A-Gps is short for assisted global positioning system. Generally speaking, when you switch your Gps on, it starts to find the orbits and clock data of the relevant satellites to acquire your location. And it may require 30 seconds to up to a few minutes to finish the whole process which is called TTEF, or time to first fix, the time depends on the interference around and your location, open fields are usually fast than urban environments.
But if you have A-Gps receiver in your mobile phone, then the whole process may be much faster. The Gps receiver and base station in the cellular network always save and update the satellite information and computing the data. If you make the request, the satellite data will be passed on to your Gps phone with the location already identified via internet connection like GPRS, so the cold start is much faster. A-Gps has many advantages over Gps:
- Faster location acquisition.
- More precise location.
- Requires less computing power.
- Better battery life.
But it should be noted when you use A-Gps, you may be charged for your internet connection.
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