03-Apr-2011 -- By looking at Google Earth beforehand, I knew that the confluence point lay in the back yard of a private residence, so I wouldn't be able to get 'all zeros'. (I don't like to bother home owners.) But, driving towards Tulsa, Oklahoma, I was curious as to whether or not I would be able to get close enough for a successful visit, just by staying on the road.
Sure enough, by staying on the road in front of the house, I was able to get within 232 feet (+/- GPS error of 9 feet) of the confluence point - close enough for a successful visit. (However, because the house is part of a gated community, it's possible that the road in front of the house is also private. Oh well...)