Drainage Network Analysis with K-Band Radar Imagery

Abstract

ADAR images of the earth's surface offer an attractive, though largely untested, tool for drainage analysis. Among the attributes of radar imagery are two that make it especially suitable for reconnaissance studies of landforms, namely, the large areal coverage and the great quantity of landform detail provided relative to image scale. Both features permit small-scale presentation of large amounts of terrain information. For example, Figure 1, a K-band' radar image of a swath of terrain ten miles wide, has a scale of approximately 1:200,000, yet the drainage information that can be derived from this image is roughly equivalent to that derived from a 1: 62,500 topographic map. Radar imagery offers several advantages over aerial photographs and topographic maps for certain types of studies, and where deficiencies exist they can often be compensated. For one thing, radar imagery is independent of solar illumination and is unaffected by clouds and rain except for heavy thunderstorms. Since clouds and darkness are no deterrent to terrain imaging, any area of the world can be viewed on demand, including the humid tropics and regions of polar night, both of which are well-known examples of terrain that is difficult to photograph. Simonett and Morain2 have demonstrated that in the humid mid-latitudes the time available for radar imaging is five to ten times greater than that for obtaining acceptable, mapping-quality aerial photographs. When an aircraft or satellite is available for use over a given area for only a specified time, it is obvious that full photographic coverage cannot be guaranteed. Radar supplements photography, at least, and can be used alone in geomorphic studies with some degree of confidence. Furthermore, the use of a synthetic aperture antenna system allows radar resolution to be independent of the altitude of the aircraft. The same resolution can