Why does the heading coming from the SSC200 appear to be in error?

The SSC200 measures the Earth’s magnetic field and before it will provide an accurate heading, it must understand how the Earth’s magnetic field is affected (or deviates from normal) due to the ferrous metals found on the vessel. Fortunately, the SSC200 compass can be calibrated to account for the magnetic deviation introduced by the ferrous metals found on the boat Unfortunately, the SSC200 compass (nor any other magnetic compass) cannot cope with changing magnetic fields (e.g., a wire running next to the compass has a changing magnetic field when the circuit is turned on and off). Therefore, wires must be kept as far away as possible from the SSC200 (small wires carrying small currents less than 1 amp are best kept at least 18 inches away from the compass, whele wires with larger currents should be kept even farther away).