AGPS是一种GPS动作方式。利用手机基地站的资讯，配合传统GPS卫星。让定位的速度更快。 GPS 使用24个人造卫星所形成的网络来三角定位接受器的位置，并提供经纬度座标。 虽然GPS提供绝佳的位置的精确度，但定位的位置需要在可看见人造卫星或轨道所经过的地方。在都会区中的使用者经常在都会峡谷"urban canyons"中，在浓密的树下或是室内。Assisted GPS, or A-GPS, 是使用协助服务的技术，用来减少定位所需的时间。在蜂巢式网络上使用定位服务已越来越普遍。
The development of these services is fuelled, in part, by the U.S. Federal Communications Commission's E911 mandate requiring the position of a cell phone to be available to emergency call dispatchers.
A-GPS differs from regular GPS by adding another element to the equation, the Assistance Server. In regular GPS networks there is only GPS satellites and GPS receivers. In A-GPS networks, the receiver, being limited in processing power and normally under less than ideal locations for position fixing, communicates with the assistance server that has high processing power and access to a reference network. Since the A-GPS receiver and the Assistance Server share tasks, the process is quicker and more efficient than regular GPS, albeit dependent on cellular coverage.
Assisted GPS describes a system where outside sources, such as assistance server (Mobile Location Server) via a network, help a GPS receiver perform the tasks required to make range measurements and position solutions. The assistance server has the ability to access information from the reference network and also has computing power far beyond that of the GPS receiver. In this case, the assistance server communicates with the GPS receiver on the mobile phone on a network. With assistance from the network, the receiver can operate more quickly and efficiently than it would unassisted, because a set of tasks that it would normally handle is shared with the assistance server. The resulting AGPS system boosts performance beyond that of the same receiver in a stand-alone mode.
Ordinarily, a standard GPS device needs to have a clear line-of-sight to at least four GPS satellites before it can calculate its position. In addition, it needs enough processing power to transform the data streams from the satellites into a position. Using AGPS, the cell tower will receive the signal from several satellites, and perform the calculations. That way, all that is required is for the phone to relay any GPS signal it receives to the tower.
The main purpose of AGPS is to provide municipalities with location-based emergency phone service, such as E911 service.
※ 原文链接: http://zh.wikipedia.org/wiki/AGPS