| 摘要 |
PURPOSE:To shorten time from the point of time when continuous positional detection becomes impossible till the restarting of positional detection by obtaining a relative velocity between a satellite and a vehicle from the position and velocity of the vehicle determined through dead-reckoning navigation, and obtaining the quantity of Doppler shift of received frequency from the relative velocity. CONSTITUTION:When the reception of a satellite signal becomes impossible, the Doppler shift quantity forming means 1 of an initial value setting means 4 obtains a relative velocity vector between a vehicle and each satellite from the position and velocity of the satellite which are estimated on the almanac data of the satellite and the position and velocity of the vehicle which are conjectured on the data of sensors 28 to 30 for the distance, direction and velocity of the vehicle for obtaining the Doppler shift quantity of carrier frequency between the vehicle and each satellite. In addition, timing for accurately synchronizing a C/A code with a satellite atomic clock is formed on a distance between the satellite and the vehicle to generate 18 the C/A code, and the frequency shift quantity equivalent to the Doppler shift quantity is set up 3 in a C/A code tracking means 19 as the initial value. Thus at the time of restarting the receiving of the satellite signal, the frequency can be instantly tuned to the satellite signal. |
