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A common compass rose as found on a nautical chart showing both true north and magnetic north with magnetic variation. Also notice the correspondence between the thirty-two point rose (inner circle) and the modern 0-360° graduat A compass rose, sometimes called a windrose, or Rose of the Winds, is a figure on a compass, map, nautical chart, or monument used to display the orientation of the cardinal directions: North, East, South, and West—and their intermediate points. It is also the term for the graduated markings found on the traditional magnetic compass. Today, the idea of a compass rose is found on, or featured in, almost all navigation systems, including nautical charts, non-directional beacons (NDB), VHF omnidirectional range (VOR) systems, global-positioning systems (GPS), and similar equipment. ==Compass points== The compass rose is an old design element found on compasses, maps, and even monuments (e.g. the Tower of the Winds in Athens and the pavement in Dougga, Tunis, during Roman times)〔Martín-Gil, F.J; Martín-Ramos, P.; Martín-Gil, J. (2005): A cryptogram in the compass roses of the Majorcan portolan charts from the Messina-Naples mapmakers school.- Almogaren XXXVI (Institutum Canarium), Wien, 285-295.〕 to show cardinal directions and frequently intermediate direction. The "rose" term arises from the fairly ornate figures used with early compasses. Older sources sometimes use the term "compass star", or ''stella maris'' ("star of the sea"), to refer to the compass rose. Early forms of the compass rose were known as ''wind roses'', since no differentiation was made between a directional point and the wind that emanated from that direction.〔Dan Reboussin (2005). (Wind Rose. ) University of Florida. Retrieved on 2009-04-26.〕 (Today, the term "wind rose" is often reserved for the object used by meteorologists to depict wind frequencies from different directions at a location.〔("The wind rose and the classical winds" ) (2001) University of Florida. Retrieved on 2010-07-29.〕〔Glossary of Meteorology (2009). (Wind rose. ) American Meteorological Society. Retrieved on 2009-04-25.〕) The modern compass rose has eight principal winds. Listed clockwise, these are: Although modern compasses use the names of the eight principal directions (N, NE, E, SE, etc.), older compasses use the traditional Italianate wind names of Medieval origin (Tramontana, Greco, Levante, etc.) 4-point compass roses use only the four "basic winds" or "cardinal directions" (North, East, South, West), with angles of difference at 90°. 8-point compass roses us the eight principal winds—that is, the four cardinal directions (N, E, S, W) plus the four "intercardinal" or "ordinal directions" (NE, SE, SW, NW), at angles of difference of 45°. 16-point compass roses are constructed by bisecting the angles of the principal winds to come up with intermediate compass points, known as half-winds, at angles of difference of 22°. The names of the half-winds are simply combinations of the principal winds to either side, principal then ordinal. E.g. North-northeast (NNE), East-northeast (ENE), etc. 32-point compass roses are constructed by bisecting these angles, and coming up with quarter-winds at 11° angles of difference. Quarter-wind names are constructed with the names "X by Y", which can be read as "one quarter wind from X toward Y", where X is one of the eight principal winds and Y is one of the two adjacent cardinal directions. E.g. North-by-east (NbE) is one quarter wind from North towards East, Northeast-by-north (NEbN) is one quarter wind from Northeast toward North. Naming all 32 points on the rose is called "boxing the compass". The 32-point rose has the uncomfortable number of 11° between points, but is easily found by halving divisions and may have been easier for those not using a 360° circle. Using gradians, of which there are 400 in a circle, the sixteen-point rose will have twenty-five gradians per point. File:Compass rose en 04p.svg| A 4-point compass rose File:Compass rose en 08p.svg| An 8-point compass rose File:Brosen windrose.svg| A 16-point compass rose File:Brosen windrose Full.svg|A 32-point compass rose 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「compass rose」の詳細全文を読む スポンサード リンク
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