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Old 07-02-2013, 00:02   #91
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Re: True or Magnetic for Electronic Nav

... add to this a dynamo battery/phone charger and you will be fine.

Anything can fail, get lost, break down ... paper charts, compass, gps, chart plotter ... what's the difference? The arguments are often about comfort level ... the digital immigrants and digital natives will have vastly different opinions ...

If you plan on using electronics first ... true, if traditional charts and compass as primary means ... magnetic. Always have charts and compass on board as a backup. I think this is not only prudent but also required.
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Old 07-02-2013, 00:03   #92
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Re: True or Magnetic for Electronic Nav

Kiwi,

You seem to be electronically highjacking this thread. True or mag for electronic nav.

Afraid your batteries do not ad to the discussion.
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Old 07-02-2013, 00:14   #93
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Re: True or Magnetic for Electronic Nav

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Kiwi,

You seem to be electronically highjacking this thread. True or mag for electronic nav.

Afraid your batteries do not ad to the discussion.
You mean I am hi-jacking a thread that I actually started. (Check whom the OP was you will find it was yours truly). I contemporaneously castigate and apologise to myself at the same time.

The battery talk started when someone that said something along the lines of that they assumed I would have a full set of paper charts on board - and it went from there. The true / magnetic has been well caterered in early posts, and as I started this thread I have no problem that it has drifted.

Ok then, mate.
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Old 07-02-2013, 00:38   #94
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Re: True or Magnetic for Electronic Nav

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That is non-sensical. If I own three cars, and one fails I infinitely improve my odds of getting to work that morning If can turn the key on the next car in my garage. Now if i had forgotten where I put the key/s for my spare car/s - just like I had forgotten to ensure I have loads of spare, cheap, long lasting AA batteries for my spare GPS units- then I truly am a dufus.

And the twin engine aircraft analogy makes even less sense. Sorry. But appreciate your input.
What I wrote is factual. It is simple math. Not an opinion. You have made errors in reading and understanding, though part of your analysis is correct.
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Old 07-02-2013, 00:46   #95
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Re: True or Magnetic for Electronic Nav

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What I wrote is factual. It is simple math. Not an opinion. You have made errors in reading and understanding, though part of your analysis is correct.
No worries Daddle. I was not actually meaning that a twin engine aircraft won't or can't fail, but I feel the analogy is drawing a long bow as far as the latter discussion on E-Charts/Nav versus trad.

I do not doubt the math, but we can agree to disagree on the analogy drawn, but I appreciate your input.

Cheers.
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Old 07-02-2013, 01:21   #96
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Re: True or Magnetic for Electronic Nav

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I contemporaneously castigate and apologise to myself at the same time.


Back to post 1....


Sitting in a bar in Brazil with some experienced long distance cruisers, and no one knew the mag variation. ( Think it was about 20deg ) No doubt every boat could have dug it out it a few minutes but everyone got there on gps.
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Old 07-02-2013, 02:50   #97
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Re: True or Magnetic for Electronic Nav

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One pack of 8 eneloop long life AA batteries for 14.30 a pack. 1x8 Sanyo Eneloop Mignon AA 2000 mAh: Amazon.co.uk: Electronics

143 quid buys you 80 long life AA batteries - which is an over-the-top number of backup batteries, but serves to illustrate my point. Even I can afford 143 to make sure I never ever never run out of battery power before embarking on a coastal or offshore passage.
Yes, but do you have enough storage?

Seriously though, look up those in probability theory:
- independent events,
- gambler's fallacy.

And then there is always the chance of a direct lightning strike

Re original topic: true north only. Compass is just an imperfect measurement tool and corrections are applied as needed.
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Old 07-02-2013, 03:48   #98
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Re: True or Magnetic for Electronic Nav

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If you plan on using electronics first ... true, if traditional charts and compass as primary means ... magnetic. Always have charts and compass on board as a backup. I think this is not only prudent but also required.
This is seriously bad advice, True has nothing to do with electronics, your chart is plotted (drawn) in TRUE, Thats a fact. Tides are given in True and Celestial almanacs are in True. Magnetic is merely given for reference, to allow you to transfer course determined in True to steering orders for the helm. All plotting on a chart is in TRUE, try working up a complex tidal course to steer in magnetic on a chart , its nonsense.

Orders go to the helm in compass. reports come from the helm in compass. everything else is in True with paper.

Dave
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Old 07-02-2013, 05:14   #99
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Re: True or Magnetic for Electronic Nav

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What I wrote is factual. It is simple math. Not an opinion.
Simple math but confused. Twin engines are an integral part of an aircraft, the aircraft needs them both to function at 100% capacity. Two GPS units on one boat are redundant duplicate capacity ... providing 200% functional capacity.
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Old 07-02-2013, 05:24   #100
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Re: True or Magnetic for Electronic Nav

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This is seriously bad advice, True has nothing to do with electronics, your chart is plotted (drawn) in TRUE, Thats a fact. Tides are given in True and Celestial almanacs are in True. Magnetic is merely given for reference, to allow you to transfer course determined in True to steering orders for the helm. All plotting on a chart is in TRUE, try working up a complex tidal course to steer in magnetic on a chart , its nonsense.

Orders go to the helm in compass. reports come from the helm in compass. everything else is in True with paper.

Dave
I agree ... it would be a bad advice, it was more of a homage.

Some insist on working in magnetic and fiddle with a compass rose on a chart ... just read the replies in this topic.

The only thing true has to do with electronics is that the electronics work natively in true mode ... and that in the electronic charting era the electronics diminished (eliminated?) the need for magnetic unless one has to fall back on a traditional compass.

As I said before, it's all about comfort level ...
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Old 07-02-2013, 05:28   #101
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Re: True or Magnetic for Electronic Nav

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This is seriously bad advice, True has nothing to do with electronics, your chart is plotted (drawn) in TRUE, Thats a fact. Tides are given in True and Celestial almanacs are in True. Magnetic is merely given for reference,
Wind forcast direction is in True, too. so in the Caribbean, for example where the variation is 14 degrees and you are forcast an ENE or a ESE to go zip between islands you might get a little surprize if you use magnetic and dont convert.
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Old 07-02-2013, 05:42   #102
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Re: True or Magnetic for Electronic Nav

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Some insist on working in magnetic and fiddle with a compass rose on a chart ... just read the replies in this topic. The only thing true has to do with electronics is that in the new electronic charting era it diminished (eliminated?) the need for magnetic unless one has to fall back on traditional compass.
yes and I cant see how anyone can seriously do any real plotting on a chart in Magnetic. So I suspect those using it are just doing simple stuff.

I do not see at all how electronics have diminished the need for magnetic Non-electronic plotting really has to be in True, for any real work. Hence the majority of chart work has always been in True , it simply has to be .

If anything I beleive that electronics has lead the way to the adoption of Magnetic over True, People like to have the "comfort" of reading off a direct steering angle from the chartplotter so many set up the chart in mag. Then they typically back plot a course on a paper chart as a kind of backup. Hence the advocates of Magnetic for nav, in reality they are merely using the paper chart as a visual log, They are not actually using a paper chart for Navigation

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Old 07-02-2013, 05:53   #103
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Re: True or Magnetic for Electronic Nav

Dave ... looks to me like we are trying to say the same thing ... just in different ways. Comfort is a key word ... whatever makes more sense to the one who is at helm.

Just FYI ... I never work in magnetic mode, even when using/looking a traditional compass. The compass is always corrected to local declination ... sailing or mountaineering ... I always navigated in true. Maybe because I started navigating on land first where a two degrees off for an hour can mean life and death difference?
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Old 07-02-2013, 05:59   #104
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Re: True or Magnetic for Electronic Nav

what i was saying is that it is the rise of Electronics and the blind acceptance of their numbers that has lead the charge to Magnetic in recent years.

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Old 07-02-2013, 06:46   #105
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Re: True or Magnetic for Electronic Nav

To add one more point of fallacy about magnetic heading. As electronics started to appear at the nav stations, designers put the magnetic variation table in the gps and delivered via NMEA0183 (using that wonderfully short-sighted method of compound NMEA sentences).

In my limited observation of this built in magnetic variation information produced by the electronics, it doesn't update with time. So if your GPS is 10 years old, the magnetic variation it reports for the current location is also 10 years old. With NMEA2000, the compound data structure has been fixed, allowing any electronic source to be an authority of magnetic variation, but I've yet to witness any electronic source considering time adjustments. I have witnessed firmware updates also updating the magnetic variation tables.

Of course, this really only matters if your electronics are of very old vintage as the magnetic variation over a relatively short time span, say 5 years, doesn't change more than compass reading error of a helmsman.

So the designers expect you to update your electronics in a timely manner, or at least before the reported magnetic variation errors become an issue.

Caveat emptor!
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