The Good Old Magnetic Compass
The Chinese invented the compass by around 1110. It improved the safety and efficiency of sailing greatly. The dry mariner’s compass was invented in Europe around 1300. It consists of a freely pivoting needle on a pin enclosed in a little box with a glass cover and a wind rose.
The GPS (Global Positioning System) has succeed the compass in certain areas but remember:
A compass won’t run out of batteries and a map will never lose its signal.
How to convert the magnetic compass course to the true course
Compass Course (magnetic).
+ Deviation
+ Variation
= True Course
The true course = the course plotted in the chart,( i.e course over ground)
The deviation = caused by nearby iron and steel
The variation = the angle between the magnetic north pole and the geographic north pole.