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Survey Vessel Geograph, North Atlantic, May 2008
Typical route survey vessel - SV Geograph

Cable and Pipeline Route Surveys

For more about hydrographic survey operation click here. For pictures of platforms and other offshore installations click here. For pipelay at Tyrihans see here.

Seabed mapping and investigations are necessary prior to designing a route and laying a subsea cable or pipeline. The initial (often the only one in the case of subsea cables) survey is usually carried out using a vessel equipped with hull mounted multibeam echosounders (MBE) such as the EM710 or, in deeper water, the EM120. In addition to the MBE systems there is usually a towed side scan sonar (SSS), a sub bottom profiler (SBP) and some kind of bottom sampling equipment such as vibrocore, CPT or drop core. Magnetometers are often used to detect existing cables or pipelines which may well be buried.


In the case of pipelines much more detailed surveys using ROVs equipped with higher resolution equipment and video are usually undertaken prior to installation.
Edgetech DF2400 SSS towfish
Combined sidescan sonar and sub-bottom profiler towfish.
An MVP winch for taking sound velocity measurements can be seen in the background

Drop corer
Drop corer being prepared for deployment

MOB boat
Good weather can be used to practise with the MOB boat.


EM120 data example
EM120 MBE data example - from Sognefjord, Norway

HUGIN 3000 AUV being launched
HUGIN 3000 AUV, the perfect route survey platfrom, being launched

ROTV
Steerable towfish known as Remotely Operated Towed Vehicles (ROTV) can be used for route surveys or pipeline inspection.

Transponder change
In deeper water it is sometimes necessary to put a transponder on the towcable too...








For  high resolution surveys AUVs are becoming more and more popular for this kind of work - and with good reason. These platforms beat ROVs on speed, noise and stability. They also have advantages over more traditional surface based MBE with towed SSS /SBP surveys in that MBE resolution is higher, line turns are quicker and the positioning of the vehicle is an order or two better than with towed patforms which often end up several kilometres behind the survey vessel.

Viperfish
Viperfish - caught ion the SSS towfish in deep water
Photo: Morten Tangen

Box core sample
Box core sample




CPT rig
CPT (Cone Penetrometer) rig


Danish Air Force
It is not uncommon to be checked out by air force or coastgaurds during surveys.....
Here the Danish Air Force takes an interest.