There are two types of data from the SRTM mission. One was processed in a systematic fashion using SRTM Ground Data Processing system (GDPS) supercomputer at Jet Propulsion Laboratory and was formatted according to the Digital Terrain Elevation Data (DTED) specification for delivery to NIMA. The GDPS data includes only the DEM and is referenced to the WGS84 geoid. The other is the PI Processor data, which was processed using the algorithm and hardware being developed for GDPS. These data are for Principal Investigators selected by NASA under the Solid Earth and Natural Hazards program and other special purposes. These data were not formatted according to DTED specification, and the terrain height data is relative to the WGS84 ellipsoid.