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Comment by carl_dr | Hacker News Reader

Magnetic north moves in a fairly predictable way.

If you are in the UK you might be interested in Standup Maths’ video https://youtu.be/HcFvegnQpPo.

Currently true north and magnetic north are broadly the same in the UK - and over the next year or so, there is a point where grid north (Ordnance Survey maps) also coincides with both other “norths”. That point will track north over the UK.

The video shows Matt visiting Cornwall at a place where that point was.

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My understanding is that the change in magnetic declination (caused by the change in magnetic north) is predictable in the short term (this is why maps state the rate of change but only for a certain time period) but is not predictable over the long term.

Ref: https://www.sco.wisc.edu/learning-center/magnetic-declinatio...

Got to love the Brits and their love for physical maps.

You can see the map he's looking at here: https://maps.walkingclub.org.uk/os.html?center=50.59818,-2.0... -- centred on the village containing the pub, not the true north place.

Note it doesn't work with an adblocker enabled. (I don't think the API to show the maps is free.)/

Thanks for the actual link, I see lots of physical details included in there, which I pretty much dig.

Related, during the last two weeks or so I've been immersing myself in exploring the topographical maps of Bulgaria the Soviets drew towards the end of the '80s (it was for a personal project of mine). For those interested the map can be found in here [1], by scrolling further down the page, a typical map-sheet looks something like this [2]

[1] http://web.uni-plovdiv.bg/vedrin/index_en.html

[2] http://web.uni-plovdiv.bg/vedrin/details/large/K-35-016-3.jp...

* Dorset

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