I am not sure I follow, assuming the electronic and paper charts come from the same raw data, wouldn’t they by equally reliable or unreliable? if not, would it always be a given one was better than the other?
Speaking of accuracy, the NOAA survey boat has been tied up next to me for a couple of weeks now and I have been telling them all the local spots to survey where the shoals have moved relative to their charted position. They have a really cool side-scanner for their sonar that will pick up stuff that an old school depth finder would miss.
Yeah, my post wasn’t clear.
Sometimes and in some places the charting accuracy, local pilots, nav aids and so forth are not sufficient. Some limited local knowledge is also required for added margin.
Gaining that knowledge is much quicker and more efficient with the aid of an ECDIS.
For example just a quick glance at Doppler under keel clearance for comparison to charted depth via ECDIS there’s no need to first obtaining a position.
1 Like
I was racing a boat a few years back when the skipper and navigator were on deck with an old handheld GPS that did exactly this - just numerical lat/lon & bearings. In heavy fog the nav was calling bearings to the Golden Gate bridge because the skipper wanted to 1-gybe to the entrance while I was below taking a nap. When I awoke I glanced at the chart plotter and immediately jumped on deck calling for an emergency gybe - turns out we were less than a minute from the surf line; by the time we completed the turn rocks had loomed out of the mist within easy potato throw. The nav and skipper had totally forgotten the shape of California and that the GG Bridge is about a mile in from the coast line. These were experienced people that had just gotten too used to modern video electronics.
1 Like
Generally ports get resurveyed, the rest of the world not likely so WGS 84 datum is not reliable.
Turkey and Greece the GPS puts you on the land lots, Africa as well
There were - maybe still are?? - places in the Bahamas that were far enough off to run you onto a reef. The issue always used to be that the charts were all 18th and 19th century work, they were really good at surveying relative to a point, but the raw lat/lon was off and no one knew any better until GPS came around.
There used to be sets of waypoints passed around to get in and out of the anchorages that could be quite dangerous to follow, you were never sure if the guy who recorded them was missing coral heads by 100 feet or 100 inches.
You post a lot of good stuff but this one is in very poor taste. Utter devastation in Fort Myers’s Beach.
4 Likes
