As was said by irishcoffee upthread, jamming GPS is not a concern. If you think carefully about that statement for a minute or two, you'll probably figure out w

As was said by irishcoffee upthread, jamming GPS is not a concern. If you think carefully about that statement for a minute or two, you'll probably figure out why: the incredibly weak, trivially-noise-jammed-into-oblivion GPS signal isn't used as a primary source of position data in battlefield conditions. I expect that military GPS signals do have some crypto to help prevent spoofing, but that doesn't do any good when you can't hear the signal over the enemy's noise.