Using Electronic Chart Display and Information Systems (ECDIS) With Dynamic Positioning (DP)
Authors: Cowie H.G. , Svanes T.A. 
Published: October 2008

USING ELECTRONIC CHART DISPLAY AND INFORMATION SYSTEMS (ECDIS) WITH DYNAMIC POSITIONING (DP)

DP BACKGROUND
Specialised requirements of the offshore oil industry has been a prime catalyst in the development of new technologies and control systems for vessels. Dynamic Positioning (DP) systems, originally developed for specialised navy recovery vessels, were quickly adopted on drilling ships, followed by diving support and offshore production vessels. Today, DP systems are common on many vessels serving the oil industry.
DP systems added a new dimension to vessel navigation. DP maintained a vessel stationary at sea when anchors could not be used because of water depth or because of fear of damage to installations on the sea bed. This ability to main station requires that the navigator on the vessel must have detailed information relating to the vessels position in a limited area geographically. Relative information on the vessel's position is more important than a true geographic position fix. On many DP vessels these requirements were adequately met by I single user' reference systems such as hydroacoustic, range - bearing and taut wire systems, systems which are of virtually no use for normal transit navigation of the vessel at sea. The ability to determine the vessel's geographical position at sea has been revolutionised by the commercial availability of GPS receivers. While the accuracy of a position fix from a GPS is not good enough for most offshore applications it is a back up system used on many offshore vessels and has introduced the possibility of easily relatinggeographical and local single user position information.

THE ADVENT OF ECDIS
The paper chart has been a fundamental navigational tool for the last century, but today the limitations of this classic approach can be overcome by using new technology, GPS and Electronic Chart Display and Information Systems - ECDrs.
Digi tal technology has not only changed the production of paper charts but enabled the charts tobe presented on a video display unit. Wi thin the shippingindustry, ECDIS is seen to be a major aid to navigational safety.
ECDIS systems are understood by many as a replacement of the traditional paper charts used on board a vessel. They are in fact much more than this. They are as much a navigator's work station as they are an information and chart display system. Furthermore ECDIS also adds a new dimension to navigational safety.
ECDIS as defined by IMO's Provisional Performance Standards, is not simply an authorised electronic chart on which vessel position is displayed in real time, but has a combination of anti-grounding and collision avoidance features not previously available on board. Furthermore by integrating both navigation, radar and steering, ECDIS will be the navigators work station of the future.

DP REGULATIONS
The regulatory authorities are specific in their requirements relating to both DP and ECDIS systems. Rules and regulations for DP vessels are related to system failure and the consequences of a vessel drifting off station.