Originally Posted by shananchie
Many years ago, my daughter did a school science project on GPS and nautical charts. We picked a bunch of spots in Biscayne Bay and the Upper Keys. A significant number of locations and channel markers were off, some by many hundreds of feet.
I wouldn't feel safe watching the dot instead of watching the water.
I guess that's the good thing about sailing in the third world; there are very few aids to navigation and they are often not lit or on station.
There is absolutely no doubt that your GPS is much more accurate than any chart, as far as physical landmarks are concerned. You only have to do the ICW to learn this lesson. GPS is a wonderful aid to navigation, but you can be hard aground when a paper chart is showing you in 1000 feet of water. I have seen sat photos of some of the islands in the SoPac, and you would bet the farm that they were not of the same island shown on the chart.
At one time, Antigua had a notation on the chart that the island was mischarted by 1/4 of a mile. Fortunately, this was before GPS, or a dark and stormy night would have been the ruin of many a small craft.
Other than that, however, the information regarding the vessel's passage through the water is not unreliable and exceedingly useful.