The act or process of orientating; determination of the points of the compass, or the east point, in taking bearings.
In the ancient days of cartography, it was necessary to have a convention for the direction facing the top of the map, and the convention chosen was to point the top towards the east -- the Orient and land of the rising sun. Although the use of magnets was common, they could be used to determine east and west just as easily as north and south, provided they were shaped properly.
As astronomy became a more accurate navigational tool, the convention of placing north at the top of maps gained favor due to the convenience of Polaris, the North Star. This practice was enforced by further understanding of the nature of magnetic fields.