The discovery and progression towards development of increasingly deepwater fields in recent years has been obvious, as has the increase in technology developed to support the technological challenges associated with this.

Developments are becoming faster and more cost efficient, but this puts pressures on schedules with offshore SIMOPs becoming ever more commonplace, and vessel and rig operations more safety critical. Maintaining position is a key part of safe SIMOPs, with the vast majority of vessels now being equipped with DP systems for station keeping. These systems are technological wonders, but are completely dependent on the quality of data being provided to them from the various sensors. Surface positioning today is very much reliant on Global Navigation Satellite Systems (GNSS) of which GPS (Global Positioning System) is the current preeminent example.

Although often perceived as ever reliable, GNSS signals are vulnerable to interference with one major source being from charged particles in the earth's atmosphere. During periods of increased sunspot activity a charged stream of solar particles (the solar wind) interacting with the earth's ionosphere can create geomagnetic ‘storms’ which can affect all radio signals (including those used by GNSS) up to and including complete loss of signal. These effects are often referred to as scintillation, which is a rapid fluctuation in signal phase and amplitude.

Acoustic positioning solutions are therefore a critical component of the DP system, but historically seen as a poor relation to satellite positioning

The challenges associated with acoustic positioning systems, from technical and commercial aspects, along with a potential solution, will be explained and discussed over the next few pages.

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