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Old 14-10-2010, 12:43   #46
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I use true, as I may use either GPS or compass, if I use the compass I correct for compass error both variation and deviation marked with quick notes at 45degs, or sight from landmark on chart. This works great for coastal, if you are passage making you may need a more exacting method.
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Old 15-10-2010, 21:26   #47
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Thanks everyone for a great discussion. Learned a lot. Great to see not everyone has gone 100% GPS and that proper navigation still exists!

I guess as long as you are comfortable with your own style, it doesnt matter which you do, I was just curious on what people do in the real world. And to bitch a bit about Lorwance not giving me the option of plotting a mag route on the plotter. At least I know what I am up against though.
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Old 15-10-2010, 21:47   #48
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I use magnetic for everything. Weather data is true, of course, but it's also inaccurate so it doesn't matter.
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Old 15-10-2010, 22:14   #49
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By the way, when the weather forcast says 'North' in an area of 20 deg Variation what do they mean? T or M?

I know the answer... be interested in what others think

Mark
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Well Mark,, what is the answer,,,,
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Old 15-10-2010, 22:20   #50
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Originally Posted by captainKJ View Post
By the way, when the weather forcast says 'North' in an area of 20 deg Variation what do they mean? T or M?

I know the answer... be interested in what others think

Mark
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Well Mark,, what is the answer,,,,

True.

People that deal with charts/maps covering large areas tend to use true as magnetic with change across the chart.
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Old 16-10-2010, 03:44   #51
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True.

People that deal with charts/maps covering large areas tend to use true as magnetic with change across the chart.
A few years ago I emailed the weather bureau and asked!
Yes, of course, correct Go to the top of the class
Daddle was, naturally, correct too and added an interesting bit: "but it's also inaccurate so it doesn't matter."

Which is the same with Mag and True. If the use of the thing makes the inaccuracy insignificant then it doesnt matter what you use.

I use the magnetic compass on the helm to basically see where the bow is (or where N, S etc is) but I run my course off the Plotter, NOT off the compas.
So if I look at the plotter and it I am doing 260 it will be allowing for leeway etc, then I can see what its showing on the compass and keep on that (if I so desire). The compass may show 255 or 270... its doesn't matter as its not an absolute I am looking for its the approximation relative to the Plotter.

Navigating by plotter and paper are 2 different things. Paper and the magnetic compass on the binnacle are inexorably linked. The compass I am linked with is the one below in the wardrobe of the aft cabin - the fluxgate compass but thats for steering not navigating. The plotter has wonderful tricks that paper doesn't do easily. It gives me more time to sit in the hammock and watch the birds go by.... feathered, of course.




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Old 17-10-2010, 11:18   #52
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Create the line on the chart in true course. That is IMO the best because the conventional chart is true N orientated.
Sailing on true or magnetic course depends on the on board equipment; if you own a gyro sail on true if you own a magnetic compass (I am not sure if that is correct English but I assume you know what I mean) sail with magnetic course.
Consider magnetic variation which can differ very much and makes the difference between both true and magnetic.
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Old 17-10-2010, 11:40   #53
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You may as well plot the course in True... coz lets face it... thats the course your going to sail.... just on a Magnetic Heading
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Old 17-10-2010, 21:14   #54
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Whether planning or plotting, I always use True, and I do use a deviation card to correct for the vessel's compass deviation. All of the vectors and bearings on the charts are plotted in True with regards to lights, aids to navigation etc... , even back in the day when all we had was a compass, watch and a 60' / 60 fathom flasher, we used True for our navigation, as all USA charts are oriented that way. Variation is easily calculated in if you are using a magnetic compass only. Using either method is acceptable as long as you are consistent in your method. Week end warriors or not, the crew should adapt to the particular method that the Master prefers.
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Old 21-10-2010, 05:05   #55
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Following some silly advice I have plotted a line True on the chart then placed a strong magnet to the left of it, then to the right of it.

Surprisingly, the line stayed put.

I guess I must be doing something wrong.

Anybody?

For all those who plot Magnetic: do you also plot your LOPs Magnetic??? Why not?

barnie
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Old 21-10-2010, 06:00   #56
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Quote:
Originally Posted by barnakiel View Post
Following some silly advice I have plotted a line True on the chart then placed a strong magnet to the left of it, then to the right of it.

Surprisingly, the line stayed put.

I guess I must be doing something wrong.

Anybody?

For all those who plot Magnetic: do you also plot your LOPs Magnetic??? Why not?

barnie
I assume you used a lead pencil...???
What makes me smile are the folks who sail the Mag Course sometimes printed on the chart which is precalculated, bar deviation, for ease of use for the customer... 5 years later they're still using that Mag Course even though the variations changed by as much as a degree in that time...
not much you may think but it can make a lot of difference over distance or tight waters...
Barnie... if you do your sums right... you'll find True and Magnetic follow the same line... the magnet is a WOFT... the rest is down to how well you can calculate tidal effect and leeway for an accurate landfall
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Old 21-10-2010, 06:13   #57
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I have plotted a line True on the chart then placed a strong magnet to the left of it, then to the right of it.

Surprisingly, the line stayed put.

I guess I must be doing something wrong.
If the line bends you are doing a Great Circle Route (Root in Australian)
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Old 21-10-2010, 06:36   #58
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I think it's personal choice, but the captain should let crew know it's always this way, or that. Otherwise, you're in for a world of confusion and possible danger. Having said that, I favor magnetic, but that's because I refuse to steer by the GPS. For me, the analog nature of the traditional compass is much better suited to the needs of the helmsman.
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Old 21-10-2010, 07:06   #59
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traditional compass is much better suited to the needs of the helmsman.
Thats an interesting thought "Helmsman"
I could not call myself the helmsman though I control the boat. Its always on auto pilot so I don't helm it in the traditional way.
The watchkeeper doesnt keep to a course he keeps the cross track error minimalised or eliminated. Its done by cliking the plus or minus 1 degree button one click every 5 minutes if necessary.
I can't call that helming.

For someone going without the autopilot any significant distance (except for breakdowns) is not really 'cruising' these days. Sure one or 2 boats of the 250 in the ARC may hand steer the whole way, but I doubt it would be more...

(The last trans-atlanitc I did 12 years ago we hand steered all the way. 6 crew)
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Old 21-10-2010, 08:24   #60
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(The last trans-atlanitc I did 12 years ago we hand steered all the way. 6 crew)
and I'll bet you used a compass.

since I don't have an autopilot at present, hand steering is it. And that's all on the Cheseapeake or near offshore - so my situation is different.

i guess i am a luddite, but i like to see (and anticipate) the swing of a magnetic compass.
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