Latest on the wandering north pole

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 Toerag 07 May 2020

https://www.bbc.co.uk/news/science-environment-52550973

Which got me thinking, will 'grid to mag...add; mag to grid...get rid' change?  Does that apply in countries on the other side of the world now?

 Red Rover 07 May 2020
In reply to Toerag:

I've never bothered with the difference between grid and mag, does that make me a cowboy or is it OK because the difference is small these days? 

 Red Rover 07 May 2020
In reply to Toerag

When the north and south poles do reverse, you get a period in between where everything is chaotic and you get multiple north and south poles all over the place. Whatever rhyming mnemonic we compose to helm us adjust from grid to mag will have about 100 verses! 

In reply to Red Rover:

> I've never bothered with the difference between grid and mag, does that make me a cowboy or is it OK because the difference is small these days? 

Because of the latter. When i was young the difference was huge, and could lead you well astray if you ignored it.

 Red Rover 07 May 2020
In reply to Gordon Stainforth:

Lucky for me then that I've got away with it! 

 Ridge 07 May 2020
In reply to Red Rover:

It's pretty much bang on now in the West Lakes, which simplies it for the moment.

 Tringa 07 May 2020
In reply to Toerag:

> Which got me thinking, will 'grid to mag...add; mag to grid...get rid' change?  Does that apply in countries on the other side of the world now?


It depends where you are but for quite a few areas of the UK the difference mag and grid is so small it is not worth considering now.

This will allow you to see the difference - http://www.geomag.bgs.ac.uk/data_service/models_compass/gma_calc.html

Dave

In reply to Toerag:

> Which got me thinking, will 'grid to mag...add; mag to grid...get rid' change?  Does that apply in countries on the other side of the world now?

It's why I've never liked that mnemonic. Not to mention that I can never remember what the mnemonic is supposed to mean...

I've always just remembered whether MN is W or E of GN, locally, and move the compass capsule accordingly when taking a bearing from map or ground. It works universally.

The 'adding/subtracting' bit is only actual arithmetic if you're quoting a bearing to someone else. If you're navigating on your own, you don't need to pay any attention to the actual numbers, as long as you set the compass correctly; just rotate the capsule by the relevant amount.

ps. try ignoring GMA if you're in NZ...

Post edited at 14:30
 wercat 07 May 2020
In reply to captain paranoia:

I learned MUGS for our region (as well as checking the map for quantity of degrees as it has changed considerably since the early 70s when I learned to navigate.

Magnetic unto Grid SUBTRACT which has always bean easy for my forgetful head.

 wercat 07 May 2020
In reply to Toerag:

MUGS becomes GUMS

if I live long enough to have to use this I will be happy!

In reply to wercat:

> I learned MUGS for our region

It's still not universal, though. And, as it is now, likely to change.

I find it much easier to think of the simple relationship between MN and GN, and what to do to convert in either direction. There's even a handy pictogram on every OS map...

 Doug 07 May 2020
In reply to captain paranoia:

I was taught that map to real world is getting larger, so add, real world to map is getting saller so subtract. Was valid at the time (>40 years ago)

 Sean Kelly 07 May 2020
In reply to Toerag:

It already has here in the South West.

In reply to Toerag:

Will I have to reprogram my GPS?  

 wercat 07 May 2020
In reply to captain paranoia:

> It's still not universal, though. And, as it is now, likely to change.

>  There's even a handy pictogram on every OS map...

That's what I mean about checking the quantity - as for regionality - that really is no longer a consideration for me. And, my easy mnemonic that makes sense was quoted in the context of another region-limited rhyme as a more logical one to remember easily.

It is highly highly unlikely that I'll ever need to navigate by map outside the UK in the future.

Post edited at 22:19
In reply to wercat:

That's a shame.

I guess my pov is biased because I teach navigation to young people, and hope that what I teach them will be universally applicable, wherever, and whenever they travel in the world.

As well as thinking my method is easier to remember...

 wintertree 08 May 2020
In reply to Toerag:

The magnetic poles may be going haywire but worries of a long pause in the solar dynamo seem unfounded; reversed polarity sunspots keep cropping up showing the start of the next cycle.  There’s goes my hope for an ice age.

1
 Trangia 08 May 2020
In reply to Gordon Stainforth:

> Because of the latter. When i was young the difference was huge, and could lead you well astray if you ignored it.

Same here, taking account of the difference was a vital part of navigation.  It's lovely being able to pretty well ignore it now

 kamala 08 May 2020
In reply to captain paranoia:

Totally agree with an understanding of the relationship as more universally applicable. (The OP's question would be unnecessary if they were applying the principle rather than a mnemonic.) My memory's rubbish anyway so I always have to go back to first principles, and I find the diagrams on the OS maps invaluable.

Just remember to check the date on your map and apply the listed correction if it's an old one!

 wercat 08 May 2020
In reply to captain paranoia:

I definitely agree that a mnemonic is only enough to get you by.  I was taught mapreading and compass rather badly and it only really became a firm skill when I bought myself a Silva compass (marked in degrees, not mils like the ones at school) and local maps in 1 in to the mile and then 1:25000 and taught myself - I think I bought the "Know the Game book to begin with".  The way we were taught backbearings depended on a memory of what to do so realizing that it was effectively inverting the angle I simply started to use the white end of the needle for back bearings, for resection etc.  Great fun and even if it was a shortcut it didn't stop me from spotting that an older student was using the wrong end of the needle on his Silva for North (in thick mist) when I went out on an early trip with the university mountaineering club.

 profitofdoom 08 May 2020
In reply to Toerag:

Anyone apart from me noticed it's now moving unerringly towards Russia??!

The Russians are drawing it in to Moscow with a giant Anti-Magnet or Plus-Magnet MARK MY WORDS they're going to turn it into a giant power station or jam factory or something

In reply to wercat:

> I simply started to use the white end of the needle for back bearings, for resection etc.

Exactly. There's no need to do arithmetic. Either use the S end of the needle, or hold the compass the other way around when taking the sighting, or plotting onto the map.  


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