Magnetism

• An electronic compass works by magneto-inductive technology, reading differences in the Earth's magnetic field. An electronic compass needs to be able to take clear readings. If it is installed near a large mass of metal, say a car, it needs to be able to subtract that reading from the reading it gets from the Earth's magnetic field in order to get a truly accurate reading.
  
  

Deviations

• Magnetic north and true north differ by an approximate angle of 11.5 degrees, which is called the variation angle. Hard iron and soft iron can also affect the readout of the compass. Hard iron is the result of permanent magnets, or magnetized metals like steel, while soft iron distortion comes from the reaction between the Earth's magnetic field and soft metals near the compass. Many electronic compasses can store the compensation for hard iron distortion in their memory.
  
  

Readouts

• Electronic compasses have a digital readout that can tell you what direction the compass is pointed in. When used with a map, such as a U.S. Topo map that shows the deviation between magnetic north and true north, it is easy to navigate to where you want to go.