Better Accuracy from Sidescan Records: The Object-Chord Method

Author : Malcolm James & P.M. Tong
Publication : Bulletin of the Geological Society of Malaysia
Page : 189-207
Volume Number : 22
Year : 1988

Bulletin of the Geological Society of Malaysia, Volume 22, Dec. 1988; pp. 189 – 207

Better Accuracy from Sidescan Records: The Object-Chord Method


Racal Survey Malaysia Sdn Bhd


Abstract: Sidescan Sonar has become a widely used and often indispensable tool for seafloor engineering and survey activities in the oil industry. This acoustic technique has the ability to create a wide and continuous ‘picture‘ of the 3-dimensional seafloor features and contours, and therefore permits quick and economical acquisition of seafloor information which is not readily available through other types of acoustic instrumentation.

The accuracy of mapped objects interpreted from this method has been limited by the fact that the fish is towed a distance from the vessel and its position is affected by different sea states and current conditions resulting in different feathering angles and layback distances.

Some present interpretation techniques do take into account the uncertain feathering angles of the fish, but they assume no errors in both the layback distances. The object-chord method takes into account both the feathering angle and layback errors and in certain circumstances, due to good field practices, eliminates them, resulting in more accurate positions mapped.