I’d like to add some thoughts from own experience. I am a Finn who did a lot of compass & map navigation in my youth, at sea and in the forests in scouting and the army. We experience this phenomenon enough for it to be relevant to naviation. So a few points to help clarify.
First, the effect of the deviance is only significant in a few parts of the world where you might experience it. If you look at the image on the page here, that has the two points, then you can see, that if someone stands in Northern Greenland, and uses a compass to determine ‘where is North’ the direction that the compass shows – is literally EXACT SOUTH. And to get to the real North pole, from that location with that magnetic compass indication, you would need to travel EXACTLY EAST.
So in VERY Northern (or very Southern) parts of the planet, the distortion to the compass can be dramatic. Now Finland is the Northernmost country on the planet (when countries are compared measuring their geographic midpoints) so as a nation, we are ‘most affected’ by this in terms of distance from the actual North Pole (if Greenland becomes Independent as Kalaalit Nunaat then it would assume this honor from Finland as the Northernmost country). But even in Finland, the typical error for a compass pointing North, and True North is something like 6% to 11% depending on where you are in FInland (effect is strongest in the North, weakest in the South). Now how many people live on the islands of Canada, or in Alaska, or in Norway, Sweden, Finland; in Northern areas of Russia, in Iceland, on the Northernmost island of Japan (Hokkaido) or yes the Greenland province of Denmark? If we say 100 million people that may be roughly the ball park (nobody lives on Antarctica, where the same phenomenon would also exist). But of the planet’s 7.5 Billion people that is a bit over 1% of all humans.
For the other 99% this will not really matter, except for the couple of Arctic fanatics who may want to explore the North (or South) Pole haha. And note, Finland has this effect in an exceptionally great degree, and even with us, the compass is ‘off’ by only under 10 degrees in typical situations (a compass dial has 360 degress so that is about 3% error).
We learn about this in school and we learn about it a lot if we get involved in compasses and mapping and navigation if in boating or scouting or any other navigation needs in Finland, plus of course we learn about this in the army (all Finnish men have to serve a year in the military). It is a real phenomenon but like I said, it only impacts the extreme Northern and Southern parts of the planet. It ALSO has a relevance limit by the East/West area. WITHIN the Northern (or Southern) Hemisphere, the FURTHER away East or West you are from Magnetic North, the more it can be measured. Let me show again with the illustration from the above.
Where the arrow points to ‘Magnetic North’ – if you follow that line South, to where the second big circle encircles the globe, that is roughly California. From California facing ‘Magnetic North’ there is no difference to real North. Even though the compass points to ‘closer’ than real North, both point GEOGRAPHICALLY in the same direction, into true North. The same would be true if you were opposite that point in Russia, in Siberia, then the compass would point ‘beyond Real North’ but the DIRECTION is identical with Magnetic North. So if you happen to be ‘directly South’ of where Magnetic North Pole is, or exactly opposite that on the other side, then there is no difference to what the compass shows and what is True North. But the further you move either East or West, so if you go the furthest East, you’d be in Iceland, and furthest West you’d be in Japan, those areas experience the worst distortion on the same latitude.
With this to add to my original guess of about 100 million people impacted, the reality is that probably only about 2/3 of those people are in both North-enough area, and far enough East/West to notice this phenomenon. Thats well less than 1% of the human population. But us in the Nordics (Scandinavia and Finland) and those in the Furthest East Asia, NorthEast Russia (Vladivostok) and Japan Hokkaido etc, they will yes, see a big difference in their compass reading vs real North.
I hope this helped.
Tomi Ahonen
In my day job, I’m a tech author
