Dynamic positioning (DP) is a computer-controlled system to automatically maintain a vessel’s position and heading by using its own propellers, rudders and thrusters. As minimum position reference sensors (DGPS), wind sensors, motion sensors and gyro compass are needed to provide the computer with information about the vessel’s position and the magnitude and direction of environmental forces affecting its position. USBL systems and other positions systems can be added to the computer to obtain a more precisely positioning.
The computer program contains a mathematical model of the vessel that includes information relating to the wind and current drag of the vessel and the location of the thrusters. This knowledge, combined with the sensor information, allows the computer to calculate the required power for propulsion, rudder angle and thrusters to keep the vessel at the position. This allows operations at sea where mooring or anchoring is not feasible due to deep water, congestion on the sea bottom (pipelines, templates) or other problems.
Dynamic positioning may either be used to hold the vessel locked to a fixed point over the sea bottom, a fixed point on the sea bottom or relative to a moving object like another ship or an underwater vehicle. It would also be possible to positioning the vessel at a favorable angle towards wind, waves and current, called weathervaning.
Examples of vessels using DP Systems are:
- Platform Supply
- Shuttle Tankers
- and many more.