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Offshore Support Journal

Offshore Support Journal

Targetless position sensor uses radar rather than lasers

Thu 13 Apr 2017

Targetless position sensor uses radar rather than lasers
Guidance Marine’s RangeGuard is ideal for multi-asset environments such as offshore wind

Position reference sensors are essential for dynamic positioning of offshore vessels but a new approach was needed in the offshore wind industry  

The OSJ award for dynamic positioning, which was sponsored by ABB, is awarded to the developer of an innovative DP product or system, or contractor responsible for an especially innovative application of DP on a project. In 2017, that product was Guidance Marine’s RangeGuard, an award that the company said was “a badge of honour that the company will wear with pride, having been made all the sweeter that it is industry recognised from the company's peers within the maritime world.”

Describing the innovation, Jan Groothuizen, group chief executive at Guidance Marine, said RangeGuard was the first time the company had brought targetless position sensing for DP to the position reference market. “RangeGuard has really moved the position reference sensor market forward, from laser radar technology to true, targetless technology. It can deliver real time savings and cost savings,” he explained. “We love innovation, but as always technology on its own cannot win. You need fantastic partners, so I would like to thank our integrator partners on this particular project, Marine Technologies and our end customer Bernhard Schulte, on whose vessel Windea la Cour RangeGuard was installed.”

As highlighted by Mr Groothuizen, RangeGuard is the first sensor from Guidance Marine that does not use physical targets. It uses radar reflections from its surroundings to calculate precisely the vessel’s range to the nearest object in its field of view. Combining the information from two sensors allows range and bearing to be calculated and input into the DP system of a vessel to give the first targetless DP local position reference sensor (PRS).

“RangeGuard introduces a new method of position measurement – fully independent of DGPS or laser systems,” said Andrew Stead, the company’s head of sales. “The elimination of targets delivers significant cost and operational benefits in sectors such as offshore wind, with every gangway or walk-to-work deployment. In a multi-asset environment such as a windfarm the case for RangeGuard becomes overwhelming.” Rather than using dedicated physical targets, the system uses the local environment as its target – typically the leg or lower tower of a wind turbine. Removing the need for physical targets to be installed makes the vessel completely independent and can increase both safety and decrease turnaround times.

A vessel usually approaches an offshore wind turbine on DP and, typically, uses differential GPS and a laser PRS to obtain precise position. If poor quality reflector targets are installed on the wind turbine it can lead to the laser sensor detecting false reflections due to their proximity to other highly reflective surfaces, such as the high vis jackets of workmen on the landing platform and walk-to-work gangway. To overcome this problem, high quality reflective prism targets should replace low quality reflectors, but the cost of installing these on every single wind turbine in a windfarm can be prohibitive. Removing the need for physical targets altogether is a step change in windfarm navigation.

After the promising results obtained during the trials on Ocean Zephyr, Bernhard Schulte decided to make full use of the potential of RangeGuard and install a fully DP integrated system on its new service operation vessels Windea La Cour.

Other advantages cited by the company include the fact that it requires little or no maintenance, can detect objects within 300m, it has no moving parts, provides an additional form of redundancy, and reduces turnaround times.

Other entrants in the DP award who were shortlisted were:

  • The Marine Training Institute, Gray, Louisiana, the first training provider to be accredited to conduct OSVDPA DPO training courses and assessments
  • DP & Marine Assurance Norway for its remote DP trials concept
  • DNV GL for its new, open industry standard for assessing the position-keeping ability of vessels.

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