Paper Charts or Just Electronic

[StuM]

Originally Posted by Kenomac

One needs to have an understanding of how to use paper charts in order to understand when things aren’t going as planned.

Example: While rounding the north eastern channel of Corfu last evening at 2am while watching the chartplotter and radar, the boat began to drift towards the rocks in such a way as to overcome the auto pilots ability to compensate. I knew immediately current was the cause and took control.

Someone only knowing how to use an electronic chartplotter... might not have figured it out in time. Probably would have wasted valuable time screwing around with the chartplotter.

That's a non sequitur. . If the chart plotter shows you heading towards the rocks, who in their right mind would "screw around with the chartplotter" instead of adjusting their heading? Who would NOT assume that there was a current?

[Kenomac]

Originally Posted by Paul L

This seems like an odd example. I must be missing something here. The continuously updated bread crumb trail on a chartplotter would make it very obvious what your actual track is. The occasional plotting of your position on a paper chart would eventually make it obvious.

You are missing something.

[Kenomac]

Originally Posted by StuM

That's a non sequitur. . If the chart plotter shows you heading towards the rocks, who in their right mind would "screw around with the chartplotter" instead of adjusting their heading? Who would NOT assume that there was a current?

Someone who believes the chartplotter to always be correct in the night and has never been required to figure out drift on a paper chart.

Hint: Current can’t be seen at night.

But nice use of a big word, I’m so impressed.

[sv Noodles]

Use both always.

[Adelie]

Originally Posted by Simi 60

But if electronic charts are derived from the same information that the paper charts are, the information is going to be the same.

Commercial charting does not necessarily rely on the same info as government charts. In the US, NZ and Brazil government charting is in the public domain and probably underlie all commercially produced charts.

Elsewhere I believe much of the government charts are under copyright. The commercially produced charts may be produced using such data obtained for a fee or they may be produced from other sources: older charts no longer under copyright or perhaps old US-DMA charts that were not not under copyright or perhaps satellite images merged with sounding data merged with info from somewhere plus info about underwater features from pilots and ????.

I know one of the commercial chart series has bad data for the Bahamas, it stands to reason that their data source was not a current government source.

Vector charts show the info differently than raster charts, zooming in and out on a vector chart info disappears. Given that the pros have occasional problems with this, it stands to reason it would be a problem for amateurs such as ourselves. It's one of the reasons I happy with charting on OpenCPN, all of my charts are raster and zooming in or out isn't going to make critical info disappear.

[Kenomac]

Originally Posted by Adelie

Commercial charting does not necessarily rely on the same info as government charts. In the US, NZ and Brazil government charting is in the public domain and probably underlie all commercially produced charts.

Elsewhere I believe much of the government charts are under copyright. The commercially produced charts may be produced using such data obtained for a fee or they may be produced from other sources: older charts no longer under copyright or perhaps old US-DMA charts that were not not under copyright or perhaps satellite images merged with sounding data merged with info from somewhere plus info about underwater features from pilots and ????.

I know one of the commercial chart series has bad data for the Bahamas, it stands to reason that their data source was not a current government source.

Vector charts show the info differently than raster charts, zooming in and out on a vector chart info disappears. Given that the pros have occasional problems with this, it stands to reason it would be a problem for amateurs such as ourselves. It's one of the reasons I happy with charting on OpenCPN, all of my charts are raster and zooming in or out isn't going to make critical info disappear.

I agree 100%. We had a problem up in Canada last season with the vector chart depths being 100% off from the raster chart depths for a fairly large area covering most of a chart. Example 10ft on one indicated 20ft on the other.

Again... someone staring at a chartplotter might not notice. The shallower depths were actually the ones that were incorrect.... which allows for stupidity.

[Paul L]

Originally Posted by Kenomac

You are missing something.

And what is it? I have a fair number of miles navigating with paper charts prior to GPS as well as a fair number of current miles with a chartplotter.

If you think you need paper charts to detect current at night, you either don't know how to use your chartplotter or your instruments are not calibrated (something that is common on a lot of boats).

[StuM]

Originally Posted by Kenomac

Someone who believes the chartplotter to always be correct in the night and has never been required to figure out drift on a paper chart.

Hint: Current can’t be seen at night.

But nice use of a big word, I’m so impressed.

Still doesn't make sense. If someone who believes the chartplotter is "always correct" sees they are tracking towards the rocks, their obvious first move is to steer away from the rocks. You don't need to "figure out drift on a paper chart" to see what is happening.

[Don C L]

I think Ken meant that anyone who was only relying on a chartplotter may have missed it, but that since radar, and autopilot response to course change, were also being monitored, it allowed for the appropriate and more rapid course correction.
I'm not sure, is that correct Ken?

[El Pinguino]

Originally Posted by StuM

Still doesn't make sense. If someone who believes the chartplotter is "always correct" sees they are tracking towards the rocks, their obvious first move is to steer away from the rocks. You don't need to "figure out drift on a paper chart" to see what is happening.

Doesn't make sense to me either.... given two choices - chartplotter or paper - I would choose the third - parallel indexing on radar.....

[transmitterdan]

Originally Posted by El Pinguino

Doesn't make sense to me either.... given two choices - chartplotter or paper - I would choose the third - parallel indexing on radar.....

+1 - a radar is immune to errors in 1880’s cartography. Nearly every case you hear about chart plotter induced groundings would have been avoided if radar was properly used. The radar doesn’t give a blankety blank what the charts say. They show what is ahead (and behind).

[Dockhead]

Originally Posted by Simi 60

But if electronic charts are derived from the same information that the paper charts are, the information is going to be the same.

That's true, but that's not the issue.


The issue is whether what the plotter tells you, about your position in relation to some danger, is correct or not. And especially -- whether it shows that danger at the zoom scale you are using, or shows it at all.



GPS is pretty reliable, but not infallible, and automatic plotting to an electronic chart is a great thing, but shouldn't be believed like religion. Charts, paper or otherwise, are even further from infallible -- I've sailed in places where there were errors exceeding one mile (Sea of Cortez; Greenland).



That's why it is prudent to do other stuff -- check what the chart shows, against what you can see with your eyes, take some bearings, work out some clearing bearings, and like Ping says in the previous post -- parallel indices with radar. All this stuff is a lot easier to do on a paper chart, but is possible on a large screen, especially if you have raster charts. It becomes pretty hard to do well on the small screen of a regular plotter.

[Simi 60]

Originally Posted by Dockhead

That's true, but that's not the issue.


The issue is whether what the plotter tells you, about your position in relation to some danger, is correct or not. And especially -- whether it shows that danger at the zoom scale you are using, or shows it at all.


GPS is pretty reliable, but not infallible, and automatic plotting to an electronic chart is a great thing, but shouldn't be believed like religion. Charts, paper or otherwise, are even further from infallible -- I've sailed in places where there were errors exceeding one mile (Sea of Cortez; Greenland).

Which is why I don't run a single system.
As mentioned earlier I run a dedicated C-map plotter on a 23 inch screen and a dedicated opencpn computer on a 23 inch screen, one zoomed out and one zoomed in and each with its own GPS antenna.

If the "danger" is not shown on either system they most likely won't be shown on paper BUT the danger will hopefully show up on google earth kap images, radar, sounder and mk 1 eyeball.

That's why it is prudent to do other stuff -- check what the chart shows, against what you can see with your eyes, take some bearings, work out some clearing bearings, and like Ping says in the previous post -- parallel indices with radar. All this stuff is a lot easier to do on a paper chart, but is possible on a large screen, especially if you have raster charts. It becomes pretty hard to do well on the small screen of a regular plotter.

Covered above.

[Kenomac]

Originally Posted by Don C L

I think Ken meant that anyone who was only relying on a chartplotter may have missed it, but that since radar, and autopilot response to course change, were also being monitored, it allowed for the appropriate and more rapid course correction.
I'm not sure, is that correct Ken?

Don,

Yes, thank you.

Plus add... many people who rely on only a chartplotter, would not understand current and it’s effect on a boat, so would not be equipped to understand why the boat was rapidly drifting off course at night, and I dare say might panic. Having plotted on paper over the years, current and having to adjust manually for current is not something easily forgotten.

Many on this forum just like to argue these days. thanks for being someone who likes to help out.

And for those who like to argue... there was no time to sit down and bring out the paper charts at night, a 30-40 degree course change needed to be done immediately.

Ken

[requiem]

Originally Posted by Simi 60

Which is why I don't run a single system.
As mentioned earlier I run a dedicated C-map plotter on a 23 inch screen and a dedicated opencpn computer on a 23 inch screen, one zoomed out and one zoomed in and each with its own GPS antenna.

The Vestas example is interesting because the C-map charts they had didn't display the Shoals at several zoom levels. There were hints that even more detailed charts should be looked at (which then goes to the user), but the accident report noted that the land and reef were displayed on all scales of paper charts reviewed. Ironically, the default world chart in the boat's chartplotter did include the Shoals, but that MFD was used mainly for AIS in busier areas and apparently not being observed.

It's worth reviewing the report as it calls out differences in software packages that might not be expected by users (e.g. not showing detailed data if you zoomed in on one area and then panned into a different region).