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Old 02-02-2015, 09:34   #1
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The Electronic Charting "Zoom Problem"

We all know how dangerous it is to rely on electronic charting for passage planning -- detail disappears at lower zoom levels, and you can crash into an island like Vestas did because you never zoomed in on the particular spot where that island is.

In complicated water it can be literally impossible to plan a passage without paper because you can't see enough of the whole picture at one time to find a way out of the maze. The Swedish and Finnish archipelagos are like this, and I'm sure plenty of other places.

Why couldn't this be solved with electronic plotting?

Here's an idea: let the user define what is safe water (more than x depth, more than y cables from land, no obstacles, etc.), and warn him on the large scale zoom levels where non-safe water is, even if you can't see the detail. With red blotches or something like that. It will tell the user where he needs to zoom in and check.

How about it, OpenCPN wizzes? Would be a real scoop on the rest of the industry, wouldn't it?
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Old 02-02-2015, 09:57   #2
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Re: The Electronic Charting "Zoom Problem"

Quote:
Originally Posted by Dockhead View Post
We all know how dangerous it is to rely on electronic charting for passage planning -- detail disappears at lower zoom levels, and you can crash into an island like Vestas did because you never zoomed in on the particular spot where that island is.

In complicated water it can be literally impossible to plan a passage without paper because you can't see enough of the whole picture at one time to find a way out of the maze. The Swedish and Finnish archipelagos are like this, and I'm sure plenty of other places.

Why couldn't this be solved with electronic plotting?

Here's an idea: let the user define what is safe water (more than x depth, more than y cables from land, no obstacles, etc.), and warn him on the large scale zoom levels where non-safe water is, even if you can't see the detail. With red blotches or something like that. It will tell the user where he needs to zoom in and check.

How about it, OpenCPN wizzes? Would be a real scoop on the rest of the industry, wouldn't it?
Opencpn 4.0 has that option. Many of us didn't like it,and we stomped around until the developers cut it's legs off, and left it whimpering in the scuppers, but it's still there in the toolbox.
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and then there's that great big OVERZOOM warning too.
and if you have vector charts you can set safety depths and so on.
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Old 02-02-2015, 09:59   #3
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Re: The Electronic Charting "Zoom Problem"

IIRC in the feature requests there is already an entry about "route checking":
laying out a route you can run an automatic check against the vector chart using the constraints defined to get alerts about hazards on your planned route.

(Something available in ECDIS systems - and in weather routing there is a first step avoiding "the hard", but using a high resolution background map, not the actual vector charts)

Your proposal to drop warning symbols would lead to just paint the complete coastlines as hazardous - lacking to point one to a specific peril.

Hubert
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Old 02-02-2015, 10:06   #4
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Re: The Electronic Charting "Zoom Problem"

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Originally Posted by HappySeagull View Post
Opencpn 4.0 has that option.
Which option? cm93 detail level?

Quote:
and if you have vector charts you can set safety depths and so on.
The safety contours eventually disappear when I zoom out more.
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Old 02-02-2015, 11:14   #5
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Re: The Electronic Charting "Zoom Problem"

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Originally Posted by bcn View Post
IIRC in the feature requests there is already an entry about "route checking":
laying out a route you can run an automatic check against the vector chart using the constraints defined to get alerts about hazards on your planned route.

(Something available in ECDIS systems - and in weather routing there is a first step avoiding "the hard", but using a high resolution background map, not the actual vector charts)

Your proposal to drop warning symbols would lead to just paint the complete coastlines as hazardous - lacking to point one to a specific peril.

Hubert

Interesting -- I didn't know that ECDIS systems do that, but it is logical, since they are allowed in lieu of paper.

It would be interesting to know how that works and whether the function could be reproduced in OpenCPN.

My proposal was not to drop warning symbols everywhere, but along a proposed route. Say, within some programmable distance from the route, so that you can see a way through an area of hazards, like an archipelago.

But if there is some well-worked out way to check routes in ECDIS systems, that would probably be a good place to start.
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Old 02-02-2015, 11:26   #6
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Re: The Electronic Charting "Zoom Problem"

I'm not so sure the problem exists. With opencpn , set the detail level high and it's easy to see dangers without having to zoom in too much. If it's that much of a maze then the pilot book is the place to look for routes. If there is a problem then it's perhaps navigators not paying enough attention to the necessary steps required to make sure all is well.
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Old 02-02-2015, 12:30   #7
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Re: The Electronic Charting "Zoom Problem"

Quote:
In complicated water it can be literally impossible to plan a passage without paper because you can't see enough of the whole picture at one time to find a way out of the maze. The Swedish and Finnish archipelagos are like this, and I'm sure plenty of other places.
ask somebody for directions Before you buy them drinks?
But I know what you mean.
There's no way you can go through without adding a ton of waypoints to some rough plan that even then merely tell you what way to go in the maze.
But I'm not waiting for Garmin or Magellan to do it- ever used a car gps? They are good right up to when they kill you.

Quote:
The safety contours eventually disappear when I zoom out more.
setting the colours works better I think. 4 colours.Maybe the safety depth set deeper too so it doesn't turn into a dot...but how deep? still has to be determined by someone looking carefully at their charts and pilot book and what all on the route.
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Old 02-02-2015, 12:55   #8
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Re: The Electronic Charting "Zoom Problem"

Several commercial systems on the market will "fly a route" and produce a report of hazards encountered. I haven't used a full blown ECDIS so can't say exactly how that would work. But I think ECDIS is not a good system to emulate for cruisers. ECDIS is predominately used by commercial vessels plying well established shipping routes that they run repeatedly.

What I do manually, well in advance of a passage, is put down a route in the computer. Then I zoom in to the typical zoom level used when making the passage. I pan through the entire route noting hazards or points of navigational interest. Some examples would be shallow water, keep out zones, high traffic area, bridges and overhead cables, locks, narrow passes with tidal currents or any number of other details that have to be dealt with on a passage. If something interesting is found I add waypoints to the route that will help work around the problem. Sometimes it's important to hit a waypoint more precisely such as a lock entrance or narrow pass. Sometimes you have to coordinate with a bridge operator to make sure the bridge is open so a waypoint some distance earlier can be used to remind to contact the bridge.

There are many many issues that need to be considered when checking a route for hazards. I don't think software will ever be able to do this to any significant degree. Neither do I think it is the proper role of software to do.

If we could define a minimum set of warnings such as depth and overhead hazards that can be automated that would be helpful. But it is no substitute for going over your route visually. And for that you can do it in much more detail with OpenCPN than with paper charts.
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Old 02-02-2015, 13:28   #9
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Re: The Electronic Charting "Zoom Problem"

The reliability of the charts in the Swedish and Finnish archipelagos diminish quickly the further you go from the recommended tracks printed on the charts. It's the old story ...no commercial traffic no updated public survey, with a few exceptions. What you need, seems more to be a way of displaying the recommended tracks when zoomed out for an overview....
There is probably someone out there with he recommended tracks documented as routes.

Thomas
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Old 02-02-2015, 13:37   #10
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Re: The Electronic Charting "Zoom Problem"

I agree that you are responsible to check the route you are to navigate but ... an aide is an aide ... it helps to locate problems and seems a smart tool so I agree with Dockhead.

I have many times made routes through the Stockholm archipelago from , say, Central Stockholm around to Södertälje or similar. I dont remember of hand, but maybe 70+ NM with several tenths of waypoints passing hundreds of islands and it takes time to scan through the full route and it can be easy to make mistakes and not zoom enough.

I like the idea with checking the route with a customizable safe width, and maybe plotting a visual warning that is seen on all magnification levels.
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Old 02-02-2015, 13:39   #11
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Re: The Electronic Charting "Zoom Problem"

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Originally Posted by cagney View Post
The reliability of the charts in the Swedish and Finnish archipelagos diminish quickly the further you go from the recommended tracks printed on the charts. It's the old story ...no commercial traffic no updated public survey, with a few exceptions. What you need, seems more to be a way of displaying the recommended tracks when zoomed out for an overview....
There is probably someone out there with he recommended tracks documented as routes.

Thomas
Yes, I am a witness to that -- big rocks awash where the chart shows 10 meters of water

Yes, if "recommended tracks" could be shown, that would be a good start. But if you explore these archipelagos, you will get off the "recommended tracks" in any case. With the present state of the art, you are lost without paper.
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Old 03-02-2015, 02:07   #12
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Re: The Electronic Charting "Zoom Problem"

Dockhead, Last summer I sailed (amongst other routes) a torturous route inside the islands between Karlskrona and Karlshamn. This is marked ont he maps aas being minimum 2.7 meters and since it is a popular route - it is 2.7 meters deep at least.

Trying to plan this on a chartplotter (I have a 12 inch screen) would have been an excercise in frustration. Zoom in and zoom out, in and out, in and out. Having the paper chart at hand made it easy to plan the route and also retain an idea of what the route was going to do further up ahead (there were some interesting side routes that lead nowhere, but were unbelievably beautiful.

The real issue, of course is the size of your screen. But even hooking you plotter up to say a 48 inch screen won't help since as you zoom out, the detail disappears - the plotter software is not made for 48 inch screens.
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Old 03-02-2015, 02:39   #13
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Re: The Electronic Charting "Zoom Problem"

AND we have the same issue in the South Pacific islands...some of the charts date back to the 19th century and have just been taken as read into the electronic charting systems....some even use third party (ie non-government, private) charts and the zooming can take you from a hill on one side to the middle of the bay to the hill on the other side.
What did we do before electronics ?
We used paper charts
We used our eyes
We used our hand bearing compass
We DEDCUCED our position
AND we navigated from A to B

When we are sailing in the south pacific islands we are doing that all the time.
We don't trust anything and use every means we have a availabke to work out where we are ALL the time.
There's no point complaining that the chart is wrong if you're stuck on a reef with an ebbing tide !!
Seamanship, it's called and it doesn't depend on electronics.
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Old 03-02-2015, 03:33   #14
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Re: The Electronic Charting "Zoom Problem"

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The real issue, of course is the size of your screen. But even hooking you plotter up to say a 48 inch screen won't help since as you zoom out, the detail disappears - the plotter software is not made for 48 inch screens.
Carsten,

with 48" you would have 16x the chart surface (at the same resolution) than compared with a 12" screen - that makes a difference.
48" would be a nice chart table, wouldn't it? Don't spill the coffee, please!!

Hubert
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Old 03-02-2015, 03:45   #15
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Re: The Electronic Charting "Zoom Problem"

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Carsten,

with 48" you would have 16x the chart surface (at the same resolution) than compared with a 12" screen - that makes a difference.
48" would be a nice chart table, wouldn't it? Don't spill the coffee, please!!

Hubert
I realize that, but as you zoom out - the detail on an electronic chart disappears - because the software is telling it to - so screen size doesn't help, unless you rewrite the software.
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