Differences between GPS and A-GPS

Since Smartphone starts to get popularized, many mobile device manufacturers integrates GPS chip into Smartphone. But a lot of users are still not sure what A-GPS is and its differences from GPS. While most GPS enabled cell phones support A-GPS, some phones which have A-GPS capabilities do not own built-in GPS chip. So it’s important for us to differentiate them.

A-GPS stands for assisted GPS, it acquire your location from GPS data downloaded from cell towers instead of GPS satellites to enable quicker positioning and 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 acquire your location. And it may require 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 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 may be much shorter. 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.
* 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. So you might as well get 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. Or 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 blocked. You can use it 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.

2009-Oct-Thu | Category: GPS | Tags: ,

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