Influences of look angle and look direction of space-borne SAR sensor in geological feature delineation in Metasedimentary terrain of Kurnool Group of rocks, Andhra Pradesh

The role of look angle and look direction of space-borne SAR sensors in enhancing signatures of geological elements is an important aspect of study. In the present study, two different look angle (IS2 and IS4) data of ENVISAT ASAR are compared to evaluate the significance of look angle in enhancing different lithovariants and structures of the Proterozoic metasedimentary terrain. The ascending and descending modes of data acquisition of ENVISAT ASAR also help to study the significance of look direction in enhancing or subduing geological features. Geometric distortion is similar in both look angles. Low-dipping sedimentary terrain with steep mesa, butte and cuesta ridges creates layover on images of IS2 (18°–25°) and IS4 (28°–36°) acquisition of ENVISAT, but low look angle facilitates less shadow zones at the back slope portion and helps in finding important geological structures. Alternate polarization channels of ENVISAT ASAR are useful in enhancing the lithovaraints based on polarization signatures characteristically developed over each rock type due to variation in surface roughness and moisture content of each rock type. Separabilty of one rock type from another based on polarization signatures is better in low look-angle data. Drainages on the other hand, are enhanced in high look-angle data as the specular surface of drainage returns appreciable energy in low look-angle acquisition. In the present study it is found that lineaments of variable trends can be mapped better from dual look-direction data.