Hydrographic Survey (Bathymetric Survey)

Bathymetry is performed to map the under-water bottom with a high level of accuracy. It will help correlation and interpretation of the data obtained from other methods, which yield sub-bottom information and allow a quality check of the results. Since the other methods measure thickness from the bottom, this accuracy is essential.

image066The principle of the method is to send an acoustic signal and measure the travel time to derive a depth. This depth conversion process is done by first measuring the velocity of sound in the water at different depths. This calibration is done twice a day to ensure a good accuracy.

The water depth measurements can be expected to be accurate to within ± 10 cm.The bathymetry equipment is a small equipment which is mounted on a boat and survey conducted along with other geo-physical methods.

Survey is conducted in a grid pattern. The line spacing is decided based on the resolution required. The accurate positioning is achieved using a Differential Global Positioning System.