I have done several algorithms for topographic correction in R including simple cosine, Minnaert, SCS. The input data aspect and slope for the hillshade raster have correctly been done in radians. The hillshade has some spots where the cos (i) is slightly below zero and these spots appear black in the corrected Landsat image. The white surroundings of the black spots are zero or slightly above. That means that cos(i) is around 90° or above in these areas. Such areas receive no direct radiation from the sun but diffuse light.
Can somebody help me with this - I mean do you know an algorithm to solve this problem? Is this phenomenon called overcorrection?
Thanks a lot S.