Color sonar for underwater object collision avoidance

Abstract

A method and apparatus for presenting elevation angle information with rect to overhanging objects to an operator of a submersible incorporates a substantial portion of the sonar equipment found onboard conventional submersibles. Reflections of radiant energy from the objects are received by a highly directional array of hydrophones. The received reflections are time varying gain attenuated to substantially compensate for range-dependent signal variations such as are due to changes in scattering areas, spreading loss and attenuation loss. Using time varying gain processing and by taking into account the known directivity pattern of the hydrophones, the received reflections are reduced to represent signal characteristics due substantially to the elevation angle of the incoming reflections. These modulated reflections are quantized by first sorting the reflections into bands according to amplitude intensity and then by assigning a distinct color to the individual bands. The quantized reflections are then converted into color display signals according to their assigned colors, and the signals are displayed upon a color visual display to reveal object elevation angle information as distinct shades of color.