Vehicle navigation system using GPS including correction of coefficients for velocity sensor

Claim 1

A vehicle navigation system comprising: a first sensor for detecting a velocity of a vehicle; a second sensor for detecting a direction of the vehicle; estimated position calculating means for calculating an estimated position of the vehicle on the basis of outputs of said first and second sensors; linear travel detecting means for detecting linear travel of the vehicle on the basis of a travel path of the vehicle obtained on the basis of a plurality of the estimated positions; means for obtaining positional data of the vehicle received from outside of the vehicle; and sensor coefficient calculating means for calculating, only when a travel section of the travel path of the vehicle detected by said linear travel detecting means is linear, a coefficient of said first sensor on the basis of a ratio between (i) a distance between two positions of the vehicle in said linear travel section of the travel path of the vehicle detected by said linear travel detecting means, said two positions being obtained by said means for obtaining positional data of the vehicle, and (ii) a distance of linear travel of the vehicle calculated on the basis of signals outputted by said first sensor during a period between (a) when one of said two positions of the vehicle is obtained by said means for obtaining positional data of the vehicle and (b) when the other of said two positions of the vehicle is obtained by said means for obtaining positional data of the vehicle.