LOCATION SYSTEM WITH CALIBRATION MONITORING

摘要

A radio signal based object location system is provided wherein location devices are provided on articles for use in locating the articles, and wherein a database is maintained relating characteristics of radio signal transmissions between the location devices and fixed devices to locations within an area. A method is provided for maintaining the database t reflect propagation conditions. Location devices are provided at fixed positions within the area. Data representing radio signal transmission characteristics between the fixed position location devices and fixed devices is recorded. Transmissions between the fixed position location devices and the fixed devices is monitored to determine changes in the characteristics of radio signal transmissions from the recorded data.