Dear all, Have someone accessed ASTER DEM today? According to the announcement, today these data will be available, but up to now I can't find a way of get some sample DEM. If you got success, please, drop us some lines with the "clips" steps.
Bests milton brazil=toronto 2009/6/26 Michael Barton <[email protected]> > See the following announcement. NASA (USA) will release high resolution > DEM's of the globe, produced from the Terra ASTER satellite, at no charge. > You can check out the web announcement at < > https://lpdaac.usgs.gov/lpdaac/about/news_archive/monday_june_22_20092>. > As a Terra ASTER user, I've been using the DEM's for several years and found > them to be a very good high-resolution (30x30m) topography source. > Michael > > ================== announcement ==================== > > 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/, respectively. > > > 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. > > ============================================================= > > > ____________________ > C. Michael Barton, Professor of Anthropology > Director of Graduate Studies, School of Human Evolution & Social Change > Director, Center for Social Dynamics & Complexity > Arizona State University > > Phone: 480-965-6262 > Fax: 480-965-7671 > www: <www.public.asu.edu/~cmbarton> > > > > > > _______________________________________________ > grass-user mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/grass-user > >
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