Abstract
The establishment of marine geodetic control is very significant not only for geodetic work but also for various scientific investigations in the oceans. Recently some attempts have been made to establish the geodetic control points on the ocean floor. Among those, it is reported that the system being consist of three acoustic transponders is very effective for practical use. However, the presently used technique for determining the transponder geometry requires that the accurate ship positions are needed to be determined in advance by using a land-based-precise positioning system. Consequently, this technique can not be used when the position of the ship is not accurate, for example, when the ship is far from the coast. In this report, a new technique is proposed which determine the transponder geometry by only acoustic ranging data without the knowledge of the ship position. The observation equation is derived from the condition that the projection vectors of three slant ranges on the sea surface lie always in the constant plane (sea surface). Based on some assumptions, the accuracy of the transponder geometry is estimated as about 1 meter for ranging accuracy of 10 at 3000 meters depth. The use of this technique in conjunction with NNSS will make it possible to deter mine the geodetic positions in the oceans with an accuracy almost comparable to that of positioning on land, even in such region that land-based-precise positioning systems are not available.
