The Electronic Charting "Zoom Problem"

[Dockhead]

Originally Posted by carstenb

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.

Exactly. But this is a technical problem which can't be hard to solve. OpenCPN anyone? I have a 32" more than HD monitor on board. I'm sure it's technically possible to quilt the small scale charts on that. Would be a boon for planning.

[rooiedirk]

Something available in ECDIS systems -

When making a route in a ECDICS the idea is that you set a track width and a safety depth for each leg.
The problem is if you set the track width to big, a check alarm is raised for every buoy etc you will pass. If you set the width small you get an alarm every time you get 'off track' when underway.
And we all know what we will do when the alarm sounds to often
That' s why in practice, I never use it on an ECDIS.

I didn' t try the lookout plugin yet, but if it is checking also for the smaller scale charts available, it would be a good alternative.

[transmitterdan]

I don't understand why all this zooming in and out. Why not zoom in to the typical on passage scale (i. e. small scale) and pan through the route? You can't do that easily with paper charts but with chart plotters it's simple and quick. Maybe we need to have a "best practices" thread for chart plotters and PC navigation.

[Dockhead]

Originally Posted by transmitterdan

I don't understand why all this zooming in and out. Why not zoom in to the typical on passage scale (i. e. small scale) and pan through the route? You can't do that easily with paper charts but with chart plotters it's simple and quick. Maybe we need to have a "best practices" thread for chart plotters and PC navigation.

Because then you never see where you are in relation to the bigger picture.

It's what I do when I need to check an already determined route for obstacles on a plotter. AFAIK, furuno plotters will do this automatically - great function. It works fine for that. But you can't find a new route through complex water without zooming In and out to collect both detail AND the big picture, and above a certain level of complexity, it becomes impossible.

[monte]

I do as transmitterdam suggested. Make a route on opencpn with a basic A to. B route which let's say it's 40M between islands. I then zoom in and pan along the route at the lowest level to inspect for hazards, and insert waypoints as required to modify the route. I usually add waypoints at each end if the route as I visualise the harbour entry and exit, even up channels just to make a complete and thorough appraisal of the anticipated route, and also an anticipated anchoring spot. Things don't always go to plan but at least we have a good idea of any hazards en route and the route usually has at least 1/2 mile clearance from hazards. We usually also do this on the plotter but to lesser degree and cross reference with opencpn while underway.
A good idea to have an alert if the planned route is within a set distance to a hazard but unfortunately it might be something some skippers would rely on and I don't like the idea of trusting a computer to steer a safe course.

[valhalla360]

I don't think "we all agree" that it is dangerous.

If you are talking long open ocean crossings, mid ocean dangers are usually shown regardless of chart scale and presumably you should have some concept of the route before departing. To miss an island or reef, is a failure of the captain not the chart system.

If you are talking about narrow inland routes (such as the swedish waters), you are typically talking about modest runs during daylight and will presumably have the chart plotter up and zoomed in with frequent verification of where you are on the chart as you travel. Again no way the charting method should be considered the cause of the problem.

It's not that hard to lay in a route and then pan thru it zoomed in. If you like your paper charts, that's fine but don't make it out that electronic charts are dangerous.

[carstenb]

Originally Posted by monte

I do as transmitterdam suggested. Make a route on opencpn with a basic A to. B route which let's say it's 40M between islands. I then zoom in and pan along the route at the lowest level to inspect for hazards, and insert waypoints as required to modify the route. I usually add waypoints at each end if the route as I visualise the harbour entry and exit, even up channels just to make a complete and thorough appraisal of the anticipated route, and also an anticipated anchoring spot. Things don't always go to plan but at least we have a good idea of any hazards en route and the route usually has at least 1/2 mile clearance from hazards. We usually also do this on the plotter but to lesser degree and cross reference with opencpn while underway.
A good idea to have an alert if the planned route is within a set distance to a hazard but unfortunately it might be something some skippers would rely on and I don't like the idea of trusting a computer to steer a safe course.

Monte - one of the issues here in the Baltic is that it is not 40 nm between the islands, but rather 400 meters (or less) and the passages snake around in and out between the islands. Passages criss-cross and you can be sure which channel you shoold take becasue the one that looks like it is going west is acutally going south and the one going east will snake around an island end up going west. So you need to be able to see the big picture all the time.

[Dockhead]

Originally Posted by valhalla360

I don't think "we all agree" that it is dangerous.

If you are talking long open ocean crossings, mid ocean dangers are usually shown regardless of chart scale and presumably you should have some concept of the route before departing. To miss an island or reef, is a failure of the captain not the chart system.

If you are talking about narrow inland routes (such as the swedish waters), you are typically talking about modest runs during daylight and will presumably have the chart plotter up and zoomed in with frequent verification of where you are on the chart as you travel. Again no way the charting method should be considered the cause of the problem.

It's not that hard to lay in a route and then pan thru it zoomed in. If you like your paper charts, that's fine but don't make it out that electronic charts are dangerous.

Nevertheless, Team Vestas managed to hit an island. For long ocean passages, of course, the planning is usually straightforward -- a great circle course which is fairly obvious, and you just need to check it for obstacles. Panning through it on a plotter is ok for that, and if Team Vestas had done that, they would not have lost their boat.

Sailing "narrow inland routes" and staying out of trouble can also be done perfectly well without paper. Just keep your eye on the plotter and keep the plotter at a sufficient zoom level and you're fine.

The problem arises when you need to plan a route -- find a way -- through complex water. That's a completely different problem.

[Dockhead]

Originally Posted by monte

I do as transmitterdam suggested. Make a route on opencpn with a basic A to. B route which let's say it's 40M between islands. I then zoom in and pan along the route at the lowest level to inspect for hazards, and insert waypoints as required to modify the route. I usually add waypoints at each end if the route as I visualise the harbour entry and exit, even up channels just to make a complete and thorough appraisal of the anticipated route, and also an anticipated anchoring spot. Things don't always go to plan but at least we have a good idea of any hazards en route and the route usually has at least 1/2 mile clearance from hazards. We usually also do this on the plotter but to lesser degree and cross reference with opencpn while underway.
A good idea to have an alert if the planned route is within a set distance to a hazard but unfortunately it might be something some skippers would rely on and I don't like the idea of trusting a computer to steer a safe course.

Since you have OpenCPN and presumably a set of CM93 charts, try this just for fun -- plan an efficient route (hint: the inland route is about half the distance of the ship channel route out to sea) from the port of Kotka, in Eastern Finland, to the island of Santio, on the Russian border (where the customs post is). Without using any paper. It's a short, easy trip by Baltic standards. Have fun and let us have your waypoints when you're done. Afterwards you'll understand exactly what Carsten and I are talking about.

The whole problem is that in waters of a certain complexity, there is no simple "A to B route". It's a maze you have to find your way through.

Where there is a simple "A" to "B" route, subject to corrections after finding obstacles, then your technique works fine, and it's what all of us, probably, do. But the problem is that there often isn't.

[colemj]

Originally Posted by Dockhead

Nevertheless, Team Vestas managed to hit an island. For long ocean passages, of course, the planning is usually straightforward -- a great circle course which is fairly obvious, and you just need to check it for obstacles. Panning through it on a plotter is ok for that, and if Team Vestas had done that, they would not have lost their boat.

Sailing "narrow inland routes" and staying out of trouble can also be done perfectly well without paper. Just keep your eye on the plotter and keep the plotter at a sufficient zoom level and you're fine.

The problem arises when you need to plan a route -- find a way -- through complex water. That's a completely different problem.

The first sentence of the OP is stated as a fact on which everything else is predicated. It is not only un-factual, there is no evidence supporting it as fact - only anecdotes being propagated as universalities.

On the other side, there are many people safely navigating solely with electronic charting - which is unexplainable if the original premise is factual and true. Similarly, there are many people getting into danger not using electronic charting - which shows that the charting mode is not the issue.

If Vestas had done 8 or 9 basic navigation things, they would not have hit that reef. Anti-electronic or pro-paper people just cherry-pick out a single supposition to assign to this accident.

Garmin chart plotters have an auto-routing feature where one puts in start and end waypoints and it charts a route through and around obstacles.

Dockhead, throughout many of these threads, you complain that your compass doesn't calibrate well, your radar doesn't do ARPA well, your chart plotter doesn't do planning well, etc. And you seem to project your choice of, and experience with, this equipment as an absolute on the rest of us.

Perhaps consider that it is quite possible some of us are not having these "factual" issues?

Mark

[seandepagnier]

Originally Posted by Dockhead

The problem arises when you need to plan a route -- find a way -- through complex water. That's a completely different problem.

Can you somehow do this easily on a paper chart because it's bigger? Or it just takes longer on a smaller screen because you run into more dead ends?

The weather routing plugin can do this if set to avoid land. Or download tracks from someone who already navigated there.

[transmitterdan]

Originally Posted by Dockhead

Since you have OpenCPN and presumably a set of CM93 charts, try this just for fun -- plan an efficient route (hint: the inland route is about half the distance of the ship channel route out to sea) from the port of Kotka, in Eastern Finland, to the island of Santio, on the Russian border (where the customs post is). Without using any paper. It's a short, easy trip by Baltic standards. Have fun and let us have your waypoints when you're done. Afterwards you'll understand exactly what Carsten and I are talking about.

The whole problem is that in waters of a certain complexity, there is no simple "A to B route". It's a maze you have to find your way through.

Where there is a simple "A" to "B" route, subject to corrections after finding obstacles, then your technique works fine, and it's what all of us, probably, do. But the problem is that there often isn't.

First, in waters of "certain complexity" a passage should not be planned by charts along. Pilot books, cruising guides, tide/current tables and any other local knowledge available should go into the process. So I don't think it's fair to say "plot me a path with the chart and nothing else".

However, as an academic challenge I'm happy to give my electronic chart only process a go. Since OpenCPN has no "search" function give us the starting and ending GPS coordinates of the hypothetical journey. Let us stipulate that weather, tide and current are not going to factor into the routing.

[carstenb]

Originally Posted by transmitterdan

First, in waters of "certain complexity" a passage should not be planned by charts along. Pilot books, cruising guides, tide/current tables and any other local knowledge available should go into the process. So I don't think it's fair to say "plot me a path with the chart and nothing else".

However, as an academic challenge I'm happy to give my electronic chart only process a go. Since OpenCPN has no "search" function give us the starting and ending GPS coordinates of the hypothetical journey. Let us stipulate that weather, tide and current are not going to factor into the routing.

The area is in the Baltic. There are no tides (well perhaps 20 centimeters, but for all practical purposes none) There are no real currents to speak of there.

I hate to tell you but I don't think you're going to find any pilot books or cruising guides for that matter (at least none in english, might be something in finnish)

Kotka = N60 28' 9.12" E26 57'
Santio = N60 27'43.2" E27 43' 30"

Correct me if I am wrong Dockhead

Good luck

[cagney]

I had the same "problem" last summer delivering my new boat from Lake Mälaren, east of Stockholm down to Southern Sweden, so I'm not unfamiliar with the scenario.

This is how it looks like with more or less default settings. It almost covers the area from Kotka to Santio.



Tweaking OpenCPNs vectorchart settings a bit and you see this. The scale is the same.



With this setting I can't find much problem in planning the route. To me the options are fairly obvious.

What I would like to see is on option with "Vectorchart Viewing Profiles", that can be saved and easily switched between. A viewing profile would just be a saved state of settings. Have one for piloting, one for planning and one for passage making for example.
The second pic above uses the value 5 for the CM93 detail slider. Would i be possible to increase this to, say 8, for using in a VVP, where most details were switched off so the impact on processing would not be to big.

Thomas

[transmitterdan]

Originally Posted by carstenb

Kotka = N60 28' 9.12" E26 57'
Santio = N60 27'43.2" E27 43' 30"

Correct me if I am wrong Dockhead

Good luck

This is all in good fun guys. Please tell me how many rocks I hit.