iPad GPS without data plan OR wi-fi...how?

Factual Questions
1

I have been trying to get a definitive answer to this and there’s too much conflicting stuff out there.

I have a 3g iPad, but no data plan and no sim. I just turned off my wifi and went to maps and it didn’t fail to locate me, it just said it would do it BETTER if I had my wi-fi turned on.

So, this is what I am trying to understand:

If I had an iPad that was “wifi-only” would it be completely incapable of receiving GPS data at all, or would it be limited to doing so with wi-fi turned on, or limited to doing so with wi-fi turned on and some app that somehow communicates with satellites?

In other words, is there something in the iPad 3g model’s hardware that has nothing to do with its 3g capability that allows it to communicate with GPS satellites, and is that hardware missing from wifi-only models?

2

Yes. The 3G iPads all have a dedicated gps receiver. The wifi-only iPads do not.

3

Your 3g ipad uses real GPS hardware in conjunction with wifi positioning.

Non-3g models use only wifi positioning.

4

The rationale presumably being that the Wi-Fi models will be used indoors, or otherwise not generally moving about much?

5

I think it’s more a hardware issue. The same sub-circuit board that houses the 3G receiver also has a gps chip on it. No 3G, no gps chip. I use my iPad for offline navigation quite a bit so I got the 3G model just for the gps functionality. I have never turned on the 3G.

6

Just as an aside, I have to say that GPS blows my mind. On my iPhone I have an app that tracks me for the purposes of exercise, and the precision is astonishing. I walked down to the local 7-11 one day, and it’s a small one, and for some reason I was going back and forth in the aisles looking for something. When I looked at my route, every single step I had taken inside the 7-11 had registered, with lines going up and back and criss-crossing in this tight little area inside the 7-11.

It’s a sci-fi kinda world…

7

WiFi plus 3G model:
has GPS hardware (assumed to be integrated with the cellular radio)
does not need 3G data or WiFi to be on to get a GPS fix, because the GPS hardware will communicate directly with GPS sattellites (i.e. no data connection needed)
even though it will accurately calculate its location with 3G/WiFi data OFF, it still needs data in order to show you the location in the Maps app, unless map data for that location was previously cached (or you use an offline maps app such as TomTom)
With 3G radio on, it also uses A-GPS to triangulate cellular towers in order to figure out location and get a quicker fix on the sattelites through the GPS hardware
With WiFi on, it also uses WiFi triangulation

WiFi only model:
does not have GPS hardware
With WiFi OFF it will only show you last known location
With WiFi ON it will use WiFi triangulation to show you location (this uses a data connection to query a database of known WiFi access points)
WiFi triangulation has nothing to do with GPS satellites. It uses a database of know WiFi hotspots and their known locations instead. They collect this data in the same manner Google maps vehicles do; drive around neighborhoods. Apple used to use a 3rd party (www.skyhook.com), but now has its own database.