Abstract: A sonar depth sounder system is provided in which a plurality of elements are combined to form a sonar transducer capable of generating a plurality of narrow overlapping beams and receiving sonar echoes. The sonar return information is filtered, amplified through a log converter, digitized and then analyzed by a high-speed microprocessor. This analysis stage combines information obtained from each one of the plurality of sound beams generated by the transducers, determines correct target location and size, distinguishes fish from other targets such as thermoclines or structure based on heuristic algorithms and provides an output data set for display. Representations of three-dimensional submerged structures are presented in a variety of formats to the user, including utilizing a grid line display of the contour of the bottom surface and location lines from displayed fish above the surface to grid lines on the bottom surface display.

Abstract: An improved microprocessor-controlled sonar depth sounder, which is automatically operative to detect and lock to the bottom of a body of water, fill in the display below the detected bottom, change display scales in response to the detected bottom going off-scale, and reformat the entire display in response to a scale change. A memory is provided for storing target data up to the operable depth limits of the device, thereby allowing display reversing and display expansion or "zoom" of a predetermined portion of the display selected by a zoom cursor. The zoom or cursor is variably positionable at different depths. The device employs an improved variable sensitivity amplifier. Also disclosed is an improved water-resistant switch construction for marine electronic equipment.