PURPOSE: To eliminate fixed stations and correct GPS position measurement data, and to improve the position measurement accuracy by correcting the GPS position measurement data with correction data found by the navigation device of the this vehicle or external correction data.

CONSTITUTION: A GPS reception part 34 finds the distance to a GPS satellite with a received satellite radio wave 16 and then finds the GPS position measurement data from the distance. Then a control part 52 compares the current travel position of this vehicle determined with the position measurement data with the position of the closest intersection on map data at a recording part, converts it into travel position coordinates X and Y, and displays them on a screen, and data ΔPk is radiated 56 from a transmission part 54 with a mobile station radio wave 57. A reception part 36, on the other hand, receives another mobile station radio wave 57 through an antenna 26, and extracts and supplies correction data ΔPk to a control part 52. The control part 52 when inputting the correction data ΔPk does not calculate the correction data ΔPk by the navigation device 50 of this vehicle, but finds the travel position coordinates with the input data ΔPk and displays it.