GPS on iPhone and Android...is there any way to get the EXACT location of the phone (not approximate)?

I know that it's mo开发者_运维知识库stly "approximate".

But, I must know the EXACT location of the phone, regardless of battery life or whatever. I need the exact location of the phone! Is it possible?

It depends on what you mean by exact!

Any location technology will have a level of accuracy and much of this depends on the hardware your using. Mil spec GPS will cost a lot more than the chipset in your iPhone and use a lot more power too.

The best I've managed to get using the browser with iPhone 3GS GPS in wide open space is +/-17m

Usually its best to design you application around this for example most turn by turn sat-nav assumes you must be on a road and correct the location for this.

Uncertainty principle says no.

Define 'exact' and then we'll tell you. If it doesn't move and you've got a month, then better than a millimeter is probably possible (they track earthquake faults this way). But if it's moving, or doesn't have a good view of the sky, then it's not going to work nearly so well. And the math to do long-term averaging is pretty heavy going.

From the point of view of fundamental physics this question is meaningless. No physical measurement can ever be EXACT. There is ALWAYS a tolerance. Even if you went back to your national datum point and surveyed your position back to the point in question there will be errors in the measurements taken that will result in a non exact position.

If you then put your device on the ground - where on the device are you measuring to - the top left corner, the intersection of the diagonals across the device, the antenna position...?

"Regardless of battery life" - are you implying that the position measurement must occur in the absence of power?

Look into fine GPS location in the location API's(on Android)...that's the most "exact" you're gonna get. If you get a good GPS lock it'll probably be <10 meters. I just tested while in my house and got <5 meters.