What's "assisted GPS"??

[twinturbostang]

Most of the smart phones these days have what is referred to as "assisted GPS". What is this? Is there a GPS receiver in the phone? Or does it rely on cell tower triangulation for position? Or maybe a combination of both?

I wonder if you can get positional information when out of range of a cell tower. For instance if you're hiking in the woods, you might not have cell reception. However, knowing exactly where you are is definitely important. And not having to also carry along a dedicated GPS unit (Garmin, etc.) would be handy.

 

[Jerry Hildenbrand]

Assisted gps means cell tower triangulation is used to "assist" and speed up the process of getting your position. aGPS still uses a gps receiver to fine tune your location or when you have no cell coverage.

 

[twinturbostang]

Cool. Thanks.

So being "assisted", how much quicker can a location lock occur compared to a standard GPS receiver?

 

[anon(12496)]

It gets a lock pretty fast, just a few seconds is all it needs like while you start the app that needs location data, however your initial position will be somewhat less accurate, since cell tower triangulation is less precise. You'll have to wait for the GPS module to find satellites to make it more precise, and that will take the usual time, depending on how clear a view of the sky you have. Just to show an example, it takes 15-20 seconds for Google Maps on my phone to get from 70 meter to a 10 meter accurate lock after opening in good cell coverage ares. Another 20-30, and it gets as good as it is going to. Please note that just cell coverage is not enough though, it just help speed up things. You need both coverage and a clear view of the sky to enjoy the benefits of aGPS, but it's definitely faster than just pure GPS.

 

[twinturbostang]

Thanks for the info.