The Kongsberg GeoSwath Plus interferometric sonar provides both underwater sound imaging as well as bathymetry. The working frequency is 250 kHz. Sound emission is similar to side-scan sonar. Reception of the scattered signal is done by an antenna array. The phase difference of the returning signal is used to calculate the grazing angle. The distance to the target is computed by precisely knowing the speed of sound in the water column. Each ping provides a cloud of approximately 5000 points distributed over the swath.
It can track the bottom to a depth of 100 meters. The vertical resolution of the bathymetric data can get down to 3 millimetres. The covered swath can get up to 12 times the water depth, a huge improvement from traditional multibeam systems, providing more coverage, reducing the survey time and greatly improving safety when surveying in hazardous shallow waters.
The positioning is done using an Applanix POS MV WaveMaster system, incorporating high quality inertial sensors with GPS/DGPS. The precision of the positioning is improved by RTK corrections radio transmitted from a Trimble BX982 base station to Pacific Crest ADL Vantage rover. The solution provides a sturdy georeferencing of the data.
This device is the best choice for working in shallow water, especially from 5 to 100 m deep, where its high frequency provides high resolution.
