Accuracy of the Taut-Line Position-Indicator for Offshore Drilling Vessels

The taut-line system measures horizontal position of a drilling vessel by using trigonometric relations with the assumption that a steel line is essentially straight from vessel to sea floor. This paper examines mathematically the accuracy of this assumption under a variety of operational circumstances. A convenient method to estimate error as a function of equipment and environment parameters is developed. Further, an on-site procedure is suggested for estimating and reducing error by use of only the taut-line system itself.