1. A system for determining surface height, comprising: a sensor array for producing data about a volume in which surface height is to be determined, said volume being divided into a plurality of voxels which are to be classified; a plurality of surface modeling rules for providing domain information for interpreting data from said sensor array, for enforcing spatial constraints vertically among voxels, and for enforcing spatial constraints horizontally among columns of voxels; and an inference engine responsive to said sensor array and said surface modeling rules so to classify each voxel, at least certain of said voxels being classified as surface.