In this paper, the equations calculating GDOP are induced in Hyperboic, and Spherical Navigation System, respectively, The GDOP diagram shows that the DGOP in the inner region of Beacons is similar each other, but the GDOP of Hyperboic Navigation System is much larger than that of Spherical Navigation System due to GDOP in the outer region of Beacons. The authors propose the algorithm estimating the pulse starting time using the Hyperboic Navigation System, and prove that if Navigation use the Spherical Navigation System by adopting the proposed Algorithm -in this case, "Pseudo Sperical Navigation System" - in the outer region where GDOP is becoming large, the position errors can be reduced.e reduced.