In the navigation of SUAV, WGS-84 geodetic coordinate is transformed into Gauss plane coordinate using reducing high-order item Gauss projection arithmetic, coordinate transformation was realized by projection transformation and coordinate transformation on projective plane. And analogue transformation were implemented to uniform the GPS received WGS-84 geodetic coordinate, to realize the coordinate matching. This arithmetic can meet the need of positional accuracy of on-vehicle GPS navigation and real-time...