Improving Navigational Systems Through Establishment of a Marine Geodetic Range

Abstract

POSITIONS OR DIRECTIONS in or on the deep oceans often cannot be determined with sufficient accuracy using ocean navigation systems now available. Present limitations on accuracy arise, in part, because of the lack of reliable marine reference systems, including permanent marine control points. Control points are needed of the type that permit such a high degree of accuracy in land positioning. The accuracy and reliability of marine navigation systems could be improved if variations from some known standard could be determined. This paper discusses a standard system that could be established, viz., a marine geodetic calibration range. Positional fixes made with present systems are sometimes a mile or more in error. These systems could be evaluated, calibrated, and compared using the suggested marine geodetic range as a standard. The systems could be adjusted to minimize errors, thereby improving their accuracy and reliability. In one possible form, a geodetically constructed calibration range could extend parallel to a portion of the U. S. continental shelf and seaward to about 1500 miles from shore. The range, based on a bottom-referenced system tied to the U. S. land geodetic network, might consist of a network of lines or grids formed, for example, by three to six permanent, and three temporary, ocean-bottom control points. In one configuration, identification of stations would be by acoustic signals tramsmitted by a set of three transponders on the sea bottom. Position on the ocean surface relative to the bottom transponders would be determined by solving a three-dimensional intersection problem, as is done in land geodesy. The most important measurements would be the line distances between the control points. It would be possible to measure these distances using aircraft line-crossing or satellite techniques. The final coordinates of the control points on the sea bottom could be determined (by applying geodetic adjustment procedures) only after distance measuremens were completed. The relative accuracy of the proposed calibration range would be equivalent to 1:200,000, or about ±50 feet along a 1500-mile calibration line.