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Japan and US launch ASTER GDEM
From the beginning, GEO has encouraged the development of a comprehensive, highly accurate, fully consistent, and freely available global Digital Elevation Model (GDEM). Japan and the US have responded to this critical need by collaborating through Work Plan Task DA-09-03d to build the ASTER GDEM. This new digital topographical map was formally launched on 29 June.
ASTER Global DEM
Digital Elevation Models use remote sensing to map the elevation and contours of the Earth’s surface, highlighting features such as mountains and rivers. They are used for a wide range of purposes, such as creating relief maps, modeling water flow to anticipate flooding impacts, predicting land slides, planning new infrastructure, and projecting the likely impacts of global environmental change.
Until now, however, GDEMs have been patched together using data gathered by different instruments surveying limited areas of the Earth’s surface at different resolutions at different times. As a result, topographical grids are marred by internal inconsistencies and large gaps in coverage, particularly of Africa and other developing regions. GDEMs also tend to be expensive and unavailable to all but the largest institutions.
Contribution to GEOSS
By contributing their new ASTER GDEM to GEOSS, Japan and the US are actively promoting the GEO data-sharing principles on the full and open exchange of Earth observation data. The announcement that ASTER GDEM will be freely available complements other recent decisions to open up access to satellite observations, notably those by the China Brazil Earth Resources Satellite (CBERS) program and by the US government’s Landsat archives program.
ASTER GDEM will also advance the development of GEOSS in many other ways. For example, the GEO collaboration on establishing a global forest monitoring system will require better topographical data on the world’s tropical forests, particularly for hilly terrain, where vertical slopes make it harder to interpret forest density and thus track changes in biomass and carbon content. Similarly, a more robust topography map will support the monitoring and analysis of sea-level rise, storm surges and other climate change impacts; coastal erosion, floods and hurricanes; and adaptation responses such as locating barriers and other coastal defenses.
Affordable and comprehensive
In addition to making Digital Elevation Models more affordable and accessible, the ASTER GDEM offers comprehensive coverage of the planet, including 99% of the area between 83°N and 83°S latitude, with data points 30m apart. As a result, many developing countries will for the first time have full access to the detailed topographical information they need for managing floods, landslides and other disasters.
High-resolution and globally comprehensive Digital Elevation Models have not been publicly available until now in part because they support a number of commercial and strategic applications. For example, the military uses high-resolution DEMs to secure the flight paths of low-flying planes and missiles, while companies use them to site TV and cell-phone towers where their transmissions will encounter minimal interference.
The ASTER GDEM is named after the Japanese Advanced Space-borne Thermal Emission and Reflection Radiometer (ASTER) remote-sensing instrument that is carried by the NASA satellite Terra. ASTER has made nearly 1.3 million individual stereo-pair images of the planet by combining two images from different angles for each location.
The ASTER GDEM “tiles” may be downloaded electronically from www.gdem.aster.ersdac.or.jp or https://wist.echo.nasa.gov/~wist/api/imswelcome/. See also the NASA press release.
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