PURPOSE: To obtain an instrument capable of surely correcting a computing position to an absolute position that is a normal position by retrieving a plurality of the absolute positions as candidate positions from the neighborhood of the computing position, selecting a running position among the candidate positions and correcting the computing position.

CONSTITUTION: When a vehicle runs, the detection signals of a distance sensor 10 and a bearing sensor 12 are cumulatively processed in a CPU and the present relative running position (computing position) with respect to a reference position is obtained. The starting position of the vehicle is given as the reference position by the operation of a console 28. Map data are stored in an external memory 18, such as a ROM card or the like, and the computing position and a running locus are displayed on a map on a CRT 20. When thereafter an error produced between the displayed position and the displayed map, depressing a correcting switch 34 causes a prescribed number of registered intersections near the computing position to be retrieved and displayed on the CRT 20. Then, the intersections are displayed by selecting switches 38 and 40 and, when the intersection is judged to agree with an actual vehicle position, the computing position is corrected to an absolute position thus detected by a setting switch 36.