Abstract: Apparatus and a method for displaying depth sounding data with nautical range are disclosed for use on vessels or the like, the device including a transceiver for transmitting an acoustic signal downwardly through surrounding water and for receiving echo signals, a motion sensor for determining nautical distance, a microprocessor for storing and conditioning the echo signals and distance signals and a display device for providing an XY display of underwater conditions represented by the echo signals. Range display means associated with or included in the display device and operated by the microprocessor display nautical range of a selected and preferably adjustable point on the X axis. The microprocessor includes a range memory stack, a stack manager and an internal register for storing bytes or distance data for successive vertical scans. The device also preferably includes a differential temperature sensor.