A convenient transponder-type telemetry system for the successive tracking of underwater objects was developed. In this system microphone A of a set of two is set up on the ship\u27s side and microphone B is suspended from the bouy at the end of the towing-rope. The distance between the two microphones and the direction from B to A compose a base line. The distances of the three sides of a triangle formed by the transponder and the two microphones are measured by converting the ultrasonic propagation time to distance. The bearing of the transponder is calculated by the direction of the base line, which is equal to the ship\u27s proceeding course, shown by the gyrocompass and the angle of intersection at microphone A\u27s set point. The ship\u27s position is fixed continuously by one of the electronic navigation systems, and consequently the position of the object is shown by geographical latitude and longitude. There are some problems to be settled on this system. In this paper, the authors discuss the results of the following tests for the problems, i. e.; (1) the deflection of the base line by the yawing of the ship\u27s head while proceeding with automatic steering; (2) the length of time while the accurate bearing of the base line is not calculated due to the curvature of the towing rope caused by altering the course; (3) the accuracy of fixes by electronic navigation systems (Decca and Loran C), which are considered the most suitable accurate systems for this plan
