The cardinal directions are the four main directions; the equal divisions of these are known as primary InterCardinal directions. Primary InterCardinal directions are the directions northeast, southeast, southwest and northwest; these directions are in general use. A set of directions that divides the cardinal and primary InterCardinal directions are called secondary Intercardinal directions. This set of directions includes north northeast, south southeast and north northwest. Cardinal directions are displayed on the cardinal rose of a map in a reliable and usable format.
The use of the compass rose and cardinal directions began to be used on paper maps commonly used on ships for nautical explorers. The cardinal directions of the compass rose include the 32 points of the compass, as these were originally based on the winds known by all mariners for successful navigation of the known seas during the Middle Ages and beyond. When people first started to use it, the compass rose showed the cardinal directions as eight major winds, eight half winds and 16 quarter winds used to navigate and provide power for ships.
The initial display of the compass rose was developed to be graphically visible onboard a ship during a nighttime voyage using candlelight to read a map. The colorings of the 32 points of the compass rose were developed to allow a mariner to easily find the direction at a glance, Fantasy of Flight reports. The eight major winds were marked in black, which stood out against the light background of the map. The half winds were marked in blue or green to differentiate them from the major winds and the 16 quarter winds were marked in red.
Despite the elaborate nature of the majority of compass rose designs, the basic information and colors used on maps and globes are the same. Elaboration was added on Portuguese maps to create a fleur-de-lis emblem. During the Middle Ages, the cardinal directions were listed as the northerly direction with the letter T for the tramontana wind, levante for east. The letter O was used for south from the word ostro and the letter P stood on the western cardinal direction. P was taken from the word ponente.
