Multibeam-echosounder Accuracy Verification Experimental Method and Initial Results

Abstract

In the past, the multibeam-echosounder (MBES), which performs seafloor depth measuring, detection, and hydrographic surveying, has been used only for observation targets that far exceed the error level. However, AUV and sea surface platform surveys, which have high positioning accuracy, is beginning to be used to the increasing needs for high-accuracy monitoring, e.g., hydrographic surveys, harbor surveys, seafloor detection such as shipwrecks, and exploration of resources, volcanoes, and faults. The significance of properly recognizing and evaluating errors of the MBES is increasing. In this study, we describe a method of acquiring the MBES observation data in the tank space precisely measured by the total stations to verify the accuracy. According to the method proposed in this study, it is feasible to evaluate the accuracy of a device itself on the order of cm. We also report the results of the actual experiment as follows; the ranging accuracy directly under the MBES was about 1–1.5 cm regardless of the distance and depends on the pulse length (T=30µs): the accuracy was worse than expected when the beam angle changed: the seafloor detection accuracy, which depends on the angular resolution, was about twice the footprint. The above experimental findings are not completely consistent with theoretical predictions and require further research, which contributes to the prediction of accuracy and detection performance.