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

[Giovanni Manghi]

> 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>