Re: GPS Accuracy - how much is actually needed
"Repeatability" of GPS postitions is not as good as Loran was. You may get the same reading from your GPS unit the next time you get near your favorite fishing spot (or wherever) but you may not be exactly in the same place. There may be several more (or many fewer) satellites over the horizon providing data, or the tide may be at a different level, or the military may have degraded the signal for some reason they didn't tell you. Tie up in a slip and watch how your GPS position changes because of these (and other?) variables. Mix that in with charts that may have last been sounded with a lead and line in 1840, and it becomes obvious that GPS is nice, but not necessarily definitive. I consider it pretty accurate, and then I look around and watch my depthsounder.