TRAVEL GUIDE FOR VEHICLE

PURPOSE:To accurately guide the vehicle travel by providing a satellite utilizing position measuring instrument and a terrestrial magnetism utilizing position measuring instrument and guiding the travel of the vehicle selecting these two position measuring instruments. CONSTITUTION:The titled guide is provided with the satellite utilizing position measuring instrument 1 and the terrestrial magnetism utilizing position measuring instrument 2. Then, the guide 1 discriminates the current position of the vehicle based on an electric wave transmitted from a satellite and the measurement can be performed with an extent of position measuring accuracy 30m. But in some cases, a receiving state is deteriorated or the reception is made impossible by the position of the satellite or an obstacle of the reception on the ground. A deteriorating coefficient (GDOP) which is the coefficient to indicate the enlargement of these position measuring errors is included in a signal from the satellite. The position measuring errors exceed a tolerance when the GDOP far exceeds a prescribed value or the intensity of the signal from the satellite is below the prescribed value. A deteriorating coefficient discrimination means 3 is provided in order to detect this. Then, a changeover means 4 selects the instrument 1 when the position measuring errors are in the tolerance and changes over an utilizing position signal from the instrument 1 to the instrument 2 when the means 3 detects the errors exceeding the tolerance.