The main difference between electronic compasses is accuracy, that is, heading, pitching and tumbling accuracy, especially heading accuracy. The heading is defined as the angle between the projection of the compass's own axis on the horizontal plane and the north direction. The pitch is defined as the angle between the compass's own axis and the ground plane, and the roll is defined as the angle at which the compass rotates about its own axis. as the picture shows.
According to the above definition, if the compass only changes its pitch, its azimuth and roll angle should be unchanged. Similarly, if the compass is rolled around itself, that is, it is self-propagating, the azimuth and elevation angle of its output should also be unchanged. When the compass is used, such as in vehicles, antenna orientation and surface buoys, the carrier often tilts back and forth. When applied to petroleum and geological logging, it often rotates, so most applications require the compass to meet the requirements. The requirement that the orientation does not change when tilting and rolling.