This is an iquiry for a co-worker, in an area of expertise which I have only a vague understanding. Is there a software available which aids in land development design in a situation where land grade interpolation can be generated based on particular criteria such as elevation at centerline in relation to elevation at building setback line, existing and proposed? My poor friend is doing these calculations by hand with magic marker and white-out on 200-lot subdivisions. What program are people using?