The Naref Buoy, a Deep-Sea Navigation Aid

Abstract

ABSTRACT NAREF is a concept of a buoy design for NAvigation REference to be moored preferably in deep sea areas to bock up positioning of survey-vessels, where land based radio navigation aids do not yield sufficient accuracy. The buoy is carrier of additional radio navigation systems to allow a considerable improvement in accuracy of positioning to the survey vessel. The layout of the NAREF concept is to grant a considerable circle of movement of the buoy about the anchoring point and therefore it requires a relatively simple mooring system. Two versions are proposed to overcome the problem of diluting accuracy of positioning due to movement of the buoy. One applies to the implementation of the system in areas with relatively constant wind and current conditions, like the trade wind zones. Here the position of the buoy is traced by mutually surveying it's position and drift rate during satellite fixes by the ship and back up the position of the vessel by data received from the buoy between satellite fixes. Another approach, which desires additional hardware expense, will permanently trace the deviation of the buoy's position to the anchoring point by an acoustical position system. This system will give a realtime information of the buoy's movement improving the overall accuracy and breaking up the environmental limitation of steady wind and current conditions. The NAREF-concept shall be a back up for integrated navigation systems employing Satellite-Sonar Doppler and ground based navaids, as they are state of the art, which normally do not yield the desired accuracy for certain survey missions in deep waters and far off land based radio-navaids. INTRODUCTION Actual deep-sea-exploration has a trend to desire more and more accurate positioning, than existing equipment can provide. Modern integrated navigation systems employing satellite-sonar- and radionavigation equipment will suffer a considerable degradiation in accuracy, when the operating area is in deep water, where the sonar system looses bottom-track and radionavigation systems yield weak and degraded signals. In this case, also the satellite navigation system will degrade, because it needs precise information of ship's movement during fixes to obtain good accuracy and dead reckoning during and between fixes will be of poor quality. Presently obtainable accuracy under such adverse conditions often does not exceed 1 NM. The NAREF-system is a navigation aid, which should improve the capability of navigation aids under deep water conditions in accuracy. THE NAREF-CONCEPT As a solution to overcome the problem of accuracy in positioning, a reference point as close to the operating vessel as possible may be of great advantage, since it can carry additional navigation aids, such as Radar-transponders and other radionavigation systems yielding an optimum in accuracy. But normally no convenient platforms is available since there is hardly a chance to find natural islands in those regions. So an artificial platform has to be provided, which as a matter of simplicity and practicability should be a moored buoy.