Adaptive computer-based spatial-filtering method for more accurate estimation of the surface velocity of debris flow.

An adaptive computer-based spatial-filtering velocimeter to measure the surface velocity of a natural debris flow with high accuracy is described that can adjust the filter parameters, specifically, the slit width of the filter, based on the surface-pattern characteristics of the flow. A computer simulation confirms the effectiveness of this technique. The surface velocity of a natural debris flow at the Mt. Yakedake Volcano, Japan, was estimated by this adaptive method, and the results were compared with those obtained by two other methods: hardware-based spatial filtering and normal computer-based spatial filtering.