GPS (Global Positioning System) is a 3-D positioning system and its positioning accuracy is about 10m under ideal condition. For two-wheeled vehicle, high accuracy positioning is difficult because of the inclination of the body when receiving signal causes loss of the signal from the satellites. In the result, positioning accuracy gets worse or positioning itself cannot be carried out. This study aims at improving the positioning result by improving the observed data and the way of calculation. Simulation results show that the proposed method can improve the positioning problem caused by loss of signal.