“This whitepaper introduces an open source toolkit that lets
mobile devices determine their locations with the aid of freely
accessible, nearby radio sources, such as fixed Bluetooth devices,
802.11 access points, and GSM cell towers. Basically, the device
reads the IDs of these local ‘radio beacons’ (each of which has a
unique or semi-unique ID), looks up their positions in a
locally-cached database, and performs a computation akin to
triangulation. Intel created Place Lab in an effort to satisfy the
emerging requirement for location-awareness within mobile devices
such as smartphones, PDAs, and laptops, or even moving vehicles.
According to the whitepaper, over four million of the required
radio beacons have already been mapped…”