To attain pseudo clock technology which can be attained with the actual time even when errors are included in the estimation of predicted propagation time without utilizing complex delay model by utilizing positioning signals of various frequencies, although the conventional technology can not be attained unless various delay models are utilized.

A method for synchronizing the time standard of a ground station with the time of a crystal oscillator installed on a satellite transmits the time set forward the delayed amount based on various delay factors from the ground station so that the time is accurately set when it arrives at the satellite. Time duration for positioning signals to propagate between the ground station and the satellite is respectively determined by using a plurality of various frequencies in order to utilize the difference of delayed amount of the positioning signal due to frequency difference. The delay correction amount is calculated based on the delay amount obtained by dividing a plurality of pseudo distances measured by a positioning signal receiver by light speed and predicted propagation time calculated in advance, and this delay correction amount is added to the delay amount for putting forward.

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