- MAIN SOURCES OF ERROR IN A DIGITAL TERRAIN MODEL FOR FREE
- MAIN SOURCES OF ERROR IN A DIGITAL TERRAIN MODEL FULL
The quality of this data is generally good, with a resolution of 30m. However, there is another source of international DEM data that is somewhat less well known: ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer).
MAIN SOURCES OF ERROR IN A DIGITAL TERRAIN MODEL FOR FREE
Although intentionally degraded to 90m resolution, SRTM data has become the global standard for free DEM topographic data. STS 99 used a 60m boom to collect stereoscopic radar imagery for all of the earth between 56 degrees south and 60 degrees north latitude. In 2000, the Space Shuttle flew one of its most useful missions ever. Since that time, two other very popular sources of DEM data have become available. This equates to about $3,500 for a 1:24000 USGS quad.) (The Digital Globe website quotes prices of $25/square kilometer. Of course IKONOS and QuickBird commercial satellite imagery are (or will soon be, in the case of QuickBird) available, but although of excellent quality, this data is quite expensive.
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The second was the reverse engineering approach of extracting DEMs from topo maps as described in my earlier article. The first is the 1 km DTED0 data available from NIMA (and the equivalent GTOPO30 data set available from USGS/EOS). However, the 90m data is a major advance over the 1km resolution DTED0 data referred to in the article.) The significantly superior resolution of ASTER data should ensure its importance as a useful GIS data source for some time to come.Īt the time I wrote the article, there were only two sources of free international DEM data.
MAIN SOURCES OF ERROR IN A DIGITAL TERRAIN MODEL FULL
(Release of the full resolution (30m) data outside of the United States was blocked by NIMA. It will be interesting to see if ASTER remains as popular now that 90m SRTM data is finally available for much of the globe. The rest of the information in this article and the companion article that follows is current as far as I know. This program may still be useful due to its simplicity and its ability to handle HDF format. I have recently modified GEOTIFF4 so that it will handle southern hemisphere data. I recommend that anyone interested in ASTER data investigate these applications carefully. Several GIS applications, including the free application MicroDem and 3DEM can handle ASTER DEM GeoTiff format with ease. Since that time, ASTER DEM data, while not realizing its full potential due to lack of global coverage, has become more widely known and popular. I wrote the GEOTIFF4 application described herein because there were very few programs capable of handling HDF and the special Geotiff format that ASTER files utilized, and none that were both free and easy to use. At that time, the ASTER instrument was unknown to many people.
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This article has been popular since it was first posted almost ten years ago. Editor's Note, May 2011: The ASTER DEM is again free and is avaialble at the NASA WIST website.