Whilst it is possibly one of the oldest pieces of navigational equipment in use on any merchant ship the Magnetic Compass still remains a critical and required piece of equipment.
 
The modern Navigators is also still required to determine and record the Magnetic Compass error at least once a watch and after any major alteration of course. This checking and recording of the error allows the Navigator to monitor the Deviation which in turn could show the need for adjusting or repairing the Magnetic Compass.
 
Brown’s Compass Observation Book is specifically designed and laid out to allow the Navigator fulfil the requirement to record the Compass error.