Apple don't disclose any specs on the GPS in the IPad. On some of the computer tech forums there is a lot of discussion about them using mobile phone tower triangulation rather than full GPS.
It is called "assisted GPS"
Assisted GPS - Wikipedia, the free encyclopedia
In my experience (on the ground in a 3G blackspot), the iPhone and iPad can lock on the satellites on their own, it just takes longer.
That said: so far I have not been without NextG while flying, ever. But if I were to go into the centre or from here to Perth, I wouldn't rely on it working on its own.
I'd invest in a bluetooth "real" GPS designed for the iPad.