Abstract
The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is a 14-channel imaging instrument operating on NASA’s Terra satellite since 1999. ASTER’s visible–near infrared (VNIR) instrument, with three bands and a 15 m Instantaneous field of view (IFOV), is accompanied by an additional band using a second, backward-looking telescope. Collecting along-track stereo pairs, the geometry produces a base-to-height ratio of 0.6. In August 2019, the ASTER Science Team released Version 3 of the global DEM (GDEM) based on stereo correlation of 1.8 million ASTER scenes. The DEM has 1 arc-second latitude and longitude postings (~30 m) and employed cloud masking to avoid cloud-contaminated pixels. Custom software was developed to reduce or eliminate artifacts found in earlier GDEM versions, and to fill holes due to the masking. Each 1×1 degree GDEM tile was manually inspected to verify the completeness of the anomaly removal, which was generally excellent except across some large ice sheets. The GDEM covers all of the Earth’s land surface from 83 degrees north to 83 degrees south latitude. This is a unique, global high spatial resolution digital elevation dataset available to all users at no cost. In addition, a second unique dataset was produced and released. The raster-based ASTER Global Water Body Dataset (ASTWBD) identifies the presence of permanent water bodies, and marks them as ocean, lake, or river. An accompanying DEM file indicates the elevation for each water pixel. To date, over 100 million 1×1 degree GDEM tiles have been distributed.
Highlights
A digital elevation model (DEM) is a digital raster representation of ground surface topography or terrain
The only other global high spatial resolution DEM in existence at the time was owned by the US National Geospatial Intelligence Agency (NGA), and remains classified to this day
This was the reprocessed Shuttle Radar Topography Mission (SRTM) (e.g., ICESat adjusted original radar swaths) that was concurrently generated for the NASADEM project. (The original SRTM had been the primary fill for all prior versions of global high spatial resolution digital elevation model (GDEM).) Some interferometric unwrapping errors were removed from the NASADEM SRTM but no further masking was applied
Summary
A digital elevation model (DEM) is a digital raster representation of ground surface topography or terrain. DEMs are used in numerous applications: extracting terrain parameters, modeling water flow, creation of relief maps, terrain analyses in geomorphology and physical geography, engineering and infrastructure design, base mapping, flight simulation, line of sight analysis, and many more. Morphometric data, such as slope, gradients, slope aspect, and hydrographic networks can be automatically extracted from DEMs. Hillshade images, curvature, contour lines, viewshed and observer points can be calculated. In addition to the improved GDEM Version 3, a second, unique dataset was created and released: the ASTER Global Water Body Dataset (ASTWBD).
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