It is pretty common here in Texas to use an 8 foot tall sheep fence with one roll of "bob wahr" (funny, that makes perfect sense to me) on the top. Use 2 3/8" pipe cemented in for your corners and 10 foot T-posts in between. Then place 'posted, no trespassing signs all around it.
That will keep out all the law abiding citizens. Nothing will keep out the others, nothing.
On a more serious note, you could get a predator drone to patrol the area and send recon pictures to your home computer.
