Table 1.

Location sources.

Location	Features
GPS	Highly accurate, directly provides velocity, only functions outdoors, quickly consumes battery power, and does not return the current location as quickly as some users may desire.
Cell towers	Works indoors and outdoors, quickly responds, uses less battery power than GPS, and is accurate up to 100 to 300 m, depending on the service provider. Cannot directly provide velocity.
WiFi	Works indoors and outdoors, quickly responds, uses less battery power than GPS, and is accurate up to 30 to 200 m, depending on the service provider. Cannot directly provide velocity.