Secondary Detection of MRU Position Deviation and Terrain Elimination of Multi-beam Abnormal Stripe

Objectives The anomaly along-track stripes which often appear in the multi-beam sounding data have significant influence on shallow water. Aiming at the problem that the mechanism of traditional methods is not perfect and the elimination of anomalies is not complete, the causes are analyzed based on the multi-beam data processing principle. It is considered that the main reason is induced heave compensation residual caused by uncompensated induced heave or inaccurate measurement of position deviation of motion reference unit（MRU).

Methods For this reason, a method of position deviation detection and elimination of abnormal stripes based on the sounding data of common coverage area is proposed. First, homologous point pairs are found by automatic nearest plane point searching. Second, the relationship model between the water depth difference of the homologous point and the position deviation to be detected was constructed, and the position deviation was estimated by support vector machine regression parameter robust estimation method. Finally, a modified model is given to eliminate the influence of abnormal stripes in the sounding data.

Results Experimental results show that: (1) After the calibration of the proposed method, the standard deviation of the difference between the common coverage area of the round-trip lines decreases from 8.5 cm to 2.6 cm. (2) The mutual difference between the detection results of each section is about 1 cm. (3) The proposed method performs (significantly different) on adjacent lines with 50% and 15% overlap area, with standard deviations decreasing from 6.9 cm to 3.9 cm and from 12.9 cm to 7.6 cm, respectively. (4) Using the detected relative position deviation to correct the entire measurement area, the standard deviation of the discrepancy value in the common coverage area is reduced from 0.07 m to 0.03 m.

Conclusions The proposed method can completely eliminate the influence of abnormal sounding stripes and provide a new method for detecting MRU installation deviation. However, the results are affected by the overlap area of the adjacent lines, so it is recommended to be performed on the round-trip lines whenever possible.