Cellular radio communication system, e.g. for GPS navigation system; has data storage unit to transmit information about variations in local magnetic field to each radio unit

摘要

The system has radio base stations (18) for radio communication with radio units (12). Information about the local magnetic variations is transferred to each radio unit from a data storage unit (14), which is central to several base stations, across an externally directed communication channel (16) of a base station, which is near to the radio unit. Independent claims are included for an electronic compass unit and a method to correct an electronic compass unit for local magnetic variations.