Single-phone source tracking in a variable environment.

M.B. Porter
Dep. of Applied Mathematics, New Jersey Institute of Technology, NJ, USA
S.M. Jesus
UCEH - Universidade do Algarve, Faro, Portugal
Y. Stephan
Centre Militaire d'Oceanographie - SHOM, Brest, France
E. Coelho
Instituto Hidrografico, Lisboa, Portugal
X. Demoulin
Centre Militaire Oceanographique - SHOM, Brest, France

Comments: download pdf file .
Ref.: in 4th European Conf. on Underwater Acoustics, (ISBN: 88-87447-02-0), pp. 575-580, Rome, Italy,  1998 (invited).

Abstract : Internal tides commonly occur along ocean coasts. They are internal waves driven by usual tidal force and generated by scattering at a sharp bottom feature such as the shelf break. The internal tides are dramatic features with crests tipically 10-30 km apart and wave heights of 20 m. On the ocean surface they cause only a gentle ripple about 10 cm high but they affect the shine of the surface. As a results, astronauts often see them as the tides propagate away from the shelf break. In June 1996, a shallow water tomography experiment (INTIMATE 96) was conducted off the coast of Portugal to observe these internal tides and learn about their acoustic effects. A source was towed around a vertical hydrophone array to produce acoustic sections along several slices. The experiment also provided and ideal opportunity for testing model-based source tracking. Acoustic sections taken parallel to the Portuguese coast allowed us to understand the propagation physics in a range-independent area. With this we have been able to develop a matched-field algorithm suitable for use in the far more complicated downslope direction which, being perpendicular to the crests of the internal tides, also experiences strong ocean-temperature variations. We will discuss both the approach and the source tracking.

ACKNOWLEDGMENT: this work was partially supported by PRAXIS XXI program under project 2./2.1/MAR/1695/95.