抄録
A modified cosine correction algorithm is developed for correcting atmospheric and topographic effects on Landsat TM imagery over rugged terrain. First, a relationship between offset component (such as path radiance) and terrain height is evaluated using 6S code as well as actual satellite data in shadowed area. It is shown that the offset component decreases significantly in visible bands as the height increases, while it can be assumed constant in infrared bands. Next, we examine the relationship between local topography and sensor radiance, which is expected to follow the cosine law of solar incident angle. Their correlation is high in all bands, but is higher in infrared bands which contains more direct solar irradiance due to high reflectance of vegetation. We apply the modified cosine correction (offset correction and the cosine law correction) to actual Landsat TM images with high solar elevation angle. The results can be judged good not only by visual interpretation but also from a statistical viewpoint. It is emphasized that the accurate DEM is necessary both for ortho rectification and cosine law correction.
