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The short-time signal anomaly of Global Positioning System (GPS) often occurs in the process of multi-beam bathymetry, which leads to the poor accuracy of multi-beam acoustic emission of instantaneous position datum and affects the underwater topographic survey accuracy to a large extent. This study proposes a novel method to reconstruct multi-beam transducer instantaneous datum in the event of the short-time GPS signal anomaly to solve this problem. First, the synchronization of GPS and inertial measurement unit (IMU) was realized by establishing the correlation coefficient model. Second, the fast Fourier transformation filter was used to extract the long-period signal from the GPS elevation signal, which was repaired according to the Heave sequence, and the instantaneous elevation datum was reconstructed through attitude correction. Finally, the original plane information was obtained through Kalman filtering. The error accumulation of the original plane information was eliminated by using the fixed solution which had returned to normal, and then the instantaneous plane datum was reconstructed. The reliability of this method was proven through simulation experiments. Results demonstrate that the similarity between the GPS elevation sequence and Heave sequence can synchronize GPS and IMU. In addition, the instantaneous datum accuracy of the multi-beam transducer reconstructed through this method can reach the necessary cm-level to satisfy the requirements for the positioning accuracy in open water. The proposed method can establish a highly precise basis of data for the underwater seabed topographic monitor of signal anomaly areas in quayside and sea-crossing bridges.

Instantaneous Datum Reconstruction Method of Multi-Beam Transducer in Short- Time GPS Signal Anomaly