The points of the compass are points on a compass, specifically on the compass rose,
marking divisions of the four cardinal directions: North, South, East, West. The number of points
may be only the 4 cardinal points, or the 8 principal points adding the intercardinal
directions northeast, southeast, southwest, and northwest. In meteorological usage further
intermediate points are added to give the sixteen points of a wind compass. Finally,
at the most complete in European tradition, are found the full thirty-two points of the
mariner's compass. In ancient China 24 points of the compass were used.
The mariner's practice of boxing the compass is the action of naming all thirty-two points
of the compass in order clockwise. The names of intermediate points are formed by the initials
of the cardinal directions and their intermediate ordinal directions, and are very handy to
refer to a heading in a general or colloquial fashion, without having to resort to computing
or recalling degrees. For most applications, the minor points have been superseded by degrees
measured clockwise from North.
Compass point names
The names of the 32-wind compass rose follow these rules:
The cardinal directions are North, East, South, West, at 90° angles on the compass rose.
The ordinal directions are Northeast, Southeast, Southwest and Northwest, formed by bisecting
the angle of the cardinal winds. The name is merely a combination of the cardinals it
bisects. The eight principal winds are the cardinals
and ordinals considered together, that is N, NE, E, SE, S, SW, W, NW. Each principal
wind is 45° from its neighbour. The principal winds form the basic eight-wind compass rose.
The eight half-winds are the points obtained by bisecting the angles between the principal
winds. The half-winds are North-northeast, East-northeast, East-southeast, South-southeast,
South-southwest, West-southwest, West-northwest and North-northwest. Notice that the name
is constructed simply by combining the names of the principal winds to either side, with
the cardinal wind coming first, the ordinal wind second. The eight principal winds and
the eight half-winds together yield a 16-wind compass rose, with each compass point at a
22 1⁄2° angle from the next. The sixteen quarter winds are the direction
points obtained by bisecting the angles between the points on a 16-wind compass rose. The
sixteen quarter-winds are North by east, Northeast by north, Northeast by east, East by north
in the first quadrant, East by south, Southeast by east, Southeast by south, South by east
in the second quadrant, South by west, Southwest by south, Southwest by west, West by south
in the third quadrant, and finally West by north, Northwest by west, Northwest by north
and North by west in the fourth quadrant. The eight principal winds, eight half-winds
and sixteen quarter winds together yield a 32-wind compass rose, with each compass direction
point at 11 1⁄4° angle from the next. The name of a quarter-wind is typically "X
by Y", where X is a principal wind and Y is a cardinal wind. As a mnemonic device, it
is useful to think of "X by Y" as a shortcut for the phrase "one quarter wind from X towards
Y", where a "quarter" is 11 1⁄4°, X is the nearest principal wind, and Y the next
cardinal wind. So "Northeast by east" means "one quarter from NE towards E", "Southwest
by south" means "one quarter from SW towards S". The title of the Alfred Hitchcock 1959
movie, North by Northwest, is actually not a direction point on the 32-wind compass,
but the film contains a reference to Northwest Airlines.
Traditional names The traditional compass rose of eight winds
was invented by seafarers in the Mediterranean Sea during the Middle Ages. The traditional
mariner's wind names were expressed in Italian - or, more precisely, the Italianate Mediterranean
lingua franca common among sailors in the 13th and 14th centuries, that was principally
composed of Genoese, mixed with Venetian, Sicilian, Provençal, Catalan, Greek and Arabic
terms from around the Mediterranean basin.
This Italianate patois was used to designate the names of the principal winds on the compass
rose found in mariner compasses and portolan charts of the 14th and 15th centuries. The
"traditional" names of the eight principal winds are:
(N) - Tramontana (NE) - Greco
(E) - Levante (SE) - Scirocco
(S) - Ostro (SW) - Libeccio
(W) - Ponente (NW) - Maestro
Local spelling variations are far more numerous than listed, e.g. Tramutana, Gregale, Grecho,
Sirocco, Xaloc, Lebeg, Libezo, Leveche, Mezzodi, Migjorn, Magistro, Mestre, etc. Traditional
compass roses will typically have the initials T, G, L, S, O, L, P, and M on the main points.
Portolan charts also colour-coded the compass winds: black for the eight principal winds,
green for the eight half-winds and red for the sixteen quarter-winds.
In the English compass, all wind names are constructed on the basis of the cardinal four
names. In the traditional compass, one needs to memorize eight basic names - one for each
of the eight principal winds. While there are more names to memorize, the payoff is
that the name construction rules for the 32-wind compass are more straightforward. The half-winds
are just a combination of the two principal winds it bisects, with the shortest name usually
coming first. The quarter winds are expressed with an Italian phrase, "Quarto di X verso
Y" or "X al Y" or "X per Y". There are no irregularities to trip over: the nearest principal
wind always comes first, the more distant one second, e.g. North-by-east is "Quarto
di Tramontana verso Greco", Northeast-by-north "Quarto di Greco verso Tramontana". The names
are perfectly symmetric. 32 cardinal points
Half- and quarter-points
By at least the middle of the eighteenth century the 32-point system had been further extended
with the use of 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
of which of the two adjoining whole points is used, for example, N3/4E is equivalent
to NbE1/4N. Either form is easily understood but differing conventions as to correct usage
developed in different countries and organisations. The table below shows how each of the 128
directions are named. The first two columns give the number of points and degrees clockwise
from north. The third gives the equivalent bearing to the nearest degree from north or
south towards east or west. The "CW" column gives the fractional-point bearings increasing
in the clockwise direction and "CCW" counter clockwise. The final three columns show three
common naming conventions: No "by" avoids the use of "by" with fractional points; "USN"
the system used by US Navy; and "RN" the Royal Navy. The colour coding illustrates where
each of the three naming systems matches the "CW" and "CCW" columns.
Compass roses very rarely named the fractional points and only showed small, unlabelled markers
as a guide for helmsmen. See also
References
External links Wind Rose – discusses the origins of the
names for compass directions.