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.

Consistency and accuracy of perturbative inversion methods for group travel time data.

Perturbation theory for ocean acoustic modal group speed responses to small environmental changes is investigated with regard to its applicability to ocean acoustic tomography. Assuming adiabaticity, the inverse problem for each vertical eigenmode is an integral equation whose kernel involves the eigenfunction and its frequency derivative. A proof is given for the equivalence of two dissimilar forms of the integral equation.