The earths magnetic field is not parallel with the earths surface, it has a vertical component force as well. At the North magnetic pole your needle would be pointing down straight at your feet if you held the compass horizontal so it would not be free to rotate. Near the equator there is little vertical component (the vertical component of the earths magnetism is called Dip) This is why compasses are balance for different magnetic latitudes. On a ship the magnetic compass is placed in a binnacle which allows for the deck officers to adjust the compass for varying magnetic latitudes as well as the deviating forces from the steel of the ship. As the vertical and horizontal components of the directing force on the compass needle change due to magnetic field latitude it also affects the deviation caused by the steel ship and electronics of the ship itself. Foreign going ship masters must correct a compass for minimum deviations as part of their certification
alittle bit of useless info for anyone who is interested
Regards
Dan
alittle bit of useless info for anyone who is interested
Regards
Dan
