Compasses are a navigational instrument giving a frame of reference based on North, South, East and West, as well as their intermediate directions such as South East, North West. This is based on Magnetic North, and not True or Grid North.

Grid North the direction of a grid line which is parallel to the central meridian on the National Grid. True North is the direction of a meridian of longitude which converges on the North Pole.

history | show excerpt | excerpt history