GPS question

[igorsky]

So I have the 3GS, and from what I read it has GPS built in. But I find often that my location on Maps is not always precise, but more like what you get with location assist. What the dealio?

Thanks in advance.

 

[Jeremy]

Is this just happening within a building or will it be inaccurate while you are driving or outside in general?

 

[igorsky]

Hey, thanks for responding.

I noticed this yesterday when I was driving. A couple of times when I was walking with it it had me on the next block over.

 

[Jeremy]

I have heard of some people having this issue but I don't think it is too common. You could try a restore and see if that gets you better results. No promises though. Sorry.

 

[igorsky]

Appreciate the advice.

It's odd that, although the 3GS has GPS, the official literature for Maps always says it offers "approximate" location. Maybe just a case of cya

 

[GMJeff]

It could also be a case of the GPS satellite network not being spot on with coordinates. The military has the best network, and consumers have a good network.

Some areas, like cities can sometimes make exact locations hard to get a fix with the satellite network, so the phone uses the A-GPS (cell tower assisted) to approximate your location through triangulation.

But, after reading a few complaints here in the forums, the device most likely has a faulty GPS chip inside. Take it to Apple and get it exchanged.

 

[flyingember]

This is part of the nature of GPS.

It can be quite a bit off and be working perfectly. I've had handheld GPS devices off by 100 meters.

 

[igorsky]

This is part of the nature of GPS.

It can be quite a bit off and be working perfectly. I've had handheld GPS devices off by 100 meters.

This is the answer, in all likelihood. This morning I was in midtown Manhattan, sky nearly blocked out by buildings, and the GPS had me almost exact.

 

[rfg17]

I've noticed that sometimes the error circles are bigger than others and that rebooting helps get back to normal. I suspect this is a memory usage issue that affects how well the phone can compute position given the GPS signals.

 

[flyingember]

I've noticed that sometimes the error circles are bigger than others and that rebooting helps get back to normal. I suspect this is a memory usage issue that affects how well the phone can compute position given the GPS signals.

The circle is actually improved by A-GPS. The A part is cellular/wifi. don't reboot, just go into airplane mode and it reconnects to the towers and updates this date.

You get better wifi data in dense areas, you get better cellular data in the country. It also works better when driving because it can follow the roads. If you turn and there's a road it's hard for it to get your location wrong if it moves the dot to a new road. It's also using the changing signal times from the cell towers to get your movement speed right. Get off road, say on a ferry, and it moves around for a bit even with a good signal near shore and may never be right.

The reason for the good location data in Manhattan is the wifi data. The tall buildings are blocking most of the GPS signals and cellular signals likely bounce some. they're just using gps to narrow down your location some more