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   robryk@qoto.org's status on Friday, 09-Feb-2024 11:29:38 JST robryk

   in reply to

   @freemo

   Mechanical compasses of that sort are more complicated, at least because you need a vertical reference and a gimbal with 2 degrees of freedom.

   Also, that's not very accurate if you don't know your longitude: the isolines of vertical strength are amusingly curvy: https://upload.wikimedia.org/wikipedia/commons/4/4c/World_Magnetic_Inclination_2020.pdf

   BTW I wonder how many sports trackers use the magnetic field to simplify their motion tracking, and then work very differently sufficiently far north or sufficiently close to the equator. (E.g. for breaststroke in swimming pools oriented east-west in Switzerland keeping a running average of the magnetic field direction at wrist is a more reliable way of counting lengths than what Garmin was doing up until something like 1-2 years ago)