Deep ocean long range underwater navigation.

A long range Underwater Navigation Algorithm (UNA) is described that provides a geolocation underwater while submerged without having to surface for a Global Navigation Satellite System (GNSS) position. The UNA only uses measured acoustic travel times from a constellation of underwater acoustic sources analogous to the constellation of satellites in GNSS. The UNA positions are calculated without any a priori track, position or sound speed information, and thus provide a "Cold Start" capability.

Optimized extraction of coherent arrivals from ambient noise correlations in a rapidly fluctuating medium.

Ambient noise correlations can be used to estimate Green's functions for passive monitoring purposes. However, this method traditionally relies on sufficient time-averaging of the noise-correlations to extract coherent arrivals (i.e.

Variability of the coherent arrivals extracted from low-frequency deep-ocean ambient noise correlations.

Correlation processing of ocean noise can be used to develop totally passive ocean monitoring methods. Using various hydrophone pair orientations, this study investigates the frequency dependence, seasonal variability, and emergence rate of coherent arrivals from cross-correlations of low frequency ambient noise (f < 40 Hz) recorded on triangular hydrophones arrays. These arrays are located at five existing hydroacoustic stations of the International Monitoring System (IMS), situated in the deep-sound channel, and distributed across the Atlantic, Pacific, and Indian Ocean basins.