Differences between GPS and A-GPS

Posted by Alex Zaah filed under GPS

Since Smartphone starts to get popularized, many mobile device manufacturers integrates GPS chip into even low budget handsets. But a lot of users are still not sure what A-GPS is and its differences from GPS. What makes the whole thing worse is that while most GPS enabled cell phones support A-GPS, some phones which have A-GPS capabilities do not own built-in GPS chips. So it’s important for us to differentiate them.

A-GPS stands for assisted GPS, it acquires your location using GPS data downloaded via cell towers instead of GPS satellites to enable quicker positioning and it is widely used in mobile devices. Usually, when you switch your GPS on, it starts to find the orbits and clock data of the relevant satellites to find your location. It may needs 30 seconds to up to a few minutes to finish the whole process. It takes especially longer if you have a cold start, which is called TTEF, or time to first fix. The time required determining the location of an object depends on the strength of interference around your place. Open fields are usually faster than urban environments where tall buildings are crowded.

But if your device is A-GPS enabled, then the whole process takes much shorter time. The GPS receivers and base stations in the cellular network always save and update the satellite information and computing the data. If your handset send a request, the satellite data will be passed on to your handset with your current location already identified via internet connection like GPRS, Wi-Fi or 3G network. So it is much faster than a cold start.

A-GPS has many advantages over GPS:

* Quicker location acquisition.
* More precise location.
* Less computing power needed.
* Longer battery life.

But keep in mind when you use A-GPS, you need mobile internet to connect to the cell towers and download GPS data and you may be charged by your mobile operator if you do not have a data plan.

Please note the satellite data you download is usually valid for 7 days, after that period you need to download it again. In the meantime, you can only download data for a small area, if you move to a new city, for example, from New York to Washington, you need another download as well.

A-GPS can help us in a lot of ways, especially if you are in a place where GPS signals are weak or blocked. In this case A-GPS can help to determine your position quickly. If you are not sure how to configure A-GPS settings, you definitely should check this out – speed up satellites acquisition on your cell phone.

Update, if you could not find your location using GPS or it takes way too much time during the whole place, you may need to consider flashing your ROM or a new ROM. I do not know why, but I get much quicker locations in some ROMs than others.

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