V-Soft Communications is now offering the Shuttle Radar Topography Mission (SRTM) terrain database for the United States, Mexico, Canada, Central and South America, the Caribbean and the lower two-thirds of Canada. This terrain database is designed for use with V-Soft Communications' propagation software. Coverage studies based on the SRTM terrain database may better reflect real-world coverage, as the elevation is based on radar returns from the tops of densely forested areas and from man-made terrain such as buildings. For a comparison of a path profile using the new 3-arc second SRTM terrain database and one using the 30-second World Terrain database, see the V-Soft Shuttle Terrain Web page. V-Soft will be showing the new terrain database and its assortment of computer programs for coverage and interference analysis at NAB 2005 in booth N508.
The USGS, on its Shuttle Radar Topography Mission DTED page offers some cautions about the STRM terrain data. It notes, "SRTM DTED elevations are with respect to the reflective surface. Some of the data may exhibit typical radar artifacts including scattered voids due to shadowing effects and poor signal returns over some terrain, as well as occasional phase unwrapping errors. However on the whole, the data are 95 percent complete over the collection area, and the SRTM DTED absolute height accuracy is significantly better than the 16-meter (90 percent confidence) specification for the mission." SRTM 1-arc second data for the United States and territorial islands is available on DVDs from USGS. However, this data would have to be processed before it could be used with other propagation software such as SPLAT, which I described in my Feb. 2, 2005 RF Technology column.
