iPad Air

Only WiFi & Cellular models of iPad have a built-in GPS receiver. 

WiFi Only models of iPad are entirely dependent upon geographical lookup against a database of WiFi networks and public IP Address of the network to which to device is connected via WiFi. As such, without an active network connection, a WiFi Only device cannot (even approximately) determine its location.

However, a WiFi Only iPad can be augmented with an external dedicated GPS Receiver - connected via WiFi.

If intending to use an iPad for navigation purposes, a WiFi&Cellular iPad (with integral GPS) is likely to be the better choice - mindful that the iPad will need good line-of-sight to provide a good positional fix (obstructions will result in reduced performance due to uncreased DOP). 

I hope you find this information helpful in informing your decision.

You can if you choose the Cellular model. The wi-fi only model does not have a GPS unit, but the cellular model does.

While the Wi-Fi only model can still be used, its accuracy may not be the best since it relies entirely on nearby Wi-Fi networks for geolocation.