This paper presents a three dimensional localization method for underwater acoustic positioning systems. In typical ultra-short baseline (USBL) acoustic positioning systems, the three dimensional position is localized by using multiple time difference of arrivals (TDOAs). Since the TDOA accuracy is less than the other sensor data, we focus on a localization method with the minimum number of TDOA. We propose a method of transmitting depth data by pulse position modulation (PPM), where the target

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... position is localized by a single TDOA, a distance, and a depth. The proposed method shows a higher positional accuracy than the conventional method with two TDOAs. The effectiveness of the proposed method has been demonstrated in the evaluation of simulation and experiment.