Pinpointing the location of a vehicle or mobile device. Also called "geotracking," mobile positioning is a location-based service (LBS) that is used for emergency purposes as well as proximity marketing, traffic updates, fleet management and asset tracking. Mobile positioning is also used for people tracking; for example, parents can install software in their children's smartphones to monitor their whereabouts (see Big Mother
). To track a location, cellular networks, Wi-Fi and GPS are employed alone or in combination.
The most basic method is cell of origin (COO), which identifies the cell tower closest to the user; however, accuracy is typically around 1,500 feet. Using additional reference beacons and antennas, accuracy can be greatly improved with methods known as Enhanced Observed Time Difference (E-OTD), Time of Arrival (TOA) and Angle of Arrival (AOA). See E-911
Wi-Fi and GPS
Wi-Fi hotspots are also used for location detection. Databases of known hotspots are constantly updated, and positioning accuracy can be within 100 feet. However, Wi-Fi only works well in dense urban areas, and it serves to augment cellular positioning rather than be the sole locating method.
GPS offers the greatest accuracy (15-75 feet), but requires line of sight to the satellites. Since this cannot be assured in cities with tall buildings, most smartphones employ Assisted GPS (A-GPS), which helps them get the initial fix on the satellites by obtaining orbit and clock data from nearby cell towers.
A-GPS Is Used to Track Everything
Assisted GPS (A-GPS) devices are available to track cars, pets, children as well as anything that may move or be moved. Users can locate the device on the Web or be alerted via email or text message if the A-GPS device moves outside a defined area. See vehicle tracking