When we moved to Maine some years back with our Bouviers, we had an Invisible Fence installed around 4 of our 13 acres. Other than occasional broken wires it worked like a charm. Out in the woods the wire just lay on the ground and they learned very quickly where the wire was. It even crossed a stream in two places. If the GPS works it will only tell you where the dogs are, not keep them where you want them. Now we just have a Standard Poodle therapy dog and she never leaves our sight. What a great breed! Good luck.