Patent ID: 8073619

Claim:
A position correction apparatus comprising: means for acquiring a position coordinate measured by a GPS (Global Positioning System) receiver; means for storing road data indicating a position coordinate of a road that is constructed; means for generating locus data indicating a plurality of position coordinates of the GPS receiver during a past specified period based on position coordinates acquired by the acquiring means; means for estimating a road section traveled by the GPS receiver during the past specified period based on road data stored by the storing means and locus data generated by the generating means; means for estimating a bias error of a position coordinate measured by the GPS receiver based on a plurality of position coordinates in a road section estimated by the road section estimating means and a plurality of position coordinates indicated by the locus data; and means for correcting a position coordinate measured by the GPS receiver based on a bias error estimated by the bias error estimating means; and means for outputting the corrected position coordinate, wherein: the road section estimating means corrects a specific position coordinate out of a plurality of position coordinates indicated by the locus data based on a bias error last estimated by the bias error estimating means, retrieves a road nearest to the corrected specific position coordinate based on the corrected specific position coordinate, and estimates a road section traveled by the GPS receiver on the retrieved nearest road during the past specified period; the bias error estimating means stops estimating a bias error based on the locus data when a distance between (i) the nearest road retrieved by the road section estimating means and (ii) the corrected specific position coordinate exceeds a specified upper bound; and during a non-estimate period, for which the bias error estimating means does not estimate a bias error, the correcting means correct a first position coordinate, which is measured by the GPS receiver, based on a bias error that is estimated before the non-estimate period by the bias error estimating means, and the outputting means then output the first corrected position coordinate.