When the compass is placed horizontally, the pointer will stop swinging, so that we can see the north-south direction accurately. If the compass can't accurately judge the north-south direction, it may be that the magnetic field interferes with the compass.
Modern electronic compass:
Electronic compass can be divided into plane electronic compass and three-dimensional electronic compass. The plane electronic compass requires the user to keep the compass level when using it, otherwise, when the compass is tilted, it will also give the change of course, but in fact the course has not changed.
Although the plane electronic compass has high requirements for use, it is a good cost-effective choice if the carrier attached to the compass can always remain horizontal.
The three-dimensional electronic compass overcomes the strict restrictions on the use of the plane electronic compass, because there is an inclination sensor in the three-dimensional electronic compass. If the compass is inclined, it can compensate the inclination of the compass, so that even if the compass is inclined, the heading data is still accurate.
Sometimes, in order to overcome the temperature drift, the compass can also build temperature compensation to minimize the temperature drift of tilt angle and pointing angle.
There are four ways to place the compass: Shui Piao method, nail screw method, bowl-lip screw method and thread hanging method. Shui Piao's method is to put the compass in a bowl filled with water and make it float on the water. The snail method is to put the magnetic needle on the surface of the nail and rotate it gently, and the bowl-lip snail method is to put it on the edge of the bowl. The thread hanging method is to coat wax in the middle of the magnetic needle, stick a thin thread and hang it in a windless place.