PURPOSE: To correct a sonar observation data by accurately surveying the position of a sonar body with respect to the sea bottom.
CONSTITUTION: A sonar buoy 40 comprises narrow beam sonar heads 80, 82 driven through a stepper motor. The buoy is operated by means of a crane wire 41 being held in stretched state by means of a float above the buoy and connected with a stationary clamp weight 46 on the sea bottom. A wire 50 is entrained about the pulley 52 of a weight 46 starting from a winch 48 and coupled with the lever 54 of a jinbal mechanism 56 having two converters 62, 70 for measuring 'X' and 'Y' positions of the buoy. A footage mechanism 76 is driven by the wire 41 and has a converter for surveying the heave position. A compass 88 and a roll/pitch converter 86 survey the orientation and the roll/ pitch position. A sonar data is compensated for the position of the buoy using a computer.