The U. S. Geological Survey (USGS) has become a major source of side-looking airborne radar (SLAR) data as a result of a Congressional mandate in 1980 to 'begin the use of side-looking airborne radar for topographic and geologic mapping, and geological resource surveys in promising areas, particularly Alaska. ' In 1982, SLAR images were acquired, with a northwest look direction of almost 13,000 km**2 of the Aleutian Islands. Although acquisitions in succeeding years concentrated on selected areas of interest in the conterminous United States, Alaskan radar data will again be collect in fiscal year 1986. Mosaics have already been prepared for more than 20 percent of the conterminous United States and 10 percent of Alaska. Although mosaics are a convenient form of compiling radar images to provide a synoptic view, the individual radar strips, especially film transparencies, have considerably more detail and are used for most serious studies.