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Mag, Grid & True North Align

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Mag, Grid & True North Align

Old 3rd Nov 2022, 22:30
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Mag, Grid & True North Align

Magnetic north, true north and grid north align over Great Britain for the first time in history.

Our calculations have discovered the three 'norths' will combine for the first time in history this week🧭

True north, magnetic north and grid north will combine at a single point - starting at Langton Matravers, a village just west of Swanage

https://www.ordnancesurvey.co.uk/new...PnhKNGR2fvNN_o


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Old 3rd Nov 2022, 23:03
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True N and Grid N don’t change do they, so I presume they have always coincided at that village?

True equals Mag, Local equals Zulu. What a day to be a navigator!
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Old 4th Nov 2022, 00:22
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So the 'add for mag, get rid for grid' beloved of hillwalkers etc becomes redundant?
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Old 4th Nov 2022, 00:30
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Originally Posted by Timelord View Post
True N and Grid N don’t change do they, so I presume they have always coincided at that village?
Yes, True N = Grid N for anywhere in the UK on the 2W meridian.
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Old 4th Nov 2022, 08:06
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Don't tell the BBC: they will start to blame it on Global Warming.
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Old 4th Nov 2022, 09:49
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Ruddy Brexit
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Old 4th Nov 2022, 10:01
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Is there an equivalent situation 180 degrees removed, eg the southern hemisphere?
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Old 4th Nov 2022, 10:03
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I remember being informed at a morning brief that due to the reduction in magnetic variation, Waddington's runway was no longer "two one" but "two zero": a co-pilot put up his hand and asked if the other end was still zero three.
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Old 4th Nov 2022, 10:06
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Originally Posted by SRFred View Post
Is there an equivalent situation 180 degrees removed, eg the southern hemisphere?
Same as the Northern Hemisphere: along the 2W line - because compasses always point to magnetic north.
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Old 4th Nov 2022, 10:10
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Bring back the LightWeightNavAid from the AH1 Gazelle so we can use it without doing Grivation calculations........
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Old 4th Nov 2022, 10:21
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Originally Posted by Wensleydale View Post
Don't tell the BBC: they will start to blame it on Global Warming.

well magnetic North has been moving somewhat faster than usual recently I understand

of course we're also getting closer to the point when the earth's field will flip and North becomes south - "it's grim up South " doesn't have the same ring to it
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Old 4th Nov 2022, 12:04
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Originally Posted by Wensleydale View Post
Same as the Northern Hemisphere: along the 2W line - because compasses always point to magnetic north.
The significance of 2W is that it is the central meridian (?) of the particular transverse Mercator projection used by OSGB. That is why TN and OS GN coincide along that line.

Last edited by Timelord; 4th Nov 2022 at 12:19.
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Old 4th Nov 2022, 12:10
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Originally Posted by Asturias56 View Post
well magnetic North has been moving somewhat faster than usual recently I understand

of course we're also getting closer to the point when the earth's field will flip and North becomes south - "it's grim up South " doesn't have the same ring to it
Just hold the chart upside down….easy.
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Old 4th Nov 2022, 13:39
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Originally Posted by Asturias56 View Post
well magnetic North has been moving somewhat faster than usual recently I understand

of course we're also getting closer to the point when the earth's field will flip and North becomes south - "it's grim up South " doesn't have the same ring to it
If you want to be ultra-pessimistic read Jim Al Khalili's book "Sunfall" which postulates a coronal mass ejection hitting Earth just at the point when the magnetic field passes through a temporary zero. Not likely but not impossible. Very nasty.
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Old 4th Nov 2022, 19:53
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Heathrow’s runway alignment

With the ever changing magnetic North does this mean that at any time in the near future we will see 27R and 27L revert to 28R and 28L? I remember it changing sometime in the 1970s and surely with the ever changing magnetic North it should change back at some point.
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Old 4th Nov 2022, 20:31
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With the proliferation of GPS/PNR equipment, and the weakening and variability of Mag, at what stage will everything switch to True at all levels rather than just the upper air?

Its been a joke for years at places such as Goose Bay to watch FJs fly the approach patterns 30+ degrees out till nudged….

kinda like the QFE/QNH thing….
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Old 4th Nov 2022, 22:06
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Originally Posted by 63000 Triple Zilch View Post
With the ever changing magnetic North does this mean that at any time in the near future we will see 27R and 27L revert to 28R and 28L? I remember it changing sometime in the 1970s and surely with the ever changing magnetic North it should change back at some point.
Heathrow's runways are closer to 260°T than to 280°T, so don't hold your breath.
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Old 4th Nov 2022, 22:06
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Originally Posted by Wensleydale View Post
I remember being informed at a morning brief that due to the reduction in magnetic variation, Waddington's runway was no longer "two one" but "two zero": a co-pilot put up his hand and asked if the other end was still zero three.
As an ex V force copilot that seems to me a sensible question as magnetic variation changes with geographic location as well as time !
Hat, coat !

Last edited by Senior Pilot; 6th Nov 2022 at 08:38. Reason: Fix quote
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Old 4th Nov 2022, 22:07
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Anyone ?

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Old 5th Nov 2022, 01:45
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Down here in the Antipodes variation varies between 18 to 25E, the isogonals lying roughly east-west across NZ. During my time as an instrument flight procedure designer we had to change runway designators on a number of occasions.
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