Improved GNSS/Acoustic Underwater Positioning with Between-Buoy Baseline Constraint

Continuous seafloor transponder positioning with moored buoy observation system is an indispensable method for detecting seafloor crustal deformation. However, the between-buoy baseline information provided by the global navigation satellite system (GNSS) relative positioning, the precision of which can be up to centimeter level or even higher, is not introduced into the conventional joint adjustment method. The accuracy of seafloor transponder positioning might be improved if high-precision baseline information is taken into account. In this contribution, a joint adjustment (IJA) method with between-buoy baseline constraints is proposed for the GNSS acoustic (GNSS/A) underwater precise positioning system with moored buoy observation system. Specifically, the positions of both acoustic transducer and transponder are treated as unknown parameters, and the positions of the acoustic transducer provided by GNSS positioning are introduced as virtual observations. Between-buoy baseline information is also introduced to further improve the precision of underwater positioning. To verify the performance of the improved joint adjustment method, a series of simulation tests were carried out. Simulation results show that the positioning accuracy with the proposed method can be improved by about 24%-53% compared with the traditional method and 7%-44% compared with the joint adjustment method.