Exploiting reliable features of the ocean channel response

M.B. Porter porter@mpl.ucsd.edu
Dep. of Applied Mathematics
New Jersey Institute of Technology, NJ, USA
S.M. Jesus sjesus@ualg.pt
UCEH - Universidade do Algarve
Faro, Portugal
Y. Stephan stephan@shom.fr
Centre Militaire d'Oceanographie - SHOM
Brest, France
X. Demoulin demoulin@shom.fr
Centre Militaire d'Oceanographie - SHOM
Brest, France
E. Coelho Instituto Hidrografico
Lisboa, Portugal

Comments: download pdf file .
Ref.: in Proc. of Shallow Water Acoustics Conference'97, p.77-82, Beijing, China, 1997 (invited).

Abstract: modelling sound propagation is notoriuosly difficult. The main difficulties are, of course, ocean variability characteristic of coastal waters the tipically downward refracting profiles that makes the acoustic field extremely sensitive to bottom characteristics. Meanwhile accurate prediction of transmission loss curves at a single frequency requires that the relative phase of each single surface and bottom echo is predicted with precision. It is a daunting task even for systems that will operate in carefully surveyed areas. On the other hand, certain features of the channel response are extremely robust. A long broadband chirp can be compressed to the equivalent of a short ping which is heard as a sequence of distinct surface and bottom echoes. Using data of the INTIMATE'96 tomography experiment we show how these characteristics can be exploited in the signal-processing to provide robust tracking of a source over several days.

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