The application of satellite imaging radars over land to the assessment, mapping and monitoring of resources

Abstract

Airborne imaging radars have been put to substantial civilian use over the past 15 years, accumulating aggregate areal ground coverage of imagery of about 18 x 10 6 km 2 . Much of this coverage has been from cloud-ridden equatorial regions that pose difficulties for systematic air photography, capitalizing upon radar’s capacity to acquire data virtually without regard to daylight and cloud conditions. The work was required mainly for regional development, land-use studies, petroleum and mineral exploration or geothermal energy studies, and was carried out by a few established groups. The Seasat SAR, operating in 1978, had a coverage essentially restricted to North America and Europe. Although not particularly suited to overland purposes it introduced many additional users to regional radar imagery. The Shuttle imaging radar SIR-A, which flew in November 1981, achieved a coverage of about 10 7 km 2 in the aggregated 8 h of operation, looking at a greater variety of terrain, particularly among arid lands, and geologic type than had been accumulated previously. Examples presented here show the even illumination of SIR-A, and a depiction of geographic and geological features superior to Seasat and in some cases superior to Landsat. Interpretability for regional geological purposes is good and is adequate for general land use and other purposes. In arid regions new applications for studies on desertification and hydrogeology are highlighted. An example of subsurface backscatter is presented. Once wide-covering multifrequency and multitemporal radar become available from N.A.S.A.’s SIR-B and SAMEX, planned for 1984 and 1987 respectively, and from other major radar satellites to be launched by the European Space Agency, the Canadian Centre of Remote Sensing and the Japanese Space Agency, and from the German Spacelab SAR, spaceborne radar imagery will join Landsat as a primary tool in thematic mapping of large areas of the Earth’s surface.