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Author Topic: Magnetic Variation.  (Read 693 times)


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Magnetic Variation.
« on: June 08, 2017 »

Hey all,

This is my first post on the forum apart from my introduction, so I hope I am posting in the correct section. I have trawled the ould interweb for days trying to find the magnetic variation for the Mourne mountains for this year and it cannot be found. There are lots of suggestions and MV's from 2012,13 etc but nothing for 2017. Can anybody help on this one?Thanks in advance.



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Re: Magnetic Variation.
« Reply #1 on: June 10, 2017 »

If you contact OSNI they could give you the updated details. As a general rule I add 2 degrees over short distances and 3 over longer distance. If in doubt keep you map and compass out and check it every 500 yards or so. As a matter of interest what Mourne map/ scale and compass do you use?


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Re: Magnetic Variation.
« Reply #2 on: June 10, 2017 »

Hi Mourneman. I'm using a Silva expedition 4 baseplate compass and the OSNI Mourne activity map 1:25000. The MV marked on the map is 6° 12' W, but I cannot find the exact date printed on the map for when it was printed.


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Re: Magnetic Variation.
« Reply #3 on: June 12, 2017 »

Some feed back. So I emailed both OSNI and OSI. The former has not replied yet, but it's early Monday so... That latter however, they sent me a couple of useful links this morning. Here is what they had to say:

"There are a few online resources for calculating this. The one OSi and the Met office use is https://www.ngdc.noaa.gov/IAGA/vmod/igrf.html

There is another one I am aware of, this has no connection to OSi but I have heard some people find it useful, I cannot stand over the accuracy of this website,  http://www.magnetic-declination.com/"

I have not had the chance to open the first link because at this moment I am working 100% from my phone and tablet. I did however have a look at the second link and what I found was quite interesting to me. OSI do say that they don't standover it so I will wait for the response from OSNI to compare the MV's. According to the website the MV for the Silent Valley area is in and around 3° 8' W, that is a difference of 3° 4' if you take it away from what is on the OSNI activity map. It would be good to see the year the MV was taken printed on the map right beside the MV so the we can make the necessary adjustments.

Just thought I'd share what I have found out so far :)
« Last Edit: June 12, 2017 by Ciaran82 »

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