Navigating by Plotter

Moderator: GreenLake

Navigating by Plotter

Postby GreenLake » Mon Jan 15, 2018 3:39 pm

I came across an interesting article in a sailing magazine the other day. They reported on some research done by a University on changes in situational awareness by users of chart plotters compared to users of paper charts. They gathered data during controlled sea trials as well as on a simulator, so this isn't just the typical "survey".

Their research indicated that long-term users of chart plotters changed the way they perceived things and that that affected their situational awareness in ways that appeared irreversible (they were no longer able to switch to the way the looked at things before on short notice).

One experiment they did was to let people navigate they way they are used to and later ask them to draw a chart from memory. They found that people using chart plotters basically only recalled their route and way points, but not the general layout of the sailing area.

They also let people plan a trip in the usual way, and then forced them to navigate by sight and memory alone (no charts or plotters). This was done on the simulator, because in real life it would have lead to groundings...

Overall,they concluded that experience counts (more experienced sailors did better) but that to get the best benefit of digital navigation you had to have the most experience using other means of navigation. Something along those lines.

I mostly sail in familiar waters where I don't need to "navigate"; the GPS I use serves to record where I was and to tell me how fast I am going, rather than where I'm at. However, when I go further afield, I tend to look up paper charts (or online versions of paper charts) and use them to plan routes and familiarize myself with local conditions.

The few times I've sailed with chart plotters would support anecdotally the results of the research.

There's a tendency to have one's attention totally sucked into the device and to reduce navigation to lining up the blue line with the red or green dot (or whatever the colors).

Sailing with someone who used a chart plotter and acted as my navigator, I averted two groundings by using landmarks and observations to override steering commands based on plotted course, had one grounding when I didn't act quickly enough (I thought the course we were steering was retracing a track from the way we came a day before, but instead it turned out to be a saved track from a year ago - in an area of shifting sand banks. I was fooled into trusting bad data.)

At another occasion, I observed the owner of one boat, with chart plotter, sailing into a big wind hole, because he (and his navigator) were too focused on their waypoints to carefully observe how the successful competition skirted the hole by sailing close under the land.

Finally, I've seen at least one person using a plotter lose track of where North was (in addition to being disoriented to where we were).

How are you navigating?
~ green ~ lake ~ ~
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Re: Navigating by Plotter

Postby DigitalMechanic » Mon Jan 15, 2018 9:25 pm

Interesting. I have not really though about navigation in great detail, as I am so used to sailing in the familiar waters that are around me (maybe I am not to adventurous.. or maybe there is just a lot of water abundantly available around here to keep me occupied?). With the daysailer, I think it is hard to get into too much trouble, even if you stick the centerboard in the mud. I have only ever managed to do so at a dock at low tide. It is so light you can just push the boat out of the situation. Outside of that, I do have a larger Catalina 22 that probably drafts a good 5ft, and it has a real blasted swing keel that weight over 500lbs. Again we have mud on the sea floor, no rocks or rough stuff, so maybe I am inherently more comfortable with not caring as much about grounding the CB or keel, as the recovery is greatly simplified and less destructive than other scenarios (just crank her out of the mud and your un-stuck). But, there is enough river here to not be able to know but pieces of it in any great detail. Considering I sail what the masses would consider small boats, maybe I (perceivably) have less worries than many others due to such a small draft? When sailing I typically just look at the surface of the water, and if it looks calmer than the rest I tend to avoid it... maybe I am still not thinking of "water depth", but it has panned out thus far... need to find wood to knock on, lol.

So, if I were to have electronics on board, then I would have to put a hole in the hull, and then have an LCD screen to worry about watching vs what is going on outside the boat (mosquito on bright light syndrome?). But even if I have a depth finder, how much notice would I actually get before running aground? Probably not enough in some scenarios? I do have Navionics maps (iPhone/IPad), but I would not typically look at them while on a water. However, I have spent quite a bit of time studying the maps while doing my morning business... It is amazing how much better my memory works in the AM vs after 5:00PM ;)

So, I think my vote is to commit map to memory when not on water, and use intuition while on the water. Again, I have not had a destination cruise into a completely foreign territory, so my opinion could be very different after doing so. You have got me thinking about navigation now though. I should cash in on some vacation time and run away for a week or 2, lol. Hopefully I come back on the same boat :D
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Re: Navigating by Plotter

Postby GreenLake » Tue Jan 16, 2018 12:37 am

In fairness, it bears pointing out that there are scenarios where digitally assisted navigation is the only way to go.

I'm thinking of finding your way when low clouds have turned to fog or when you need to navigate in places without obvious landmarks, but hidden sandbanks, oyster reefs or other perhaps rocks.

Even then, I've navigated both with paper charts (manually transposing the coordinates from a map-less GPS and working out bearings to steer by) or with a plotter (whether mounted permanently on a big boat, or hand held by the navigator on a small boat).

The former method is more laborious, but also more satisfying and allows for better mental integration of other data (like the direction that you can hear a bell buoys sound in the fog, or shadows or ripples in the water that indicate a hidden feature).

One of the more fun ways to navigate with analog to digital assistance I was shown in the same waters where the method gained literary fame in "Riddle of the Sands": navigating the edge of a submerged channel using a depth finder in the fog.

Memorizing a chart in the morning, or updating a position occasionally on a paper chart all seem to have one thing in common: they engage the inner map-making in your head, which is somehow very different from watching a moving dot on a chart. In the latter case, your activity reduces to what I call "sailing the video game" -- your brain focuses (too much, if not exclusively) on keeping some dot centered or a heading line aimed at a waypoint - no matter what this action means in reality. In the former case, you end up visualizing, or actually navigating, and that makes all the difference.

The article I mentioned earlier also added two more things.

The first one was the observation that other kinds of electronic data (like computed wind angles and shifts, recommended tacks and the like) seemed to initially help new sailors, but that more experienced sailors reported feeling distracted.

The final one was the observation that we go out sailing because we want to experience being out on the water, and we should thing twice about anything that comes between us and that experience!

What are your experiences? What little helpers do you use?
~ green ~ lake ~ ~
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Re: Navigating by Plotter

Postby Shagbark » Sun Jan 21, 2018 9:25 am

The only navigation system I've been using on the ds are my eyes. However, for Christmas my kids got me a small, removable deck-mounted Richie compass. This should allow me to go further out into Lake Michigan without fear of losing sight of land. Haven't installed it yet, too darn cold in Northern IN.
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Re: Navigating by Plotter

Postby GreenLake » Mon Jan 22, 2018 1:34 pm

A compass is great for things other than navigation.

For example, you can compare the compass directions on the respective tacks going upwind and determine your tacking angle.

You may even be able so see how the wind direction oscillates, and try to sail on the favored tack. Lake Michigan should be a great place to observe that.
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Re: Navigating by Plotter

Postby Fly4rfun » Fri Nov 20, 2020 4:42 am

Good information, I ferried a small aircraft (Cessna 150) from McMinnville Or to Deming,NM the owner had moved to Deming right after he had bought it. before he had tamed his pilot license. he wanted to fly down with me for the experience. we were friends so no problem. another pilot friend loaned me his portable GPS, this was when GPS was fairly new. The owner wanted to use it when he flew but i wouldn't let him. the reason was not to foster dependence on it. if you don't learn the basics of pilotage (looking at the terrain below you and finding that on a map by triangulation or dead reckoning when the equipment fails you will be up a creek. personally i like dead reckoning, but in bad weather GPS sure relives the work load. I do realize this is a old thread. :roll:
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