Xix . Detection and Estimation Theory

a. Current echo sounders for oceanographic survey ships have a quoted accuracy of 2-3o which implies a topographic resolution in excess of 700-1000 ft at deep-water depths of 20, 000 ft. The random characteristics of the ocean channel caused by effects, such as turbulence, internal waves, scattering, and ambient noise, in addition to the random errors in measuring platform orientation, will limit further improvements in accuracy. Work has commenced for determining the following. (i) The point at which these effects become significant for conventional echosounding methods with a large array. (ii) Potential improvements that could be obtained by signal processing which exploits the statistical characteristics of the signal. (iii) Data processing methods of multibeam signals that would permit surveillance of large geographical regions with enhanced accuracy. b. There are many situations in which the propagation effects of the channel have a significant effect upon the signals observed. These effects are particularly interesting when the signal propagates through a layered medium where appreciable distortion and multiple travel paths are often encountered. Current analyses are deterministic and are confined to methods such as ray tracing or mode analysis. While there is a limited number of results available, at present, which involve the characteristics of random processes propagated over these channels, we are investigating several topics in this area of process propagation for the sonar, or underwater, channel where random effects and receiver structure implementation are issues in the analysis.