Putting aGPS To The Test

Earlier today I installed Herg’s latest ROM on my Fuze and with all ROMs the first thing I do is put it through its paces and one of the tests is the dreaded GPS test. I’ve always noticed that some ROMs can get a fix in seconds and on others it just sits even though I’m using the same radio regardless of the ROM. So after loading his ROM I manually turned off aGPS and even though I was indoors I was hoping to get one or two satellites but it couldn’t connect. The rest of the guys said they were getting a fix in seconds and asked if I had disabled aGPS. Once I turned it back on I had an immediate fix. So, the error was mine for doubting Herg’s settings…if I just stuck with them I wouldn’t have had any problems.

So, why did I turn off aGPS? Well aGPS works by getting GPS data from local cell towers to help to get a quicker fix (if you want more detail take a look at WMExperts’ tutorial on it) but I had read an article a while back stating that because some areas do not have enough cell tower density and in some locations the towers won’t provide aGPS data the end result is a slower GPS fix because you lose time trying to communicate blindly with cell towers that are essentially GPS zombies. Well after my earlier experience it was time to put it to the test.

So the question is, what is best to get an initial GPS fix from a cold start on a Fuze? The first time you try to get a GPS lock after a soft reset your phone has no data, but if you had a lock and then put your phone to sleep and try to get a GPS fix you get a hot fix which takes less time. So what I did was restart my phone, open Internet Explorer and ensure I had a data connection and ran Google Maps. I did this several times with aGPS turned on and with it turned off and each time restarting my phone. Outdoors in cloudy conditions I was able to get a GPS fix using aGPS in an average time of 9 seconds. From the same location (and yes, I took turns between aGPS on and off) with aGPS disabled I had an average first fix time of 19 seconds. I performed 5 rounds of each and the results were consistent (usually within a few seconds in either case).

So now it was time to take the testing a little further and I moved indoors where I know I have a weak GPS signal. The results were even more dramatic. With aGPS on I was still getting a fix in under 15 seconds (it was less satellites than outdoor conditions as expected). Without aGPS turned on I had several cases of Google Maps timing out without getting a fix and in some cases it would get a fix with the best time being just over 30 seconds. I don’t know what causes the swing in values, but it was clear that aGPS was the hands down winner.

So I learned a lesson…aGPS will be enabled on my Fuze for now on and i will not doubt Herg’s settings any longer:) To check if you have aGPS enabled go to Settings – System – aGPS Systems. And as usual, I’m open to your findings.  Try running a GPS program with and without aGPS enabled (both times from a fresh restart) and report back to the community in the comments making sure to mention what carrier you use if it’s not AT&T.