You really think terrorists are going to spend all that time building a GPS guided UAV with enough explosives to do damage? Just because GPS is now cheap and widely available? Spending millions of dollars on weapons with all the latest gadgets to accurately hit targets is something the military do. If you're a terrorist, use the KISS principle - Keep It Simple Stupid - especially if you want it to be effective.
kalavo, a GPS guided mini UAV bomb with a 500 plus mile range and able to hit a target within eight odd metres would probably cost less then a couple of thousand dollars. The terrorists have already been testing UAV's.
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