For a true accurate reading three sats are required at a min the more the better. 100m as far as weapons goes are for weapons that use GPS and not say a land mine. Thus if off more than 10m a target for which a GPS aided weapon would be selected would result in a miss; most smart weapons look for about 3m. Yes vendors have found someways to get around the SA but government has found ways to put it back. And due to it being turned off for sometime most vendors have actually moved on from tryng to over come the government SA actions do to cost and need.
You must also take in to account that any damage done over and above the target will get the military hammered.