Genesis 
So here's a random thing that I learnt yesterday. Compasses are region-specific and the needle will "stick" if a normal compass is used in the wrong region! Australia and New Zealand are in magnetic zone 5. If you want a #compass that works anywhere in the world, it needs to have a "global needle", which is built a bit differently to account for the problem of the magnet aiming directly through the earth to magnetic north and dragging the needle down with it.
Tim Gent@Genesis so does a global compass have some sort of adjustable weighting or spring? Or something else? I'm guessing a ball shape in fluid might work, which I've seen on boats.
jz@tgent_fens @Genesis on those global models there’s only a very small disc that’s magnetic. The needles aren’t so due to the small diameter of the disk and the decoupling of the needles from that disk the inclination isn’t affecting it to a degree that renders the compass useless.
Those systems are more complex thus more expensive. It’s cheaper to have one compass for each hemisphere.
Those systems are more complex thus more expensive. It’s cheaper to have one compass for each hemisphere.