In focus: HMS Scott, the Royal Navy’s ocean survey vessel

HMS Scott is the Royal Navy’s Ocean Survey vessel. Although the 5th largest ship in the RN fleet, she maintains a relatively low profile, spending long periods at sea on her primary duty, mapping the bottom of the world’s oceans. Here we look at the history, design and role of the ship.


The RN’s Hydrographic Squadron has a long and illustrious heritage that could be traced back to 1681 when the navy was ordered to conduct the first survey of the British coast for King Charles II. British charts of the oceans were a critical enabler in Britain’s domination of the seas in the 18th and 19th Centuries. Today the United Kingdom Hydrographic Office (UKHO) employs around 1,000 people in Taunton and is a world-renowned organisation which generates considerable revenue by the sale of data for commercial use. The needs of the RN are its top priority but the commercial operations of the UKHO turned over around £150M and made a profit of £29M in 2017-18. RN survey vessels, including HMS Scott, supply much of the data although there is now considerable sharing of information between member nations of the International Hydrographic Organization (IHO).

When the US agreed to sell the submarine-based Polaris ballistic missile system to the UK in 1963, the arrangement included bi-lateral sharing of highly accurate bathymetric charts. Maps of the seabed and the thermal layers of the water column are particularly important for the safe navigation and concealment of ballistic missile submarines in the deep ocean. The US Navy had developed the world’s first wide-swath, multibeam bathymetric survey and navigation system which produced charts used by the submarines of both nations. The RN also contributed to the survey work by ordering four Hecla-class combined hydrographic and oceanographic survey vessels, built between 1966-74.

These 2,800-tonne vessels were designed for both deep ocean and coastal surveys and were fitted with air conditioning for hot climates and ice-strengthened. Their diesel-electric propulsion was unusual for the time but gave them a range of 12,000 nautical miles, allowing for long periods at sea. The H-class made use of early side-scan sonars which were towed behind the ship and colloquially referred to as ‘fish’ with data being recorded on reel-reel magnetic tapes. The ships were fitted with modest flight deck and hangar for small Wasp helicopter. When embarked, the aircraft was used to conduct aerial photography, photometric surveys, install tide gauges and move equipment and personnel around.

  • Lead ship of the class, HMS Hecla seen at Devonport South Yard, July 1995. These versatile ships were deployed on surveys all over the world but were also used in other roles. Hecla and Hydra were used as ambulance vessels during the Falklands war. Hecla paid off in 1997, HMS Scott being officially her replacement. (Photo: Tony Davis)

  • HMS Herald, late in her career seen in Portsmouth around 1999. She had a varied career serving as a casualty reception vessel during the Falklands War. She was the first of this class of survey ships to be painted grey and returned to conduct patrols in the South Atlantic in 1983. She deployed to the Mediterranean and Gulf in support of minehunters during the first Gulf war and was used as a temporary Antarctic Patrol Ship in 1991-92. She was decommissioned in 2001. (Photo: Imperial War Museum)

  • The second HMS Scott was Halcyon-class minesweeper built in 1937 but adapted for hydrographic survey work. She served through WWII until scrapped in 1965. Seen here at Tilbury January 1943. (Photo: Imperial War Museum)

  • HMS Scott fitting out Appledore

    Rare image of the third HMS Scott under construction at Appledore, late 1996. The main superstructure block is being lowered into position at the fitting out wharf. The hull was built in the covered dry dock up river. (Photo: North Devon Maritime Museum)

  • HMS Scott (May 2007). During her time in service, the external appearance of the ship has not changed significantly. Prior to her first deployment to Antarctica, the forward port side crane was replaced in 2010 by a sea boat davit to provide a second rescue boat capability to satisfy SOLAS requirements. The A-frame and davits originally fitted on the quarterdeck have also been removed.

  • Stop-gap Antarctic Patrol Ship 2010. The ship is ice-strengthened to Lloyds Class 1A and can operate in first-year ice up to 80cm thick. Fuel and water ballast tanks are fitted with an oil heating system and upper deck fire hydrants have trace heating to prevent freezing in cold climates.

  • (Left) RAF Sea King helicopter delivering Devonport Flotilla staff via winch to HMS Scott off the Falklands, January 2010. The large expanse of the foredeck permits winching operations but this is not a flight deck where a helicopter can land. (Right) View from the bridge as ship encounters a force 8 storm while crossing the notorious Drake Passage, February 2010.

  • Arriving in Plymouth Sound after a lengthy period at sea (September 2016)

  • This image provides a good view of the 6-decks of the superstructure, note the penguin funnel badge. Alongside in Malta, January 2017. (Photo: Derek Lilley)

  • A perfect aerial view of the ship seen while at anchor off the Falkland Islands, February 2020.

  • A rare moment in the limelight, during the Trafalgar Fleet Review in June 2005. HMS Scott sailed out of Portsmouth into the Solent and passed down the lines of ships, following the Queen on HMS Endurance as one of inspecting vessels. (Photo: NavyLookout)

In the late 1990s, there was a debate over whether the hydrographic survey squadron should be privatised and outsourced to civilian vessels. Their increasingly important part in supporting submarine operations and very much lower manning requirements of the future vessels meant that the RN thankfully retained its hydrographers and ships. It was also decided that the traditional white hulls and buff funnels would be abandoned permanently and all ships would be painted grey to reflect their closer involvement with warfare and integration with the surface flotilla.

In tandem with planning for the Vanguard-class Trident submarines, in 1987 the MoD concluded that it needed the renew and update its ocean-surveying capability. Several options were considered but ultimately the US Navy’s fully integrated Ocean Survey System (OSS) was selected which would be carried by a large purpose-built vessel. HMS Scott was ordered in 1995 from BAeSEMA (a joint venture between British Aerospace and the French Sema Group 1991-98) and the construction was sub-contracted to Appledore Shipbuilders. Although a relatively expensive initial outlay on a high-end solution, the low ‘cost per survey mile’ and quality of data were the prime factors in the decision.

Big ship, small crew

The construction of HMS Scott proceeded smoothly and her hull was floated out of the covered dry dock at Appledore and onto the river Torridge in October 1996. She commissioned in June 1997, just 30 months after she was ordered. She was built to mostly commercial shipbuilding standards and was one of the first ships of the RN to conform to Lloyds ship classification (enhanced in some areas to meet naval requirements). She is a large vessel displacing 13,500 tonnes with a length of 131.1 meters to provide a stable platform for surveying. Her deep draught of 8.3m is due to ballast tanks at the bottom of the ship which hold 8,000 tonnes of water to further improve stability. Water ballast is pumped around 23 inter-connected tanks to control the trim of the ship.

The ship is propelled by two Krupp MaK 9M32 nine-cylinder diesel engines driving a controllable pitch propeller through a single shaft, giving a top speed of 18 knots. A vertically-retracted bow thruster is fitted for slow-speed manoeuvring and to assist with berthing. The ship is intended to operate with unattended machinery spaces and is fitted with remote surveillance and fixed fire fighting equipment.

HMS Scott has an exceptionally small complement which operates a three-watch system. 72 men and women are assigned to the ship’s company, around 42 are on board at any one time while the others are ashore on leave or training. Typically each sailor will spend about 70 days onboard followed by 30 days ashore in a cycle repeating 3 times per year. Onboard systems are low maintenance and a 3-year planned docking cycle was intended to allow the ship to spend an exceptional average for a naval vessel of 300 days at sea each year.

Accommodation is probably the most comfortable of any RN vessel afloat, appropriate for a ship that may spend many weeks in mid-ocean on monotonous survey work. More in line with RFAs or merchant vessels, each sailor is has a single cabin and one bathroom is provided for every two people. Cabins are all in the superstructure and the majority have large windows. The large hull and small crew has resulted in such an excess of space onboard that HMS Scott a large gym area and is even equipped with a squash court.


The components of the Integrated Ocean Survey System are installed in the mission space on four decks in the centre of the vessel and consists of four sub-systems; navigation, sonar, power and mission control and processing (MCAPS).

MCAP collects, processes and records time-correlated bathymetric, gravity, magnetic and other oceanographic data. Seabed information is displayed in real-time as 3D images monitored by the hydrographers in the mission spaces. The data is further processed and checked before being transferred to the hydrographic office in Taunton.

Out of sight and fitted along the bottom of the hull is the most important equipment carried by HMS Scott, the Sonar Array Sounding System (SASS IV). The SASS low-frequency array is 10 meters long and emits 90 adjoining beams in a 120º fan-shaped acoustic swath pattern transverse to the ship’s track. Their returning echoes are received by a separate large hydrophone containing 144 elements. Digital signal-processing algorithms process the returning signal to develop an across-track profile of the ocean bottom. Thousands of data points are corrected in real-time for sound-velocity variations and for the ship’s roll, pitch, heading, and heave variations between the time of transmission and reception.

An additional narrow-beam sonar uses a 9-degree conical pattern to measure the ocean depth directly beneath the ship. This is used to verify the depth data of the main wide-swath-array sonar and used in waters (less than 50 fathoms) too shallow for the main array.

In order to make accurate depth measurements using sonar, the speed of the sound wave through seawater must be known. Temperature and salinity layers in the waters column affect the density of seawater and the speed that sound travels. Knowledge of this phenomenon is vital in hydrography as well as submarine and anti-submarine operations. HMS Scott takes periodic measurements of the water column by lowering an expendable bathythermograph (XBT) or by towing an aquashuttle oceanographic profiler behind the ships at varying depths

During a run the ship proceeds at around 12kt and surveys the ocean floor at depths between 50 to 2,500 fathoms. At a typical depth of 2,000 fathoms, the sonar scans a swathe of ocean floor about 5.6km wide. Depending on conditions, Scott can map up to 150Km2 in an hour. During one 3-month deployment in the North Atlantic Scott surveyed 74,000 Km2 area of seabed.

  • In the large mission spaces, huge amounts of hydrographic data collected by the sonars is processed.

  • Hydrographer at work.

  • Concentrating hard on the bridge as the ship is navigated out of Devonport.

  • Engineers monitor the propulsion and electrical systems from the Machinery Control Room.

  • The Wardroom is spacious and comfortable with large windows.

  • Gym

  • The only Royal Navy vessel with its own Squash Court – a benefit of the extraordinary amount of surplus space.

Service history

Despite most of her career spent far out to sea, there have been some notable moments in the career of HMS Scott. Following the Boxing Day tsunami of 2004 which killed around 228,000 people, the ship conducted seabed surveys off the Sumatran coast which revealed huge underwater landslides. The information collected was used by scientists to understand exactly where and why the earthquake had occurred and to inform the placement of sensors to provide warning of future events. Later that year, the ship was chosen as one of the reviewing platforms and hosted the Duke and Duchess of Cornwall and various VIPs during the Trafalgar Fleet Review held in the Solent.

Scott completed a 10-month refit in Portsmouth during 2009 and was then tasked to conduct some of the Antarctic Patrol Vessel duties to replace HMS Endurance (after her catastrophic flood and near loss in 2008). Scott had two spells during the 2009/10 and 2010/11 seasons in the South Atlantic.

In 2013 Babcock was awarded a through-life support (TLS) contract for the ship. Between November 2013 – May 2015 she had her biggest refit at Devonport which included installing a new sewage treatment plant and two new lifeboat davits, as well as a new uninterrupted power supply to the ship’s sonar suite. The propeller and shaft were overhauled and the port main engine crankshaft replaced along with the rudder horn due to cracks in the original casting

Following a serious starboard main engine failure at sea she turned to Devonport in June 2017. For some time her future was in doubt and there were media reports the ship would be scrapped. However, in early 2018 she was prepared to make the 700-mile trip to Babcock’s facility in Rosyth on a single-engine. She was dry-docked and a new 35-tonne replacement engine installed through a hole cut in her hull. The refit period also included a complete overhaul of the sonar array.

On completion of the repairs and work up period, she sailed from Devonport in July 2019 for 10 months in the Atlantic. Further technical issues saw her spend September in dock at Gibraltar. HMS Protector was due to arrive for Antarctica in late 2019 but in October a serious defect was found during planned maintenance in Charleston, USA and she returned to the UK for repair. HMS Scott was again called on as a partial replacement and spent several months in the South Atlantic. During December 2019 she was involved in searching for a Chilean airforce C130 aircraft that went missing. After 95 days continuously at sea, HMS Scott arrived back in Falmouth, just in time for lockdown in March 2020.

  • In number 3 dock at Rosyth during major overhaul and engine change, May-December 2018. The ships’ company remained on board for the entire time.

  • (Left) The aftermath of a catastrophic starboard main engine failure, June 2017. The force of the blast buckled the deck plates between the engines. The broken piston connecting rod can be seen lying between the two engines. (Right) A 23-metre long section of hull plating is removed to enable the engine to be replaced.

  • A replacement for the defective starboard main engine is lowered into the dry dock ready for sledging into place.

  • (Left) Looking smart as major refit work is nearly complete, Rosyth, December 2018. (Right) A brief dry docking for inspection at Falmouth, April 2020.

  • The deep draught of the ship is clear from this view of the ship in Number 10 Dock, Devonport, November 2013.

  • Exercising abandon ship drills in the Falkland Islands in preparation for sailing south to the Antarctic, February 2011.

  • Sailing from Mare Harbour in the Falkland Islands, February 2011.

  • (Right) Photo-drone image of the ship at anchor off the Falklands, January 2020

Going, going, gone

In Oct 2017 the MoD said that HMS Scott would be decommissioned in 2022 on completion of her intended 25 year-life. With less than two years left, there is no plan to replace her, at least with another naval vessel. Navy Command stated in October 2019 that “Work is underway to understand current and future requirements and how they will be delivered after HMS Scott leaves service”. Scott’s annual running cost is just £4.5M and the profits of the UKHO cover this and the Navy’s other Hydrographic ships. Like several important UK defence assets, there is no funding line for the capital cost of replacement. Either the RN’s deep ocean survey capability will be much reduced, the work contracted to a commercial company or we must rely on data supplied by other nations. The cost of installing a new engine was deemed worthwhile in 2018 to give Scott just 3 more years of service, it is possible she could undergo a life-extension refit but whether it would be worthwhile would depend on the material state of the hull.

During her career, HMS Scott has gathered vast amounts of data and contributed to the scientific understanding of the oceans as well as helped makes charts used by mariners and submariners. To date, mankind in its entirety has mapped less than 10% of 40 million square miles of seafloor. We know more about the topography of other planets in our solar system than we do about the ocean floors. It is worth noting that the Seabed 2030 project has been established, attempting to map the entire seabed by 2030. Commercial sponsorship will fund around 100 survey ships that will circumscribe the globe. The information will be available to everyone (with potential implications for submarine operations). Despite such initiatives, given the UK’s continued commitment to a submarine-based nuclear deterrent, a sovereign surveying capability remains crucial.