Calibrating high-precision transdu cer acoustic phase centers in outfield experiments: Track design, performance analysis and model improvement

Underwater acoustic positioning is applied in seabed exploration, resource development, and environmental monitoring. The transducer plays an essential role in enabling underwater acoustic localization. To address the issue of the non-coincidence between the acoustic phase center and the geometric center of the transducer, this paper proposes a high-precision calibration method for the acoustic phase center of a transducer, specifically designed for implementation in outfield experiments. This method involves creating a virtual long baseline by converting a fixed beacon into a moving point in the carrier coordinate system via coordinate transformation. The acoustic phase center of the transducer can then be reverse-calibrated. By combining principles of observability, symmetry, and round-trip behavior with changes in the original and virtual tracks, several unresolvable features and corresponding tracks are revealed which contribute to the calibration's precision. Additionally, an improved model to resolve mismatching in the outfield response mode is also established. Outfield experiment results show that compared to the uncalibrated acoustic phase center, the proposed method improves positioning accuracy from 0.63 m to 0.22 m. Compared with the internal field calibration method, the positioning accuracy is equivalent, furthermore, this method overcomes the defect of demanding requirement of measurement environment.