Natural Born Birder - Offshore - Hydrographic Survey

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Hydrographic Survey

I'm often asked what it is I do for a living so here's a little about working as a hydrographic surveyor.....

Hydrographic (or offshore) surveyors work on all kinds of projects all over the world, the vast majority of it connected with engineering for the offshore oil and gas industry. Cable surveys, seismic exploration and a whole host of other activities - anything that involves subsea positioning or data collection - likely to involve surveyors. Various types of surface and acoustic positioning systems are used to determine the position of towed and remotely operated vehicles during these operations. Surveyors are generally part of a team which may include ROV crew, geologists, geophysicists, draughtsmen, engineers and others - all in addition to the marine crew required to operate the vessel itself.

In addition to surveys and various types of inspection and investigation offshore survey vessels, at least those equipped with ROVs (Remotely Operated Vehicles), are often involved with a variety of construction and engineering projects. For examples and pictures of such click on the following link: Offshore construction and engineering . For pictures of offshore platforms and other structures see here.

Most survey and construction vessels are in operation 24 hours a day, with the majority of the crew working 12 hour shifts. The amount of time spent onboard varies greatly but in general varies from two to six weeks with a corresponding length of time on leave.

Outside of the seismic industry there are two broad types of survey vessels, one is vessels equipped with ROVs which perform surveys using sensors such as high resolution MBE (MultiBeam Echosounders), Pipetrackers, video and more. They often assist in a variety of contstruction tasks using manipulators to operate valves on subsea templates, install things on the seabed and more. The second type of survey vessel may be equipped with hull mounted MBE systems and an assortment of towed sensors such as Side Scan sonars , Sub-bottom profilers, caesium magnetometers, sparkers and boomers.

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3D View of a wreck - made from MBE data gridded at 0.5x0.5m

100 kHz SSS image of shipwreck

The same shipwreck as above as "seen" by the 100 kHz Side Scan Sonar

After an acoustic survey geotechnical sampling is often conducted using vibrocorers, CPT rigs, drop cores or other sediment sampling equipment. This information is used to "ground truth" the interpreation of geophysical data and to find out how the various sediments will affect a pipelay (or other engineering activity)..

SBP data example showing two wrecks on the seabed and layers of various sediments types under the seabed

A Sub Bottom Profiler trace showing two wrecks and various sediment layers..

Surveyors tend to either have a university background or come into the industry from the navy. Graduates have usually taken a course such as those offered by the Department of Geomatics at University of Newcastle-upon Tyne, University College London or Plymouth - some courses offered by these establishments specialise in hydrographic survey. There is a high proportion of freelancers operating in the offshore survey branch, most of whom work through agencies.

Geomatics at Newcastle University

Geomatic Engineering at UCL

Hydrography at Plymouth University


Pipelay vessel S7000 with survey support vessel	SV Geobay, ROV survey / construction support vessel

Before an oil or gas field is developed detailed maps of the seabed are made in order to design pipeline routes and the like. All kinds of information are gathered regarding the shape of the seabed and the sub-surface sediments. These data are commonly presented as composite charts which present all the necessary data for engineering design. Digital Terrain Models are often also viewd in 3D in order to improve the visualisation of the seabed.

Prior to pipelay there is often a requirement seabed intervention work such as rock dumping, dredging and trenching, all of which needs to be documented. Surveyors work on rock dumpers, pipelay barges and pipelay support vessels during these operations. Once a pipeline has been laid detailed surveys are conducted to document its as-laid status.


Allsea's pipelay vessel "Solitaire"	Saipem's S7000, the largest pipelay vessel in the world.	CSO Apache laying an umbilical

Piper Acergy, formerly LB200, near Kristin platform, May 2007

Frequently ROVs are used, either as a platform for survey sensors or in order to investigate targets located during other types of survey.

Cod as seen by ROV in almost 300m of water

Rabbit fish - not an unusal sight in deep water....

It is not unusual to find wrecks during seabed surveys, the excitement of unexpectedly finding the remains of a Greek wreck in 2000 metres of water is indescribable. However, I have only occasionally been invloved in projects where we have specifically looked for wrecks.

The ultimate survey experience - finding an uncharted Greek wreck in 2000m of water

HUGIN AUV

An exciting development in recent years is the introduction of AUVs - these Autonomous Underwater Vehicles are not physically connected to the support vessel but are pre-programmed to a specified line plan and then launched. Data are downloaded on recovery. This type of vehicle can produce high resolution data with outstanding accuracy in water depths down to at least 3000m.

The images of shipwrecks above are taken from 100 kHz Side scan sonar records operating at 200m range

Below are some pictures of some other ROV survey / construction vessels, pictures taken during September 2006 at work on the Ormen Lange field.


Acergy Falcon - pipelay vessel	FFPV Tertnes - rock dumping vessel

Edda Freya	Normand Cutter


Acergy Piper	Acergy Petrel

Geosund	Seisranger (Subsea 7)

New build "Hull 02" ROV Support vessel under tow, Øygarden, February 2007