To sum up:
GPS is an independant system that does not require any other connection, such as WiFi or 3G in order to determine your co-ordinates.
You will, however, require an internet connection in order to download map data in the Map app. You can avoid this by using a programme that stores complete maps on your iPad.
You will also notice that without the assistance of cellular and WiFi locationing services that the initial position acquisition will take considerably longer, as well as reduced functioning in areas of high interference - that is the beuty of AGPS - a multiple systems approach to supplementing GPS functioning to increase positioning acquisition speed and accuracy.