SRTM.
Radar data acquired by the Shuttle Radar Topography Mission (SRTM) has been used by NASA to produce a digital elevation model (DEM) covering 80 percent of Earth’s land area. SRTM DEM tiles with 1 arc-second cell size are available for North America, and 3 arc-second DEMs are available for other areas. These SRTM
DEMs, however, include data voids (holes) due to localized problems with the radar acquisition process, including layover, shadowing, and lack of signal return from smooth water surfaces.
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NED. USGS National Elevation Dataset (NED) incorporates the "best available" DEM data with approximately 30-meter and 10-meter
coverage of the United States.
SRTM global (holes filled)
90-meter resolution
lat/lon coordinate system
10:1 JPEG2000 compression
source: King's College: www.kcl.ac.uk/