I know most phones use cell tower triangulation although more are using actual gps. And I've read that most phones using gps are accurate to around 100 meters 95% of the time, or that's the standard for E 911. But, really, if you are stalking your girlfriend, how much can you really say for sure about her exact position at any given time?

What's the error on these things? Can you really be sure she was lying when she said she was on one side of the street instead of the other? Or is it absurd to place that much faith in this technology?

Here is some info: Mobile phone tracking - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Mobile_phone_tracking)

Thanks, KISS,
I looked at that. It's good but not exactly user friendly!
This (http://searchengineland.com/cell-phone-triangulation-accuracy-is-all-over-the-map-14790) is helpful also.

But Wikipedia does say that under 100 meters is "very high accuracy." Well, that's 328 feet. We have a guy in the relationships thread who thinks his wife is cheating on him because the iPhone she's carrying says she was on the other side of a street and up an alley instead of in front of his house (when she says she was walking home). Obviously, he's nuts. But aside from that, what I'm trying to get at is, in real use, instead of just theoretical discussions, what does phone tracking really tell the tracker?

Worst case, I get that it can be off by 35 km or in rural areas. In contrast, in dense urban areas where there are hardly any tall buildings and there are lots of cell towers, even cell triangulation can be pretty accurate (< 100 m). But why does a phone seem very accurate one day, putting you in the right room of your house, and then put you half a mile off the next day?

I know that buildings, trees, and hills can affect the accuracy in both gps and triangulation, but what else affects the readout and how MUCH do they affect it, and why in each case?

Gps is supposed to be more accurate, but when I read around, I'm seeing the same 100 m figure quoted for both gps and triangulation (in urban areas). How much more accurate is gps than cell triangulation in a big city where there are lots of towers? And, in a given area on a given phone, what's the best you could count on on a regular basis? 50 feet? 25 feet? I'm not counting the occasional reading that seems to put you in your own bathroom but can't replicate that accuracy. It has to be consistent or it doesn't count as information you "know." Hope that makes sense.

How can I explain to someone like this guy that he doesn't know what he thinks he knows?

I think it also depends on the phone in use.
My current HTC Desire can use both GPS and Cell for triangulation, whereas my older iPaq just used simple GPS.

The HTC's use of both systems makes discovery massively faster and more accurate, down to mere feet.

Thank you! So how many feet?
How do you know it's mere feet?
And how consistent are those readings? 90% of the time, 99% of the time?

How many feet? - VERY low
How do you know it's mere feet? - Satellite image overlay on Google Maps ;)
And how consistent are those readings? 90% of the time, 99% of the time? - So far 100%, but I haven't tried all that many locations.

Hi I have a big problem I am living with my fiancé , he put a gps tracker on my phone.. nuts.. which I didn't care when he did that , cause I know I am not doing anything wrong , but every night when we go to bed around 1 till 6 am the gps shows I am not home , like am 50 feet to 200 feet from my house , now my fiancé think I am cheating on him when he is sleeping I am outside with another man. He doesn't believe me when I tell him don't go outside at night time, now I am living a nightmare for no reason.. please tell me what to do

Hi I have a big problem I am living with my fiancé , he put a gps tracker on my phone.. nuts.. which I didn't care when he did that , cause I know I am not doing anything wrong , but every night when we go to bed around 1 till 6 am the gps shows I am not home , like am 50 feet to 200 feet from my house , now my fiancé think I am cheating on him when he is sleeping I am outside with another man. He doesn't believe me when I tell him don't go outside at night time, now I am living a nightmare for no reason.. please tell me what to do

Dump him right away.

The guy's a jerk. Have you insisted that he put a GPS tracker on his phone so that you can track where he's been? If not, why not? What's good for the goose is good for the gander...