A system stores reference data generated by associating image feature point data with an image-capturing position and a recorded vehicle event. The system generates data for matching by extracting image feature points from an actually-captured image. The system generates information on an actual vehicle event, extracts first reference data whose image-capturing position is located in a vicinity of an estimated position of the vehicle, and extracts second reference data that includes a recorded vehicle event that matches the actual vehicle event. The system performs matching between at least one of the first reference data and the second reference data, and the data for matching, and determines a position of the vehicle based on the matching.