Qualitative and Quantitative Description of Multibeam Echosounder Systematic Errors on Rocky Areas

This paper deals with the problem of systematic depth errors made in surveying dumped rocks with multibeam echosounder. These errors may induce dangers for navigation in very shallow water areas or huge costs for coastal engineering contractors who perform rock dumping operation and surveying. We analyze results from four different multibeam echosounder systems and compare those data to a reference digital terrain model of a dumped rocks area obtained from a 3D terrestrial laser scanner. The systematic depth errors are statistically described and analysed on local areas. Finally, we propose a look-up table linking the error amplitude with the rock size, resulting from our error analysis.