Compass rose
From Wikipedia, the free encyclopedia
A compass rose is a figure displaying the orientation of the cardinal directions, north, south, east and west on a map or nautical chart. Today the use and idea of a compass rose is found on or featured in almost all navigation systems, including nautical charts, NDB and VOR systems, some GPS sets and similar.
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[edit] History
Naming all 32 points on the rose is called boxing the compass.
The "rose" term arises from the fairly ornate figures used with early compasses. A fleur-de-lis figure, evolved from the initial T in the north wind's name Tramontane, is sometimes used to indicate the north direction. Similarly, on old maps the east was marked with an L for Levante, or with a + indicating the direction of Jerusalem from the point of view of western Europe's countries.
Early roses were depicted with 12 points at 30º each, as was favored by the Romans. In the Middle Ages map makers moved to the 16 point rose complaining that sailors did not have the education to understand the previous design. Perhaps this claim had merit, as education had declined since Roman times. The 16 point rose has the uncomfortable number of 22 1/2º between points, but is easily found by halving divisions and may have been easier for those not using a 360º circle. Using gradians, the sixteen-point rose will have exactly twenty-five gradians per point.
A Rose of the Winds is an ancient version of a compass rose which personified compass directions as winds with individual names, such as the west wind Zephyrus and the east wind Eurus. A fountain in Taranto, Italy was inspired by and named after the Rose of the Winds.
[edit] Modern Depictions
The contemporary compass rose appears as two rings, one smaller and set inside the other. The outside ring denotes true cardinal directions while the smaller inside ring denotes magnetic cardinal directions. True north refers to the geographical location of the north pole while magnetic north refers to the direction towards which the south pole of a magnetic object (as found in a compass) will point. The angular difference between true and magnetic north is called variation, which varies depending on location. The angular difference between magnetic heading and compass heading is called deviation which varies by vessel and its heading.
[edit] In Popular Media
HMS Compass Rose is the name of a fictional Royal Navy corvette in the novel The Cruel Sea.
[edit] Gallery
 Wind rose of an old nautical chart, by Portuguese cartographer Pedro Reinel (1504) |
 A historic compass rose |
 An 8-point compass rose |
 16-point compass rose with north highlighted at top |
 A 32-point compass rose |
 The world's largest compass rose, drawn on the desert floor at Edwards Air Force Base in the US |
[edit] External links
- Origins of the Compass Rose
- The Rose of the Winds - An example of a rose with 26 directions.
- Wind rose
- Rose of Piedro Reinel, 1504 - an example of a 32-point rose with cross for east (the Christian Holy Land) and fleur-di-lis for north.
