What is the location for IP address of POST request prepared using ASIHTTP, if user is on 3G?

If I prepare an HTTP request using ASIHTTP in my iPhone app, POST it to a php site, and have the site log the IP address, and if the user is not on WiFi but using a 3G connection, what will the logged IP address represent?

I happen to be interested, in particular, in getting the time zone of the users using the IP address, so I can analyze what time of day my users are using the app. Obvious开发者_开发知识库ly, I should have had the POST request include the local time zone of the user instead of just the time of day (in GMT) that the action took place. But I didn't do that, and I'm wondering whether I can still figure out the time zones of the users based on the IP address, which I was logging. For users using WiFi I can be relatively sure of what time zone they were in. But what if the users were on 3G?

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The IP address is ... whatever their carrier assigns to them. It's likely that it's local to the tower they're on, but there's no guarantee of that.

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Chances are that it will be an IP that closely represents the area that they are currently in.

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Virtually all cell providers use NAT gateways for their data network exit points. It is highly unlikely that a phone would ever get a non-private IP (it'll be 192.168.x.x, 10.x.x.x, 172.[16-31].x.x).

As such, while your phone itself will be posting from one of those IPs, the site that's receiving the post will see the IP of the cellprovider's gateway.