To acquire appropriate position information.

By the definition of position information acquired periodically or non-periodically on the basis of information from an artificial satellite to be first position information, and position information acquired periodically or non-periodically on the basis of information from a base station to be connected to be second position information, a detection unit compares the second position information with either the first position information or second position information acquired before the timing of acquiring the second position information in the time axis, so as to detect an error of the second position information. A determination unit determines a present position on the basis of the first position information or the second position information. If the first position information cannot be acquired at the determination timing and if an error is detected in the second position information acquired at the determination timing, the determination unit determines the present position, on the basis of other position information identified by the base station related to the second position information.