PURPOSE: To accurately position an image and a map by calculating transformation coefficients in order for all combinations of reference points for coefficient calculation and a reference point on retrieved map data and verifying which transformation coefficient is adequate with a reference point for verification.

CONSTITUTION: When a transformation coefficient for positioning an image and a map is calculated, reference points on the image for coefficient calculation and verification are extracted and transformation coefficients for all combinations of the reference point for coefficient calculation and retrieved reference points on the map data are calculated in order and which transformation coefficient is adequate is verified with the reference point for verification. Consequently, the image and map can be positioned speedily with high accuracy without any person's intervention. In this example, reference points 2, 4, 8, and 11 in such a combination that the sum of mutual distances is maximum are used for coefficient calculation and others are used for verification.