A location and tracking system

A location and tracking system (1) comprises a site survey tool (2), a location engine (3), a self-calibration engine (4), and a fingerprint database (5). The system (1) operates for a wireless network of access points in a building and it generates from initialization data a model of the physical environment. The model may for example be in the form of data representing geometry of ones in plan and signal attenuation values for the lines. The system then uses this model to generate a fingerprint of projected signal strengths in the environment. The system may maintains a fingerprint for every environment model or there may be only one model at any one time, or there may be a number. Where the latter, the system may assign a weighting to each model to indicate its confidence value. Upon detection of a mobile node in the environment the system (1)estimates position of the node according to the current fingerprint, and in real-time performs self-calibration of the environment model, in turn giving rise to fresh updated fingerprints for future tracking. This continuous self-calibration ensures excellent tracking accuracy even with modification of the environment, such as changing of an access point configuration, moving a partition wall, or movement of a metal filing cabinet.