How does the global positioning system work?

GPS functionality can be used by emergency services and location-based services to locate mobile phones. Assisted GPS is a GPS technology often used by the mobile phone because it reduces the power requirements of the mobile phone and increases the accuracy of the location obtained. GPS provides a location solution which is less dependent on the telecommunications network topology, but more dependent on the mobile phone than methods using radiolocation. The ability to locate a mobile phone to reasonable accuracy is mandated in the United States by E911 emergency services legislation. However, as of September 2006 such a system is not in place in all parts of the country. The mobile phone location may also be used to provide location specific information to the mobile phone, such as location specific advertising, or providing service information specific to the phone user's geographic location.