Image-scale and look-direction effects on the detectability of lineaments in radar images

Abstract

The effects of image-scale and radar look-direction on the detectability of lineaments are investigated using synthetic aperture radar images of the Japanese Islands. To make clear the optimum image-scale, various kinds of image data including Landsat images and aerial photographs were interpreted. The result indicates that lineament interpretation can be performed most efficiently if R × S = 0.1 mm, where R is the ground resolution and S is the image-scale. The value of 0.1 mm corresponds to the limitation of human eyes. Then, selective enhancement of lineaments caused by radar shadowing was examined by using a topographic model, which was modified from the model of Wise (1969) to fit dissected topographic relief in mature stage of the Japanese Islands. That is, a lineament corresponds to a straight valley of the second order, on whose walls small valleys of the first order develop. Optimum shadow enhancement is achieved when the strike of the lineament is ranging from 20° to 30° to the radar look-direction.