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Old 08-01-2015, 06:58   #106
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Re: Another foundering how do chart plotters get it wrong

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Originally Posted by rwidman View Post
Considering that we are at the helm piloting the boat, that would seem to be accurate enough. The GPS is a tool to help navigate. What you see in front of you with your own eyes is the most important.
I agree. I was just pointing out that geological and other high-precision GPS's are different than consumer ones.

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Old 08-01-2015, 07:35   #107
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Re: Another foundering how do chart plotters get it wrong

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I had that problem when sailing into Tonga. Upon radioing for some help, I was told the same thing happens quite often as charts have errors for that particular entrance. When sailing into new port or island I always planned my trip to allow me to arrive after sunrise. Not to make the fastest time but the needed speed to arrive safely and not in the dark. Iceman
Right on. When creating routes the chart is used as a 'general reference' for identifying approximate locations of possible hazards. Given enough space between your DTK and hazards, particularly at night or in poor visibility, slow down to approach the hazardous area in better conditions or in daylight, even if this involves heaving-to.

Create a route that skirts the hazardous area entirely, even if longer and your arrival will be significantly later. A good example is approaching Fiiji from Tonga. You can take your chances trying to cut through the reefs, or avoid them altogether by passing a healthy distance to the south - in daylight. Most sailors that run into problems could have avoided them with better planning, slowing down and taking advantage of sea room to heave-to until daylight. One more precaution worth considering. If possible pass hazards keeping them to windward. This reduces the possibility of being blown down on them in adverse conditions. Finally, never fail to take into account the strength and direction of current...

Charts and electronics are only 'aids to navigation'. Responsibility for planning and the many decisions involved in making a safe passage are yours.
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Old 08-01-2015, 13:28   #108
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Re: Another foundering how do chart plotters get it wrong

Radar is wonderful, except for the hazards a few feet down...
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Old 08-01-2015, 14:11   #109
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Re: Another foundering how do chart plotters get it wrong

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Such a feature is not nearly as simple to implement as it would seem. And it would invite even more reliance on machinery in lieu of seamanship which seems to me the wrong direction we should be heading.
OK... Why? The data is there. We do similar types of algorithms all the time in other industries. I've personally done a lot of financial industry programing and the concept is the same. The screen you see is an abstraction of real "vector" data and internally, it can be used however we choose to use it. The only reason you do not see all that data on the screen is because of the resolution of the screen, not the resolution of the data.

I do not see this as a particularly difficult solution to implement. Heck, the have auto-plotting now. No need to even plot your course.

As far as "enhancing reliance"... people are already relying on their chartplotters. That answer is like saying "gee, lets not try to make smoking any safer because people will just continue to rely on cigarettes."

This may not be a "perfect" solution but if it stops a dozen boats from crashing into reefs every year then its better than no solution.
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Old 08-01-2015, 14:18   #110
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Re: Another foundering how do chart plotters get it wrong

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...if it stops a dozen boats from crashing into reefs every year then its better than no solution.
Yeah, "it's for the children."
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Old 08-01-2015, 15:01   #111
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Re: Another foundering how do chart plotters get it wrong

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Originally Posted by zboss View Post
It seems to me that a very basic addition to chart plotter software would be to issue a warning when the autopilot plot crosses over a hazard. The data is there even if you cannot see it on the chartplotter.
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Originally Posted by transmitterdan View Post
Such a feature is not nearly as simple to implement as it would seem. And it would invite even more reliance on machinery in lieu of seamanship which seems to me the wrong direction we should be heading.
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Originally Posted by Terra Nova View Post
Yeah, "it's for the children."
It is rather easy to incorporate a "terrain" warning system and yes, it is only as accurate as the chart (terrain) data but that is the same data as the human navigator would use anyway. The aviation world use such systems (TAWS /EGPWS etc). It works.

However I am ambivalent about it on a few levels. The principle objection is best expressed by Terra Nova (above).

It would become (IMO), another way of dumbing down the already low standard exhibited by some (many?) small vessel navigators.

To answer the OP's question 109 posts back, I think the problem exists because it has become too easy get out on the water and start heading off into the "unknown". The GPS and the electronic chart is very seductive to the unwary. It's basic operation is simple - turn it on and look at the pretty picture. No training required . Oh look, boats still running aground - lets put a warning system in place. IMO, , this is not the way to fix stupid. Back in the pre GPS era, fear of the unknown kept the foolish at bay and let the intrepid get on with the serious business of crossing oceans and closing with unknown coasts. Now technology makes it a free for all.

Many others have probably expressed it better but I say:

Accuracy and hi-resolution data (GPS & Chartplotters) are very seductive for the untrained / unskilled navigator (thus consequently very dangerous for them) yet at the same time, they are a saviour for the trained / skilled navigator.

If this is so, the answer is simple - skill up! However human nature will allow some (many?) to ignore the simple solution. The Darwinian solution used to help us here but no longer is it PC to allow this most elegant solution to flourish.

However, regardless of my feelings on the subject, I expect to see such "terrain ahead / below" warning systems becoming normal some time soon
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Old 08-01-2015, 15:06   #112
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Re: Another foundering how do chart plotters get it wrong

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OK... Why? The data is there.
Sometimes it is and sometimes it isn't. There are cases where the chart data has unknown quality. More importantly, much of the future course of the vessel depends on events and data unknowable by the chart plotter such as wind, current, etc. Then there is the problem of when do you declare an alarm? The chart plotter can't know with precision where the vessel will be in 2-3 hours but the time to raise the alarm for Vestas Wind was probably 2 hours before they hit the reef. How can the chart plotter guess where the vessel will be hours down the track?

What can and is being done is to plot a candidate route. Have the chart plotter "fly" the route and alert about any hazards that lie within X distance of that route. There are systems that do that quite well. But a real time warning system will not be easy to implement. And that's what would be needed because cruisers seldom sail an exact pre-built route. Vessels that run pre-built and proven routes don't need this technology anyway.

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Originally Posted by zboss View Post
As far as "enhancing reliance"... people are already relying on their chartplotters. That answer is like saying "gee, lets not try to make smoking any safer because people will just continue to rely on cigarettes."
Good example, except many people are saying exactly that. Look at all the noise about banning e-cigarettes.

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Originally Posted by zboss View Post
This may not be a "perfect" solution but if it stops a dozen boats from crashing into reefs every year then its better than no solution.
I disagree that it will reduce the number of boats crashing into reefs. I think it would most likely increase the number of such incidents due to over reliance, overly complex software and inadequate input data. These can be a toxic cocktail. Similar arguments were used to justify the air-bag mandate that killed a lot of people even though the regulators were well intentioned.
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Old 08-01-2015, 15:14   #113
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Re: Another foundering how do chart plotters get it wrong

Again, there are charting programs that already do this type of thing. Coastal Explorer is one that not only finds obstacles, it lists them as you go along and can sound warnings if you approach them. Furuno "flys" a route looking for obstacles. I think Garmin has an autorouting feature that avoids obstacles as you make a route.

I'm sure there are others also - I don't spend a lot of time evaluating charting systems.

I don't think this dumbs things down at all, or makes it "for the children" (BTW, these arguments have been used continually in boating from automatic depth sounders to GPS to roller furling to reverse gear transmissions - they have always proved to be misplaced and luddish in hindsight).

I use these features as valuable navigation tools. I don't blissfully lay routes wherever I want without care, but do appreciate that I can always look at a list page containing all close obstacles on the chart along my route. I also like to push the "flyover" button after making a route on a vector chart to make sure that I didn't miss a feature due to zoom level, etc.

I personally hate pretty much all audio alarms and most visual alarms and rely on myself having situational awareness that doesn't require them, but can readily see the advantage of alarms for others.

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Old 08-01-2015, 15:49   #114
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Re: Another foundering how do chart plotters get it wrong

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Originally Posted by lordgeoff View Post
The plotter seamlessly selects the electronic chart for the area you are in. (Remembering the Paper/Electronic charts still contain errors from Captain Cook) As you zoom in on the chart plotter the plotter software seamlessly moves to the more/most detailed chart. The one that shows the small hard objects...
Uhhh, not necessarily... At least not in a place like Labrador... :-)

I ran into a couple of these sort of anomalies/voids in my C-Map coverage last summer, where charts had been 'stitched' together... C-Map is considered by many to be the gold standard for that region, yet no amount of further zooming would pull up greater detail...





I was running in very heavy fog at the time (with an inoperative radar, unfortunately), and the northern approach to Frenchman's Run is a pretty tricky spot... One could easily get into serious trouble there, relying on a plotter running C-Map alone... No way would I cruise a region like Labrador without the requisite paper (I also carried an iPad loaded with Navionics), but that's probably just me... I just look at them as my 'Insurance' when sailing to such a place, since I'm doing so without the real thing... :-)

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Unless you are carrying the full range of paper charts ( read dozens or hundreds and they are up to date) you will likely not have all the information required to safely navigate your route. Now lets all fess up. Is there any one that carried a full set of paper charts, that are up to date and don't have stains or creases, for their last passage? Using a good quality plotter and an up to date SD card you do have all the up to date information for your passage.
Again, not necessarily... :-)

Here's a shot of my CHS chart of the approaches to Cape St Charles, just south of Battle Harbor... A bit hard to see, but in the lower middle of the pic, there is a buoy marking a ledge named "Inner Shoal", which breaks heavily with even a moderate sea running...





All of my paper charts for Labrador were purchased last February from Maryland Nautical Sales...

Both my C-Map chip for Labrador/Ungava Bay, and the Canadian Navionics were purchased in May, shortly prior to my departure, which presumably would ensure they contained all the latest updates...

NEITHER of them showed the buoy marking Inner Shoal, shown clearly on my 'older' paper chart... Given the fact that there are likely no more than perhaps 3 dozen floating aids to navigation spread out along the entire 600 miles of Labrador's coastline, I'd say that's a pretty significant omission... :-)

Go figure, eh? But in my experience, those pricey paper thingies can still come in handy from time to time...

:-)
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Old 08-01-2015, 17:22   #115
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Re: Another foundering how do chart plotters get it wrong

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Sometimes it is and sometimes it isn't. There are cases where the chart data has unknown quality. More importantly, much of the future course of the vessel depends on events and data unknowable by the chart plotter such as wind, current, etc.
How is this any worse than what the average joe faces every day right now? If a hazard isn't marked on a paper chart or via incorrect electronic datum, they are still going to plot their course over that hazard. Sure, if you maintain a lookout you will see it upcoming but I'm not suggesting you do not maintain a lookout.

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Then there is the problem of when do you declare an alarm?
Doesn't matter for this discussion, either different manufacturers will set up different specifications for this feature or parameterize the feature so the users can set the values most important to them.

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Originally Posted by transmitterdan View Post
The chart plotter can't know with precision where the vessel will be in 2-3 hours but the time to raise the alarm for Vestas Wind was probably 2 hours before they hit the reef. How can the chart plotter guess where the vessel will be hours down the track?
Doesn't really matter either. You are only notifying on the intended and plotted course, not deviations due to XTE. However, If you were using a compass heading or wind heading on the autopilot and could not account for XTE you could instead then just have a 1 mile lookahead or whatever, also user programmable. AIS on my chartplotter already has this feature... if there is another boat with AIS heading my way, I know at least 15 minutes before hand.

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Originally Posted by transmitterdan View Post
What can and is being done is to plot a candidate route. Have the chart plotter "fly" the route and alert about any hazards that lie within X distance of that route. There are systems that do that quite well. But a real time warning system will not be easy to implement. And that's what would be needed because cruisers seldom sail an exact pre-built route.
I almost always run the exact route I plot with the exception of dodging hazards or entering or exiting a busy or difficult area, or unless I change route for a more favorable course, but then I update my chartplotter on the fly as I do so. Of course, I do my plot on my iPad the day before and then zoom in and "run the route" as you say, adjusting the route as needed to avoid hazards. At least on the East Coast this has worked well for us 99% of the time because we have such good navigation beacons, so I can say "hey, we are supposed to be coming up on 1A and here we are at 1A".

Please lets not even get into the Coast Guard Virtual nav... I have one experience with it and I already hate it. When I am entering a busy local (e.g. Key West two weeks ago) I am not really looking at my chartplotter that much. What am I going to do, stare at my chartplotter as I tear into the inlet?
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Old 08-01-2015, 17:27   #116
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Re: Another foundering how do chart plotters get it wrong

Carsten-
"3- The boat was then moved about 100 meters (yards) to one side"
Are you certain of that? In the US, boats usually move forward much easier than "to one side". Perhaps this is a Colonial idiosyncracy? (G)
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Old 08-01-2015, 20:08   #117
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Re: Another foundering how do chart plotters get it wrong

Like the quote in my sig line ""Id rather drown than have computers take over my life."--d design"", if I am such a lazy navigator that I cannot be bothered to draw a few lines on a chart, prior to leaving on a voyage, then I would well deserve whatever befell me.
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Old 09-01-2015, 01:21   #118
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Re: Another foundering how do chart plotters get it wrong

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Carsten-
"3- The boat was then moved about 100 meters (yards) to one side"
Are you certain of that? In the US, boats usually move forward much easier than "to one side". Perhaps this is a Colonial idiosyncracy? (G)
Yes I am, Although if you prefer we could say the boat was then sailed 100 meters ot one side and a new track begun.

If I misspoke and the meaning became unclear - what was meant that the tracks were 100 meters apart - and noone ever made sure of what was between those tracks 100 meters apart.
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Old 09-01-2015, 01:30   #119
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Re: Another foundering how do chart plotters get it wrong

It has been noted that chartplotters allow the unwary to go further to sea. I beive this to be a truism. Before plotters became everymans toy, going to sea (or sailing at all) required having a knowledge of charts, ow to read them and how to interpert them. Acquiring this knowledge meant becoming aware of what was shown on the chart.

With the advent of plotters, this knowledge is no longer needed, indeed many have no idea of to truly read the chart (or the chart on the plotter). This makes for inherently unsafe sailing.

I'm reminded of a boat we rafted up against in a Marina a couple of years ago. As is usual, we chatted across the cockpits and shared a glass of wine. The couple were going to sail to copenhagen for the first time (we were in western denmark). I told them that if they wanted to see and experience one of the best and most beautiful sails in denmark to go via Bøgestrømmen.

We were in their cockpit so I asked if they had a paper chart we could look at so they could see the route.

They didn't have any paper charts. The husband explained he had a plotter and that was all he needed. I got my charts out and we looked at them. Whilst navigating the Bøgestrøm is really not that difficult - it does require some planning and awareness.

They decided it was much too difficult for them (good decision)

I expect there are a number of sailors like this - becasue they have an electronic gadget, they don't feel the need to truly understand what is going on. Of course they will learn along the way, but it can be an expensive process.
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Old 09-01-2015, 04:15   #120
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Re: Another foundering how do chart plotters get it wrong

From a friend who knows....

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Hey there Mark.

Funny I just saw a post on cruisers forum from you and others about a grounding at Flinders Island Tassie. I am not on that forum but somewhat know the area but can't comment on the forums site.

That area is notorious for moving sand and shoaling. There are also numerous approaches to get to where they were heading. Some I would never approach at night. Some I have done during the day and it was hair raising. So as a paid navigator in numerous Hobart races I would stand off the approaches to Flinders Island till daylight unless you had a previous track from a few weeks prior.

The boat concerned had just won every division of their race to Hobart so don't think they were novices. Just too keen to get in for a beer at the pub.
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