Not to be used for ...

[AntarcticPilot]

I suppose that the provider of electronic charts cannot be responsible for the way your electronic device displays them, adding an additional layer of uncertainty. The chart should display as intended, the provider may provide guidance for manufacturer of displays but they may not reproduced them exactly as intended. A "feature" of the display, hardware or firmware.

Indeed, that's true. What is more, many display systems allow a high degree of customisation so the chart provider can't be certain what the end user will see. There's also the issue that the display system could be faulty and not display colours correctly.

Ship systems are highly integrated and are signed off by classification societies; they have to use much more expensive electronic data than we do, which includes a lot of information we don't use.
The system itself can't be changed without involving the classification society, and is less customizable than ours. If you want to get a flavour, look at the widely available CM93 charts in OpenCPN; the attributes of objects are much more detailed including stuff about provenance etc. We don't have that - in general it would not be used anyway; I'm a map geek so I looked at it!

There are useful forms of customization, such as colours for dark viewing, and reduction of clutter - but in the latter case it should result from a positive action by the user, not a default setting. If you're reducing the amount of information shown, the user should be aware of it. Any customization should be restricted in ways that the chart provider controls, so that the user can't "accidentally" switch off a class of hazards.

The problem is that users expect to have a choice of chart data available on a plotter, so the chart provider ends up with little or no control over the visualization the end user sees. Between choices made by plotter manufacturers and users, the chart provider has little control over the final visualization. Hence the need for careful disclaimers, though I personally think "Not for Navigation" is inadequate, and that sooner or later a chart provider will find it so in court.

 

[TiggerToo]

I suppose that the provider of electronic charts cannot be responsible for the way your electronic device displays them, adding an additional layer of uncertainty. The chart should display as intended, the provider may provide guidance for manufacturer of displays but they may not reproduced them exactly as intended. A "feature" of the display, hardware or firmware.

but isn't this also the case for "Traditional" means of displaying information (like paper charts)?

 

[TiggerToo]

"Not for Navigation" is inadequate, and that sooner or later a chart provider will find it so in court.

that is what I was trying to convey, in my OP.... It seems rather ridiculous.

 

[Lucy52]

but isn't this also the case for "Traditional" means of displaying information (like paper charts)?

No. I think you would be rather ingenious to misinterpret a paper chart. There is no extra layer of abstraction before you read it. You get the chart exactly as the publisher intended.

 

[AntarcticPilot]

No. I think you would be rather ingenious to misinterpret a paper chart. There is no extra layer of abstraction before you read it. You get the chart exactly as the publisher intended.

Though there are issues over differing symbolizations being used by different publishers, each with their own idea of what works best. That's one reason I'm a bit luke-warm about alternative publishers of printed charts; not that I don't think they do as good a job as they can (though it should be noted that they introduce extra potential for error), but because they don't adhere to well-established standard representations, as laid down by the IHO. If you use charts published by national hydrographic offices, they will adhere to international standards, and be compatible across the whole world. But if you use charts published by others, the representation may vary from one publisher to another, and few publishers produce charts for the whole world. Sadly, the electronic charts produced by national HOs are only available in big ship formats for use in ECDID systems, so we are forced to use third-party suppliers in our chart-plotters. The UKHO does provide raster charts available through suppliers like Visit My Harbour, but they are not as flexible or as widely useable in chart plotters as vector data.

 

[johnalison]

Whtever they say, large numbers of sailors do use electronic charts for navigation and pilotage. The first time I did this with GPS, ie not including Decca, was when approaching Braye in fog, when I used a hand-held Magellan unit before Clinton did what I told him to and switched off selective-availability. I felt safe enough, even though I knew that the errors could be large.

I don't disagree with the wording, which I have no doubt is legally necessary, but I think that many of us would reinterpret it as "only to be used for navigation if the limitations are known and accepted and preferably cross-checked against traditional systems".

 

[TiggerToo]

, but I think that many of us would reinterpret it as "only to be used for navigation if the limitations are known and accepted and preferably cross-checked against traditional systems".

Isn't this what all safe navigation is about?

Can someone better informed than I am enlighten me, please: do sophisticated/professional navigation systems not rely on some sort of "Independent" input to make decisions? A but like "radar", "ais", "mk-1 eyeball"... etc

 

[LadyInBed]

No. I think you would be rather ingenious to misinterpret a paper chart. There is no extra layer of abstraction before you read it. You get the chart exactly as the publisher intended.

True.
If you use a Small Scale Passage Planning Chart you will not see small obstructions, exactly the same as using a zoomed out Electronic Vector Chart.
It is incumbent on the navigator, onces he has drawn his line(s) from point A to point B to dig out all the Large Scale Charts that cover from point A to point B, reproduce his lines and ensure that there is no obstructions.
The beauty (simplicity) of using an Electronic Vector Chart is that once the electronic line is drawn, it's easy to zoom in and follow the proposed route in detail, or if like my (now old) Standard Horizon Plotter, it has a 'check route' facility to do it for you.

 

[Stemar]

like my (now old) Standard Horizon Plotter, it has a 'check route' facility to do it for you.

I have to assume from that RTW boat that found a reef that that facility isn't standard on all plotters. Surely it should be - and automatically, not relying on a potentially inexperienced and overtired navigator to do it

 

[AntarcticPilot]

I have to assume from that RTW boat that found a reef that that facility isn't standard on all plotters. Surely it should be - and automatically, not relying on a potentially inexperienced and overtired navigator to do it

It certainly isn't standard, and would be ruled out on older plotters because of lack of computing resources. Given a route, it isn't a particularly difficult task for a computer using vector charts (it would be next to impossible with raster charts). But it does require a reasonably powerful processor with lots of memory, and plotters tend to be designed with low power usage in mind. For the technically minded, it would involve creating a buffer zone round the proposed route, then intersecting that zone with the chart data to select everything that lies partly or wholly within the buffer. Finally, the software would inspect the selected chart objects to determine if any posed a danger - it would have to be given suitable parameters such as minimum safe depth, etc. Ideally it would take into account chart accuracy - in many places "off the beaten track", charts can be significantly in error. Finally, the results would have to include a warning to the effect that while the route keeps clear of known, charted dangers, it cannot take uncharted dangers into account, and a good lookout is still essential.

I don't think I'm unusual in that I have a 14 year old Chartplotter still operating; I've just had a modern one installed alongside it, but the old one is still operating and will be used for planning.

 

[TiggerToo]

True.
If you use a Small Scale Passage Planning Chart you will not see small obstructions, exactly the same as using a zoomed out Electronic Vector Chart.
It is incumbent on the navigator, onces he has drawn his line(s) from point A to point B to dig out all the Large Scale Charts that cover from point A to point B, reproduce his lines and ensure that there is no obstructions.
The beauty (simplicity) of using an Electronic Vector Chart is that once the electronic line is drawn, it's easy to zoom in and follow the proposed route in detail, or if like my (now old) Standard Horizon Plotter, it has a 'check route' facility to do it for you.

deleted reply because I got it wrong... no guarantees that I will not get it wrong again next time

 

[AntarcticPilot]

eerrrmm

I think you may have your scales mixed up.

On small scale, you see small obstructions (e.g. a rock)
On large scale, you see large obstructions (e.g. a continent)

SI'm sorry, but you've got it wrong way round. Small scale = small scale fraction (e.g. 1:10,000,000), Large-scale = large scale fraction (e.g. 1:1000). So a large-scale map shows more detail; a small-scale map shows less.
I am entirely sympathetic - despite working with maps for all my career, I still think it's counter-intuitive and have to think about it! I prefer to actually state the scale.

 

[TiggerToo]

SI'm sorry, but you've got it wrong way round. Small scale = small scale fraction (e.g. 1:10,000,000), Large-scale = large scale fraction (e.g. 1:1000). So a large-scale map shows more detail; a small-scale map shows less.
I am entirely sympathetic - despite working with maps for all my career, I still think it's counter-intuitive and have to think about it! I prefer to actually state the scale.

my bad....

 

[Koeketiene]

I use my binoculars for navigation. Should they come with a warning too!

Objects in the binoculars could appear closer than they are.

 

[Dukester52]

Going back to the OP... isn't that screen shot from the Navionics Web App rather than a plotter? (The free thing you can use on t'internet). If so, seems fair for it to say 'Not for Navigation' or similar.

 

[Mark-1]

"Not for Navigation" is unlikely to hold up in court on a product sold for navigation

This.

In any event, aren't these caveats worthless on products sold expressly for the purpose?

....and this.

Not so much a legal fig leaf as a legal pine needle IMHO.

 

[kaj]

...
Cannot remember the name of the round the world boat that ran aground on a reef, but if they had zoomed in on the chart they would have seen the reef.
...

"Team Vestas Wind", the report at VOLVO OCEAN RACE INDEPENDENT REPORT INTO THE STRANDING OF VESTAS WIND

 

[DJE]

Seems to me that a paper passage chart - or a raster scan derived therefrom - would not completely omit a dangerous shoal.

 

[WoodyP]

Objects in the binoculars could appear closer than they are.

 

[Graham376]

Seems to me that a paper passage chart - or a raster scan derived therefrom - would not completely omit a dangerous shoal.

Yes they do, we had The Bitches rocks (off Ramsey) missing off one electronic chart some years ago.