First of all, the wifi only ipads dont have any gps. They use network locatiing triangulation. Its decent...but you need to be on a network!
The 3g ipad does have GPS..its called A-GPS. Reports are conflicted on whether this is a true chip gps...but one thing is for certain, it uses cell tower triangulation to assist the gps in getting a fix be it faster and more detailed location awareness. Not good when you're out there.
There is a dedicated GPS that can attach to the ipad through its data port...but at that point, why spend the money. Better alternatives.