A method to eliminate refraction artifacts in EM1002 multibeam echosounder system (Swath bathymetry and seabed surveys of EEZ)

Abstract

The multi-beam echo-sounder systems acquire bathymetry data with additional information. This supplementary data along with proper bathymetry can be further used in scientific studies. As observed most of the multi-beam data is occasionally recorded with errors, either geometrical or refraction in nature. But to obtain a map that can be used either for navigation or scientific purposes, it is necessary that the data is error free. As per IHO standards the refraction affected data in shallow waters include uncertainties from navigation point of view. Also, to use in scientific applications it is vital to eliminate these errors from the bathymetry data. The refraction error influences the slant ranged beams and can be easily identified, as the swath shape deviates creating artificial features known as refraction artifacts. In 2007, we conducted an experiment off Goa region and collected multi-beam depth data and sound speed profiles. The reason for this experiment was to analyze the data, identify the errors and develop a software to eliminate the refraction artifacts (in bathymetry data) caused due to the combined effect of wrong sound speed profile and the beam steering offsets (stored in 'calib.txt' file)