North - Roles of North As Prime Direction

Roles of North As Prime Direction

The visible rotation of the night sky around the visible celestial pole provides a vivid metaphor of that direction corresponding to up. Thus the choice of the north as corresponding to up in the northern hemisphere, or of south in that role in the southern, is, prior to world-wide communication, anything but an arbitrary one. On the contrary, it is of interest that Chinese and Islamic culture even considered south as the proper top end for maps.

In Western culture:

• Maps tend to be drawn for viewing with either true north or magnetic north at the top
• Globes of the earth have the North Pole at the top, or if the Earth's axis is represented as inclined from vertical (normally by the angle it has relative to the axis of the Earth's orbit), in the top half.
• Maps are usually labelled to indicate which direction on the map corresponds to a direction on the earth,
  • usually with a single arrow oriented to the map's representation of true north,
  • occasionally with a single arrow oriented to the map's representation of magnetic north, or two arrows oriented to true and magnetic north respectively,
  • occasionally with a compass rose, but if so, usually on a map with north at the top and usually with north decorated more prominently than any other compass point.
• Up is a metaphor for north. The notion that north should always be up and east at the right was established by the Greek astronomer Ptolemy. The historian Daniel Boorstin suggests that perhaps this was because the better-known places in his world were in the northern hemisphere, and on a flat map these were most convenient for study if they were in the upper right-hand corner.