A-GPS is a system created to improve work GPS. GPS does not allow defining a site in an environment of high buildings, inside buildings and under a dense cover of trees. Under these conditions signal of GPS satellites has the poor quality complicating positioning. A-GPS receivers solve the problem receiving the information on the current coordinates of all satellites from ground station.

Term A-GPS (Assisted GPS) means an operating mode of the GPS-receiver, in which part information is transferred for the GPS-receiver on the additional channel, Internet for example. A-GPS service provider can accept the satellite data from client's GPS device, then process and return ready coordinates. Other variants of use of the technology are possible.

A-GPS technologies:

1. A-GPS Online, this technology allows to receive data quickly via ground channels each time when it is necessary. It is important each time if the receiver did not work more than 2 hours (cold start).

2. A-GPS Offline - allows to receive on ground channels of satellite's coordinates once in 15 days and to use the data each time when it is necessary to define coordinates after long deenergizing. Positions of satellites are calculated inside module GPS and GPS receiver after reception of coordinates on ground channels, corrects the model one time in 15 days. That allows predicting coordinates of satellites for the following 15 days period.

Such modules are used in cell phones, a handheld computer and other devices with various liaison channels (Internet). Besides there should be a supplier of such services, that is some organization which will sell to you this information. Now, service while is given free-of-charge, and you pay only for the Internet traffic.

The main advantage: A-GPS is improved time TTFF and higher speed of work GPS-module. Another: A-GPS is economy of energy that increases time of independent work of the navigating device.

For example in iPhone, that the current position will be defined with help GPS, Wi-Fi and stations of cellular operators. With simple GPS receiver for positioning you need some strong signals and some time for reception of coordinates. At A-GPS the auxiliary server itself informs your phone where there are the nearest satellites..