NCS Subsea to Boost Survey Positioning Efficiency

NCS has purchased the equipment specifically to reduce the vessel time needed to position seismic cables and ground stations once they have been deployed on the seabed. Conventional techniques require a recording vessel to pass down both sides of the cable, collecting multiple acoustic ranges from transponders attached to the cable at regular intervals. Whilst this method is very accurate, the process takes time and also relies upon good geometry from the vessel to each transponder.

The NCS survey team's approach has been to use the Scout-Pro USBL systems interfaced to their own survey instruments to create a fully integrated navigation solution. With Scout, a vessel-mounted transceiver measures both the range and bearing to each cable-mounted transponder. The recording vessel is therefore able to position the cable in one overhead pass, saving vessel time and making for very efficient surveys.

Sonardyne's HydroPos navigation software remotely controls the Scout USBL system. It manages the large number of acoustic transponders deployed and creates pre-plot data for the system to follow and automatically search for the correct transponders along the cable. Position solutions are calculated in HydroPos and can be outputted in various industry standard file formats.

The Scout transceiver is small and lightweight and ideal for deploying over the side of small survey boats. An internal heading, pitch and roll sensor eliminates the need for the unit to be interfaced to external motion sensors in order to both calibrate the system and provide the necessary compensation for vessel movement all USBL systems require. After data acquisition, the deployment pole to which the transceiver is attached is lifted, enabling the recording vessel to quickly move to its next survey location.