DP Systems allow a propulsive power units. The reference points determine the vessels position relative to a datum,they do not necessarily determine the vessels exact location on the earths surface-only DGPS attempts to do this monitor the environmental effects on the vessel,such as the effects of swell and wind and use this to error compensate the reference systems. gersR7gonnaeanenpepcemrese6aamtbct6engnaaa Thay be systems,sensors and propulsion units is determined by the required duties of the vessel Types of reference systems of refer available · o very poor that it is a ·Laser(Fanbeam)- This cheap reference can be initially very reliable reducing as the target com Is a Taut Wire-Very reliable simple system.Can introduce movement restrictions when in use. Taut Wire A substantial weight is lowered to the sea bed attached by a high tensile steel wire or minimum diameter(reduces effect of current). DP Systems Dynamic Positionning systems allow a vessel to remain at a fixed point independent of the influences of the environment. This is achieved by a system of reference points, sensors and propulsive power units. The reference points determine the vessels position relative to a datum, they do not necessarily determine the vessels exact location on the earths surface- only DGPS attempts to do this. Sensors monitor the environmental effects on the vessel, such as the effects of swell and wind and use this to error compensate the reference systems. Propulsive power units take the form of the main propulsion unit, thrusters and steeering gear system ( in conjunction with propulsive unit). These units are mounted for and aft and may be either fixed or steerable. The number of reference systems, sensors and propulsion units is determined by the required duties of the vessel Types of reference systems This is a non exhaustive list of the types of reference systems available; z Differential GPS- The reliability of this system is very much dependent on the location and can range from good to very poor z Microwave (Artemis)- Is limited in that it is a line of site only system, the advantage is that a communication link is available and emergency shut down systems are sometimes built in z Laser (Fanbeam)- This cheap reference can be initially very reliable reducing as the target becomes dirty or due to atmospherics. It is a line of site reference z Acoustic (HPR)-Can be reliable but is reliant on batteries in portable transponders ( no limitation exists with fixed transponders) z Taut Wire- Very reliable simple system. Can introduce movement restrictions when in use. Taut Wire A substantial weight is lowered to the sea bed attached by a high tensile steel wire or minimum diameter ( reduces effect of current). 1