Robust source localization using the generalized array invariant and a vertical array

The array invariant approach for passive localization utilizes multiple arrivals separated in beam angle and travel time via conventional plane-wave beamforming using either a horizontal or vertical array in shallow-water. Since this approach does not require precise knowledge of the environment and an acoustic propagation model, it is robust to environmental fluctuations. In addition, the approach is essentially equivalent to the waveguide invariant β based on the dispersion relationship between the group and phase speeds when β = 1, a generic value in ideal waveguides. However, the array invariant can be applicable to many shallow-water environments where the surface-bottom reflected arrivals behave similarly to those in ideal waveguides, simply using β = 1. By incorporating the waveguide invariant, the array invariant can be extended to general waveguides, referred to as generalized array invariant that is fully supported by the waveguide invariant physics. This dissertation presents the relationship between the waveguide invariant and array invariant, demonstrations with several experimental data using the generalized array invariant with a short- or long-aperture vertical array, and an impact of array tilt on the array invariant-based source-range estimation.• HF97 (High Frequency 1997) experiment: Demonstration of the robustness of source-range estimation using a 12-m vertical array for a source (2–3 kHz) at 6-km range in ∼100-m deep water in a fluctuating ocean environment over a day.• RADAR07 (Random Array of Drifting Acoustic Receivers 2007) experiment: Range-dependent environment with a sloping bottom using a 2.8-m vertical array for a moving source (2–3.5 kHz) between 0.5 and 5 km in range with the water depth varying from 80 to 50 m.• SAVEX15 (Shallow-water Acoustic Variability EXperiment 2015) experiment: Range-independent environment using a large-aperture (about 56 m) sparse vertical array for a moving source (0.5–2 kHz) between 1.5 and 3.5 km in range in ∼100-m deep water.• KAM11 (The Kauai Acomms MURI 2011) experiment: Impact of array tilt on source range using a 1.2-m vertical array for a moored source (7–19 kHz) at 3-km range in ∼100-m deep water