[GRASS-user] NASA to release no cost 30m DEMs with world-wide coverage on 29 June

Milton Cezar Ribeiro miltinho.astronauta at gmail.com
Mon Jun 29 11:27:18 EDT 2009

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.



2009/6/26 Michael Barton <michael.barton at asu.edu>

> 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>
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