Matched field processing for a short vertical array in shallow water using the geoacoustic parameters inversed from short range source data

In shallow water ocean, the multi-path structure information of acoustic signals received by a vertical array is useful for target localization. Matched field processing (MFP) is a perfect method for localization using this multi-path structure information when the environment knowledge is known completely. But the environment knowledge usually cannot be known exactly in real ocean - especially as regards the geoacoustic parameters, such as the density, sound speed and attenuation coefficient of the seabed, which are all difficult to acquire. The environment knowledge mismatch restricts matched field processing localization performance. This paper presents a method of matched field localization for a short vertical array in shallow water which can be used for target localization when knowledge of the geoacoustic parameters of the seabed is unknown. This is based on geoacoustic parameters inversion with short-range co-operative source data. The presented localization method combines a geoacoustic parameters inversion method and a broadband matched field localization method. On one hand, a geoacoustic parameters inversion method based on plane wave reflection theory is studied, using low frequency impulsive data from a short-range co-operative point source recorded on a vertical array. On the other hand, a robust broadband coherent matched field localization method in beam domain is also studied. Through real experimental data analysis it can be shown that the presented method has a good localization performance. The range estimation error of the presented method is 5% and the depth estimation error is 2 meters using the data recorded by a 7-meter vertical received array - when the signal-to-noise ratio (SNR) of array element output is 2 dB, and the target distance is 2.2 kilometers away from the received array.