| 摘要 |
PURPOSE:To improve the accuracy of a position by receiving a radiowave from a GPS satellite, estimating the present position of a vehicle on a specified circle which is drawn on the earth, and sequentially estimating the present position based on the information of a road map. CONSTITUTION:At a point P2 where a vehicle enters into an urban area, a radiowave from a GPS (Global Positioning System) satellite is temporarily cut out. The passing time at the point P2 is assumed to be T2. When the polar- coordinate position Si of the satellite is detected with a GPS receiving apparatus 12, a distance Di from the present position P2 to the satellite Si is measured. A circle Ci which is the locus of the intersection of a sphere Bi having a radius Di with the satellite Si as the center and the earth E is obtained on the ground. When the Expression II holds true by using Di in the Expression I, DELTAx>=1 and DELTAy1 which are the coordinates of the point P1 are accurately obtained. The present position P2(T2;x2,y2) can be obtained accurately as the intersection between the circle Ci which is expressed by the Expression III and a road MR on which the vehicle is running. |
