The geological value of simultaneously produced like- and cross-polarized radar imagery

The potential of imaging radar as a tool for the geoscientist has been continuously expanded since its value was first demonstrated in the late 1940's. In areas of diverse topographic configuration, geologic structure, and earth surface composition, monoscopic radar imagery has proved to be a valuable supplement [Pierson et al., 1965[ to the aerial photograph and, in fact, to field work itself. Side-looking radars [Levine, 1960] developed in recent years are capable of much better resolution than previous scanning radars. The result is images of near-photographic quality obtainable almost independently of weather and daylight conditions. Synthetic aperture techniques [Cutrona et al., 1961] permit the extension of this capability from millimeter wavelengths to wavelengths in the decimeter, and perhaps even the meter, range. Radars ordinarily transmit either horizontally or vertically polarized radiation and receive the same polarization transmitted. Because planetary surfaces return the two polarizations differently, and because components orthogonal to those transmitted may also be observed, experiments have been initiated to determine the value of multiple polarization images to geologists. The lack of a full understanding of the causes of differences between like- and cross-polarized radar return should not prevent the interpreter from taking advantage of the data presented.