A Semi-empirical Topographic Correction Method based on the Relation between Slope-aspect and Mean Radiance.

摘要

This study describes the process and theory behind the development of a topographic correction method for practical application to mountainous forest areas. The algorithm for the method is based on the relation between the slope-aspect and the mean radiance of each slope. First we developed a hypothesis about this relationship by visualizing rugged terrain as an aggregation of cones (representing mountains). From this, it can be observed that the sun facing slope is the brightest, gradually loosing its brightness as the slope-aspect moves to the side facing away from the sun. Then, we verified the hypothesis by applying actual data - IKONOS data taken from a test site in Minami Gifu, and found that the method was able to compensate the topographic effect. Then we checked the method using another sensor, other data sources - Aster, LANDSAT and orthophotos, and another test site. Distinct features of the method are its simplicity and general applicability. We can compensate the topographic effect ofa variety of geo-coded data sources (i.e. Aster, LANDAT TM, IKONOS, orthophotos etc) using only digital elevation models. In addition, consistent results can be obtained no matter who operates the method, because the directional and vegetation parametersneeded are almost given. With these 2 parameters the compensation will be automatically done from the images.