1. A system for determining surface height, comprising: a sensor array that produces data about a volume in which surface height is determined, said volume being divided into a plurality of voxels; a plurality of surface modeling rules that provide 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; wherein the classification of a voxel is based on the classification of neighboring voxels, wherein said surface modeling rules for enforcing spatial constraints horizontally include two interacting Markov random fields and a latent variable that interact across columns of voxels.