A minimum of three reference points is required for a diving operation.For example tautwire, DGPS and HPR. Each of these systesm have a known reliab ility record.The DP computer 'weights' th the other n of the wn e de coincide exactly the cor uters measured value position it uses in a combination of the determined positions suitably weighted.In this case it would hace the postion closer to where the ta t wire belleved it was e taut wire gaiefhsPoiteneoaetee8nathegembahes weighting for that system reduced,below a certain value and the reference system will be automatically disconnected and a warning alarm sounded.A continuous read out of the positions from all three systems the computer determined postion and the degree of weighting are all permenantly displayed Black out protection This takes the form of pitch reduction for the thrusters in the event that the reserve power on the main switchboard falls below a set value. 6A minimum of three reference points is required for a diving operation. For example tautwire, DGPS and HPR. Each of these systesm have a known reliability record. The DP computer 'weights' the measured position depending on the known reliability , say 60% for the taut wire, and 20% each for the other two. The position of the vessel determined by each system are unlikely to coincide exactly, the computers measured value position it uses in a combination of the determined positions suitably weighted. In this case it would hace the postion closer to where the taut wire believed it was. Should a fault occur with the taut wire ( say one of the potentiometers on the gimball heads begins tracking giving a noisy output signal), then this will be detected and the amount of weighting for that system reduced, below a certain value and the reference system will be automatically disconnected and a warning alarm sounded. A continuous read out of the positions from all three systems, the computer determined postion and the degree of weighting are all permenantly displayed. Black out protection This takes the form of pitch reduction for the thrusters in the event that the reserve power on the main switchboard falls below a set value. 6