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IPhone 4 GPS not working properly

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What's the deal with the GPS on the IPhone on Verizon not working properly, I was in Times square last week and the GPS had me marked about 6 blocks off.

 

My friend who happens to have the same phone (AT&T) was Right On!!

 

Is there a problem with the GPS structure for Verizon that the locations is about 3/4 to 1 mile away???

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Re: IPhone 4 GPS not working properly

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Sometimes if I am in a building my GPS will be off but if I am outside, any of my GPS signals have been spot on

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Re: IPhone 4 GPS not working properly

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For me sometimes it's working, sometimes it's not.

 

I was told that when you calibrate it and you move the phone side to side it is supposed to calibrate to the position and the compass would work accordingly, but that's not the case.

 

Right now it's marking my position to the nearest tower around me, not the actual position I'm currently at.

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Re: IPhone 4 GPS not working properly

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It's "possible" that AT&T had a cell tower very close to where you were.  I'm surprised if ANY GPS unit can reliably get a fix inside the heart of NY.  The multipath (and "masking" angles to the GPS satellites) make it very difficult to get an accurate fix FROM GPS ALONE.  My understanding is that the iPhone uses a combination of navigation inputs (cell tower location & triangulation, GPS satellites, and accelerometers, etc) to provide a navigation "fix" under these types of conditions.  Several years ago I tried using a fairly expensive GPS receiver in downtown Los Angeles, and had very "intermittent" results... largely from the multipath, and reflected signals.  Remember, to do a pure GPS "fix", the receiver has to SEE at least 3 or 4 satellites (accuracy is dependent on the geometry of the "visible" satellites).  

...and if you have big TALL BUILDINGS everywhere, you are lucky to "see" more than one or two GPS "birds" at any time.

 

(that's one reason the military would like "spot beams" on future GPS satellites... to provide a strong enough signal to ensure better coverage in dense cities with skyscrapers, etc)

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