Seasat Range Measurements Verified on a 3-D Ice Sheet

The Seasat radar altimeter observations of a 100 km2 area in South Greenland are compared to a detailed, ground-based survey, using “geoceivers” and pressure altimeters. The comparison shows the Seasat measurement of distance between satellite and earth to be accurate to the level of the geoceiver determined surface (±2 m). Due to the great distance between satellite and surface, finer details of surface topography are not revealed in the satellite measurements. As the satellite tends to lock onto hills in the vicinity of the sub-satellite track, the satellite tends to overestimate the true surface elevation. However, a similar altimeter would make a similar overestimate, allowing accurate differential measurement of volume changes between the two surveys.