The points of the compass are a set of horizontal, radially arrayed compass directions (or azimuths) used in navigation and cartography. A compass rose is primarily composed of four cardinal directions—north, east, south, and west—each separated by 90 degrees, and secondarily divided by four ordinal (intercardinal) directions—northeast, southeast, southwest, and northwest—each located halfway between two cardinal directions. Some disciplines such as meteorology and navigation further divide the compass with additional azimuths. Within European tradition, a fully defined compass has 32 "points" (and any finer subdivisions are described in fractions of points). Compass points or compass directions are valuable in that they allow a user to refer to a specific azimuth in a colloquial fashion, without having to compute or remember degrees.
Designations
The names of the compass point directions follow these rules:
8-wind compass rose
The four cardinal directions are north (N), east (E), south (S), west (W), at 90° angles on the compass rose. The four intercardinal (or ordinal) directions are formed by bisecting the above, giving: northeast (NE), southeast (SE), southwest (SW), and northwest (NW). In English and many other tongues, these are compound words. Different style guides for the four mandate spaces, dashes, or none. In Bulgarian, Catalan, Czech, Danish, Dutch, English, Esperanto, French, Galician, German, Greek, Hungarian, Ido, Italian, Japanese (usually), Macedonian, Norwegian (both Bokmal and Nynorsk), Polish, Portuguese, Romanian, Romansch, Russian, Serbian, Croatian, Spanish, Swedish, Turkish, Ukrainian, and Welsh the part meaning north or south precedes the part meaning east or west. In Chinese, Vietnamese, Gaelic, and less commonly Japanese, the part meaning east or west precedes the other. In Estonian, Finnish, Breton, the "Italianate system" (see section "Traditional Mediterranean compass points" below), and many South Asian and Southeast Asian languages such as Telugu, the intercardinals have distinct words. The eight principal winds (or main winds) are the set union of the cardinals and intercardinals. Taken in turn, each is 45° from the next. These form the 8-wind compass rose, the rose at its usual basic level today.
16-wind compass rose
The eight half-winds are the direction points obtained by bisecting the angles between the principal winds. The half-winds are north-northeast (NNE), east-northeast (ENE), east-southeast (ESE), south-southeast (SSE), south-southwest (SSW), west-southwest (WSW), west-northwest (WNW), and north-northwest (NNW). The name of each half-wind is constructed by combining the names of the principal winds to either side, with the cardinal wind coming first and the intercardinal wind second. The eight principal winds and the eight half-winds together form the 16-wind compass rose, with each compass point at a 22+1⁄2° angle from its two neighbours.
32-wind compass rose
The sixteen quarter-winds are the direction points obtained by bisecting the angles between each of the points in the 16 sets of two adjacent points on the 16-wind compass rose (above). The resulting directions, named quarter-winds, are as follows (here arranged by quadrant, or in other words clockwise): in NE quadrant: north by east (NbE), northeast by north (NEbN), northeast by east (NEbE), and east by north (EbN); in SE quadrant: east by south (EbS), southeast by east (SEbE), southeast by south (SEbS), and south by east (SbE); in SW quadrant: south by west (SbW), southwest by south (SWbS), southwest by west (SWbW), and west by south (WbS); in NW quadrant: west by north (WbN), northwest by west (NWbW), northwest by north (NWbN), and north by west (NbW) All of the points in the 16-wind compass rose plus the sixteen quarter-winds together form the 32-wind compass rose. If breaking down for study/signalling the subcomponents are called the "principal" followed by the "cardinal" wind/direction. As a mnemonic (memory device), minds familiar encode the meaning of "X by Y" as "one small measure from X towards Y". It can be noted such measure ('one point') is 11+1⁄4°. So, for example, "northeast by east" means "one quarter of the gap from NE towards E". In summary, the 32-wind compass rose comes from the eight principal winds, eight half-winds, and sixteen quarter-winds combined, with each compass point at an 11+1⁄4° angle from the next.
Half- and quarter-points
By the middle of the 18th century, the 32-point system had been further extended by using half- and quarter-points to give a total of 128 directions. These fractional points are named by appending, for example, 1/4east, 1/2east, or 3/4east to the name of one of the 32 points. Each of the 96 fractional points can be named in two ways, depending on which of the two adjoining whole points is used, for example, N3/4E is equivalent to NbE1/4N. Either form is easily understood, but alternative conventions as to correct usage developed in different countries and organisations. "It is the custom in the United States Navy to box from north and south toward east and west, with the exception that divisions adjacent to a cardinal or inter-cardinal point are always referred to that point." The Royal Navy used the additional "rule that quarter points were never read from a point beginning and ending with the same letter". Compass roses very rarely named the fractional points and only showed small, unlabelled markers as a guide for helmsmen.
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