Another Navionics Victim in Georgetown

[gmakhs]

Maps are suggestions, a captain should never follow them blindly, I feel sorry for the cat but it's not navionics mistake but captains mistake.
The captain should realize that and learn from his mistakes .

Ps let's say the map was showing a passage, he didn't check the depth sounder ????

[Captain Bill]

Just an update on the boat. The local salvage operator managed to Epoxy a patch over the hole and pump all of the water out. The boat also lost its starboard rudder. There is no place here that can haul the boat. The boat is en-route to Freeport on one engine and one rudder to get hauled and repaired. Fortunately for the captain it's a pretty calm week here weather wise so hopefully he won't have any significant problems getting up there.

[a64pilot]

Originally Posted by Captain Bill

I've only seen a significant GPS error once and that was tied to a dock in Whortonville, NC. I was getting ready to go out and had the chartplotter on and suddenly I was 14 miles away in the Bay river. I heard a jet flying over and looked up and saw an EA6B heading for Cherry Point. When he went over the horizon I was suddenly back at my dock.

He shouldn’t have had his gear on, but who knows?

I’ve looked into the cockpit of an EF-111, where the Master Arm switch usually is, is a Master Radiate switch

I’ve heard stories of the capabilities that are hard to believe, but have been told in briefings of what they can provide and it’s surprising.

We used to tease them that they had better be through with having kids.

[a64pilot]

Originally Posted by conachair

This is a little usb gps just resting against a window inside on a steel boat, is horizontal dilation the best indicator of accuracy?

In truth I don’t know enough of what I’m looking at to comment.

Usually a manufacturer will give you ESTIMATED error, based on number of satellites, signal strength and satellite geometry.
It’s usually awfully accurate, they know almost exactly how much they are off, but of course don’t know where they are in that circle of error.

However less than 10 meters is very common and likely it’s better than that. Many GPS’s will use the software to correct your position to where it assumes you are, that is why a car GPS won’t display you driving down the sidewalk or alongside of the road, to actually get that kind of accuracy would require less than a meter accuracy, and that’s difficult in a moving platform, beyond what an inexpensive car GPS can do.

Of course 10 meters on some channels can put you aground, so best to back up what the GPS is displaying with what your seeing.
That and the Geo referencing of the charts may have some error too.
One spot in the Gulf of Mexico, just East of Panama City is way off, your in the middle of a bay and the GPS shows you on an island, that is the charts inaccuracy, not the GPS.

[belizesailor]

Just reinforces: never trust any chart (paper or electronic 100%). At best this boat was navigating an area which called for eyeball navigation...at 7PM! Bad decision regardless of chart.

[Group9]

My passage plan in the Bahamas is “don’t go through reef passes I’m not familiar with in bad light conditions, no matter what the darn chartplotter says”. So far, it has worked.

[Vasco]

Originally Posted by FreeSpearit

My husband and I use Navionics throughout the Caribbean and Bahamas. It has worked really well for us. But yes, we ALWAYS have someone on watch, actually physically watching with their eyes (watching the water and surroundings, NOT the chart) because no matter how amazing the chart is, there is no way to be everywhere in the world every time something changes in bottom contours.

And if anyone is wondering what the chart looks like and you want to explore a specific area you can see (for free) the data that's available on the Navionics charts by going to Navionics ChartViewer and zooming in on the area you want to explore. It's the same data that is in the app and on the chips. You just don't get the 3D view like you do on a Platinum version of the Navionics chip.

There is also a feature in the Navionics app that lets you add an edit to the chart if you find something is incorrect. It's called Community Edits. Here is how to add them: https://youtu.be/QvXKMB50xXA

You can see it and explore it online but until you're there you cannot tell if it is accurate. Lots of geo-referencing errors in Navionics Bahamas charts.

[Captain Bill]

A couple of updates: We got word yesterday afternoon that the cat was in Freeport and was on the hard being repaired. It was calm today so the admiral and I went out to the reef to survey any damage. We found the impact point which was marked by a couple of pieces of fiberglass that appeared to be part of a rudder. Fortunately damage to the reef was minimal. There was a bit of damaged fire coral where the sail drive/rudder had impacted the reef, but the damage was only about 30cm wide and perhaps a meter long. We were there near low tide and there was only about a half meter of water over the top of the coral and and the damaged area appeared to be about 30cm deep. The impact happened about mid-tide so there would have been perhaps another half meter of water over the rock. There was a deeper area to the south where the port hull would have passed which explains why only the starboard hull was damaged. Not that I would ever suggest anyone attempt crossing this reef but if he had been 30 feet to port he probably would have made it.

[kas_1611]

Originally Posted by Captain Bill

A couple of updates: We got word yesterday afternoon that the cat was in Freeport and was on the hard being repaired. It was calm today so the admiral and I went out to the reef to survey any damage. We found the impact point which was marked by a couple of pieces of fiberglass that appeared to be part of a rudder. Fortunately damage to the reef was minimal. There was a bit of damaged fire coral where the sail drive/rudder had impacted the reef, but the damage was only about 30cm wide and perhaps a meter long. We were there near low tide and there was only about a half meter of water over the top of the coral and and the damaged area appeared to be about 30cm deep. The impact happened about mid-tide so there would have been perhaps another half meter of water over the rock. There was a deeper area to the south where the port hull would have passed which explains why only the starboard hull was damaged. Not that I would ever suggest anyone attempt crossing this reef but if he had been 30 feet to port he probably would have made it.

30ft to port? 10m, sounds exactly like a GPS error margin to me. My guess he thought he was safe because he was blindly following the chartplotter and not looking. Not a Navionics/Garmin/C-Map et al problem but the pink thing at the helm problem.

[Tollesbury]

Really sad that so many people rely on electronic aids to navigation. Not just Navionics, any manufacturers’ systems require expertise for safe use. Bottom line - get with it, guys, get learning, get navigating ... no blaming the tools.

[Palarran]

Originally Posted by Tollesbury

Really sad that so many people rely on electronic aids to navigation. Not just Navionics, any manufacturers’ systems require expertise for safe use. Bottom line - get with it, guys, get learning, get navigating ... no blaming the tools.

Thank you for that really insightful post. It helped me a lot so I'm going to get with it from now on, learn how to use my chart plotter, or maybe not use a chart plotter. Which is it?

[Tollesbury]

Originally Posted by Palarran

Thank you for that really insightful post. It helped me a lot so I'm going to get with it from now on, learn how to use my chart plotter, or maybe not use a chart plotter. Which is it?

I’d say both. Learn to work with your chart plotter; and learn to do without it.

[jimisbell]

Some years ago I was in the Carribean and went into the small lagoon of Rendevue Cay off Belize. It was a shallow break in the reef. I had my daughter in the bow pulpit. We got through with only a tiny bump, no problem, going very slow under power. Later in the afternoon we were sitting in the cockpit eating lunch and saw, in the distance, a much larger boat heading toward the reef with a 30 degree heel, obviously fast, wind driven. My daughter commented, "We are like the cheese in a rat trap." We expected that they would slow down and consult their charts. Apparently they didnt. Suddenly the mast flipped from starboard to port and then again back to starboard. They had obviously hit the reef. Charts dont work if you dont look at them. And a daughter in the pulpit is worth two charts in the hand,

[Doek]

Actually, Garmin/Navionics is probably at fault to a great degree. When Garmin bought Navionics something became corrupted in the process. Information that was clearly shown on previous Navionics Charting suddenly changed or was completely lost. I ran aground off Man O War Cay on a spot clearly showing 8 feet of water on updated Navionics Charting. I checked an old phone with Un-updated Navionics charts and they showed the 4 foot shoal that I was sitting on. Somehow it and many other things were lost in the Garmin/Navionics transfer. I discussed it with Garmin and they are clueless as to how or why. Beware of updated Navionics Charts! They went from being the best to now untrustable. A big step backwards.

[Vasco]

Originally Posted by quackedo

Actually, Garmin/Navionics is probably at fault to a great degree. When Garmin bought Navionics something became corrupted in the process. Information that was clearly shown on previous Navionics Charting suddenly changed or was completely lost. I ran aground off Man O War Cay on a spot clearly showing 8 feet of water on updated Navionics Charting. I checked an old phone with Un-updated Navionics charts and they showed the 4 foot shoal that I was sitting on. Somehow it and many other things were lost in the Garmin/Navionics transfer. I discussed it with Garmin and they are clueless as to how or why. Beware of updated Navionics Charts! They went from being the best to now untrustable. A big step backwards.

Garmin used to use Explorer data which is very reliable in the Bahamas Navionics Bahamas data is very unreliable.