Another thing you should keep in mind about GPS accuracy. The DOD owns and operates the Global Positioning System. in case of an attack on the US govt. DOD can and will change the gps algorithm. This is too confuse the enemy/attacker(s) if they use GPS for tracking their 'smart' ammunitions.
A buddy od mine who serve in the Armed Forces told me this little tidbit.
If your GPS goes crazy we must be under attack!
