PORTABLE NAVIGATION SYSTEM

摘要

At least three magnetic field sources (4a to 4c) that generate alternating-current magnetic fields of which frequencies differ from each other are disposed at predetermined positions. A mobile terminal (2) detects the alternating-current magnetic fields using a triaxial magnetic sensor (3a) installed therein. The alternating-current magnetic fields are resolved for each frequency, and the intensities of the magnetic fields for each frequency are calculated. Distances from the mobile terminal (2) to the magnetic field sources are calculated from the intensity values, and the position of the mobile terminal (2) is determined. In this manner, a travel start position of a user (6) can be precisely determined even when the user is at a site where GPS radio waves do not easily reach. Moreover, the current position of the user (6) is determined by autonomous navigation when the user (6) moves.