ASTER is capable of collecting in-track stereo using nadir- and aft-looking near infrared cameras. Since 2001, these stereo pairs have been used to produce single-scene (60- x 60-kilomenter (km)) digital elevation models (DEM) having vertical (root-mean-squared-error) accuracies generally between 10- and 25-meters (m). The methodology used by Japan's Sensor Information Laboratory Corporation (SILC) to produce the ASTER GDEM involves automated processing of the entire ASTER Level-1A archive. Stereo-correlation is used to produce over one million individual scene-based ASTER DEMs, to which cloud masking is applied to remove cloudy pixels. All cloud-screened DEMS are stacked and residual bad values and outliers are removed. Selected data are averaged to create final pixel values, and residual anomalies are corrected before partitioning the data into 1 degree (°) x 1° tiles. The ASTER GDEM covers land surfaces between 83°N and 83°S and is comprised of 22,702 tiles. Tiles that contain at least 0.01% land area are included. The ASTER GDEM is distributed as Geographic Tagged Image File Format (GeoTIFF) files with geographic coordinates (latitude, longitude). The data are posted on a 1 arc-second (approximately 30–m at the equator) grid and referenced to the 1984 World Geodetic System (WGS84)/ 1996 Earth Gravitational Model (EGM96) geoid.

The ASTER Global Digital Elevation Model (GDEM) Version 3 (ASTGTM) provides a global digital elevation model (DEM) of land areas on Earth at a spatial resolution of 1 arc second (approximately 30 meter horizontal posting at the equator).

The development of the ASTER GDEM data products is a collaborative effort between National Aeronautics and Space Administration (NASA) and Japan’s Ministry of Economy, Trade, and Industry (METI). The ASTER GDEM data products are created by the Sensor Information Laboratory Corporation (SILC) in Tokyo.

The ASTER GDEM Version 3 data product was created from the automated processing of the entire ASTER Level 1A (https://doi.org/10.5067/ASTER/AST_L1A.003) archive of scenes acquired between March 1, 2000, and November 30, 2013. Stereo correlation was used to produce over one million individual scene based ASTER DEMs, to which cloud masking was applied. All cloud screened DEMs and non-cloud screened DEMs were stacked. Residual bad values and outliers were removed. In areas with limited data stacking, several existing reference DEMs were used to supplement ASTER data to correct for residual anomalies. Selected data were averaged to create final pixel values before partitioning the data into 1 degree latitude by 1 degree longitude tiles with a one pixel overlap. To correct elevation values of water body surfaces, the ASTER Global Water Bodies Database (ASTWBD) (https://doi.org/10.5067/ASTER/ASTWBD.001) Version 1 data product was also generated.

The geographic coverage of the ASTER GDEM extends from 83° North to 83° South. Each tile is distributed in GeoTIFF format and projected on the 1984 World Geodetic System (WGS84)/1996 Earth Gravitational Model (EGM96) geoid. Each of the 22,912 tiles in the collection contain at least 0.01% land area.

Provided in the ASTER GDEM product are layers for DEM and number of scenes (NUM). The NUM layer indicates the number of scenes that were processed for each pixel and the source of the data.

While the ASTER GDEM Version 3 data products offer substantial improvements over Version 2, users are advised that the products still may contain anomalies and artifacts that will reduce its usability for certain applications.

Improvements/Changes from Previous Versions • Expansion of acquisition coverage to increase the amount of cloud-free input scenes from about 1.5 million in Version 2 to about 1.88 million scenes in Version 3. • Separation of rivers from lakes in the water body processing. • Minimum water body detection size decreased from 1 km2 to 0.2 km2.

The ASTER Global Digital Elevation Model (GDEM) Version 3 (ASTGTM) provides a global digital elevation model (DEM) of land areas on Earth at a spatial resolution of 1 arc second (approximately 30 meter horizontal posting at the equator).

The development of the ASTER GDEM data products is a collaborative effort between National Aeronautics and Space Administration (NASA) and Japan’s Ministry of Economy, Trade, and Industry (METI). The ASTER GDEM data products are created by the Sensor Information Laboratory Corporation (SILC) in Tokyo.

The ASTER GDEM Version 3 data product was created from the automated processing of the entire ASTER Level 1A archive of scenes acquired between March 1, 2000, and November 30, 2013. Stereo correlation was used to produce over one million individual scene based ASTER DEMs, to which cloud masking was applied. All cloud screened DEMs and non-cloud screened DEMs were stacked. Residual bad values and outliers were removed. In areas with limited data stacking, several existing reference DEMs were used to supplement ASTER data to correct for residual anomalies. Selected data were averaged to create final pixel values before partitioning the data into 1° by 1° tiles with a one pixel overlap. To correct elevation values of water body surfaces, the ASTER Global Water Bodies Database (ASTWBD) Version 1 data product was also generated.

The geographic coverage of the ASTER GDEM extends from 83° North to 83° South. Each tile is distributed in GeoTIFF format and projected on the 1984 World Geodetic System (WGS84)/1996 Earth Gravitational Model (EGM96) geoid. Each of the 22,912 tiles in the collection contain at least 0.01% land area.

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 second version of the ASTER GDEM (GDEM2) was released by NASA and METI on 17 October, 2011. Improvements in the GDEM2 result from acquiring 260,000 additional scenes to improve coverage, a smaller correlation kernel to yield higher spatial resolution, and improved water masking. The ASTER GDEM V2 maintains the GeoTIFF format and the same gridding and tile structure as V1, with 30-meter postings and 1 x 1 degree tiles. Version 2 shows significant improvements over the previous release. The GDEM is available for download from NASA Reverb, LP DAAC Global Data Explorer, and J-spacesystems ASTER GDEM Page.

Source: http://www.jspacesystems.or.jp/ersdac/GDEM/ver2Validation/Summary_GDEM2_validation_report_final.pdf ASTER Global Digital Elevation Model Version 2 Summary of Validation Results Accessed 05/11/2013 And http://asterweb.jpl.nasa.gov/gdem.asp

The ASTER Digital Elevation Model and Orthorectified Registered Radiance at the Sensor (AST14DMO) product (https://lpdaac.usgs.gov/documents/996/ASTER_Earthdata_Search_Order_Instructions.pdf) form a multi-file product. The product contains both a Digital Elevation Model (DEM) and up to 15 orthorectified images representing Visible and Near Infrared (VNIR), Shortwave Infrared (SWIR), and Thermal Infrared (TIR) data layers for each available ASTER scene, if acquired. The spatial resolution is 15 m (VNIR), 30 m (SWIR), and 90 m (TIR) with a temporal coverage of 2000 to present.

For more information, see the links below:

(AST14DEM) (https://doi.org/10.5067/ASTER/AST14DEM.003) (AST14OTH) (https://doi.org/10.5067/ASTER/AST14OTH.003)

Improvements/Changes from Previous Versions

As of January 2021, the LP DAAC has implemented version 3.0 of the Sensor Information Laboratory Corporation ASTER DEM/Ortho (SILCAST) software, which is used to generate the Level 2 on-demand ASTER Orthorectified and Digital Elevation Model (DEM) products (AST14). The updated software provides digital elevation extraction and orthorectification from ASTER L1B input data without needing to enter ground control points or depending on external global DEMs at 30-arc-second resolution (GTOPO30). It utilizes the ephemeris and attitude data derived from both the ASTER instrument and the Terra spacecraft platform. The outputs are geoid height-corrected and waterbodies are automatically detected in this version. Users will notice differences between AST14DEM, AST14DMO, and AST14OTH products ordered before January 2021 (generated with SILCAST V1) and those generated with the updated version of the production software (version 3.0). Differences may include slight elevation changes over different surface types, including waterbodies. Differences have also been observed over cloudy portions of ASTER scenes. Additional information on SILCAST version 3.0 can be found on the SILCAST website (http://www.silc.co.jp/en/products.html).

Starting June 23, 2021, radiometric calibration coefficient Version 5 (RCC V5) will be applied to newly observed ASTER data and archived ASTER data products. Details regarding RCC V5 are described in the following journal article.

Tsuchida, S., Yamamoto, H., Kouyama, T., Obata, K., Sakuma, F., Tachikawa, T., Kamei, A., Arai, K., Czapla-Myers, J.S., Biggar, S.F., and Thome, K.J., 2020, Radiometric Degradation Curves for the ASTER VNIR Processing Using Vicarious and Lunar Calibrations: Remote Sensing, v. 12, no. 3, at https://doi.org/10.3390/rs12030427.

This data set provides a 100 meter resolution surface topography Digital Elevation Model (DEM) of the Antarctic Peninsula. The DEM is based on Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Global Digital Elevation Model (GDEM) data.

The data set includes ASTER GDEM data and its Mosaic. ASTER Global DEM (ASTER GDEM) is a Global digital elevation data product jointly released by NASA and Japan's ministry of economy, trade and industry (METI) on June 29, 2009. The DEM data is based on the observation results of NASA's new earth observation satellite TERRA.It is produced by the ASTER(Advanced Space borne Thermal Emission and Reflection Radio meter) sensor, which collects 1.3 million stereo image data, covering more than 99% of the earth's land surface.The data has a horizontal accuracy of 30 m (95% confidence) and an elevation accuracy of 7-14 m (95% confidence).This data is the third global elevation data, which is significantly higher than previous SRTM3 DEM and GTOPO30 data. We from NASA's web site (http://wist.echo.nasa.gov/api) to download the data of heihe river basin, and through the data center to distribute.The data distributed by the center completely retains the original appearance of the data without any modification to the data.If users need details about ASTER GDEM preparation process, please refer to the data documents of metadata connections, or visit http://www.ersdac.or.jp/GDEM/E/3.html or directly from https://lpdaac.usgs.gov/ reading and ASTER Global DEM related documents. ASTER GDEM is divided into several data blocks of 1×1 degree in distribution, and the distribution format is zip compression format. Each compressed file includes three files. The file naming format is as follows: ASTGTM_NxxEyyy_dem.tif ASTGTM_NxxEyyy_num.tif reademe.pdf Where xx is the starting latitude and yyy is the starting longitude._dem. Tif is the dem data file, _num. Tif is the data quality file, and reademe is the data description file. In order to facilitate users to use the data, on the basis of the fractional ASTER GDEM data, we splice fractional SRTM data to prepare the ASTER GDEM Mosaic map of the black river basin, which retains all the original features of ASTER GDEM without any resamulation.
This data includes two files: heihe_aster_gdem_mosaic_dem.img Heihe_Aster_GDEM_Mosaic_num. Img The data is stored in the format of Erdas image, where the file _dem.img is the dem data file and the file _num. Img is the data quality file.

The ASTER Global Water Bodies Database (ASTWBD) Version 1 data product provides global coverage of water bodies larger than 0.2 square kilometers at a spatial resolution of 1 arc second (approximately 30 meters) at the equator, along with associated elevation information.

The ASTWBD data product was created in conjunction with the ASTER Global Digital Elevation Model (ASTER GDEM) Version 3 data product by the Sensor Information Laboratory Corporation (SILC) in Tokyo. The ASTER GDEM Version 3 data product was generated using ASTER Level 1A (https://doi.org/10.5067/ASTER/AST_L1A.003) scenes acquired between March 1, 2000, and November 30, 2013. The ASTWBD data product was then generated to correct elevation values of water body surfaces.

To generate the ASTWBD data product, water bodies were separated from land areas and then classified into three categories: ocean, river, or lake. Oceans and lakes have a flattened, constant elevation value. The effects of sea ice were manually removed from areas classified as oceans to better delineate ocean shorelines in high latitude areas. For lake waterbodies, the elevation for each lake was calculated from the perimeter elevation data using the mosaic image that covers the entire area of the lake. Rivers presented a unique challenge given that their elevations gradually step down from upstream to downstream; therefore, visual inspection and other manual detection methods were required.

The geographic coverage of the ASTWBD extends from 83°N to 83°S. Each tile is distributed in GeoTIFF format and referenced to the 1984 World Geodetic System (WGS84)/1996 Earth Gravitational Model (EGM96) geoid. Each data product is provided as a zipped file that contains an attribute file with the water body classification information and a DEM file, which provides elevation information in meters.

A 'Digital Elevation Model (DEM)' is a 3D approximation of the terrain's surface created from elevation data. The term 'Digital Surface Model (DSM)' represents the earth's surface and includes all objects including e.g. forests, buildings. The Digital Elevation Model over Europe from the GMES Reference Data Access project (EU-DEM) is a Digital Surface Model (DSM) representing the first surface as illuminated by the sensors. EU-DEM covers the 39 member and cooperating countries of EEA. The EU-DEM is a hybrid product based on SRTM and ASTER GDEM data fused by a weighted averaging approach. Different products have been derived from the EU-DEM, including raster’s of the slope, terrain aspect and hillshade. The different products are made available in both full-European coverage as in a set of 25 tiles covering 1000x1000km each. The EU-DEM map shows a colour shaded relief image over Europe, which has been created by EEA using a hillshade dataset derived from the ETRS89-LAEA version of EU-DEM. As this data cannot be used for analysis purposes (and that there are some known artefacts West of Norway), the downloadable data are single band raster’s with values relating to the actual elevation. The datasets are encoded as GeoTIFF with LZW compression (tiles) or DEFLATE compression (European mosaics as single files). The Web maps include WFS, WMS and WCS services. The EU-DEM statistical validation documents a relatively unbiased (-0.56 meters) overall vertical accuracy of 2.9 meters RMSE, which is fully within the contractual specification of 7m RMSE and the full report can be found at [1].

[1] https://cws-download.eea.europa.eu/in-situ/eudem/Report-EU-DEM-statistical-validation-August2014.pdf

The Copernicus DEM is a Digital Surface Model (DSM) which represents the bare-Earth surface and all above ground natural and built features. It is based on WorldDEM™ DSM that is derived from TanDEM-X and is infilled on a local basis with the following DEMs: ASTER, SRTM90, SRTM30, SRTM30plus, GMTED2010, TerraSAR-X Radargrammetric DEM, ALOS World 3D-30m. Copernicus Programme provides Copernicus DEM in 3 different instances: COP-DEM EEA-10, COP-DEM GLO-30 and COP-DEM GLO-90 where "COP-DEM GLO-90" tiles and most of the "COP-DEM GLO-30 " tiles are available worldwide with free license. Sentinel Hub provides two instances named COPERNICUS_90 which uses "COP-DEM GLO-90" and COPERNICUS_30 which uses "COP-DEM GLO-30 Public" and "COP-DEM GLO-90" in areas where "COP-DEM GLO-30 Public" tiles are not yet released to the public by Copernicus Programme. Copernicus DEM provides elevation data and can also be used for the orthorectification of satellite imagery (e.g Sentinel 1).

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.

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

This dataset is the Digital Elevation Model （DEM）in the Qilian Mountain， spatial resolution 30m. This dataset is based on the Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Model （ASTER-GDEM）. The data set has a vertical accuracy of 20 m and a horizontal accuracy of 30 m. Through the data download, preprocessing and splicing, the 30m×30m DEM data of Qilian Mountain is generated. This data set can extract a large amount of surface morphology information, which is an important basic data for terrain analysis and feature recognition in Qilian Mountain. The data will serve the ecological environment monitoring, ecological environmental protection and treatment project implementation, hydrology and water resources analysis and evaluation in Qilian Mountain area.