Patent ID: 7623069

Claim:
A present position locating method used when receiving satellite signals transmitted from positioning satellites and repeating present position positioning calculations based on the received satellite signals, the method comprising: selecting satellite sets based on the received satellite signals, each of the satellite sets being a combination of satellites used for present positioning calculations; calculating present position candidates corresponding to the respective satellite sets using the satellite signals from the satellites included in the respective satellite sets; calculating APR (A Priori Residual) values of the respective satellite sets, the APR value being the sum of the square of a difference between 1) a pseudo-range and 2) an approximate distance of a target satellite of a target satellite set, the approximate distance being a distance between the target satellite and the present position candidate of the target satellite set; calculating an average value of the APR values of the respective satellite sets; changing weighting of an evaluation function of an evaluation point calculation equation used to calculate an evaluation point of the present position candidate corresponding to the average value of the APR values, the evaluation point calculation equation being a composite function of at least one evaluation function selected from 1) an evaluation function with respect to the APR value, 2) an evaluation function with respect to a number of satellites included in the target satellite set, and 3) an evaluation function with respect to a PDOP (Position Dilution of precision) value of the constellation of the satellites included in the target satellite set; calculating the evaluation points of the present position candidates corresponding to the respective satellite sets using the evaluation point calculation equation; and selecting a present position candidate from the present position candidates corresponding to the respective satellite sets based on the evaluation points, and determining the selected present position candidate to be a present located position.