Grid Magnetic Angle?

[Tartan_Terrier]

Just reading this article about the fact that the GMA is now actually East of grid North in some areas, and will align in some areas at some point in the near future.

How do they teach GMA now? Have they come up with a new phrase to replace "Grid to mag - add, mag to grid - get rid"

The Great North Run - British Geological Survey

The directions of true, grid and magnetic north will, for the first time, coincide at various locations in Great Britain between 2022 and 2026.

www.bgs.ac.uk

Here is a handy site for checking the magnetic decination at any given location: Magnetic Declination on Map

 

[Portree Kid]

Just reading this article about the fact that the GMA is now actually East of grid North in some areas, and will align in some areas at some point in the near future.

How do they teach GMA now? Have they come up with a new phrase to replace "Grid to mag - add, mag to grid - get rid"

It always moved slightly.

Year of map and annual change ( printed on map ) always had to be taken into consideration.

 

[Tappet]

How do they teach GMA now? Have they come up with a new phrase to replace "Grid to mag - add, mag to grid - get rid"

I think it's either now "Mag to Grid; Add, Grid to Mag; Get Rid", or "To Google Maps....go".

 

[Boxy]

We’ve not taught it to cadets, NNAS, syllabus for a good few years now

the reasoning being that it’s that small and they should only be travelling a short distance on each leg that the effect is negligible

 

[Queensman]

It always moved slightly.

Year of map and annual change ( printed on map ) always had to be taken into consideration.

No shit, Sherlock. AKA the magnetic variation.

 

[solomon88]

Just reading this article about the fact that the GMA is now actually East of grid North in some areas, and will align in some areas at some point in the near future.

How do they teach GMA now? Have they come up with a new phrase to replace "Grid to mag - add, mag to grid - get rid"

View attachment 599675

The Great North Run - British Geological Survey

The directions of true, grid and magnetic north will, for the first time, coincide at various locations in Great Britain between 2022 and 2026.

www.bgs.ac.uk

Here is a handy site for checking the magnetic decination at any given location: Magnetic Declination on Map

It did occur to me a couple of years ago that a lot of the mnemonics are now wrong. I've never been a great fan of these, I prefer to think from first principles, visualising your diagram.

Hard to explain without pencil and paper, but I thought you could call clockwise/east "positive" and anticlockwise/west "negative", then the rules of arithmetic would always give the right answer.

 

[solomon88]

It always moved slightly.

Year of map and annual change ( printed on map ) always had to be taken into consideration.

Yes, but it's now moved past North, so the add/subtract thing is reversed.

 

[AlienFTM]

It always moved slightly.

Year of map and annual change ( printed on map ) always had to be taken into consideration.

Decades ago I found an old BAOR map, did the sums and decided it would be changing in the early 2000s.

Then in the mid 2000s I was told it had. If I could be arrsed, I'd flex my ArrseSearch-fu to find where I posted it.

 

[CutLunchCommando]

Have they come up with a new phrase to replace "Grid to mag - add, mag to grid - get rid"

Presumably we just use whatever the people in places where the declination is the opposite use.

 

[solomon88]

Decades ago I found an old BAOR map, did the sums and decided it would be changing in the early 2000s.

Then in the mid 2000s I was told it had. If I could be arrsed, I'd flex my ArrseSearch-fu to find where I posted it.

I've found a chart, over the last 400 years in the UK it's moved from 11 deg East to 24 deg West in 1818, and now back to about 0 deg. There's about 5 degrees difference across the country East to West.

 

[Bravo_Bravo]

I remember when I did MAPRIC, seeing a map of ?Denmark with GMA pointing in two different directions as the land mass coincided with the join of a Mercator projection petal ( or however its described...)

 

[Ortholith]

We’ve not taught it to cadets, NNAS, syllabus for a good few years now

the reasoning being that it’s that small and they should only be travelling a short distance on each leg that the effect is negligible

Same here with my DofE miscreants. When the declination is only a few degrees it's really not an issue, especially when you bear in mind that a standard baseplate type compass will have a significant error margin anyway (the last cheapo batch I looked at agreed to within about 10 degrees).

Unless you're walking on very precise bearings with a prismatic compass it's not worth worrying about in the UK in my opinion. Obviously that will change in the future as magnetic north shifts further from grid north.

 

[shiny_arrse]

Same here with my DofE miscreants. When the declination is only a few degrees it's really not an issue, especially when you bear in mind that a standard baseplate type compass will have a significant error margin anyway (the last cheapo batch I looked at agreed to within about 10 degrees).

Unless you're walking on very precise bearings with a prismatic compass it's not worth worrying about in the UK in my opinion. Obviously that will change in the future as magnetic north shifts further from grid north.

We'll be fine as long a it doesn't flip.

Earth's magnetic field flipping linked to extinctions 42,000 years ago

Earth’s most recent magnetic pole reversal, called the Laschamp event, has been dated to 42,000 years ago and coincides with extreme weather and the extinction of large mammals

www.newscientist.com

 

[AsterixTG]

We'll be fine as long a it doesn't flip.

Earth's magnetic field flipping linked to extinctions 42,000 years ago

Earth’s most recent magnetic pole reversal, called the Laschamp event, has been dated to 42,000 years ago and coincides with extreme weather and the extinction of large mammals

www.newscientist.com

No doubt they'll say if we pay extra tax they can slow the effects...