Terrain height mapping using interferometric satellite radar data

The use of ground height databases is fundamental for computerised mobile and broadcast area coverage predictions in the UHF and VHF bands. As satellite data becomes more readily available, new techniques are evolving to produce high resolution ground height information. Radar interferometry using satellite-borne synthetic-aperture radars (SARs) is a new technique being explored for a number of applications over land and ice surfaces. One of the most significant of these may be the provision of terrain height maps. The technique relies upon the measurement of phase differences between pairs of high-resolution coherent radar images acquired on near-repeat orbits of a satellite. The phase differences at a given point in the image pair can be related via the orbital geometry to terrain height above a reference surface. The principal is identical to that of illuminating a target simultaneously from a pair of displaced antennas but uses a single antenna to acquire both images at different times. Thus, the technique places a requirement on the temporal coherence of the surface imaged. The author outlines the technique, including theoretical performance limits, and discusses aspects of the associated processing tasks