Nav Work 101 - Cardinal Directions and Declination

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Grannyhiker
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Re: Nav Work 101 - Cardinal Directions and Declination

Post by Grannyhiker » August 13th, 2013, 11:49 am

How to calculate your current magnetic declination: http://www.ngdc.noaa.gov/geomag-web/#declination

Good idea to check this every 4-5 years, also if you go to another region, such as Wyoming or the French Alps. The table even calculates your approximate location if you don't know the latitude and longitude.

Current declination for Troutdale: 15° 48' 58" E changing by 9.2' W per year

That's probably a lot more detail than you need to know!
May your trails be crooked, winding, lonesome, dangerous, leading to the most amazing view.--E.Abbey

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retired jerry
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Re: Nav Work 101 - Cardinal Directions and Declination

Post by retired jerry » August 13th, 2013, 12:14 pm

100 years until magnetic reversal? :)

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retired jerry
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Re: Nav Work 101 - Cardinal Directions and Declination

Post by retired jerry » August 13th, 2013, 12:15 pm

nevermind, that's backwards

regardless, we are "due" for a reversal

raven
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Re: Nav Work 101 - Cardinal Directions and Declination

Post by raven » August 13th, 2013, 12:34 pm

The easiest way I know to find declination is to go to the place in Gmap4 -- which I most likely will do anyway -- and turn on declination.

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johngo
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Re: Nav Work 101 - Cardinal Directions and Declination

Post by johngo » July 30th, 2015, 10:15 am

Folks,

A couple of tips:

1) For the magnetic declination of any point on earth, just Google it. The first link that should appear is magnetic-declination.com
Click on any point on the map, and you get a pop-up window that tells you the precise declination.

2) And some smart people here already pointed out, please please please just buy a quality compass with adjustable declination and forget about all the confusing backcountry arithmetic. The "East is least, west is best" clever word games might sound simple when you're in front of your nice warm computer screen, but trust me, years from now when you're lost and stressed and need to make a critical navigation decision, the chances of you remembering this correctly are slim to none.

When you use a compass with adjustable declination, you are essentially moving the orienteering arrow. When you do this, all bearings are taken to true north, and there's absolutely no adding or subtracting declination to be done. It's the modern and much more sensible way to use a compass.

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texasbb
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Re: Nav Work 101 - Cardinal Directions and Declination

Post by texasbb » June 30th, 2016, 11:34 am

johngo wrote:2) And some smart people here already pointed out, please please please just buy a quality compass with adjustable declination and forget about all the confusing backcountry arithmetic.
Gotta disagree in part. Certainly get a declinating compass if it helps (I use one), but whatever you do, don't "forget about all the...arithmetic." Skipping the understanding part is never a good idea.

Plus, there are times you'll want to use one of the teeny-tiny things that aren't adjustable and you'll feel silly not to have remembered "declination east, magnetic least." :)

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Lurch
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Re: Nav Work 101 - Cardinal Directions and Declination

Post by Lurch » July 1st, 2016, 7:20 am

I agree that people should have a fundamental understanding of declination, and how to implement it, which is why it's mandatory when I teach navigation to people. But I disagree that you should ever want to use a button compass like that :lol: ;)

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texasbb
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Re: Nav Work 101 - Cardinal Directions and Declination

Post by texasbb » July 1st, 2016, 2:08 pm

Lurch wrote:... But I disagree that you should ever want to use a button compass like that :lol: ;)
Don't knock it till you've tried it! Mine was a gift but I've fallen in love with it. :P Clipped to my trekking pole strap it's perfect for low-precision work like getting through a forested section to whatever "fence" I'm looking for on an overcast day. It weighs about 5 grams, so there is that penalty. :)

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johngo
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Re: Nav Work 101 - Cardinal Directions and Declination

Post by johngo » July 4th, 2016, 7:57 am

Well, perhaps we will agree to disagree on this.
You don't have to understand how a fuel injection system works order to drive a car, right? =^)

I would never carry a button compass like that, and therefore I don't need to know how to use it.
And, if I for some reason was ever forced to use a button compass, I would not be relying on it to find a pinpoint objective, but for general direction of travel.
But hey, if you choose to carry a tool that has limitations, it's your responsibility to learn how to use it.

I agree with most everything that Mssr. Lurch has so generously posted so far.
It is important to know what declination is, that it changes over time and location, how to compensate for it with an adjustable declination compass, and understand situations when you do and do not need to care about it.

You DO need to care about it if you were trying to locate a small objective over a larger distance, like your tent and a small clearing. That is when the declination error of 92 feet per degree per mile can become important.

You (generally) DO NOT need to care about declination (in the USA) if you are trying to find a large objective is in a general direction, such as "if we walk east, we will hit the road."

And as you yourself said in your post, you're using a button compass for "low precision work". In this case, dealing with declination is probably not required.

Here's the takeaway: whatever tools you choose to carry in the backcountry, know how to use them and any limitations they may have.

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texasbb
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Re: Nav Work 101 - Cardinal Directions and Declination

Post by texasbb » July 4th, 2016, 9:40 am

johngo wrote:Well, perhaps we will agree to disagree on this.
I can't tell if we're disagreeing or not. :)
Here's the takeaway: whatever tools you choose to carry in the backcountry, know how to use them and any limitations they may have.
Yes, know how to use your tools, but that's secondary. If my tool is a GPS, I arguably don't even need to know the difference between North and South. :? I'm just saying it's smart to understand the concept apart from any particular tool.

(And yes, I seriously do love my Suunto Clipper. :lol: :P )

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