Get the best accuracy from your electronic compass
Military, marine navigation, unmanned vehicles and more depend on the accuracy of an electronic compass. There are several factors that can greatly influence how a compass takes its readings. Here are three of these factors and how to be aware of them.
#1 Time Varying Magnetic Fields
A time varying magnetic field in the vicinity of an electronic compass cannot be compensated. Its frequency must be above the pass band of the compass (i.e. greater than 30 Hz), or it must be eliminated. The compass’ measurement cycle rate of 27.5 Hz is chosen to maximize attenuation of 50 Hz to 60 Hz signals associated with AC power systems.
Read more: http://www.jewellinstruments.com/3-factors-that-influence-electronic-compass-accuracy/