Points of the compass Points of the compass The points of the compass mark the divisions on a compass, which is primarily divided into the four cardinal directions: north, south, east, and west. These points are further subdivided by the addition of the four intercardinal (or ordinal) directions—northeast (NE), southeast (SE), southwest (SW), and northwest (NW)—to indicate the eight principal winds. In meteorological usage, further intermediate points between the cardinal and intercardinal directions, such as north-northeast (NNE) are added to give the sixteen points of a compass rose. At the most complete division are the full thirty-two points of the mariner's compass, which adds
Compass equivalence theorem only a collapsing compass and no straightedge. There are several proofs of the correctness of this construction and it is often left as an exercise for the reader. Here is a modern one using transformations. Compass equivalence theorem The compass equivalence theorem is an important statement in compass and straightedge constructions. The tool advocated by Plato in these constructions is a "divider" or "collapsing compass", that is, a compass that "collapses" whenever it is lifted from a page, so that it may not be directly used to transfer distances. The "modern compass" with its fixable aperture can be used to