Matched field source localization in an uncertain environment using constraints based on sound-speed perturbations
Matched field source localization methods can be seriously degraded due to errors in modeling the propagation characteristics of the ocean channel. A maximum likelihood (ML) matched field beamformer is presented which achieves greater robustness to model mismatch caused bay uncertainty in the sound-speed profile between the source and receiver. The proposed modification of the standard ML beamformer consists of using multiple linear constraints derived from predicted pressure fields obtained using a set of perturbed sound-speed profiles. To investigate the nature of wavefront variations due to random sound-speed perturbations, a normal mode model based on adiabatic and first-order perturbation approximations is examined. This model suggests that the dimension of the new beamformer's signal constraint space can be small for moderate source ranges and sound-speed variations. Simulation results in a realistic deep-water Pacific ocean environment are reported which suggest that unambiguous source location estimates can be achieved at low frequencies with a sound-speed profile mismatch as large as 5 meters/second.