Posted on 29.07.2009 - 10:00 EDT in SURVEY NEWS by Rons_ROV_Links
Marine navigation services company NCS SubSea Inc. based in Houston, has invested in Sonardyne Scout-Pro USBL (Ultra-Short BaseLine) acoustic positioning technology for a major ocean bottom seismic survey offshore Kazakhstan. The order also includes low-cost acoustic beacons, advanced Wideband Sub-Mini (WSM) tracking transponders, lightweight acoustic release transponders and Sonardyne's HydroPos navigation software.
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.
Commenting on the benefits gained from using Scout-Pro and transponder hardware in this way, Curtis Sims Jr, general manager of NCS SubSea said, "Scout is now an integral component of our Distributed Navigation System which we have developed for TZ and OBC seismic acquisition. It can be rapidly deployed on vessels of opportunity from the smallest skiff to the largest gun boat." He added, "Our crews in the field have reported that the Sonardyne system has been a real boost to productivity. At times they have had the system operating in less than three metres of water and the recording boat right over the top of the cable without any loss of positioning data."
The Scout-Pro systems and transponders were manufactured at Sonardyne's factory and head office in Yateley, Hampshire, UK. The company also has regional operating subsidiaries in Singapore, Houston, Aberdeen and Brazil and is recognised as a world leader in the design and manufacture of underwater acoustic positioning, inertial navigation, subsea communications and sonar technology systems for the offshore oil and gas, ocean scientific and maritime security industries.