CAR NAVIGATION SYSTEM AND METHOD, SOFTWARE FOR CAR NAVIGATION AND RECORDING MEDIUM HAVING RECORDED CAR NAVIGATION SOFTWARE

摘要

PROBLEM TO BE SOLVED: To achieve accurate judgment of whether own vehicle is running on an upper or lower road even when the roads parallel vertically in a high level roadway or the like. SOLUTION: A reception state monitoring part 43 monitors the state of reception of each GPS radio wave from individual GPS satellites. An upper/ lower level judging part 44 judges whether the own vehicle is under the elevated road or not based on a reception impossible region where a satellite sending radio waves not being received exists in the sky according to the state of reception. The upper/lower level judging part 44 makes the judgment in a road section having an elevated structure based on the data within a CD-ROM. A map matching part 45 judges on which of a plurality of roads the own vehicle is running based on the result of the judgment by the upper/lower level judging part 44 and the current position calculated.