Patent ID: 7498984

Claim:
A positioning system, comprising: a communication base station; a terminal communicable with the communication base station; and an information supply device communicable with the communication base station and the terminal, the communication base station including a signal transmitting section that transmits a base station timing signal to the terminal, the base station timing signal being a signal at a predetermined time interval, the terminal including a local clock, a time error of the local clock being calibrated at any time based on a satellite time of positioning satellites, a positioning section that locates a current position based on satellite signals that are signals from the positioning satellites, a receiving section that receives the base station timing signal, a total delay time calculating section that calculates a timing difference between the base station timing signal and a standard timing signal indicated by the local clock as a total delay time that includes a drift of the local clock depending on a temperature, a delay time based on signal processing in the communication base station and the terminal, and a propagation delay time between the communication base station and the terminal, and a basic information transmitting section that transmits basic information including the position located by the positioning section and the total delay time to the information supply device via the communication base station, the information supply device including a base station position information storage section that stores base station position information indicating a position of the communication base station, a basic information receiving section that receives the basic information including the position located by the positioning section and the total delay time from the terminal via the communication base station, a propagation delay time calculating section that calculates a distance between the terminal and the communication base station based on the position located by the positioning section and the base station position information to calculate a propagation delay time required for a signal to propagate the distance, a device peculiar delay time calculating section that calculates a delay time other than the propagation delay time as a device peculiar delay time by subtracting the propagation delay time from the total delay time, a device peculiar delay time transmitting section that transmits the device peculiar delay time to a positioning terminal that carries out positioning using a net propagation delay time so that the positioning terminal calculates the net propagation delay time, the positioning terminal having a configuration identical to the terminal with respect to reception of the base station timing signal.