Dynamic Positioning System
A dynamic positioning system, or DP, helps a ship’s crew maintain and adjust their ship’s exact position in the water. That ability is especially useful when operating sensitive equipment like remotely operated vehicles (ROVs), which are attached to the ship by a cable.
Deck crew and engineers aboard NOAA Ship Okeanos Explorer recover ROV Deep Discoverer after a dive during the 2022 ROV and Mapping Shakedown. Maintaining the ship’s exact position relative to the seafloor using a dynamic positioning system makes such deployments and recoveries much simpler. Image courtesy of Caitlin Bailey, GFOE, 2022 Mapping and Shakedown. Download largest version (jpg, 1.8 MB).
How Does a Dynamic Positioning System Work?
Ships on the ocean move even when they’re not using their engines. That’s because currents and winds push ships around relative to the seafloor below. Anchors and mooring systems can keep a ship in a general area, but they aren’t perfect: Many such tools still allow some movement. Mooring systems can also be impractical in deep water, and anchors can damage artifacts or habitats on the seafloor.
A dynamic positioning system allows a ship to automatically stay in one place using nothing but its thrusters and propellers. A central computer collects data from various tools that judge the ship’s position and movement. These tools can include GPS or other satellite systems, wind sensors, motion sensors, and gyrocompasses (tools that use a fast-spinning disc and the Earth’s rotation to act as a non-magnetic compass). When the crew needs the ship to stay in one place, the computer uses the data it collects to control the ship’s thrusters and propellers. By making minor adjustments, the dynamic positioning system maintains the ship’s exact position over the seafloor.
Pilots operate NOAA Ocean Exploration’s remotely operated vehicles (ROVs) from the front row of the control room on NOAA Ship Okeanos Explorer during Windows to the Deep 2019. ROV pilots can request adjustments to Okeanos Explorer’s position to allow for further exploration. Image courtesy of NOAA Ocean Exploration, Windows to the Deep 2019.
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A dynamic positioning system also provides a convenient way to move a ship over small but specific distances. If the crew wants the ship to move 10 meters (33 feet) to the east, for example, the dynamic positioning system can make that adjustment and hold the ship in its new position.
Why Is a Dynamic Positioning System Important?
ROVs for exploring the deep ocean are powered and controlled from surface vessels using long cables. If a ship drifts out of position, an ROV could be damaged or lost. Unexpected drifting also poses risks to sensitive habitats and maritime heritage sites, which could be damaged if an ROV moves in an unpredictable way. A dynamic positioning system helps solve those problems, keeping equipment and exploration targets safe. ROV pilots can also request very specific moves by the ship, allowing them to efficiently explore nearby areas during a dive. If a single site in the deep ocean is the target of multiple dives during one expedition, such as USS Yorktown in 2025, maintaining the exploration vessel’s position makes the site of interest much simpler to find after the first dive.
Remotely operated vehicle Deep Discoverer images the hand-painted mural, “A Chart of the Cruises of the USS Yorktown.” as part of the Papahānaumokuākea ROV and Mapping expedition. During this dive, pilots guided Deep Discoverer inside the wreck of USS Yorktown (CV-5). Navigating such tight spaces would not have been possible without tools such as the dynamic positioning system to maintain NOAA Ship Okeanos Explorer’s position above the wreck.
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Other ocean exploration tools like conductivity, temperature, and depth sensors (CTD) also benefit from dynamic positioning systems. These tools are often lowered directly off a research vessel using a tether, which is safer and easier to do when the vessel can hold its exact position.