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Old 01-06-2010, 03:33   #1
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Question What Do People Use to Plot Routes ?

Hello,

Over here in France, to plot routes on ships and know what direction to tell their helmsman/steerer to aim for, people use the Règle Cras ("Cras ruler", invented by Rear Admiral Jean Cras) shown in this picture with my explanations on how it's used:

http://img12.imageshack.us/img12/886...ereglecras.jpg

The nice thing about the Cras ruler, is that it's compact and has no moving parts, so it's pretty long-lasting.

I'm curious to know what sailors use in other countries to plot routes.

Thank you.
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Old 01-06-2010, 03:46   #2
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Parallel rules.
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Old 01-06-2010, 03:56   #3
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Originally Posted by littlebigfred View Post
Règle Cras ("Cras ruler", .
My system is though as being crass too: I use the chartplotter or Laptop charting OpenCpn or Google earth.

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Old 01-06-2010, 03:56   #4
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Thanks for the reply. Does it mean that people use a parallel ruler + a protactor (if there's none printed on the map)?

How to use parallel rulers
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Old 01-06-2010, 05:47   #5
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I use my mouse--very quick, convenient, and accurate.
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Old 01-06-2010, 05:50   #6
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My system is though as being crass too: I use the chartplotter or Laptop charting OpenCpn or Google earth.

Mark
I'd say that was practical.
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Old 01-06-2010, 06:44   #7
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Thanks for the reply. Does it mean that people use a parallel ruler + a protactor (if there's none printed on the map)?

How to use parallel rulers
Charts do have a compass rose on them. Some parallel rules have degree marks on them like a protractor, just put the bottom line on a meridian and the top line on the same meridian with the angle you want.
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Old 01-06-2010, 08:51   #8
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Do you mean this type of parallel rules?

http://www.waypoints.com/images/90.jpg
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Old 01-06-2010, 10:12   #9
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Do you mean this type of parallel rules?

http://www.waypoints.com/images/90.jpg

Yes, that's the type.
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Old 01-06-2010, 10:39   #10
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Interesting. I'll have to play with those when I get the chance. Thanks for the education.
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Old 01-06-2010, 10:57   #11
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Welcome to CF littlebigfred….

Most of the commercial mariners have been trained to use a pair of navigational triangles like this:
Amazon.com: Weems & Plath Marine Navigation Protractor Triangle with Handle: Sports & Outdoors

The main reason other than accuracy and speed in doing the examinations is that in preparing charts for parallel indexing, using 2 Triangles is very quick to draw safety perpendiculars off your course lines, without having to shift or walk the rulers.


Very quick and accurate once you get used to them and as Rick says, you dont bother with the compass rose but read off the meridians
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Old 01-06-2010, 11:10   #12
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I've seen those things but Google didn't return videos on how they're used while sailing to know what direction to take.

What is "parallel indexing"?
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Old 01-06-2010, 11:49   #13
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Plotting routes is hardly necessary. You certainly do need to be prepared to navigate complex channels or landfalls and leaving ports. But for the most part you have enough time to go below and select a way point for your next mark, enter into the GPS and get back to watch keeping and sail trim.

Route planning is a creation of the geeks who had no understanding of sailing a boat. You certainly need to keep a fix and your plotter does that.

If you plot onto a chart, parallel rules, and dividers are all you need.
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Old 01-06-2010, 11:57   #14
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Breton / Portland Plotter.



Breton plotter - Wikipedia, the free encyclopedia
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Old 01-06-2010, 12:09   #15
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Don't forget you've got to correct for variation and deviation, if you're steering with a magnetic compass. Also any set of current.

I am a great believer in having and using paper charts, but here they suck compared to putting the plotter's cursor on your destination and pressing "go to". Presto, you've got a true bearing and range, and you also know your true course over ground compensated for absolutely everything.

We do have a Portland plotter on board, but it is more a curiosity.
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