<div>Dear all,</div>
<div> </div>
<div>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.</div>
<div>If you got success, please, drop us some lines with the "clips" steps.</div>
<div> </div>
<div>Bests</div>
<div> </div>
<div>milton</div>
<div>brazil=toronto<br><br></div>
<div class="gmail_quote">2009/6/26 Michael Barton <span dir="ltr"><<a href="mailto:michael.barton@asu.edu">michael.barton@asu.edu</a>></span><br>
<blockquote class="gmail_quote" style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid">
<div style="WORD-WRAP: break-word">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 <<a href="https://lpdaac.usgs.gov/lpdaac/about/news_archive/monday_june_22_20092" target="_blank">https://lpdaac.usgs.gov/lpdaac/about/news_archive/monday_june_22_20092</a>>. 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.
<div><br></div>
<div>Michael</div>
<div><br></div>
<div>================== announcement ====================<br>
<div><br></div>
<div>
<div style="MARGIN: 0px">ASTER Global DEM </div>
<p style="MIN-HEIGHT: 15px; MARGIN: 0px; FONT: 12px Times New Roman"> <br></p>
<div style="MARGIN: 0px">Following review of the validation results, METI and NASA have decided to jointly release the </div>
<div style="MARGIN: 0px">ASTER GDEM on <b>June 29, 2009</b>. Previously, METI and NASA announced their intent to </div>
<div style="MARGIN: 0px">contribute the ASTER GDEM to the Global Earth Observation System of Systems (GEOSS). </div>
<div style="MARGIN: 0px">Upon release, the ASTER GDEM will be available at no charge to users worldwide via </div>
<div style="MARGIN: 0px">electronic download from ERSDAC and from NASA’s Land Processes Distributed Active </div>
<div style="MARGIN: 0px">Archive Center (LP DAAC) by visiting <a href="http://www.gdem.aster.ersdac.or.jp/" target="_blank">http://www.gdem.aster.ersdac.or.jp/</a> </div>
<div style="MARGIN: 0px">and <a href="https://wist.echo.nasa.gov/~wist/api/imswelcome/" target="_blank">https://wist.echo.nasa.gov/~wist/api/imswelcome/</a>, respectively. </div>
<p style="MIN-HEIGHT: 15px; MARGIN: 0px; FONT: 12px Times New Roman"> <br></p>
<div style="MARGIN: 0px">The ASTER instrument was built by METI and launched onboard NASA’s Terra spacecraft in </div>
<div style="MARGIN: 0px">December 1999. The ASTER instrument uses the nadir-viewing and the backward-viewing </div>
<div style="MARGIN: 0px">telescopes; together they enable along-track stereoscopic capability to generate stereo data with </div>
<div style="MARGIN: 0px">a base-to-height ratio of 0.6. The spatial resolution is 15 m in the horizontal plane. One nadir-<span style="FONT: 12px Helvetica"> </span></div>
<div style="MARGIN: 0px">looking ASTER VNIR scene consists of 4,100 samples by 4,200 lines, corresponding to about </div>
<div style="MARGIN: 0px">60 km-by-60 km ground area. </div>
<p style="MIN-HEIGHT: 15px; MARGIN: 0px; FONT: 12px Times New Roman"> <br></p>
<div style="MARGIN: 0px">The methodology used to produce the ASTER GDEM involved automated processing of the </div>
<div style="MARGIN: 0px">entire 1.5-million-scene ASTER archive, including stereo-correlation to produce 1,264,118 </div>
<div style="MARGIN: 0px">individual scene-based ASTER DEMs, cloud masking to remove cloudy pixels, stacking all </div>
<div style="MARGIN: 0px">cloud-screened DEMs, removing residual bad values and outliers, averaging selected data to </div>
<div style="MARGIN: 0px">create final pixel values, and then correcting residual anomalies before partitioning the data into </div>
<div style="MARGIN: 0px">1<span style="FONT: 12px Helvetica">°</span>-by-1<span style="FONT: 12px Helvetica">°</span> tiles. It took approximately one year to complete production of the beta version of the </div>
<div style="MARGIN: 0px">ASTER GDEM using a fully automated approach. </div>
<p style="MIN-HEIGHT: 15px; MARGIN: 0px; FONT: 12px Times New Roman"> <br></p>
<div style="MARGIN: 0px">The ASTER GDEM covers land surfaces between 83<span style="FONT: 12px Helvetica">°</span>N and 83<span style="FONT: 12px Helvetica">°</span>S and is composed of 22,600 </div>
<div style="MARGIN: 0px">1<span style="FONT: 12px Helvetica">°</span>-by-1<span style="FONT: 12px Helvetica">°</span> tiles. Tiles that contain at least 0.01% land area are included. The ASTER GDEM is </div>
<div style="MARGIN: 0px">in GeoTIFF with geographic lat/long coordinates and a 1 arc-second (30 m) grid of elevation </div>
<div style="MARGIN: 0px">postings. GDEM is referenced to the WGS84/EGM96 geoid. Pre-production estimated </div>
<div style="MARGIN: 0px">accuracies for this global product were 20 meters at 95% confidence for vertical data and 30 </div>
<div style="MARGIN: 0px">meters at 95 % confidence for horizontal data. Initial validation studies concluded that the </div>
<div style="MARGIN: 0px">ASTER GDEM generally meets the pre-production accuracy predictions, but results do vary </div>
<div style="MARGIN: 0px">and include areas where GDEM accuracy does not meet<b> </b>the<b> </b>pre-production estimates<b>. </b></div>
<p style="MIN-HEIGHT: 15px; MARGIN: 0px; FONT: 12px Times New Roman"> <br></p>
<div style="MARGIN: 0px">Land surface topography is one of the most fundamental geophysical measurements of the </div>
<div style="MARGIN: 0px">Earth, and it is a dominant controlling factor in virtually all physical processes that occur on the </div>
<div style="MARGIN: 0px">land surface. Land surface topography also significantly controls processes within the </div>
<div style="MARGIN: 0px">overlying atmosphere and reflects the processes within the underlying lithosphere. </div>
<div style="MARGIN: 0px">Consequently, topographic information<b> </b>is<b> </b>important across the full spectrum of earth sciences, </div>
<div style="MARGIN: 0px">and the availability of an up-to-date, high resolution (1-arc-sec or less) global DEM remains a </div>
<div style="MARGIN: 0px">priority of earth scientists for a long time. The ASTER GDEM is expected to meet the </div>
<div style="MARGIN: 0px">requirements of many users for global topographic information. </div>
<div style="MARGIN: 0px"><br></div>
<div style="MARGIN: 0px">=============================================================</div>
<div style="MARGIN: 0px"><br></div>
<div style="MARGIN: 0px"><br></div>
<div>
<div style="WORD-WRAP: break-word">
<div>
<div>
<div>____________________</div>
<div>C. Michael Barton, Professor of Anthropology</div>
<div>Director of Graduate Studies, School of Human Evolution & Social Change</div>
<div>Director, Center for Social Dynamics & Complexity</div>
<div>Arizona State University</div>
<div><br></div>
<div>Phone: 480-965-6262</div>
<div>Fax: 480-965-7671</div>
<div>www: <<a href="http://www.public.asu.edu/~cmbarton" target="_blank">www.public.asu.edu/~cmbarton</a>></div><br></div></div><br></div><br></div><br></div></div></div><br>_______________________________________________<br>
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<br></blockquote></div><br>