Adaptive array invariant for source-range estimation in shallow water

Abstract

The array invariant (χ) developed for source-range estimation in shallow water is based on the broadband dispersion characteristics in ideal waveguides, summarized by the waveguide invariant, β = cos2θ. This approach relies on the waveguide invariant being constant (e.g., β = 1), valid for small propagation angles, but introduces a significant range error as the propagation angle increases. In this talk, the standard array invariant is extended to fully incorporate the angle dependence of the waveguide invariant, referred to as the adaptive array invariant, denoted by χβ = χ/β. The remarkable performance enhancement is demonstrated (1) using a 56.25 m vertical array for a surface ship (200–900 Hz) in approximately 100-m shallow water and (2) using a 2.8 m vertical array for a broadband source (0.5–3.5 kHz) towed on a continental slope where the water depth varies from 87.5 to 55 m over a 5-km range.