll. The RMSE of the TBDEM over the land area is 0.197 m using over 70,000 Global Navigation Satellite

  14. Pore Type Classification on Carbonate Reservoir in Offshore Sarawak using Rock Physics Model and Rock Digital Images

    International Nuclear Information System (INIS)

    Lubis, L A; Harith, Z Z T

    2014-01-01

    It has been recognized that carbonate reservoirs are one of the biggest sources of hydrocarbon. Clearly, the evaluation of these reservoirs is important and critical. For rigorous reservoir characterization and performance prediction from geophysical measurements, the exact interpretation of geophysical response of different carbonate pore types is crucial. Yet, the characterization of carbonate reservoir rocks is difficult due to their complex pore systems. The significant diagenesis process and complex depositional environment makes pore systems in carbonates far more complicated than in clastics. Therefore, it is difficult to establish rock physics model for carbonate rock type. In this paper, we evaluate the possible rock physics model of 20 core plugs of a Miocene carbonate platform in Central Luconia, Sarawak. The published laboratory data of this area were used as an input to create the carbonate rock physics models. The elastic properties were analyzed to examine the validity of an existing analytical carbonate rock physics model. We integrate the Xu-Payne Differential Effective Medium (DEM) Model and the elastic modulus which was simulated from a digital carbonate rock image using Finite Element Modeling. The results of this integration matched well for the separation of carbonate pore types and sonic P-wave velocity obtained from laboratory measurement. Thus, the results of this study show that the integration of rock digital image and theoretical rock physics might improve the elastic properties prediction and useful for more advance geophysical techniques (e.g. Seismic Inversion) of carbonate reservoir in Sarawak

  15. Research on the method of extracting DEM based on GBInSAR

    Science.gov (United States)

    Yue, Jianping; Yue, Shun; Qiu, Zhiwei; Wang, Xueqin; Guo, Leping

    2016-05-01

    Precise topographical information has a very important role in geology, hydrology, natural resources survey and deformation monitoring. The extracting DEM technology based on synthetic aperture radar interferometry (InSAR) obtains the three-dimensional elevation of the target area through the phase information of the radar image data. The technology has large-scale, high-precision, all-weather features. By changing track in the location of the ground radar system up and down, it can form spatial baseline. Then we can achieve the DEM of the target area by acquiring image data from different angles. Three-dimensional laser scanning technology can quickly, efficiently and accurately obtain DEM of target area, which can verify the accuracy of DEM extracted by GBInSAR. But research on GBInSAR in extracting DEM of the target area is a little. For lack of theory and lower accuracy problems in extracting DEM based on GBInSAR now, this article conducted research and analysis on its principle deeply. The article extracted the DEM of the target area, combined with GBInSAR data. Then it compared the DEM obtained by GBInSAR with the DEM obtained by three-dimensional laser scan data and made statistical analysis and normal distribution test. The results showed the DEM obtained by GBInSAR was broadly consistent with the DEM obtained by three-dimensional laser scanning. And its accuracy is high. The difference of both DEM approximately obeys normal distribution. It indicated that extracting the DEM of target area based on GBInSAR is feasible and provided the foundation for the promotion and application of GBInSAR.

  16. Extracting Urban Morphology for Atmospheric Modeling from Multispectral and SAR Satellite Imagery

    Science.gov (United States)

    Wittke, S.; Karila, K.; Puttonen, E.; Hellsten, A.; Auvinen, M.; Karjalainen, M.

    2017-05-01

    This paper presents an approach designed to derive an urban morphology map from satellite data while aiming to minimize the cost of data and user interference. The approach will help to provide updates to the current morphological databases around the world. The proposed urban morphology maps consist of two layers: 1) Digital Elevation Model (DEM) and 2) land cover map. Sentinel-2 data was used to create a land cover map, which was realized through image classification using optical range indices calculated from image data. For the purpose of atmospheric modeling, the most important classes are water and vegetation areas. The rest of the area includes bare soil and built-up areas among others, and they were merged into one class in the end. The classification result was validated with ground truth data collected both from field measurements and aerial imagery. The overall classification accuracy for the three classes is 91 %. TanDEM-X data was processed into two DEMs with different grid sizes using interferometric SAR processing. The resulting DEM has a RMSE of 3.2 meters compared to a high resolution DEM, which was estimated through 20 control points in flat areas. Comparing the derived DEM with the ground truth DEM from airborne LIDAR data, it can be seen that the street canyons, that are of high importance for urban atmospheric modeling are not detectable in the TanDEM-X DEM. However, the derived DEM is suitable for a class of urban atmospheric models. Based on the numerical modeling needs for regional atmospheric pollutant dispersion studies, the generated files enable the extraction of relevant parametrizations, such as Urban Canopy Parameters (UCP).

  17. EXTRACTING URBAN MORPHOLOGY FOR ATMOSPHERIC MODELING FROM MULTISPECTRAL AND SAR SATELLITE IMAGERY

    Directory of Open Access Journals (Sweden)

    S. Wittke

    2017-05-01

    Full Text Available This paper presents an approach designed to derive an urban morphology map from satellite data while aiming to minimize the cost of data and user interference. The approach will help to provide updates to the current morphological databases around the world. The proposed urban morphology maps consist of two layers: 1 Digital Elevation Model (DEM and 2 land cover map. Sentinel-2 data was used to create a land cover map, which was realized through image classification using optical range indices calculated from image data. For the purpose of atmospheric modeling, the most important classes are water and vegetation areas. The rest of the area includes bare soil and built-up areas among others, and they were merged into one class in the end. The classification result was validated with ground truth data collected both from field measurements and aerial imagery. The overall classification accuracy for the three classes is 91 %. TanDEM-X data was processed into two DEMs with different grid sizes using interferometric SAR processing. The resulting DEM has a RMSE of 3.2 meters compared to a high resolution DEM, which was estimated through 20 control points in flat areas. Comparing the derived DEM with the ground truth DEM from airborne LIDAR data, it can be seen that the street canyons, that are of high importance for urban atmospheric modeling are not detectable in the TanDEM-X DEM. However, the derived DEM is suitable for a class of urban atmospheric models. Based on the numerical modeling needs for regional atmospheric pollutant dispersion studies, the generated files enable the extraction of relevant parametrizations, such as Urban Canopy Parameters (UCP.

  18. Evaluation of TanDEMx and SRTM DEM on watershed simulated ...

    Indian Academy of Sciences (India)

    57

    **Department of Environmental and Water Resource Engineering. School of Civil .... Few studies have investigated the impact of DEM on watershed delineation like ..... on Integrating GIS and Environmental Modelling, Santa Fe, New. Mexico.

  19. 2005 Hawaii IfSAR Digital Terrain Model (DTM)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Intermap DEMs populate its data store. The DEM products are generated using Intermap's STAR technology (Interferometric Synthetic Aperture Radar). The system is...

  20. Modeling bubble heat transfer in gas-solid fluidized beds using DEM

    NARCIS (Netherlands)

    Patil, A.V.; Peters, E.A.J.F.; Kolkman, T.; Kuipers, J.A.M.

    2014-01-01

    Discrete element method (DEM) simulations of a pseudo 2-D fluidized bed at non-isothermal conditions are presented. First implementation details are discussed. This is followed by a validation study where heating of a packed column by a flow of heated fluid is considered. Next hot gas injected into

  1. All you need is shape: Predicting shear banding in sand with LS-DEM

    Science.gov (United States)

    Kawamoto, Reid; Andò, Edward; Viggiani, Gioacchino; Andrade, José E.

    2018-02-01

    This paper presents discrete element method (DEM) simulations with experimental comparisons at multiple length scales-underscoring the crucial role of particle shape. The simulations build on technological advances in the DEM furnished by level sets (LS-DEM), which enable the mathematical representation of the surface of arbitrarily-shaped particles such as grains of sand. We show that this ability to model shape enables unprecedented capture of the mechanics of granular materials across scales ranging from macroscopic behavior to local behavior to particle behavior. Specifically, the model is able to predict the onset and evolution of shear banding in sands, replicating the most advanced high-fidelity experiments in triaxial compression equipped with sequential X-ray tomography imaging. We present comparisons of the model and experiment at an unprecedented level of quantitative agreement-building a one-to-one model where every particle in the more than 53,000-particle array has its own avatar or numerical twin. Furthermore, the boundary conditions of the experiment are faithfully captured by modeling the membrane effect as well as the platen displacement and tilting. The results show a computational tool that can give insight into the physics and mechanics of granular materials undergoing shear deformation and failure, with computational times comparable to those of the experiment. One quantitative measure that is extracted from the LS-DEM simulations that is currently not available experimentally is the evolution of three dimensional force chains inside and outside of the shear band. We show that the rotations on the force chains are correlated to the rotations in stress principal directions.

  2. Digital Modeling Phenomenon Of Surface Ground Movement

    Directory of Open Access Journals (Sweden)

    Ioan Voina

    2016-11-01

    Full Text Available With the development of specialized software applications it was possible to approach and resolve complex problems concerning automating and process optimization for which are being used field data. Computerized representation of the shape and dimensions of the Earth requires a detailed mathematical modeling, known as "digital terrain model". The paper aims to present the digital terrain model of Vulcan mining, Hunedoara County, Romania. Modeling consists of a set of mathematical equations that define in detail the surface of Earth and has an approximate surface rigorously and mathematical, that calculated the land area. Therefore, the digital terrain model means a digital representation of the earth's surface through a mathematical model that approximates the land surface modeling, which can be used in various civil and industrial applications in. To achieve the digital terrain model of data recorded using linear and nonlinear interpolation method based on point survey which highlights the natural surface studied. Given the complexity of this work it is absolutely necessary to know in detail of all topographic elements of work area, without the actions to be undertaken to project and manipulate would not be possible. To achieve digital terrain model, within a specialized software were set appropriate parameters required to achieve this case study. After performing all steps we obtained digital terrain model of Vulcan Mine. Digital terrain model is the complex product, which has characteristics that are equivalent to the specialists that use satellite images and information stored in a digital model, this is easier to use.

  3. Recent glacier mass balance and area changes in the Kangri Karpo Mountains from DEMs and glacier inventories

    Directory of Open Access Journals (Sweden)

    K. Wu

    2018-01-01

    Full Text Available Due to the influence of the Indian monsoon, the Kangri Karpo Mountains in the south-east of the Tibetan Plateau is in the most humid and one of the most important and concentrated regions containing maritime (temperate glaciers. Glacier mass loss in the Kangri Karpo is an important contributor to global mean sea level rise, and changes run-off distribution, increasing the risk of glacial-lake outburst floods (GLOFs. Because of its inaccessibility and high labour costs, information about the Kangri Karpo glaciers is still limited. Using geodetic methods based on digital elevation models (DEMs derived from 1980 topographic maps from the Shuttle Radar Topography Mission (SRTM (2000 and from TerraSAR-X/TanDEM-X (2014, this study has determined glacier elevation changes. Glacier area and length changes between 1980 and 2015 were derived from topographical maps and Landsat TM/ETM+/OLI images. Results show that the Kangri Karpo contained 1166 glaciers with an area of 2048.50 ± 48.65 km2 in 2015. Ice cover diminished by 679.51 ± 59.49 km2 (24.9 ± 2.2 % or 0.71 ± 0.06 % a−1 from 1980 to 2015, although nine glaciers advanced. A glacierized area of 788.28 km2, derived from DEM differencing, experienced a mean mass loss of 0.46 ± 0.08 m w.e. a−1 from 1980 to 2014. Shrinkage and mass loss accelerated significantly from 2000 to 2015 compared to 1980–2000, consistent with a warming climate.

  4. Delineating wetland catchments and modeling hydrologic connectivity using lidar data and aerial imagery

    Science.gov (United States)

    In traditional watershed delineation and topographic modeling, surface depressions are generally treated as spurious features and simply removed from a digital elevation model (DEM) to enforce flow continuity of water across the topographic surface to the watershed outlets. In re...

  5. Systematic Digital Forensic Investigation Model

    OpenAIRE

    Systematic Digital Forensic Investigation Model

    2011-01-01

    Law practitioners are in an uninterrupted battle with criminals in the application of digital/computertechnologies, and require the development of a proper methodology to systematically searchdigital devices for significant evidence. Computer fraud and digital crimes are growing day by dayand unfortunately less than two percent of the reported cases result in confidence. This paperexplores the development of the digital forensics process model, compares digital forensicmethodologies, and fina...

  6. Volcanic geomorphology using TanDEM-X

    Science.gov (United States)

    Poland, Michael; Kubanek, Julia

    2016-04-01

    Topography is perhaps the most fundamental dataset for any volcano, yet is surprisingly difficult to collect, especially during the course of an eruption. For example, photogrammetry and lidar are time-intensive and often expensive, and they cannot be employed when the surface is obscured by clouds. Ground-based surveys can operate in poor weather but have poor spatial resolution and may expose personnel to hazardous conditions. Repeat passes of synthetic aperture radar (SAR) data provide excellent spatial resolution, but topography in areas of surface change (from vegetation swaying in the wind to physical changes in the landscape) between radar passes cannot be imaged. The German Space Agency's TanDEM-X satellite system, however, solves this issue by simultaneously acquiring SAR data of the surface using a pair of orbiting satellites, thereby removing temporal change as a complicating factor in SAR-based topographic mapping. TanDEM-X measurements have demonstrated exceptional value in mapping the topography of volcanic environments in as-yet limited applications. The data provide excellent resolution (down to ~3-m pixel size) and are useful for updating topographic data at volcanoes where surface change has occurred since the most recent topographic dataset was collected. Such data can be used for applications ranging from correcting radar interferograms for topography, to modeling flow pathways in support of hazards mitigation. The most valuable contributions, however, relate to calculating volume changes related to eruptive activity. For example, limited datasets have provided critical measurements of lava dome growth and collapse at volcanoes including Merapi (Indonesia), Colima (Mexico), and Soufriere Hills (Montserrat), and of basaltic lava flow emplacement at Tolbachik (Kamchatka), Etna (Italy), and Kīlauea (Hawai`i). With topographic data spanning an eruption, it is possible to calculate eruption rates - information that might not otherwise be available

  7. Algumas anedotas sobre Demóstenes: uma releitura

    Directory of Open Access Journals (Sweden)

    Maddalena Vallozza

    2013-06-01

    Full Text Available Muitas das anedotas sobre Demóstenes estão relacionados a seus problemas de voz e a suas dificuldades no momento da hypokrisis. Eu proponho uma reinterpretação das páginas em que eles nos são transmitidos: de Quintiliano (11, 3, a principal testemunha, a Cícero (Orator 26 e 56-58, Brutus 142, De Oratore I 261 e III 213, do autor da seção sobre Demóstenes nas Vidas dos Dez Oradores (844 d-845 b à Vida de Demóstene, de Plutarco. Com base nisso, particularmente graças a Plutarco, que cita Hermipo e Demétrio de Fáleros, é possível formular a hipótese de que a tradição nasceu no Perípato, na área de interesses pela hypokrisis que demonstram o perdido Perì hypokríseos de Teofrasto e os fragmentos da Retórica de Demétrio de Fáleros.

  8. Digital modelling of landscape and soil in a mountainous region: A neuro-fuzzy approach

    Science.gov (United States)

    Viloria, Jesús A.; Viloria-Botello, Alvaro; Pineda, María Corina; Valera, Angel

    2016-01-01

    Research on genetic relationships between soil and landforms has largely improved soil mapping. Recent technological advances have created innovative methods for modelling the spatial soil variation from digital elevation models (DEMs) and remote sensors. This generates new opportunities for the application of geomorphology to soil mapping. This study applied a method based on artificial neural networks and fuzzy clustering to recognize digital classes of land surfaces in a mountainous area in north-central Venezuela. The spatial variation of the fuzzy memberships exposed the areas where each class predominates, while the class centres helped to recognize the topographic attributes and vegetation cover of each class. The obtained classes of terrain revealed the structure of the land surface, which showed regional differences in climate, vegetation, and topography and landscape stability. The land-surface classes were subdivided on the basis of the geological substratum to produce landscape classes that additionally considered the influence of soil parent material. These classes were used as a framework for soil sampling. A redundancy analysis confirmed that changes of landscape classes explained the variation in soil properties (p = 0.01), and a Kruskal-Wallis test showed significant differences (p = 0.01) in clay, hydraulic conductivity, soil organic carbon, base saturation, and exchangeable Ca and Mg between classes. Thus, the produced landscape classes correspond to three-dimensional bodies that differ in soil conditions. Some changes of land-surface classes coincide with abrupt boundaries in the landscape, such as ridges and thalwegs. However, as the model is continuous, it disclosed the remaining variation between those boundaries.

  9. Scoops3D: software to analyze 3D slope stability throughout a digital landscape

    Science.gov (United States)

    Reid, Mark E.; Christian, Sarah B.; Brien, Dianne L.; Henderson, Scott T.

    2015-01-01

    The computer program, Scoops3D, evaluates slope stability throughout a digital landscape represented by a digital elevation model (DEM). The program uses a three-dimensional (3D) method of columns approach to assess the stability of many (typically millions) potential landslides within a user-defined size range. For each potential landslide (or failure), Scoops3D assesses the stability of a rotational, spherical slip surface encompassing many DEM cells using a 3D version of either Bishop’s simplified method or the Ordinary (Fellenius) method of limit-equilibrium analysis. Scoops3D has several options for the user to systematically and efficiently search throughout an entire DEM, thereby incorporating the effects of complex surface topography. In a thorough search, each DEM cell is included in multiple potential failures, and Scoops3D records the lowest stability (factor of safety) for each DEM cell, as well as the size (volume or area) associated with each of these potential landslides. It also determines the least-stable potential failure for the entire DEM. The user has a variety of options for building a 3D domain, including layers or full 3D distributions of strength and pore-water pressures, simplistic earthquake loading, and unsaturated suction conditions. Results from Scoops3D can be readily incorporated into a geographic information system (GIS) or other visualization software. This manual includes information on the theoretical basis for the slope-stability analysis, requirements for constructing and searching a 3D domain, a detailed operational guide (including step-by-step instructions for using the graphical user interface [GUI] software, Scoops3D-i) and input/output file specifications, practical considerations for conducting an analysis, results of verification tests, and multiple examples illustrating the capabilities of Scoops3D. Easy-to-use software installation packages are available for the Windows or Macintosh operating systems; these packages

  10. High-accuracy single-pass InSAR DEM for large-scale flood hazard applications

    Science.gov (United States)

    Schumann, G.; Faherty, D.; Moller, D.

    2017-12-01

    In this study, we used a unique opportunity of the GLISTIN-A (NASA airborne mission designed to characterizing the cryosphere) track to Greenland to acquire a high-resolution InSAR DEM of a large area in the Red River of the North Basin (north of Grand Forks, ND, USA), which is a very flood-vulnerable valley, particularly in spring time due to increased soil moisture content near state of saturation and/or, typical for this region, snowmelt. Having an InSAR DEM that meets flood inundation modeling and mapping requirements comparable to LiDAR, would demonstrate great application potential of new radar technology for national agencies with an operational flood forecasting mandate and also local state governments active in flood event prediction, disaster response and mitigation. Specifically, we derived a bare-earth DEM in SAR geometry by first removing the inherent far range bias related to airborne operation, which at the more typical large-scale DEM resolution of 30 m has a sensor accuracy of plus or minus 2.5 cm. Subsequently, an intelligent classifier based on informed relationships between InSAR height, intensity and correlation was used to distinguish between bare-earth, roads or embankments, buildings and tall vegetation in order to facilitate the creation of a bare-earth DEM that would meet the requirements for accurate floodplain inundation mapping. Using state-of-the-art LiDAR terrain data, we demonstrate that capability by achieving a root mean squared error of approximately 25 cm and further illustrating its applicability to flood modeling.

  11. 3D DEM analyses of the 1963 Vajont rock slide

    Science.gov (United States)

    Boon, Chia Weng; Houlsby, Guy; Utili, Stefano

    2013-04-01

    The 1963 Vajont rock slide has been modelled using the distinct element method (DEM). The open-source DEM code, YADE (Kozicki & Donzé, 2008), was used together with the contact detection algorithm proposed by Boon et al. (2012). The critical sliding friction angle at the slide surface was sought using a strength reduction approach. A shear-softening contact model was used to model the shear resistance of the clayey layer at the slide surface. The results suggest that the critical sliding friction angle can be conservative if stability analyses are calculated based on the peak friction angles. The water table was assumed to be horizontal and the pore pressure at the clay layer was assumed to be hydrostatic. The influence of reservoir filling was marginal, increasing the sliding friction angle by only 1.6˚. The results of the DEM calculations were found to be sensitive to the orientations of the bedding planes and cross-joints. Finally, the failure mechanism was investigated and arching was found to be present at the bend of the chair-shaped slope. References Boon C.W., Houlsby G.T., Utili S. (2012). A new algorithm for contact detection between convex polygonal and polyhedral particles in the discrete element method. Computers and Geotechnics, vol 44, 73-82, doi.org/10.1016/j.compgeo.2012.03.012. Kozicki, J., & Donzé, F. V. (2008). A new open-source software developed for numerical simulations using discrete modeling methods. Computer Methods in Applied Mechanics and Engineering, 197(49-50), 4429-4443.

  12. An experimentally validated DEM study of powder mixing in a paddle blade mixer

    OpenAIRE

    Pantaleev, Stefan; Yordanova, Slavina; Janda, Alvaro; Marigo, Michele; Ooi, Jin

    2017-01-01

    An investigation on the predictive capabilities of Discrete Element Method simulations of a powder mixing process in a laboratory scale paddle blade mixer is presented. The visco-elasto-plastic frictional adhesive DEM contactmodel of Thakur et al. (2014) was used to represent the cohesive behaviour of an aluminosilicate powder in which the model parameters were determined using experimental flow energy measurements from the FT4powder rheometer. DEM simulations of the mixing process using the ...

  13. FEM × DEM: a new efficient multi-scale approach for geotechnical problems with strain localization

    Directory of Open Access Journals (Sweden)

    Nguyen Trung Kien

    2017-01-01

    Full Text Available The paper presents a multi-scale modeling of Boundary Value Problem (BVP approach involving cohesive-frictional granular materials in the FEM × DEM multi-scale framework. On the DEM side, a 3D model is defined based on the interactions of spherical particles. This DEM model is built through a numerical homogenization process applied to a Volume Element (VE. It is then paired with a Finite Element code. Using this numerical tool that combines two scales within the same framework, we conducted simulations of biaxial and pressuremeter tests on a cohesive-frictional granular medium. In these cases, it is known that strain localization does occur at the macroscopic level, but since FEMs suffer from severe mesh dependency as soon as shear band starts to develop, the second gradient regularization technique has been used. As a consequence, the objectivity of the computation with respect to mesh dependency is restored.

  14. Shoreline Erosion and Slope Failure Detection over Southwest Lakeshore Michigan using Temporal Radar and Digital Elevation Model

    Science.gov (United States)

    Sataer, G.; Sultan, M.; Yellich, J. A.; Becker, R.; Emil, M. K.; Palaseanu, M.

    2017-12-01

    Throughout the 20th century and into the 21st century, significant losses of residential, commercial and governmental property were reported along the shores of the Great Lakes region due to one or more of the following factors: high lake levels, wave actions, groundwater discharge. A collaborative effort (Western Michigan University, University of Toledo, Michigan Geological Survey [MGS], United States Geological Survey [USGS], National Oceanographic and Atmospheric Administration [NOAA]) is underway to examine the temporal topographic variations along the shoreline and the adjacent bluff extending from the City of South Haven in the south to the City of Saugatuck in the north within the Allegan County. Our objectives include two main tasks: (1) identification of the timing of, and the areas, witnessing slope failure and shoreline erosion, and (2) investigating the factors causing the observed failures and erosion. This is being accomplished over the study area by: (1) detecting and measuring slope subsidence rates (velocities along line of site) and failures using radar interferometric persistent scatter (PS) techniques applied to ESA's European Remote Sensing (ERS) satellites, ERS-1 and -2 (spatial resolution: 25 m) that were acquired in 1995 to 2007, (2) extracting temporal high resolution (20 cm) digital elevation models (DEM) for the study area from temporal imagery acquired by Unmanned Aerial Vehicles (UAVs), and applying change detection techniques to the extracted DEMs, (3) detecting change in elevation and slope profiles extracted from two LIDAR Coastal National Elevation Database (CoNED) DEMs (spatial resolution: 0.5m), acquired on 2008 and 2012, and (4) spatial and temporal correlation of the detected changes in elevation with relevant data sets (e.g., lake levels, precipitation, groundwater levels) in search of causal effects.

  15. Evaluation of CBCT digital models and traditional models using the Little's Index.

    Science.gov (United States)

    Kau, Chung How; Littlefield, Jay; Rainy, Neal; Nguyen, Jennifer T; Creed, Ben

    2010-05-01

    To determine if measurements obtained from digital models from cone beam computed tomography (CBCT) images were comparable to the traditional method of digital study models by impressions. Digital models of 30 subjects were used. InVivoDental (Anatomage, San Jose, Calif) software was used to analyze CBCT scans taken by a Galileos cone beam scanner (Sirona, Charlotte, NC) with a field of view of 15 x 15 x 15 cm(3) and a voxel resolution of 0.125 mm. OrthoCAD (Cadent, Fairview, NJ) software was used to analyze impression scans of patients at different stages of orthodontic treatment. Impressions were taken using alginate and were mailed to OrthoCAD for digital conversion. The scans were then electronically returned in digital format for analysis. The maxillary mean scores for the Little's Index were 9.65 mm for digital models and 8.87 mm for InVivoDental models, respectively. The mandibular mean scores for the Little's Index were 6.41 mm for digital models and 6.27 mm for InVivoDental models, respectively. The mean overjet measurements were 3.32 mm for digital models and 3.52 mm for InVivoDental models, respectively. The overbite measurements were 2.29 mm for digital models and 2.26 mm for InVivoDental models, respectively. The paired t-test showed no statistical significance between the differences in all measurements. CBCT digital models are as accurate as OrthoCAD digital models in making linear measurements for overjet, overbite, and crowding measurements.

  16. Releasing the digital elevation model for the whole Italian territory: a case study reporting two years of core-data dissemination for Earth Sciences communities and other stakeholders

    Science.gov (United States)

    Tarquini, Simone; Nannipieri, Luca

    2014-05-01

    EPOS (European Plate Observing System) is the European initiative for the implementation and integration of European Research Infrastructures in the field of Solid Earth Sciences. In particular, EPOS is aimed at creating a common environment for data exchange for both the scientific community and relevant stakeholders interested in Earth Sciences. In such a context, a service providing access to the complete topography of one of the countries participating in EPOS represents a step forward towards the realization of the EPOS mission. Here we report about two years of activity of a data dissemination service which released (for free) a digital elevation model (DEM) of the whole Italian territory at 10 m-resolution named TINTALY/01. The new TINITALY/01 DEM for the whole Italian territory was completed and presented by INGV in 2007. This DEM was the final result of a project funded by the Italian Ministry of the Environment. TINITALY/01 was completed in two phases: in a first phase, independent elevation models for single regions were derived, and in a second phase, all the regional models were merged into a single, seamless model covering the whole territory of Italy. In early 2012, a web portal was published (http://tinitaly.pi.ingv.it/) through which the above DEM is open for a full web-GIS navigation (3-D navigation in anaglyph mode or standard 2-D hillshade), and where internet navigators can ask for the download of the DEM dataset (in grid format, 10 m-resolution) through the compilation of an online form (http://tinitaly.pi.ingv.it/account_request_form.html). Submission of the form implies stating the destination of use for the data, and acceptance of the policy of use (i.e. no-profit use). After nearly two years from the opening of the portal, the DEM is still browsed by up to 10-20 users per day (about 3000 visits throughout 2013). As of 31 December 2013, about 220 users affiliated to nearly 150 different institutions or associations (i.e. universities

  17. Improving maps of ice-sheet surface elevation change using combined laser altimeter and stereoscopic elevation model data

    DEFF Research Database (Denmark)

    Fredenslund Levinsen, Joanna; Howat, I. M.; Tscherning, C. C.

    2013-01-01

    We combine the complementary characteristics of laser altimeter data and stereoscopic digital elevation models (DEMs) to construct high-resolution (_100 m) maps of surface elevations and elevation changes over rapidly changing outlet glaciers in Greenland. Measurements from spaceborne and airborne...... laser altimeters have relatively low errors but are spatially limited to the ground tracks, while DEMs have larger errors but provide spatially continuous surfaces. The principle of our method is to fit the DEM surface to the altimeter point clouds in time and space to minimize the DEM errors and use...... that surface to extrapolate elevations away from altimeter flight lines. This reduces the DEM registration errors and fills the gap between the altimeter paths. We use data from ICESat and ATM as well as SPOT 5 DEMs from 2007 and 2008 and apply them to the outlet glaciers Jakobshavn Isbræ (JI...

  18. DEM Simulation of Biaxial Compression Experiments of Inherently Anisotropic Granular Materials and the Boundary Effects

    Directory of Open Access Journals (Sweden)

    Zhao-Xia Tong

    2013-01-01

    Full Text Available The reliability of discrete element method (DEM numerical simulations is significantly dependent on the particle-scale parameters and boundary conditions. To verify the DEM models, two series of biaxial compression tests on ellipse-shaped steel rods are used. The comparisons on the stress-strain relationship, strength, and deformation pattern of experiments and simulations indicate that the DEM models are able to capture the key macro- and micromechanical behavior of inherently anisotropic granular materials with high fidelity. By using the validated DEM models, the boundary effects on the macrodeformation, strain localization, and nonuniformity of stress distribution inside the specimens are investigated using two rigid boundaries and one flexible boundary. The results demonstrate that the boundary condition plays a significant role on the stress-strain relationship and strength of granular materials with inherent fabric anisotropy if the stresses are calculated by the force applied on the wall. However, the responses of the particle assembly measured inside the specimens are almost the same with little influence from the boundary conditions. The peak friction angle obtained from the compression tests with flexible boundary represents the real friction angle of particle assembly. Due to the weak lateral constraints, the degree of stress nonuniformity under flexible boundary is higher than that under rigid boundary.

  19. Topogrid Derived 10 Meter Resolution Digital Elevation Model of the Shenandoah National Park and Surrounding Region, Virginia

    Science.gov (United States)

    Chirico, Peter G.; Tanner, Seth D.

    2004-01-01

    Explanation The purpose of developing a new 10m resolution DEM of the Shenandoah National Park Region was to more accurately depict geologic structure, surfical geology, and landforms of the Shenandoah National Park Region in preparation for automated landform classification. Previously, only a 30m resolution DEM was available through the National Elevation Dataset (NED). During production of the Shenandoah10m DEM of the Park the Geography Discipline of the USGS completed a revised 10m DEM to be included into the NED. However, different methodologies were used to produce the two similar DEMs. The ANUDEM algorithm was used to develop the Shenadoah DEM data. This algorithm allows for the inclusion of contours, streams, rivers, lake and water body polygons as well as spot height data to control the elevation model. A statistical analysis using over 800 National Geodetic Survey (NGS) first and second order vertical control points reveals that the Shenandoah10m DEM, produced as a part of the Appalachian Blue Ridge Landscape project, has a vertical accuracy of ?4.87 meters. The metadata for the 10m NED data reports a vertical accuracy of ?7m. A table listing the NGS control points, the elevation comparison, and the RMSE for the Shenandoah10m DEM is provided. The process of automated terrain classification involves developing statistical signatures from the DEM for each type of surficial deposit and landform type. The signature will be a measure of several characteristics derived from the elevation data including slope, aspect, planform curvature, and profile curvature. The quality of the DEM is of critical importance when extracting terrain signatures. The highest possible horizontal and vertical accuracy is required. The more accurate Shenandoah 10m DEM can now be analyzed and integrated with the geologic observations to yield statistical correlations between the two in the development of landform and surface geology mapping projects.

  20. Exploring Digital News Publishing Business Models

    DEFF Research Database (Denmark)

    Lindskow, Kasper

    News publishers in the industrialized world are experiencing a fundamental challenge to their business models because of the changing modes of consumption, competition, and production of their offerings that are associated with the emergence of the networked information society. The erosion...... of the traditional business models poses an existential threat to news publishing and has given rise to a continuing struggle among news publishers to design digital business models that will be sustainable in the future. This dissertation argues that a central and underresearched aspect of digital news publishing...... business models concerns the production networks that support the co-production of digital news offerings. To fill this knowledge gap, this dissertation explores the strategic design of the digital news publishing production networks that are associated with HTML-based news offerings on the open Web...

  1. A method to assess collision hazard of falling rock due to slope collapse application of DEM on modeling of earthquake triggered slope failure for nuclear power plants

    International Nuclear Information System (INIS)

    Nakase, Hitoshi; Cao, Guoqiang; Tabei, Kazuto; Tochigi, Hitoshi; Matsushima, Takashi

    2015-01-01

    Risk evaluation of slope failure against nuclear power plants, which is induced by unexpectedly large earthquakes, has been urgent need for disaster prevention measures. Specially, for risk evaluation of slope failure, understanding of information such as traveling distances, collision velocities, and collision energies is very important. Discrete Element Method (DEM) such as particle simulation method contributes important role on predicting the detailed behavior of slope failure physics. In this study, instead of accurately predicting the complicated behavior of sliding and falling for each rock, we introduce the DEM modeling to evaluate the average traveling distance of collapsed rocks and its statistical variability. First, we conduct the validation test of the proposed DEM model on the basis of reconstruction of experiment results. Next, we conducted the parametric studies to examine sensitivities of important parameters. Finally, validity of the proposed method is evaluated and its applicability and technical assignments are also discussed. (author)

  2. Generation of a new Greenland Ice Sheet Digital Elevation Model

    DEFF Research Database (Denmark)

    Nagarajan, Sudhagar; Csatho, Beata M; Schenk, Anton F

    conditions, by fusing a photoclinometry DEM, SPOT and ASTER DEMs as well as elevations from ICESat, ATM and LVIS laser altimetry. The new multi-resolution DEM has a resolution of 40 m x 40 m in the marginal ice sheet regions and 250 m elsewhere. The ice sheet margin is mapped from SPOT and Landsat imagery...

  3. The EVE plus RHESSI DEM for Solar Flares, and Implications for Residual Non-Thermal X-Ray Emission

    Science.gov (United States)

    McTiernan, James; Caspi, Amir; Warren, Harry

    2016-05-01

    Solar flare spectra are typically dominated by thermal emission in the soft X-ray energy range. The low energy extent of non-thermal emission can only be loosely quantified using currently available X-ray data. To address this issue, we combine observations from the EUV Variability Experiment (EVE) on-board the Solar Dynamics Observatory (SDO) with X-ray data from the Reuven Ramaty High Energy Spectroscopic Imager (RHESSI) to calculate the Differential Emission Measure (DEM) for solar flares. This improvement over the isothermal approximation helps to resolve the ambiguity in the range where the thermal and non-thermal components may have similar photon fluxes. This "crossover" range can extend up to 30 keV.Previous work (Caspi et.al. 2014ApJ...788L..31C) concentrated on obtaining DEM models that fit both instruments' observations well. For this current project we are interested in breaks and cutoffs in the "residual" non-thermal spectrum; i.e., the RHESSI spectrum that is left over after the DEM has accounted for the bulk of the soft X-ray emission. As in our earlier work, thermal emission is modeled using a DEM that is parametrized as multiple gaussians in temperature. Non-thermal emission is modeled as a photon spectrum obtained using a thin-target emission model ('thin2' from the SolarSoft Xray IDL package). Spectra for both instruments are fit simultaneously in a self-consistent manner.For this study, we have examined the DEM and non-thermal resuidual emission for a sample of relatively large (GOES M class and above) solar flares observed from 2011 to 2014. The results for the DEM and non-thermal parameters found using the combined EVE-RHESSI data are compared with those found using only RHESSI data.

  4. Algorithm for dealing with depressions in dynamic landscape evolution models

    NARCIS (Netherlands)

    Temme, A.J.A.M.; Schoorl, J.M.; Veldkamp, A.

    2006-01-01

    Depressions in landscapes function as buffers for water and sediment. A landscape with depressions has less runoff, less erosion and more sedimentation than a landscape without depressions. Sinks in digital elevation models (DEMs) can be existing features that correctly represent depressions in

  5. S1-Leitlinie Lipödem.

    Science.gov (United States)

    Reich-Schupke, Stefanie; Schmeller, Wilfried; Brauer, Wolfgang Justus; Cornely, Manuel E; Faerber, Gabriele; Ludwig, Malte; Lulay, Gerd; Miller, Anya; Rapprich, Stefan; Richter, Dirk Frank; Schacht, Vivien; Schrader, Klaus; Stücker, Markus; Ure, Christian

    2017-07-01

    Die vorliegende überarbeitete Leitlinie zum Lipödem wurde unter der Federführung der Deutschen Gesellschaft für Phlebologie (DGP) erstellt und finanziert. Die Inhalte beruhen auf einer systematischen Literaturrecherche und dem Konsens von acht medizinischen Fachgesellschaften und Berufsverbänden. Die Leitlinie beinhaltet Empfehlungen zu Diagnostik und Therapie des Lipödems. Die Diagnose ist dabei auf der Basis von Anamnese und klinischem Befund zu stellen. Charakteristisch ist eine umschriebene, symmetrisch lokalisierte Vermehrung des Unterhautfettgewebes an den Extremitäten mit deutlicher Disproportion zum Stamm. Zusätzlich finden sich Ödeme, Hämatomneigung und eine gesteigerte Schmerzhaftigkeit der betroffenen Körperabschnitte. Weitere apparative Untersuchungen sind bisher besonderen Fragestellungen vorbehalten. Die Erkrankung ist chronisch progredient mit individuell unterschiedlichem und nicht vorhersehbarem Verlauf. Die Therapie besteht aus vier Säulen, die individuell kombiniert und an das aktuelle Beschwerdebild angepasst werden sollten: komplexe physikalische Entstauungstherapie (manuelle Lymphdrainage, Kompressionstherapie, Bewegungstherapie, Hautpflege), Liposuktion und plastisch-chirurgische Interventionen, Ernährung und körperliche Aktivität sowie ggf. additive Psychotherapie. Operative Maßnahmen sind insbesondere dann angezeigt, wenn trotz konsequent durchgeführter konservativer Therapie noch Beschwerden bestehen bzw. eine Progredienz des Befundes und/oder der Beschwerden auftritt. Eine begleitend zum Lipödem bestehende morbide Adipositas sollte vor einer Liposuktion therapeutisch angegangen werden. © 2017 The Authors | Journal compilation © Blackwell Verlag GmbH, Berlin.

  6. Automated classifications of topography from DEMs by an unsupervised nested-means algorithm and a three-part geometric signature

    Science.gov (United States)

    Iwahashi, J.; Pike, R.J.

    2007-01-01

    An iterative procedure that implements the classification of continuous topography as a problem in digital image-processing automatically divides an area into categories of surface form; three taxonomic criteria-slope gradient, local convexity, and surface texture-are calculated from a square-grid digital elevation model (DEM). The sequence of programmed operations combines twofold-partitioned maps of the three variables converted to greyscale images, using the mean of each variable as the dividing threshold. To subdivide increasingly subtle topography, grid cells sloping at less than mean gradient of the input DEM are classified by designating mean values of successively lower-sloping subsets of the study area (nested means) as taxonomic thresholds, thereby increasing the number of output categories from the minimum 8 to 12 or 16. Program output is exemplified by 16 topographic types for the world at 1-km spatial resolution (SRTM30 data), the Japanese Islands at 270??m, and part of Hokkaido at 55??m. Because the procedure is unsupervised and reflects frequency distributions of the input variables rather than pre-set criteria, the resulting classes are undefined and must be calibrated empirically by subsequent analysis. Maps of the example classifications reflect physiographic regions, geological structure, and landform as well as slope materials and processes; fine-textured terrain categories tend to correlate with erosional topography or older surfaces, coarse-textured classes with areas of little dissection. In Japan the resulting classes approximate landform types mapped from airphoto analysis, while in the Americas they create map patterns resembling Hammond's terrain types or surface-form classes; SRTM30 output for the United States compares favorably with Fenneman's physical divisions. Experiments are suggested for further developing the method; the Arc/Info AML and the map of terrain classes for the world are available as online downloads. ?? 2006 Elsevier

  7. Delineation of Nested Wetland Catchments and Modeling of Hydrologic Connectivity Using LiDAR Data and Aerial Imagery

    Science.gov (United States)

    In traditional watershed delineation and topographic modelling, surface depressions are generally treated as spurious features and simply removed from a digital elevation model (DEM) to enforce flow continuity of water across the topographic surface to the watershed outlets. In r...

  8. Large Scale Landform Mapping Using Lidar DEM

    Directory of Open Access Journals (Sweden)

    Türkay Gökgöz

    2015-08-01

    Full Text Available In this study, LIDAR DEM data was used to obtain a primary landform map in accordance with a well-known methodology. This primary landform map was generalized using the Focal Statistics tool (Majority, considering the minimum area condition in cartographic generalization in order to obtain landform maps at 1:1000 and 1:5000 scales. Both the primary and the generalized landform maps were verified visually with hillshaded DEM and an orthophoto. As a result, these maps provide satisfactory visuals of the landforms. In order to show the effect of generalization, the area of each landform in both the primary and the generalized maps was computed. Consequently, landform maps at large scales could be obtained with the proposed methodology, including generalization using LIDAR DEM.

  9. Bathymetry and digital elevation models of Coyote Creek and Alviso Slough, South San Francisco Bay, California

    Science.gov (United States)

    Foxgrover, Amy C.; Finlayson, David P.; Jaffe, Bruce E.; Fregoso, Theresa A.

    2012-01-05

    In 2010 the U.S. Geological Survey (USGS), Pacific Coastal and Marine Science Center completed three cruises to map the bathymetry of the main channel and shallow intertidal mudflats in the southernmost part of south San Francisco Bay. The three surveys were merged to generate comprehensive maps of Coyote Creek (from Calaveras Point east to the railroad bridge) and Alviso Slough (from the bay to the town of Alviso) to establish baseline bathymetry prior to the breaching of levees adjacent to Alviso and Guadalupe Sloughs as part of the South Bay Salt Pond Restoration Project (http://www.southbayrestoration.org). Since 2010 the USGS has conducted twelve additional surveys to monitor bathymetric change in this region as restoration progresses.The bathymetry surveys were conducted using the state-of-the-art research vessel R/V Parke Snavely outfitted with an interferometric sidescan sonar for swath mapping in extremely shallow water. This publication provides high-resolution bathymetric data collected by the USGS. For the 2010 baseline survey we have merged the bathymetry with aerial lidar data that were collected for the USGS during the same time period to create a seamless, high-resolution digital elevation model (DEM) of the study area. The series of bathymetry datasets are provided at 1 m resolution and the 2010 bathymetric/topographic DEM at 2 m resolution. The data are formatted as both X, Y, Z text files and ESRI Arc ASCII files that are accompanied by Federal Geographic Data Committee (FGDC) compliant metadata.

  10. Evaluating the potential for site-specific modification of LiDAR DEM derivatives to improve environmental planning-scale wetland identification using Random Forest classification

    Science.gov (United States)

    O'Neil, Gina L.; Goodall, Jonathan L.; Watson, Layne T.

    2018-04-01

    Wetlands are important ecosystems that provide many ecological benefits, and their quality and presence are protected by federal regulations. These regulations require wetland delineations, which can be costly and time-consuming to perform. Computer models can assist in this process, but lack the accuracy necessary for environmental planning-scale wetland identification. In this study, the potential for improvement of wetland identification models through modification of digital elevation model (DEM) derivatives, derived from high-resolution and increasingly available light detection and ranging (LiDAR) data, at a scale necessary for small-scale wetland delineations is evaluated. A novel approach of flow convergence modelling is presented where Topographic Wetness Index (TWI), curvature, and Cartographic Depth-to-Water index (DTW), are modified to better distinguish wetland from upland areas, combined with ancillary soil data, and used in a Random Forest classification. This approach is applied to four study sites in Virginia, implemented as an ArcGIS model. The model resulted in significant improvement in average wetland accuracy compared to the commonly used National Wetland Inventory (84.9% vs. 32.1%), at the expense of a moderately lower average non-wetland accuracy (85.6% vs. 98.0%) and average overall accuracy (85.6% vs. 92.0%). From this, we concluded that modifying TWI, curvature, and DTW provides more robust wetland and non-wetland signatures to the models by improving accuracy rates compared to classifications using the original indices. The resulting ArcGIS model is a general tool able to modify these local LiDAR DEM derivatives based on site characteristics to identify wetlands at a high resolution.

  11. Digital Elevation Model (DEM) file of topographic elevations for the Death Valley region of southern Nevada and southeastern California processed from US Geological Survey 1-degree Digital Elevation Model data files

    International Nuclear Information System (INIS)

    Turner, A.K.; D'Agnese, F.A.; Faunt, C.C.

    1996-01-01

    Elevation data have been compiled into a digital data base for an ∼100,000-km 2 area of the southern Great Basin, the Death Valley region of southern Nevada, and SE Calif., located between lat 35 degree N, long 115 degree W, and lat 38 degree N, long 118 degree W. This region includes the Nevada Test Site, Yucca Mountain, and adjacent parts of southern Nevada and eastern California and encompasses the Death Valley regional ground-water system. Because digital maps are often useful for applications other than that for which they were originally intended, and because the area corresponds to a region under continuing investigation by several groups, these digital files are being released by USGS

  12. Mapeo de lineamientos a partir de un DEM (SRTM3: desarrollo y aplicaciones para el estudio de un área de los Andes Patagónicos Septentrionales

    Directory of Open Access Journals (Sweden)

    Ernesto Gallegos

    2008-12-01

    correlación entre lineamientos obtenidos con la técnica presentada y geología, fallas y fracturas sugiere que los DEM pueden ser un componente importante en el mapeo geológico. Sin embargo, los lineamientos regionales obtenidos deben ser contrastados con la información estructural obtenida en el campo.This paper explores the usefulness of mapping lineaments with shaded relief maps produced by satellite image analysis software from Digital Elevation Models (DEM of three seconds spatial resolution. The area of study is located between 39ºS and 39º30´S and between 71ºW and 71º30'W and three shaded relief maps were use with incident light at 45º from the horizontal and azimuths of 120º, 240º and 360º. Three operators mapped lineaments separately in the different images obtaining a result of nine independent maps. Reproducible lineaments were considered only those mapped in at least two shaded relief maps by at least two operators or by three operators in at least one image, in the end 23 lineaments were obtained. The tendencies observed were 55º, 106º, 140º and 153º. These lineaments were compared with lineaments mapped in a GeoCoverTM Landsat Enhanced Thematic Mapper Imagery ortorrectified compressed mosaic, in the geologic map 1:200.000 (SEGEMAR and in topographic maps 1: 50.000 (IGM. Some lineaments that were clearly identified with the DEM were not observed in the geological and topographic maps or in the Landsat imagery. The authors consider there are certain advantages in applying digital elevation models in the mapping of regional lineaments: 1 the users can control the incident angle and its azimuth; 2 The working scale can be change as needed; 3 in contrast to aerial photography, the satellite data have no deformation and it doesn't show any kind influences with anthropologic features or interference in the interpretation due to vegetation. Another advantage of the DEM (SRTM3 V2 and the GeoCoverT image used in this procedure is that the data is for

  13. Computation of spatial significance of mountain objects extracted from multiscale digital elevation models

    International Nuclear Information System (INIS)

    Sathyamoorthy, Dinesh

    2014-01-01

    The derivation of spatial significance is an important aspect of geospatial analysis and hence, various methods have been proposed to compute the spatial significance of entities based on spatial distances with other entities within the cluster. This paper is aimed at studying the spatial significance of mountain objects extracted from multiscale digital elevation models (DEMs). At each scale, the value of spatial significance index SSI of a mountain object is the minimum number of morphological dilation iterations required to occupy all the other mountain objects in the terrain. The mountain object with the lowest value of SSI is the spatially most significant mountain object, indicating that it has the shortest distance to the other mountain objects. It is observed that as the area of the mountain objects reduce with increasing scale, the distances between the mountain objects increase, resulting in increasing values of SSI. The results obtained indicate that the strategic location of a mountain object at the centre of the terrain is more important than its size in determining its reach to other mountain objects and thus, its spatial significance

  14. Modelling groundwater discharge areas using only digital elevation models as input data

    International Nuclear Information System (INIS)

    Brydsten, Lars

    2006-10-01

    Advanced geohydrological models require data on topography, soil distribution in three dimensions, vegetation, land use, bedrock fracture zones. To model present geohydrological conditions, these factors can be gathered with different techniques. If a future geohydrological condition is modelled in an area with positive shore displacement (say 5,000 or 10,000 years), some of these factors can be difficult to measure. This could include the development of wetlands and the filling of lakes. If the goal of the model is to predict distribution of groundwater recharge and discharge areas in the landscape, the most important factor is topography. The question is how much can topography alone explain the distribution of geohydrological objects in the landscape. A simplified description of the distribution of geohydrological objects in the landscape is that groundwater recharge areas occur at local elevation curvatures and discharge occurs in lakes, brooks, and low situated slopes. Areas in-between these make up discharge areas during wet periods and recharge areas during dry periods. A model that could predict this pattern only using topography data needs to be able to predict high ridges and future lakes and brooks. This study uses GIS software with four different functions using digital elevation models as input data, geomorphometrical parameters to predict landscape ridges, basin fill for predicting lakes, flow accumulations for predicting future waterways, and topographical wetness indexes for dividing in-between areas based on degree of wetness. An area between the village of and Forsmarks' Nuclear Power Plant has been used to calibrate the model. The area is within the SKB 10-metre Elevation Model (DEM) and has a high-resolution orienteering map for wetlands. Wetlands are assumed to be groundwater discharge areas. Five hundred points were randomly distributed across the wetlands. These are potential discharge points. Model parameters were chosen with the

  15. Applicability of computer-aided comprehensive tool (LINDA: LINeament Detection and Analysis) and shaded digital elevation model for characterizing and interpreting morphotectonic features from lineaments

    Science.gov (United States)

    Masoud, Alaa; Koike, Katsuaki

    2017-09-01

    Detection and analysis of linear features related to surface and subsurface structures have been deemed necessary in natural resource exploration and earth surface instability assessment. Subjectivity in choosing control parameters required in conventional methods of lineament detection may cause unreliable results. To reduce this ambiguity, we developed LINDA (LINeament Detection and Analysis), an integrated tool with graphical user interface in Visual Basic. This tool automates processes of detection and analysis of linear features from grid data of topography (digital elevation model; DEM), gravity and magnetic surfaces, as well as data from remote sensing imagery. A simple interface with five display windows forms a user-friendly interactive environment. The interface facilitates grid data shading, detection and grouping of segments, lineament analyses for calculating strike and dip and estimating fault type, and interactive viewing of lineament geometry. Density maps of the center and intersection points of linear features (segments and lineaments) are also included. A systematic analysis of test DEMs and Landsat 7 ETM+ imagery datasets in the North and South Eastern Deserts of Egypt is implemented to demonstrate the capability of LINDA and correct use of its functions. Linear features from the DEM are superior to those from the imagery in terms of frequency, but both linear features agree with location and direction of V-shaped valleys and dykes and reference fault data. Through the case studies, LINDA applicability is demonstrated to highlight dominant structural trends, which can aid understanding of geodynamic frameworks in any region.

  16. Modelling vertical error in LiDAR-derived digital elevation models

    Science.gov (United States)

    Aguilar, Fernando J.; Mills, Jon P.; Delgado, Jorge; Aguilar, Manuel A.; Negreiros, J. G.; Pérez, José L.

    2010-01-01

    A hybrid theoretical-empirical model has been developed for modelling the error in LiDAR-derived digital elevation models (DEMs) of non-open terrain. The theoretical component seeks to model the propagation of the sample data error (SDE), i.e. the error from light detection and ranging (LiDAR) data capture of ground sampled points in open terrain, towards interpolated points. The interpolation methods used for infilling gaps may produce a non-negligible error that is referred to as gridding error. In this case, interpolation is performed using an inverse distance weighting (IDW) method with the local support of the five closest neighbours, although it would be possible to utilize other interpolation methods. The empirical component refers to what is known as "information loss". This is the error purely due to modelling the continuous terrain surface from only a discrete number of points plus the error arising from the interpolation process. The SDE must be previously calculated from a suitable number of check points located in open terrain and assumes that the LiDAR point density was sufficiently high to neglect the gridding error. For model calibration, data for 29 study sites, 200×200 m in size, belonging to different areas around Almeria province, south-east Spain, were acquired by means of stereo photogrammetric methods. The developed methodology was validated against two different LiDAR datasets. The first dataset used was an Ordnance Survey (OS) LiDAR survey carried out over a region of Bristol in the UK. The second dataset was an area located at Gador mountain range, south of Almería province, Spain. Both terrain slope and sampling density were incorporated in the empirical component through the calibration phase, resulting in a very good agreement between predicted and observed data (R2 = 0.9856 ; p reasonably good fit to the predicted errors. Even better results were achieved in the more rugged morphology of the Gador mountain range dataset. The findings

  17. Extraction of Terraces on the Loess Plateau from High-Resolution DEMs and Imagery Utilizing Object-Based Image Analysis

    Directory of Open Access Journals (Sweden)

    Hanqing Zhao

    2017-05-01

    Full Text Available Abstract: Terraces are typical artificial landforms on the Loess Plateau, with ecological functions in water and soil conservation, agricultural production, and biodiversity. Recording the spatial distribution of terraces is the basis of monitoring their extent and understanding their ecological effects. The current terrace extraction method mainly relies on high-resolution imagery, but its accuracy is limited due to vegetation coverage distorting the features of terraces in imagery. High-resolution topographic data reflecting the morphology of true terrace surfaces are needed. Terraces extraction on the Loess Plateau is challenging because of the complex terrain and diverse vegetation after the implementation of “vegetation recovery”. This study presents an automatic method of extracting terraces based on 1 m resolution digital elevation models (DEMs and 0.3 m resolution Worldview-3 imagery as auxiliary information used for object-based image analysis (OBIA. A multi-resolution segmentation method was used where slope, positive and negative terrain index (PN, accumulative curvature slope (AC, and slope of slope (SOS were determined as input layers for image segmentation by correlation analysis and Sheffield entropy method. The main classification features based on DEMs were chosen from the terrain features derived from terrain factors and texture features by gray-level co-occurrence matrix (GLCM analysis; subsequently, these features were determined by the importance analysis on classification and regression tree (CART analysis. Extraction rules based on DEMs were generated from the classification features with a total classification accuracy of 89.96%. The red band and near-infrared band of images were used to exclude construction land, which is easily confused with small-size terraces. As a result, the total classification accuracy was increased to 94%. The proposed method ensures comprehensive consideration of terrain, texture, shape, and

  18. Digital Model of Railway Electric Traction Lines

    Science.gov (United States)

    Garg, Rachana; Mahajan, Priya; Kumar, Parmod

    2017-08-01

    The characteristic impedance and propagation constant define the behavior of signal propagation over the transmission lines. The digital model for railway traction lines which includes railway tracks is developed, using curve fitting technique in MATLAB. The sensitivity of this model has been computed with respect to frequency. The digital sensitivity values are compared with the values of analog sensitivity. The developed model is useful for digital protection, integrated operation, control and planning of the system.

  19. Dissipation consistent fabric tensor definition from DEM to continuum for granular media

    Science.gov (United States)

    Li, X. S.; Dafalias, Y. F.

    2015-05-01

    In elastoplastic soil models aimed at capturing the impact of fabric anisotropy, a necessary ingredient is a measure of anisotropic fabric in the form of an evolving tensor. While it is possible to formulate such a fabric tensor based on indirect phenomenological observations at the continuum level, it is more effective and insightful to have the tensor defined first based on direct particle level microstructural observations and subsequently deduce a corresponding continuum definition. A practical means able to provide such observations, at least in the context of fabric evolution mechanisms, is the discrete element method (DEM). Some DEM defined fabric tensors such as the one based on the statistics of interparticle contact normals have already gained widespread acceptance as a quantitative measure of fabric anisotropy among researchers of granular material behavior. On the other hand, a fabric tensor in continuum elastoplastic modeling has been treated as a tensor-valued internal variable whose evolution must be properly linked to physical dissipation. Accordingly, the adaptation of a DEM fabric tensor definition to a continuum constitutive modeling theory must be thermodynamically consistent in regards to dissipation mechanisms. The present paper addresses this issue in detail, brings up possible pitfalls if such consistency is violated and proposes remedies and guidelines for such adaptation within a recently developed Anisotropic Critical State Theory (ACST) for granular materials.

  20. Towards Trustable Digital Evidence with PKIDEV: PKI Based Digital Evidence Verification Model

    Science.gov (United States)

    Uzunay, Yusuf; Incebacak, Davut; Bicakci, Kemal

    How to Capture and Preserve Digital Evidence Securely? For the investigation and prosecution of criminal activities that involve computers, digital evidence collected in the crime scene has a vital importance. On one side, it is a very challenging task for forensics professionals to collect them without any loss or damage. On the other, there is the second problem of providing the integrity and authenticity in order to achieve legal acceptance in a court of law. By conceiving digital evidence simply as one instance of digital data, it is evident that modern cryptography offers elegant solutions for this second problem. However, to our knowledge, there is not any previous work proposing a systematic model having a holistic view to address all the related security problems in this particular case of digital evidence verification. In this paper, we present PKIDEV (Public Key Infrastructure based Digital Evidence Verification model) as an integrated solution to provide security for the process of capturing and preserving digital evidence. PKIDEV employs, inter alia, cryptographic techniques like digital signatures and secure time-stamping as well as latest technologies such as GPS and EDGE. In our study, we also identify the problems public-key cryptography brings when it is applied to the verification of digital evidence.