W. Kenneth Steward Xiaoou Tang Dezhang Chu
Dept. of Appl. Ocean Phys. and Eng., Woods Hole Oceanogr. Inst., Woods Hole, MA 02543
It is usually difficult to use autonomous underwater vehicles (AUV) for locating targets in shallow-water ocean environments due to the strong wave surge and multipath acoustic reverberations. A preliminary study of some environmental effects unique for a shallow-water sound channel helps place bounds on possible solutions and reduce program uncertainty. Accordingly, three interrelated issues are addressed in this paper: Signal masking by shallow-water reverberation, signal loss caused by extreme platform motions, and shallow-water acoustic navigation. A model estimating the signal motion loss and the average reverberation intensity in the shallow-water environment is developed. The computer simulation of multisensor navigation serves not only as a precise vehicle-positioning device but also as the platform motion data input for the model. As a result of the shallow-water experiments and acoustic modeling, conclusions of this preliminary study are (1) SML is not the dominant factor for sonars in the frequency range of interest (>200 kHz) with respect to target detectability, (2) beam patterns can be manipulated to effectively reject most interferences caused by surface reverberation and noise, and (3) a multisensor navigation filter is practical even with limited sensor data quality.