by tonytran2015 (Melbourne, Australia).
A magnetic compass uses the local magnetic field generated by the rotating core of the earth to give the rotational axis of the earth. The two directions are reasonably close.
The magnetic compass is a secondary directional instrument to people who can observe celestial bodies for navigation but is a primary practical directional instrument to people who cannot observe any Celestial body. (Gyro-compasses are too expensive for most people).
Here is the list of desirable features for selecting a compass and different usage modes of magnetic compasses.
A compass should have at least the following desirable features:
3. Wide operational conditions (being stable despite harsh operating conditions),
4. Accuracy (being true and sensitive),
6. Portability, and
Figure 1:(Left to right) Tiny liquid filled disc compass, simple compasses with and without needle lock.
Figure 2: A HAZARDOUS…
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