Low environmental impact cabling using GPS

08 Mar 2017

Jan de Nul completed 5km of cabling through an environmentally sensitive area in just five days with the help of centimetre-level RTK positioning using Septentrio’s AsteRx-U GPS system.

The Race Bank windfarm, located about 27 km off the Norfolk
coast in England, will be home to 91 wind turbines come 2018.

Because cabling from the new windfarm will reach the English
coast at a national nature reserve known as The Wash, an important staging post
for migratory seabirds, the development had to comply with strict environmental

For Jan De Nul, the challenge was how to lay underground
cables through the salt marshes and mud flats with minimal disturbance to the

The project involved the use of its two large low-impact
cable laying machines called Sunfish and Moonfish.

Sunfish, which is able to operate in water up to 16.4 ft
deep and lay cable 4.92 ft below ground, laid the cable on the salt marsh

When the cable reached the mud flats and a deeper burial
depth was required, Moonfish took over. The remotely operated Moonfish can work
fully submerged laying cables to a depth of 19.68 ft.

Septentrio’s AsteRx-U GPS system was installed at the top of
the two 18m high masts on either side of Moonfish which provided a dual-antenna
system locating both the position and heading of the vehicle. This ensured that
the position of the cable route could be easily marked out.

When the water got too deep for Moonfish, the cable-laying
vessel Isaac Newton took over to lay the final section. The same high-precision
GPS system was used to lay the cable in exactly the right position.

Septentrio designs, manufactures and sells high-precision
multi-frequency multi-constellation GPS/GNSS equipment for a variety of
different applications.

By Anne-Marie Causer

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