The iPad only has GPS on the 3G model. Wi-Fi only iPads simulate GPS by using Skyhook type positioning by triangulating based on supposed Wi-Fi router locations.
It looks like a Wi-Fi only iPad is using real GPS (reading the signal from the GPS satellites) but it's not. Accuracy isn't anywhere close to real GPS.
That's true but if iPad 2 is tethered or Hotspot'd from iPhone 4 (and some other smartphones), it will get true A-GPS signal from the phone.