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Old 13-10-2012, 21:26   #796
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Re: Paper Charts Now Unnecessary

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Originally Posted by downunder View Post
compass deviation ??????? whats that???????????


I copied this for you which explains it better than I can...
All information on a chart, including your own plotting, is related to TRUE North.

Thus all bearings on a chart are related to TRUE NORTH. Compasses point to MAGNETIC NORTH, which varies from True North by an error called VARIATION.
Compasses also are subject to their own errors; this is called DEVIATION.
COMPASS BEARING = TRUE BEARING +/- MAGNETIC VARIATION +/- COMPASS DEVIATION
Magnetic Variation is due to the differing positions of the Geographic North Pole and the Magnetic North Pole. The boat's compass and a hand bearing compass point to the Magnetic Pole, but all bearings on charts are related to the Geographic Pole (True North).
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Old 13-10-2012, 21:28   #797
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Re: Paper Charts Now Unnecessary

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Originally Posted by Celestialsailor View Post
The very first thing we learned was proper navigation, How to calculate current set, variation of compass, how and why it changes, where to find that information and so on.

<snip>

They really emphasized compass deviation. Hell...I doubt one skipper you talk to these days actually knows if his compass has been swung in or not.
I am guessing this was an incomplete thought?

Compasses don't have variation - in the sense of navigation.

Variation - The difference between true north and magnetic north caused by the difference between the location of true north vs. magnetic north and the changes in the earth's magnetic field over time.

Deviation - The errors in every compass caused by inherent design of the compass and influences of installation. Some error of deviation will always exist and a compass deviation card is prepared so that the error can be added or subtracted from calculated mag heading to get compass heading.
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Old 13-10-2012, 21:30   #798
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Re: Paper Charts Now Unnecessary

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Originally Posted by rebel heart View Post
The chart plotter is not the problem. The "hey look I have a chart plotter I don't need to know a single other god damn thing about navigation!" is the problem.

+1
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Old 13-10-2012, 21:30   #799
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Re: Paper Charts Now Unnecessary

well I knew I would be dissected for this...after all it is the Internet
I meant the Variation true to magnetic but feel free to cross examine
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Old 13-10-2012, 21:34   #800
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Re: Paper Charts Now Unnecessary

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Originally Posted by Ex-Calif View Post

Deviation - The errors in every compass caused by inherent design of the compass and influences of installation. Some error of deviation will always exist and a compass deviation card is prepared so that the error can be added or subtracted from calculated mag heading to get compass heading.
Right below your binnacle compass is a large chuck of ferrous metal called an engine. It will play havoc with the magnetic field around your boat.

Once your deviation card has been prepared do not move your anchor and the chain.
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Old 13-10-2012, 21:35   #801
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Re: Paper Charts Now Unnecessary

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Originally Posted by wolfenzee View Post
If a magnetic compass says one thing and the GPS compass (based on your movement) says another...is one right and one wrong. The compass shows your heading and the GPS shows your bearing, these can be different due to current or wind. And/or the compass could be out of adjustment and/or the GPS could not have been tracking in a straight line long enough to have an accurate reading.
Oh, no...

GPS shows many things - You may be confusing COG with bearing.

COG is the actual direction the boat is moving - even if backwards.

Bearing is the angle to a waypoint or fix or target.
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Old 13-10-2012, 21:37   #802
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Re: Paper Charts Now Unnecessary

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well I knew I would be dissected for this...after all it is the Internet
I meant the Variation true to magnetic but feel free to cross examine
I know and recognize your skills - that's why I guessed incomplete thought.

It's the internet and we are all a bit anal...
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Old 13-10-2012, 21:43   #803
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Re: Paper Charts Now Unnecessary

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Oh, no...

GPS shows many things - You may be confusing COG with bearing.

COG is the actual direction the boat is moving - even if backwards.

Bearing is the angle to a waypoint or fix or target.

Yes, indeedy.
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Old 13-10-2012, 22:12   #804
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Re: Paper Charts Now Unnecessary

Straight out inexperience, The learning curve, Etc Etc, and not knowing enough about a GPS and what it does,
I changed my GPS chart from Fiji to Australia a couple of days after I left Fiji, The Australian one had a section that went out from OZ across the coral sea, I assumed it went to Vanuatu and New Caledonia,

Wrong, It only went to Norfolk Island,

Well it does do Darwin to Adelaide and the whole east coast of OZ, Except for bits that have never been charted at all, By any one,

Any way, coming into Vanuatu just above Efate, and under a small little island, and not too much room to manouvre, About 10-00 PM to dark to see any thing,

I was travelling 5 knots side ways and 1.5 knots forwards, according to the GPS, The GPS was going round in circles as well.

I was doing 7 knots forwards, but the current and wind was giving me side drift chronically, Throwing the GPS into a fit.

My GPS and Paper chart both gave the same info, not much, So I got onto the VHF and picked up a sailor anchored on the other side of Efate,
And after checking his computer charts, He advised me to change course and drop down a few points as I was heading for a rock not listed on my charts or GPS, But listed on his computer chart,

He gave me his position and I found him the next day with the GPS, I promptly gave him and his wife an ice cold beer for his troubles, about 10-00 in the morning,

He then sorted my problems with my GPS, I just had the wrong chart in the GPS, I had changed the chart too early,
The GPS had all the info in it, the paper charts did not, My Paper charts were the latest issue as well.

He then down loaded the computer chart he had into my lap top, That was incredible for info, More than my GPS and Paper charts had,

The paper chart sat on the table, it gave a general overall piccy of where I was,

The lap top and GPS gave me the info for what was there at the point of where I was,

But when they had the hissy fit, It was the Compass that I was using to sail with, and the stars,

The GPS still gave me my position, So I did know precisely where I was at all times, And it has way marks on it, So I know how far I have come, and the speed I am travelling at, the GPS also has a trip meter on it that tells me how far the boat has travelled since new,

The paper charts dont do any of that,

When you buy your brand new and latest up to date chart,
Check the fine print on it,
It states in tiny writing, when the chart was actually charted, and from what chart it was taken from,

Your 2008 printed latest Paper chart, was actually taken from a chart that was charted in 1978 or earlier,

Some area's of OZ have never been charted, And the charts quite clearly say so,

But I would say that the UK and the USA have been charted to death, Those charts would be excellent to have on board.

There is a world of difference between sailing up the coast in sight of land and cruising across oceans,
I was fortunate that I had all the charts for the area's that I sailed through, But as for detail where I was sailing, The GPS was the thing that had all the Information, not the paper charts,
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Old 13-10-2012, 22:16   #805
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Re: Paper Charts Now Unnecessary

True north and magnetic north is about 10 degrees difference,
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Old 13-10-2012, 22:24   #806
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Re: Paper Charts Now Unnecessary

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True north and magnetic north is about 10 degrees difference,
Where?

Which way?
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Old 13-10-2012, 22:27   #807
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Re: Paper Charts Now Unnecessary

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Yes...This is what I never hear on any forum...deviation and variation. I first started my sailing journey in 1976. I was in the Canadian Power Squadron classes. The very first thing we learned was proper navigation, How to calculate current set, variation of compass, how and why it changes, where to find that information and so on. They really emphasized compass deviation. Hell...I doubt one skipper you talk to these days actually knows if his compass has been swung in or not.
So I know plotters are the rave and for good reason but it does not take the place of seat of the pants navigation.
I'll put on my hard hat now...
Not that it's right or good or anything..

But sitting in a bar up a muddy river in Brazil with a bunch of ocean crossing cruisers this topic came up... and not one of us knew what the local variation was. From memory everyone would have had the info somewhere onboard and definitely knew all about it but we all did the same thing, gps offshore then gps/visual pilotage for the last tiny bit when the land appeared.
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Old 13-10-2012, 23:03   #808
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Re: Paper Charts Now Unnecessary

Its easy to figure East and West, it only gets hard when ya wanta go North or South !! !! all ya need is eyeballs !! Just sayin it's a lot easier to get where ya wanta get without spending big bucks for all the fancy stuff !! O well some folks just grew up in the wrong time to undestand why some folks just don't care for eletrictronics!! Some of us feel that anything but a simple hand held GPS and a paper chart are a waste of boat bucks !!! Just sayin it's all Ive ever needed I have other stuff too but they are Connies babys ! I do ck it at the end fo a sailin day just to see how close we are !!
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Old 14-10-2012, 01:30   #809
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Re: Paper Charts Now Unnecessary

Electronics are great and convenient....but that is no reason to give up the knowledge and ability to think that comes with knowing how to navigate...just because something can think for you doesn't mean you have to give up knowing how to think.
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Old 14-10-2012, 01:53   #810
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Re: Paper Charts Now Unnecessary

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Electronics are great and convenient....but that is no reason to give up the knowledge and ability to think that comes with knowing how to navigate...just because something can think for you doesn't mean you have to give up knowing how to think.
This.

GPS is fabulous for offshore, as long as it keeps working. Every hour or two I'll mark the paper chart with an exact fix and the speed/heading so I can dead reckon if all the electronics simultaneously go kaputt. This is probably unnecessary, but it makes me feel better.

I prefer paper charts for coastal cruising. This is mostly because they are fun. Linking physical, real life features to the chart, taking bearings, and drawing on the chart gives me a sense of place that the GPS can't match. It also keeps my eyes outside the cockpit.
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