Depth-based passive tracking of submerged sources in the deep ocean using a vertical line array

Vertical line arrays (VLAs) deployed below the critical depth in deep ocean environments have been shown to have lower levels of distant shipping noise [1]. In addition, acoustic energy from nearby targets travels via the Reliable Acoustic Path (RAP), and thus has an enhanced signal level. The combination of these two factors produces a favorable detection scenario. However, nearby surface ship interference will also travel via the RAP and can obscure targets of interest. In this paper, a method is presented for discrimination of surface versus submerged sources. The method exploits a robust feature of the propagation physics and is implemented by taking a transform of the beam output to produce an estimate of the source depth. Results are shown for submerged sources in the presence of surface interference.