[Spanish] geodata MDT de la NASA 30x30m libre desde hoy

[Agustin Diez Castillo]

Buenas noticias,
A partir de hoy está libre el MDT de 30m de la NASA
https://lpdaac.usgs.gov/lpdaac/about/news_archive/monday_june_01_2009_coming_soon_aster_global_dem
https://lpdaac.usgs.gov/lpdaac/content/download/3934/19673/file/ASTER%20GDEM%20Pre-Release%20Announcement%2023June09(2).pdf
METI and NASA Announce Plans for ASTER Global DEM Release
The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) Global Digital Elevation Model (GDEM) was
developed jointly by the Ministry of Economy, Trade, and Industry (METI) of Japan and the United States National
Aeronautics and Space Administration (NASA). Initial studies to validate and characterize the ASTER GDEM recently were
completed by NASA and METI, in cooperation with the U.S. Geological Survey (USGS) and the Earth Remote Sensing Data
Analysis Center (ERSDAC) of Japan, as well as with support from the U.S. National Geospatial-Intelligence Agency (NGA)
and numerous other collaborators from around the world.
ASTER Global DEM
Following review of the validation results, METI and NASA have decided to jointly release the ASTER GDEM on June 29,
2009. Previously, METI and NASA announced their intent to contribute the ASTER GDEM to the Global Earth Observation
System of Systems (GEOSS). Upon release, the ASTER GDEM will be available at no charge to users worldwide via electronic
download from ERSDAC and from NASA’s Land Processes Distributed Active Archive Center (LP DAAC) by visiting
http://www.gdem.aster.ersdac.or.jp/ and https://wist.echo.nasa.gov/~wist/api/imswelcome/, respective
The ASTER instrument was built by METI and launched onboard NASA’s Terra spacecraft in December 1999. The ASTER
instrument uses the nadir-viewing and the backward-viewing telescopes; together they enable along-track stereoscopic
capability to generate stereo data with a base-to-height ratio of 0.6. The spatial resolution is 15 m in the horizontal
plane. One nadir-looking ASTER VNIR scene consists of 4,100 samples by 4,200 lines, corresponding to about 60 km-by-60
km ground area.
The methodology used to produce the ASTER GDEM involved automated processing of the entire 1.5-million-scene ASTER
archive, including stereo-correlation to produce 1,264,118
individual scene-based ASTER DEMs, cloud masking to remove cloudy pixels, stacking all cloud-screened DEMs, removing
residual bad values and outliers, averaging selected data to create final pixel values, and then correcting residual
anomalies before partitioning the data into 1°-by-1° tiles. It took approximately one year to complete production of the
beta version of the ASTER GDEM using a fully automated approach.
The ASTER GDEM covers land surfaces between 83°N and 83°S and is composed of 22,600 1°-by-1° tiles. Tiles that contain
at least 0.01% land area are included. The ASTER GDEM is in GeoTIFF with geographic lat/long coordinates and a 1
arc-second (30 m) grid of elevation postings. GDEM is referenced to the WGS84/EGM96 geoid. Pre-production estimated
accuracies for this global product were 20 meters at 95% confidence for vertical data and 30 meters at 95 % confidence
for horizontal data. Initial validation studies concluded that the ASTER GDEM generally meets the pre-production
accuracy predictions, but results do vary and include areas where GDEM accuracy does not meet the pre-production estimates.
Land surface topography is one of the most fundamental geophysical measurements of the Earth, and it is a dominant
controlling factor in virtually all physical processes that occur on the land surface. Land surface topography also
significantly controls processes within the overlying atmosphere and reflects the processes within the underlying
lithosphere. Consequently, topographic information is important across the full spectrum of earth sciences, and the
availability of an up-to-date, high resolution (1-arc-sec or less) global DEM remains a priority of earth scientists for
a long time. The ASTER GDEM is expected to meet the requirements of many users for global topographic information.