The Shuttle Radar Topography Mission (SRTM, see Farr et al. 2007) digital elevation data is an international research effort that obtained digital elevation models on a near-global scale. This SRTM V3 product (SRTM Plus) is provided by NASA JPL at a resolution of 1 arc-second (approximately 30m). This dataset has undergone a void-filling process using open-source data (ASTER GDEM2, GMTED2010, and NED), as opposed to other versions that contain voids or have been void-filled with commercial sources. For more information on the different versions see the SRTM Quick Guide. Documentation: User's Guide General Documentation Algorithm Theoretical Basis Document (ATBD)

This is a tiled collection of the 3D Elevation Program (3DEP) and is one meter resolution. The 3DEP data holdings serve as the elevation layer of The National Map, and provide foundational elevation information for earth science studies and mapping applications in the United States. Scientists and resource managers use 3DEP data for hydrologic modeling, resource monitoring, mapping and visualization, and many other applications. The elevations in this DEM represent the topographic bare-earth surface. USGS standard one-meter DEMs are produced exclusively from high resolution light detection and ranging (lidar) source data of one-meter or higher resolution. One-meter DEM surfaces are seamless within collection projects, but, not necessarily seamless across projects. The spatial reference used for tiles of the one-meter DEM within the conterminous United States (CONUS) is Universal Transverse Mercator (UTM) in units of meters, and in conformance with the North American Datum of 1983 ...

This is a tiled collection of the 3D Elevation Program (3DEP) and is 1/3 arc-second (approximately 10 m) resolution. The 3DEP data holdings serve as the elevation layer of The National Map, and provide foundational elevation information for earth science studies and mapping applications in the United States. Scientists and resource managers use 3DEP data for hydrologic modeling, resource monitoring, mapping and visualization, and many other applications. The elevations in this DEM represent the topographic bare-earth surface. The seamless 1/3 arc-second DEM layers are derived from diverse source data that are processed to a common coordinate system and unit of vertical measure. These data are distributed in geographic coordinates in units of decimal degrees, and in conformance with the North American Datum of 1983 (NAD 83). All elevation values are in meters and, over the continental United States, are referenced to the North American Vertical Datum of 1988 (NAVD88). The seamless ...

The Shuttle Radar Topography Mission (SRTM) was flown aboard the space shuttle Endeavour February 11-22, 2000. The National Aeronautics and Space Administration (NASA) and the National Geospatial-Intelligence Agency (NGA) participated in an international project to acquire radar data which were used to create the first near-global set of land elevations.

The radars used during the SRTM mission were actually developed and flown on two Endeavour missions in 1994. The C-band Spaceborne Imaging Radar and the X-Band Synthetic Aperture Radar (X-SAR) hardware were used on board the space shuttle in April and October 1994 to gather data about Earth's environment. The technology was modified for the SRTM mission to collect interferometric radar, which compared two radar images or signals taken at slightly different angles. This mission used single-pass interferometry, which acquired two signals at the same time by using two different radar antennas. An antenna located on board the space shuttle collected one data set and the other data set was collected by an antenna located at the end of a 60-meter mast that extended from the shuttle. Differences between the two signals allowed for the calculation of surface elevation.

Endeavour orbited Earth 16 times each day during the 11-day mission, completing 176 orbits. SRTM successfully collected radar data over 80% of the Earth's land surface between 60° north and 56° south latitude with data points posted every 1 arc-second (approximately 30 meters).

Two resolutions of finished grade SRTM data are available through EarthExplorer from the collection held in the USGS EROS archive:

1 arc-second (approximately 30-meter) high resolution elevation data offer worldwide coverage of void filled data at a resolution of 1 arc-second (30 meters) and provide open distribution of this high-resolution global data set. Some tiles may still contain voids. The SRTM 1 Arc-Second Global (30 meters) data set will be released in phases starting September 24, 2014. Users should check the coverage map in EarthExplorer to verify if their area of interest is available.

3 arc-second (approximately 90-meter) medium resolution elevation data are available for global coverage. The 3 arc-second data were resampled using cubic convolution interpolation for regions between 60° north and 56° south latitude.

[Summary provided by the USGS.]

Culminating more than four years of processing data, NASA and the National Geospatial-Intelligence Agency (NGA) have completed Earth's most extensive global topographic map. The mission is a collaboration among NASA, NGA, and the German and Italian space agencies. For 11 days in February 2000, the space shuttle Endeavour conducted the Shuttle Radar Topography Mission (SRTM) using C-Band and X-Band interferometric synthetic aperture radars to acquire topographic data over 80% of the Earth's land mass, creating the first-ever near-global data set of land elevations. This data was used to produce topographic maps (digital elevation maps) 30 times as precise as the best global maps used today. The SRTM system gathered data at the rate of 40,000 per minute over land. They reveal for the first time large, detailed swaths of Earth's topography previously obscured by persistent cloudiness. The data will benefit scientists, engineers, government agencies and the public with an ever-growing array of uses. The SRTM radar system mapped Earth from 56 degrees south to 60 degrees north of the equator. The resolution of the publicly available data is three arc-seconds (1/1,200th of a degree of latitude and longitude, about 295 feet, at Earth's equator). The final data release covers Australia and New Zealand in unprecedented uniform detail. It also covers more than 1,000 islands comprising much of Polynesia and Melanesia in the South Pacific, as well as islands in the South Indian and Atlantic oceans. SRTM data are being used for applications ranging from land use planning to "virtual" Earth exploration. Currently, the mission's homepage "http://www.jpl.nasa.gov/srtm" provides direct access to recently obtained earth images. The Shuttle Radar Topography Mission C-band data for North America and South America are available to the public. A list of complete public data set is available at "http://www2.jpl.nasa.gov/srtm/dataprod.htm" The data specifications are within the following parameters: 30-meter X 30-meter spatial sampling with 16 meter absolute vertical height accuracy, 10-meter relative vertical height accuracy, and 20-meter absolute horizontal circular accuracy. From the JPL Mission Products Summary, "http://www.jpl.nasa.gov/srtm/dataprelimdescriptions.html". The primary products of the SRTM mission are the digital elevation maps of most of the Earth's surface. Visualized images of these maps are available for viewing online. Below you will find descriptions of the types of images that are being generated:

• Radar Image
• Radar Image with Color as Height
• Radar Image with Color Wrapped Fringes
  -Shaded Relief
• Perspective View with B/W Radar Image Overlaid
• Perspective View with Radar Image Overlaid, Color as Height
• Perspective View of Shaded Relief
• Perspective View with Landsat or other Image Overlaid
• Contour Map - B/W with Contour Lines
• Stereo Pair
• Anaglypgh

The SRTM radar contained two types of antenna panels, C-band and X-band. The near-global topographic maps of Earth called Digital Elevation Models (DEMs) are made from the C-band radar data. These data were processed at the Jet Propulsion Laboratory and are being distributed through the United States Geological Survey's EROS Data Center. Data from the X-band radar are used to create slightly higher resolution DEMs but without the global coverage of the C-band radar. The SRTM X-band radar data are being processed and distributed by the German Aerospace Center, DLR.

The Shuttle Radar Topography Mission (SRTM) was a partnership between NASA and the National Geospatial-Intelligence Agency (NGA). Flown aboard the NASA Space Shuttle Endeavour (11-22 February 2000), SRTM fulfilled its mission to map the world in three dimensions. The USGS is under agreement with NGA and NASA's Jet Propulsion Laboratory to distribute SRTM elevation products derived from the C-band radar data. SRTM utilized interferometric C-band Spaceborne Imaging Radar to generate elevation data over 80 percent of the Earth's land surface. Global SRTM data at a resolution of 1 arc-second have been edited to delineate and flatten water bodies, better define coastlines, remove spikes and wells, and fill small voids. Larger areas of missing data or voids were filled by the NGA using interpolation algorithms in conjunction with other sources of elevation data. The SRTM 1 Arc-Second Global data offer worldwide coverage of void filled data at a resolution of 1 arc-second (30 meters) and provide open distribution of this high-resolution global data set.

The Shuttle Radar Topography Mission (SRTM) successfully collected Interferometric Synthetic Aperture Radar (IFSAR) data over 80 percent of the landmass of the Earth between 60 degrees North and 56 degrees South latitudes in February 2000. The mission was co-sponsored by the National Aeronautics and Space Administration (NASA) and National Geospatial-Intelligence Agency (NGA). NASA's Jet Propulsion Laboratory (JPL) performed preliminary processing of SRTM data and forwarded partially finished data directly to NGA for finishing by NGA's contractors and subsequent monthly deliveries to the NGA Digital Products Data Wharehouse (DPDW). All the data products delivered by the contractors conform to the NGA SRTM products and the NGA Digital Terrain Elevation Data (DTED) to the Earth Resources Observation & Science (EROS) Center. The DPDW ingests the SRTM data products, checks them for formatting errors, loads the SRTM DTED into the NGA data distribution system, and ships the public domain SRTM DTED to the U.S. Geological Survey (USGS) Earth Resources Observation & Science (EROS) Center.

Two resolutions of finished grade SRTM data are available through EarthExplorer from the collection held in the USGS EROS archive:

1 arc-second (approximately 30-meter) high resolution elevation data are only available for the United States.

3 arc-second (approximately 90-meter) medium resolution elevation data are available for global coverage. The 3 arc-second data were resampled using cubic convolution interpolation for regions between 60° north and 56° south latitude.

[Summary provided by the USGS.]

This dataset contains the Digital Elevation Model (DEM) for North America from the Hydrologic Derivatives for Modeling and Analysis (HDMA) database. The DEM data were developed and distributed by processing units. There are 13 processing units for North America. The distribution files have the number of the processing unit appended to the end of the zip file name (e.g. na_dem_3_2.zip contains the DEM data for unit 3-2). The HDMA database provides comprehensive and consistent global coverage of raster and vector topographically derived layers, including raster layers of digital elevation model (DEM) data, flow direction, flow accumulation, slope, and compound topographic index (CTI); and vector layers of streams and catchment boundaries. The coverage of the data is global (-180º, 180º, -90º, 90º) with the underlying DEM being a hybrid of three datasets: HydroSHEDS (Hydrological data and maps based on SHuttle Elevation Derivatives at multiple Scales), Global Multi-resolution Terrain Elevation Data 2010 (GMTED2010) and the Shuttle Radar Topography Mission (SRTM). For most of the globe south of 60º North, the raster resolution of the data is 3-arc-seconds, corresponding to the resolution of the SRTM. For the areas North of 60º, the resolution is 7.5-arc-seconds (the smallest resolution of the GMTED2010 dataset) except for Greenland, where the resolution is 30-arc-seconds. The streams and catchments are attributed with Pfafstetter codes, based on a hierarchical numbering system, that carry important topological information.

SRTM v4.1 is based on the finished-grade 2006 SRTM v2 release by NASA that was post-processed and published in 2008 by CGIAR-CSI (Consortium for Spatial Information). The SRTM v4.1 data set offers 3 arc-second (approximately 90 meters) spatial resolution and covers about 80% of Earth’s landmass, between 60° North and 56° South. SRTM v4.1 is divided onto 5° x 5° of latitude and longitude tiles in “geographic” projection, shown here.

The original SRTM v2 release contained voids (areas not or not well observed by the SRTM radar), mostly occurring in topographically steep terrain. The overcome this problem, CGIAR-CSI focused on filling the voids (holes) using various interpolation techniques, such as Kriging, moving window averaging, and importantly, the use of auxiliary elevation data sets (DEMs from other sources, e.g., national DEMs). CGIAR-CSI DEM v4.1 data comes at 5 deg x 5 deg tiles, and has a typical file size of 23 MB for one tile, which comprises two kinds of information; the DEM file and a mask file. The mask file is a binary file which identifies areas within the DEM that have been interpolated. The SRTM v4.1 datasets are available in ArcInfo ASCII and GeoTIFF (.tif) formats.

Geodetic information: The SRTM V4.1 DEMs are vertically referenced to the EGM96 geoid and horizontally referenced to the WGS84 (World Geodetic System 1984).

Further notes: This data set contains artefacts, e.g., pits or steps, over parts of the Himalayas, the Andes and other mountainous regions. Artefacts in SRTM v4.1 tend to occur over void-filled areas. The SRTM DEM represents bare ground elevations only where vegetation cover and buildings are absent. Over most areas, the DEM elevations reside between the bare ground (terrain) and top of canopies (surface), so are technically a mixture of a terrain and surface model.

Data access to the v4.1 data set: A detailed description is found at http://www.cgiar-csi.org/data/srtm-90m-digital-elevation-database-v4-1 and access is possible via the data search page on http://srtm.csi.cgiar.org/SELECTION/inputCoord.asp.

References:Reuter H.I, A. Nelson, A. Jarvis, 2007, An evaluation of void filling interpolation methods for SRTM data, International Journal of Geographic Information Science, 21:9, 983-1008. Available on http://srtm.csi.cgiar.org/download/Reuteretal2007.pdf

The Shuttle Radar Topography Mission (SRTM) is a collaborative effort from NASA (National Aeronautics and Space Administration) and NGA (National Geospatial-Intelligence Agency) as well as DLR (Deutsches Zentrum für Luft-und Raumfahrt) and ASI (Agenzia Spaziale Italiana). SRTM was flown aboard the Endeavour space shuttle in February 2000 to provide a high-resolution Digital Elevation Model (DEM). The SRTM instrumentation consisted of the Spaceborne Imaging Radar-C (SIR-C) with an additional antenna to form a 60 meters long baseline. As a result of the SRTM mission, several DEM versions have been released since 2003, which differ in terms of data processing and procedures applied for the filling of voids (areas not or poorly observed by the SRTM radar observations).

SRTM v3.0 (SRTM Plus) is the newest version, published in 2015 by NASA as a part of NASA Making Earth System Data Records for Use in Research Environments (MEaSUREs) project, which incorporates topographic data to fill the gaps or voids in earlier versions of SRTM data. For the void filling with the Delta Surface Fill algorithm, ASTER DEMs have been used as auxiliary data source, or interpolations have been applied. Many variants of DEM are available in SRTM v3.0, with SRTMGL1 being one of the key products from SRTM v3.0. ‘GL1’ on its name stands for “Global 1-arc second”. It provides regularly spaced DEM grids of 1 arc-second (approximately 30 meters) and covering 80% of Earth’s landmass, between 60° North and 56° South. This product is divided into 1° x 1° latitude and longitude tiles in “geographic” projection, as shown here.

A typical file of the SRTMGL1 dataset requires 25 MB memory (without compression) and stores exactly one 1°x1° tile; it contains 3,601 lines and 3,601 columns, which sum up to around 100 GB (compressed) and 350 GB (uncompressed) for the global data set of 14297 tiles. Individual tile names refer to the latitude and longitude of southwest (lower left) corner of the tile, e.g., tile N20W030 has lower left corner at 20°N and 30°W, covering area of 20-21°N and 30-29°W. The absolute vertical accuracy for SRTM heights has been found to be ~9 m (90 % confidence) or better (Rodriguez et al. 2005).

Geodetic information: The SRTM GL1 DEMs are vertically referenced to the EGM96 geoid and horizontally referenced to the WGS84 (World Geodetic System 1984).

Further notes: The SRTM DEM represents bare ground elevations only where vegetation cover and buildings are absent. Over most areas, the DEM elevations reside between the bare ground (terrain) and top of canopies (surface), so are technically a mixture of terrain and surface models. Few artefacts, e.g., pits or spikes may still be present in the data set.

Data access: The homepage of SRTM mission is http://www2.jpl.nasa.gov/srtm/. SRTM v3.0 datasets can be searched in MEASURES webpage and acquired freely from USGS website (http://earthexplorer.usgs.gov/) and USGS data pool (http://e4ftl01.cr.usgs.gov/SRTM/).References:Farr, T.G., E. Caro, R. Crippen, R. Duren, S. Hensley, M. Kobrick, M. Paller, E. Rodriguez, P. Rosen, L. Roth, D. Seal, S. Shaffer, J. Shimada, J. Umland, M. Werner, 2007, The Shuttle Radar Topography Mission. Reviews of Geophysics, volume 45, RG2004, doi:10.1029/2005RG000183.NASA, The Shuttle Radar Topography Mission (SRTM) Collection User Guide. Available on https://lpdaac.usgs.gov/sites/default/files/public/measures/docs/NASA_SRTM_V3.pdfRodriguez, E., C.S. Morris, J.E. Belz, E.C. Chapin, J.M. Martin, W. Daffer, S.Hensley, 2005, An assessment of the SRTM topographic products, Technical Report JPL D-31639, Jet Propulsion Laboratory, Pasadena, California, 143 pp. available on http://www2.jpl.nasa.gov/srtm/SRTM_D31639.pdf

The Shuttle Radar Topography Mission (SRTM) obtained elevation data on a near-global scale to generate the most complete high-resolution digital topographic database of Earth. SRTM consisted of a specially modified radar system that flew onboard the Space Shuttle Endeavour during an 11-day mission in February of 2000. SRTM is an international project spearheaded by the National Geospatial-Intelligence Agency (NGA) and the National Aeronautics and Space Administration (NASA).

Version 3: Elimination of the voids in the NASA SRTM DEM was the primary goal of a project under the NASA MEaSUREs (Making Earth System Data Records for Use in Research Environments) Program. Ultimately this was achieved by filling the voids with elevation data primarily from the ASTER GDEM2 (Global Digital Elevation Model Version 2) and secondarily from the USGS GMTED2010 elevation model or the USGS National Elevation Dataset (NED). For more information on this dataset visit the LP DAAC NASA Shuttle Radar Topography Mission Global 3 arc second page.

UPDATE: Data no longer available from this page. All non-working links have been removed (19/7/21)

Users must follow instructions below from NASA to access data:

SRTM data are also available globally at 1 arc second resolution (SRTMGL1.003) through the Data Pool (https://e4ftl01.cr.usgs.gov/MEASURES/SRTMGL1.003/) or from EarthExplorer where it is listed as NASA SRTM3 SRTMGL1. Please sign in with NASA Earthdata Login Credentials to download data from the NASA LP DAAC Collections. These datasets require login on both NASA Earthdata and USGS EarthExplorer systems to access data. After you create your account, you will also need to “authorize” the LP DAAC Data Pool application. On the Profile page in your Earthdata account you will need to select My Applications. On that page make sure the LP DAAC Data Pool is listed. If it isn't then select Authorize More Applications. In the dialog box type in LP DAAC Data Pool and click Search For Applications. Select Approve when presented with the lpdaac_datapool. Keep everything checked but you can uncheck the Yes, I would like to be notified box. Select Authorize and the LP DAAC Data Pool should be added to your Approved Applications. You might benefit from using the AppEEARS tool. ·
o AppEEARS landing page: https://lpdaacsvc.cr.usgs.gov/appeears/

·
o The users will need and https://urs.earthdata.nasa.gov/?_ga=2.148606453.334533939.1615325167-1213876668.1613754504. Click or tap if you trust this link.">Earthdata Login

·
o Getting started instructions can be found here: https://lpdaacsvc.cr.usgs.gov/appeears/help

Previously available here: Digital Elevation Model of Ireland, from NASA's Shuttle Radar Topography Mission (SRTM), sampled at 3 arc second intervals in latitude & longitude (about every 90m) in heightmap (.HGT) format.''Latitudes & longitudes are referenced to WGS84, heights are in meters referenced to the WGS84/EGM96 geoid.'' Please see the linked pdf files for further documentation.''A QGIS project for the hgt files is also attached.

A global 1-km resolution land surface digital elevation model (DEM) derived from U.S. Geological Survey (USGS) 30 arc-second SRTM30 gridded DEM data created from the NASA Shuttle Radar Topography Mission (SRTM). GTOPO30 data are used for high latitudes where SRTM data are not available. For a grayscale hillshade image layer of this dataset, see "world_srtm30plus_dem1km_hillshade" in the distribution links listed in the metadata.

The Shuttle Radar Topography Mission (SRTM) digital elevation dataset was originally produced to provide consistent, high-quality elevation data at near global scope. This version of the SRTM digital elevation data has been processed to fill data voids, and to facilitate its ease of use.

NASA has released version 2 of the Shuttle Radar Topography Mission digital topographic data (also known as the "finished" version). Version 2 is the result of a substantial editing effort by the National Geospatial Intelligence Agency and exhibits well-defined water bodies and coastlines and the absence of spikes and wells (single pixel errors), although some areas of missing data ('voids') are still present. The Version 2 directory also contains the vector coastline mask derived by NGA during the editing, called the SRTM Water Body Data (SWBD), in ESRI Shapefile format.

                [Summary provided by NASA.]

Note: This version of the SRTM GL1 dataset is provided in a WGS84 ellipsoidal vertical datum. This is a non-standard version of the SRTM dataset that is often used for InSAR analysis. This dataset was converted from the orthometric version using the EGM96 geoid model available here. For additional conversion details feel free to contact us.

The Shuttle Radar Topography Mission (SRTM) obtained elevation data on a near-global scale to generate the most complete high-resolution digital topographic database of Earth. SRTM consisted of a specially modified radar system that flew onboard the Space Shuttle Endeavour during an 11-day mission in February of 2000. SRTM is an international project spearheaded by the National Geospatial-Intelligence Agency (NGA) and the National Aeronautics and Space Administration (NASA).

Version 3: Elimination of the voids in the NASA SRTM DEM was the primary goal of a project under the NASA MEaSUREs (Making Earth System Data Records for Use in Research Environments) Program. Ultimately this was achieved by filling the voids with elevation data primarily from the ASTER GDEM2 (Global Digital Elevation Model Version 2) and secondarily from the USGS GMTED2010 elevation model or the USGS National Elevation Dataset (NED). NASA SRTM V3.0 three-arc-second data are provided in two forms: (1) by three-by-three averaging of the one arc-second samples, and (2) by extracting the middle sample of those same three-by-three samples. For more information on this dataset visit the LP DAAC NASA Shuttle Radar Topography Mission Global 1 arc second page.

This dataset corresponds to a reformatting of the SRTM30_PLUS digital elevation dataset from 33 NetCDF files into a single GeoTiff for use in GIS applications. No other modifications to the data were done. The rest of this metadata describes the original SRTM30_PLUS dataset itself.

This dataset is a 30-arc second resolution global topography/bathymetry grid (SRTM30_PLUS) developed from a wide variety of data sources. Land and ice topography comes from the SRTM30 and ICESat topography, respectively. Ocean bathymetry is based on a new satellite-gravity model where the gravity-to-topography ratio is calibrated using 298 million edited soundings. The main contribution of this dataset is the compilation and editing of the raw soundings, which come from NOAA, individual scientists, SIO, NGA, JAMSTEC, IFREMER, GEBCO, and NAVOCEANO.

The SRTM30_PLUS dataset developed by Scripps Institute Of Oceanography, University of California San Diego (UCSD).

Land data are based on the 1-km averages of topography derived from the USGS SRTM30 grided DEM data product created with data from the NASA Shuttle Radar Topography Mission. GTOPO30 data are used for high latitudes where SRTM data are not available.

Ocean data are based on the Smith and Sandwell global 1-minute grid between latitudes +/- 81 degrees. Higher resolution grids have been added from the LDEO Ridge Multibeam Synthesis Project, the JAMSTEC Data Site for Research Cruises, and the NGDC Coastal Relief Model. Arctic bathymetry is from the International Bathymetric Chart of the Oceans (IBCAO) [Jakobsson et al., 2003].

This data consists of 33 files of global topography in the same format as the SRTM30 products distributed by the USGS EROS data center. The grid resolution is 30 second which is roughly one kilometer. In addition the global data are also available in a single large file ready for GMT and as 33 NetCDF files. The eAtlas has also merged and formatted the data as a single GeoTiff file with overviews (1.6 GB).

The pixel-registered data are stored in 33 files with names corresponding to the upper left corner of the array shown below. The data are also merged into a single large (1.9 Gbyte, 2-byte integer) file as well as smaller 1-minute and 2-minute netcdf versions. Matching files of source identification number are available for determining the data source for every pixel.

This new version (v8.0) includes all of the multibeam bathymetry data collected by U.S. research vessels over the past three decades including 287 Scripps expeditions from research vessels Washington, Melville and Revelle. UCSD undergraduate student Alexis Shakas processed all the U.S. multibeam data and then worked with Google researchers on the global integration.

The data is available from UCSD FTP server as 33 NetCDF files and from the eAtlas as a merged GeoTiff.

If you are after high resolution bathymetry/elevation data for regional areas please check the related links.

Reference, sounding data: Becker, J. J., D. T. Sandwell, W. H. F. Smith, J. Braud, B. Binder, J. Depner, D. Fabre, J. Factor, S. Ingalls, S-H. Kim, R. Ladner, K. Marks, S. Nelson, A. Pharaoh, R. Trimmer, J. Von Rosenberg, G. Wallace, P. Weatherall., Global Bathymetry and Elevation Data at 30 Arc Seconds Resolution: SRTM30_PLUS, Marine Geodesy, 32:4, 355-371, 2009. http://topex.ucsd.edu/sandwell/publications/124_MG_Becker.pdf

Reference, gravity data: Sandwell, D. T., and W. H. F. Smith, Global marine gravity from retracked Geosat and ERS-1 altimetry: Ridge Segmentation versus spreading rate, J. Geophys. Res., 114, B01411, doi:10.1029/2008JB006008, 2009. http://dx.doi.org/10.1029/2008JB006008

eAtlas Processing:

A set of Batch scripts were developed to perform the conversion of the data from NetCDF to GeoTiff and the generation of the hillshading. This processing was based on the GDAL command line tools. Full details of the processing can be found in the downloadable Scripts associated with this dataset.

Data Location:

This dataset is filed in the eAtlas enduring data repository at: data\NERP-TE\13.1_eAtlas\World_UCSD_SRTM30-plus

This dataset includes a suite of pre-seismic 2m resolution DEMs pre-dating the 2013 Mw7.7 Baluchistan earthquake. The DEMs were constructed using the open-source software package SETSM (https://mjremotesensing.wordpress.com/setsm/) from DigitalGlobe base imagery (©DigitalGlobe 2018). DEMs were mosaicked and vertically registered using the Ames StereoPipeline (https://ti.arc.nasa.gov/tech/asr/groups/intelligent-robotics/ngt/stereo/).

The base imagery included 0.5m and 0.3m resolution panchromatic imagery from QuickBird, GEOEYE, WorldView1, WorldView2, and WorldView3 (©DigitalGlobe 2018). The dataset includes DEMs generated from in-track stereo imagery, as well as DEMs constructed from mixed pairs of non-in-track stereo images. The pre-event DEMs are all vertically registered to the 30 m Shuttle Radar Topography Mission (SRTM) DEM. The generation of this dataset was funded by NASA in cooperation with the U.S. Geological Survey. A complete description of the generation of this dataset and the images that were used to construct the DEMs can be found in the associated manuscript:

Barnhart WD, Gold RD, Shea HN, Peterson KE, Briggs RW, Harbor DJ (2019) Vertical coseismic offsets derived from high-resolution stereogrammetric DSM differencing: The 2013 Baluchistan, Pakistan earthquake, JGR-Solid Earth DOI:10.1029/2018JB017107

The naming convention of individual DEMs is detailed in the metadata.

Note: The source data for this project are the individual 2 meter DEMs that were constructed with the SETSM open-source software (described above). However, in order to utilize the OpenTopography webmap interface, these DEMs were mosaiced into a single seamless mosaic of pre-earthquake topography. Details on how this single mosaic was created are in the metadata. Users are cautioned that files created using the webmap interface will use the averaged, mosaic data. For certain applications, users may wish to utilize the source datasets by downloading the original DEMs via the "Source" directory under the "Bulk Download" section of the OpenTopography website.

MERIT (Multi-Error-Removed Improved Terrain DEM) is a substantially improved near-global terrain description with 90 m (3 arc-seconds) spatial resolution (Yamazaki et al. 2017). MERIT covers almost all of Earth’s land areas within 90N-60S, except of Antarctica. Different to most other global DEM data sets, MERIT provides – in good approximation – elevations of the bare ground. This has been achieved by reducing vegetation heights (known as tree height bias) using tree density and tree height maps as auxiliary information in the production of the MERIT DEM. However, over built areas, MERIT elevations may contain a bias due to urban canopy.MERIT relies on SRTM v2.1 South of 60° latitude, ALOS AW3D North of 60° latitude, and uses elevations from Viewfinder Panoramas (VFP-DEM) to fill voids (unobserved areas) where present. For the void-filling with VFP-DEM, an average matching method has been applied by Yamazaki et al. (2017) to ensure smooth transitions. Within the SRTM data area, about 0.5 % of MERIT land cells rely on VFP-DEM. North of 60°, the contribution of VFP-DEM is about ~30 %. As a result, elevation errors previously present in the SRTM model have been reduced such that actual terrain features stand out more clearly.

Geodetic information: The MERIT DEMs are vertically referenced to the EGM96 geoid and horizontally referenced to the WGS84 (World Geodetic System 1984).

Further notes: The MERIT DEM mostly represents bare ground elevations, so is technically close to a digital terrain model (DTM). This makes the data set suitable for applications requiring heights of the bare ground. Example areas are hydrology, hydrodynamics, physical geodesy and geophysics.

Data access: The authors freely share their model for non-commercial applications (e.g. science and education) via URL: hydro.iis.u-tokyo.ac.jp/~yamadai/MERIT_DEM/

References:

Yamazaki, D., D. Ikeshima, R. Tawatari, T. Yamaguchi, F. O’Loughlin, J.C. Neal, C.C. Sampson, S. Kanae, P.D. Bates (2017), A high accuracy map of global terrain elevations, Geophysical Research Letters, Doi: 10.1002/2017GL072874

Dữ liệu độ cao kỹ thuật số của Dự án đo đạc địa hình bằng radar trên tàu con thoi (SRTM, xem Farr và cộng sự, 2007) là một nỗ lực nghiên cứu quốc tế nhằm thu thập các mô hình độ cao kỹ thuật số trên quy mô gần như toàn cầu. Sản phẩm SRTM phiên bản 3 (SRTM Plus) này do NASA JPL cung cấp với độ phân giải 1 giây cung (khoảng 30 m). Tập dữ liệu này đã trải qua quy trình lấp đầy khoảng trống bằng dữ liệu nguồn mở (ASTER GDEM2, GMTED2010 và NED), không giống như các phiên bản khác có chứa khoảng trống hoặc đã được lấp đầy khoảng trống bằng các nguồn thương mại. Để biết thêm thông tin về các phiên bản, hãy xem Hướng dẫn nhanh về SRTM. Tài liệu: Hướng dẫn sử dụng Tài liệu chung Tài liệu cơ sở lý thuyết về thuật toán (ATBD)