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.
Combined
sidescan sonar and sub-bottom profiler towfish.
An MVP winch for taking sound velocity measurements can be seen in the
background
Drop
corer being prepared for deployment
Good weather can be used to practise with the MOB boat.
EM120 MBE data example - from Sognefjord, Norway
In deeper water it is sometimes necessary to put a transponder on the
towcable too...
Viperfish
- caught ion the SSS towfish in deep water
Photo: Morten Tangen
It is not uncommon to be
checked out by air force or coastgaurds during surveys.....
Here the Danish Air Force takes an interest.
