A computer control system and method is disclosed. Such a system may include a processor and an ultrasonic area-array sensor configured to receive a ridged surface, such as one or more digits of a hand. The processor may be configured to: (a) acquire a first information set from the sensor, the first information set representing at least a portion of the ridged surface, (b) acquire a second information set from the sensor, the second information set representing at least a portion of the ridged surface, (c) compare the first information set with the second information set to identify a common feature of the ridged surface that is present in both the first information set and the second information set, (d) determine a first position of the common feature using the first information set, (e) determine a second position of the common feature using the second information set, and (f) calculate a control measurement by comparing the first position and the second position.