Optimizing hydrographic operations for bathymetric measurements using multibeam echosounders

Abstract

Detailed information about the sea and river bed is of high importance for a large number of applications, such as marine geology, coastal engineering, safe navigation and offshore construction. Acoustic remote sensing techniques have become extremely attractive for obtaining bathymetry measurements and for mapping the sediment properties, due to their high coverage capabilities and relatively low costs. Among the available tools for remotely mapping the seafloor, the MultiBeam EchoSounder (MBES) belongs to the state-of-the-art technology enabling acquisition of high resolution measurements of bathymetry within a relatively short time period. Despite the widespread use of MBESs for hydrographic operations and the considerable efforts devoted to optimize these operations, the existing knowledge with regard to the measurement capabilities of the MBES is lacking in some respects. This can lead to an unreliable and inaccurate representation of the seafloor and/or unrealistic estimates of the measurement uncertainties. Moreover, realistic pre-survey predictions of the contribution of the various uncertainty sources affecting the quality of the bathymetric measurements is of importance to ensure sufficient accuracy of the soundings and a correct interpretation of the sediment properties. This thesis thus aims at bringing the insight of the MBES measurement capabilities to a new stage by addressing these issues. The contribution of this thesis to the field of MBES bathymetric mapping is to bring the knowledge of the MBES measurements capabilities to a stage such that hydrographic operations are optimized. This leads to a reliable and accurate representation of the bottom and a realistic expectation of the associated uncertainties. Optimizing hydrographic operations is accomplished by correcting the systematic errors (if present), using a realistic depth uncertainty prediction model and addressing proper distribution of the soundings while ensuring low uncertainties of the measurement. These issues allow for realistic bathymetry maps and need to be accounted for in survey planning.