Abstract：On the basis of buoy long baseline network of differential underwater GPS a resolution formela is developed under polar coordinate system and then a set of analytic equations are deduced which are about the respective effects of the net shape and baseline accuracies,acoustic ranging accuracy on positioning result. The analytic results of the spatial distribution of the accuracy obtained after the hyperbolic positioning model show that there exists distinct area in which the hyperbolic intersection algorithm becomes instability,but if the baseline distribution with radiated net shape is used,thus,in the range of baseline network,the accuracy of plane positioning is even and no matter using any baseline distribution,the depth surveying accuracy will be clearly lower than the plane accuracy.
