The Three-Dimensional Surface Shell Correlator uses range-only data from an active ranging sensor and a 3-D model of the target area stored in memory to guide a missile during its terminal phase. For each trial position the algorithm simulates a sensed range image using the 3-D model and a fast hidden-surface suppression routine, and compares it to the actual sensed range image. The resulting correlation surface is searched selectively rather than exhaustively to find the best estimate of vehicle position. A selective search is described which is highly efficient because it uses a certain inherent "ridge" structure in the correlation surface to guide it.
Charles B. Grosch,
"Three-Dimensional Surface Shell Correlator", Proc. SPIE 0186, Digital Processing of Aerial Images, (4 September 1979); doi: 10.1117/12.957497; https://doi.org/10.1117/12.957497