Compass roses were used for sailors to draw the angles at which they wished to sail--northeast, north by northeast, south, and so on--on a map.
Portuguese map-maker Pedro Reinel first drew the the fleur-de-lis indicating north at the top of the standard 32 point compass rose. He also used a cross (on the right side) to show east (toward the Holy Land). His son Jorge Reinel drew the compass rose below.

The alternating green and red points inside the compass and red and gree lines were chosen so that the differences between directions would be very clear.

See how easy it would be to make a mistake (and get lost at sea) using the traditional Mediterranean line compass from 1440.


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