Apparatus for detecting the position of a vehicle

An apparatus for detecting the position of a vehicle, comprising:

• electric wave receiving means for receiving electric waves from a plurality of satellites revolving around the earth to supply vehicle position data;
• satellite designating means for designating at least three satellites from said plurality of satellites to form a designated satellite combination;
• vehicle position estimating means for estimating an estimated vehicle position on the basis of said vehicle position data supplied from said designated satellite combination and received by said electric wave receiving means, said estimated vehicle position including a position error area symmetrically surrounding the estimated vehicle position;
• satellite combination fixing means for fixing said designated satellite combination to make constant an offset representing a deviation between said estimated vehicle position and a true vehicle position;
• road network data storing means for storing road network data having a plurality of road network patterns, said estimated vehicle position and said position error area being indicated on said road network patterns;
• estimated table making means for dividing said position error area into a plurality of mesh sections, for determining a value of the probability of the vehicle existence in each mesh section of said position error area and making an estimated table containing estimated values each corresponding to each of the determined values of the probability in all mesh sections of said position error area;
• repeating means for repeating, as the vehicle travels, the operation of said estimated table making means at intervals under the condition that said designated satellite combination is fixed by said satellite combination fixing means;
• table updating means for updating a previously updated estimated table having previously updated estimated values each time said estimated table is made by said estimated table making means, by adding the estimated values of the estimated table to the previously updated estimated values, respectively, of the previously updated estimated table;
• deviation calculating means for calculating a deviation between said estimated vehicle position and the position of a mesh section of said position error area specified by a largest value within the updated estimated values of said updated estimated table, said deviation being indicative of said offset;
• and
• true vehicle position calculating means for calculating the true vehicle position on the basis of said offset and said estimated vehicle position.