Long and Ultra-Short BaseLine (LUSBL) positioning systems are particularly suited to deep water applications as they combines the repeatability derived from Long BaseLine (LBL) subsea positioning, where accuracy is virtually independent of water depth, with the operational convenience of Ultra Short BaseLine (USBL) positioning.

The high level of range redundancy ensures that in poor acoustic conditions in which deep water DP vessels often operate, or when recovering transponders for maintenance, many range measurements can be corrupted before the computed vessel position degrades.

Sonardyne’s LUSBL system design circumvents the delays of calibrating the LBL arrays by using a ‘Top Down’ calibration technique as the transponders are deployed. By not having to take baseline measurements, arrays can be calibrated quickly and reliably. An important advantage of this approach is the uninterrupted supply of acoustic information to the vessel’s DP system. This can be from arrival on station and the deployment of the first transponder, through the array calibration process and during the long term maintenance of the array.

The primary role for an acoustic positioning system on a mobile drilling unit is to provide accurate and repeatable subsea positioning for the vessel’s Dynamic Positioning (DP) system. Requirements for vessels to work in close proximity to each other and, in some instances, adopt the use of two independent acoustic systems, are demands that further extend the requirement for advanced acoustic signalling technology.

Sonardyne is meeting these challenges with Marksman LUSBL.

Marksman is a new Long and Ultra- Short BaseLine (LUSBL) acoustic positioning system that incorporates Sonardyne Wideband® signal technology to provide precise deepwater positioning, mitigate the problems of interference between vessels and allow multiple systems performing different tasks to be operated on the same vessel.

Sonardyne LUSBL systems have a proven track record on the world’s deepwater drilling and production fleet. Marksman builds upon this heritage by introducing users to the benefits of Wideband signal technology.

Sonardyne Wideband® is the first step-change in performance since acoustic positioning was introduced. It addresses the contemporary requirements of the offshore survey, construction and drilling industries for subsea acoustic positioning, communications and control and in only a few short years has become widely adopted.

Wideband signals are generated through the modulation of carrier frequencies using digital codes. Separation of signals in both frequency and code greatly extends the number of unique signals that can be supported within a defined bandwidth. This generates hundreds of truly independent navigation channels enabling multiple users to work in the same environment without causing acoustic pollution to each other. For example, using Marksman LUSBL, a rig can operate safely on DP whilst simultaneous survey operations are conducted from nearby vessels.

The technology within Marksman provides a dramatic improvement in ranging accuracy and is more robust against the levels of noise created by the thrusters of mobile drilling units.

Wideband acoustic signals are also fundamentally more robust against false detections than traditional analogue signals and are therefore better suited to real time monitoring applications such as the acoustic telemetry of BOP and riser monitoring data.

Marksman’s dual independent capability allows these operations to be conducted in parallel with positioning for drilling operations.

To find out more about Marksman LUSBL click here