Confused by GPS and AGPS

[jerethi]

The subject says it all.

I understand what AGPS is: it stands for assisted GPS, requires a data connection, and is supposed to speed up the time it takes the GPS device in our phones to lock on to the GPS satellites. But my understanding sorta ends there.

I'm using a stock Droid Incredible. Is AGPS always enabled on my phone? How can I tell? In some forum posts I've read through, people seem to reference a "use wireless networks" option in the Location menu - I don't seem to have one. Would that be different from turning my wifi radio on?

At one point, my GPS was taking forever to lock on. I downloaded the app GPS test and used the option to "clear AGPS data" in the settings menu, and now my GPS locks on almost instantly, regardless of whether I have my wifi radio enabled or not. So what the heck did that do? Am I not using AGPS anymore? That doesn't seem to be the case, since it's locking on very quickly these days.

I feel like I'm out to sea on this issue. If there are any gurus out there, I'd love to be educated!

 

[jean15paul]

+1 ... I'd like to know more too.

 

[Kevin OQuinn]

It all depends on if you've changed geographic location by a significant distance or not. That will have an affect on how long a lock takes.

As to where those settings are in your phone, there's usually a "location" button in the settings menu. Maybe there's an advanced button, maybe not.

GPS is exactly what it sounds like. It uses the GPS satellites to lock in to your location. Some phones that have a barometer use that for altitude also, because that allows for a more precise location (remember, location typically requires x, y, and z axis, since space is three dimensional). What aGPS does is use cellular triangulation to narrow down your location. This lets your phone know what satellites it should be able to see. A cellular connection isn't required for GPS use, but it usually helps.