Automatic matched-field tracking with table lookup

In matched-field processing, the signals measured at sensors in an array are correlated with the expected signals for a target at a specified point in the environment. This tends to be a computer intensive process because there are a large number of possible target locations and the calculation of the sound field may be complicated. A search by an operator for the target involves examination of various cuts through a multi-dimensional search space. In this paper it is shown that use of table lookup simplifies the modeling problem. Also, by use of matched-field tracking, the data can be processed in large time (∼3 to 10 min) blocks. Using these methods, the processing can be done in real time with little, or no, operator intervention. An example of automatic matched-field tracking is presented using data collected during a shallow water test near San Clemente Island. Finally, a simple sensitivity study is made. The actual sound speed profile is replaced by one modified by low-pass filtering and, in a second case, by a constant speed profile. The results show that matched-field tracking, although degraded, still provides useful tracking data.