Many dangerous errors in new Navionics cartography

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tony_lavelle

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Shock, horror! On Sunday night, coming up the Medway in the dark, navigating with my iPad and watching out for the big iron mooring buoys, I noticed some weird features on the Navionics charts, for which I have downloaded the latest updates.

You can check the Navionics cartography for yourself on their free web app here: http://webapp.navionics.com/#@13&key=ip{xHigdC
a. Supposedly there are three mooring buoys (one is a “group of 3”). The one labelled "B.7" just NW of Stangate Spit shows at moderate zoom, to see the other two you have to zoom in a bit. I'm pretty sure none of these exist and never have.
b. The drying patch at bottom left (by Sharp Ness) does not exist and the depths along the shore of Burntwick Island are shown much too shallow.

Pan to the south and east a bit, around Stangate/Queenborough area, and you will see many “rocks” close to the HW mark. They are suspiciously evenly spaced. I don’t believe any of these exist, even allowing for a wide interpretation of what a “rock” might mean in the local context.

It’s only because of my detailed local knowledge that I noticed these anomalies. In an unfamiliar place it could be very misleading, which kind of defeats the object of having charts, does it not?

I have some experience of geographic data and map making but can’t understand how such errors could occur since the cartography must surely come from UKHO and the sources (harbour authority, Trinity House etc) would be the same as for other charts. Navionics does have a “community edit” feature but such additions are shown with a small “+” sign.

However Navionics have recently introduced an add-on called “Sonar Charts” which I understand is bathymetry based on user-reported depths, Though I have not knowingly opted for this feature it might explain the potentially dangerous incorrect depths shown. A friend who has an older Navionics app on his Android phone seems to get more believable cartography than I see on my Android phone, iPad and PC.

There does not seem to be any way to find out the source of Navionics cartography or to report errors, other than “community edit” features. Does anyone else know?

I have not seen anyone report this kind of error yet on YBW.COM but the French have (see St Vaast/Tatihou example):
http://blog.francis-fustier.fr/en/la-cartographie-navionics-devient-elle-dangereuse/
 
When you wrote to me about this yesterday I didn't notice that those 'rocks' are plentiful on the Medway too.
Incidentally I pointed out that the Swale No.4 buoy was missing from the screen shot off your iPad, but I see that it is present on the Webapp chart.
 
There is a buoy shown on the Navionics electronic and Imray paper charts in the Wash. It is shown on all the latest updated charts and all the charts preceding them. To my local knowledge it has not been there for at least 8 years..... certainly much longer.
 
Tiller Girl said:
I have never understood how Navionics achieve a reduction to chart datum with their user supplied data. Seems to me to be a pretty massive job.
Click to expand...

It has to be an automated process, there's no way it could be otherwise. For that reason alone I don't turn sonar charts on, far too many possibilities for errors

I wish navionics would concentrate on getting the core data and functionality right instead of constantly trying to add knobs, bells and whistles!
 
Alpha22 said:
There is a buoy shown on the Navionics electronic and Imray paper charts in the Wash. It is shown on all the latest updated charts and all the charts preceding them. To my local knowledge it has not been there for at least 8 years..... certainly much longer.
Click to expand...

All the charts and pilot books refer to a set of visitors' moorings in the mouth of Langstone Harbour that don't exist either.

Pete
 
Erbas said:
It has to be an automated process, there's no way it could be otherwise. For that reason alone I don't turn sonar charts on, far too many possibilities for errors

I wish navionics would concentrate on getting the core data and functionality right instead of constantly trying to add knobs, bells and whistles!
Click to expand...

Well you know I am a luddite but the forumula that would convert that into an automatic process is massively complicated. I spend hours comparing and contrasting data from various sources to get it right for a relatively tiny area of sea. The more that formula is short-cut, the more inaccurate and pointless it becomes.
 
Tiller Girl said:
Well you know I am a luddite but the forumula that would convert that into an automatic process is massively complicated. I spend hours comparing and contrasting data from various sources to get it right for a relatively tiny area of sea. The more that formula is short-cut, the more inaccurate and pointless it becomes.
Click to expand...

If there's actually a formula then it would be easy to program, however complicated. In a sense a "massively complicated formula" is what a computer program is.

The problem is if the process also requires human skill and judgement.

Pete
 
[smug mode on] Yet another reason for using iSailor instead of Navionics! No buoys shown off Standgate Spit or in Langstone Harbour entrance.[/smug mode off] :cool:
 
It's lucky you don't sail in Venzuela the coast is half a nautical mile out and the out islands three quarters of a nautical mile out, as is the island Klein Curacao and most lights don't work because they are not maintained. The windward reefs are littered with yachts and coasters who believed their chart/plotter at night. A yacht hit Klein Curacao the night before we arrived and was a good demonstration of the light not working. The north west corner of a Greek island is also out by three quarters of a nautical mile on the Admiralty chart so it happens in Europe too.
 
"Pan to the south and east a bit, around Stangate/Queenborough area, and you will see many “rocks” close to the HW mark. They are suspiciously evenly spaced. I don’t believe any of these exist, even allowing for a wide interpretation of what a “rock” might mean in the local context."


I have the Navionics downloadable, free, PC, thingy (which is very good for gawping at at home, btw) and am also foxed by what seems to be a series of isolated rocks, dotted here and there.

In some places they seem to indicate spot heights or isolated pinnacles, on an otherwise rock coast. Looking at the chart tho, you might imagine sand with the odd rock. Odd.

I first had a moan up about these charts 10 years ago and there is still seems a good deal of room for improvement. My latest C Map effort gives me a lot of daft and useless photographs of random bits of coastline but a simple thing like clicking on a feature to get full details (lights, depth over hazards etc) is missing. I think I might just like a raster copy of the Admiralty chart, like the one I have downstairs
 
prv said:
If there's actually a formula then it would be easy to program, however complicated. In a sense a "massively complicated formula" is what a computer program is.

The problem is if the process also requires human skill and judgement.

Pete
Click to expand...

'preciate that. Didn't express myself fully or well. They would also have to hoover up live data from a range of sources. Everything is possible, it's just sums but the complexity is just something you cannot see them bothering with. There is an element of human judgement but I suppose that could be reduced to sums as well. I am just wrestling with interpolation for a point between Shivering Sands and Walton where the live data shows that both high waters were below prediction but Walton only just but Shivering Sands quite so.
 
tony_lavelle said:
Pan to the south and east a bit, around Stangate/Queenborough area, and you will see many “rocks” close to the HW mark. They are suspiciously evenly spaced. I don’t believe any of these exist, even allowing for a wide interpretation of what a “rock” might mean in the local context.
Click to expand...

Not a row of old pile stumps by any chance?

Pete
 
"Pan to the south and east a bit, around Stangate/Queenborough area, and you will see many “rocks” close to the HW mark. They are suspiciously evenly spaced. I don’t believe any of these exist, even allowing for a wide interpretation of what a “rock” might mean in the local context."

The "rocks" shown evenly along Dead Man's Creek are in fact wooden piles and clearly seen. Have you ever Googled Dead Man's Island? There are some quite interesting videos, showing the tide line littered with exposed old coffins and human bones left over from when the area housed Quarantine ships.
 
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