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Compass rose

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A compass rose, also called a compass star or wind rose, is a polar diagram. It displays the orientation of cardinal directions like north, east, south, and west. It also shows the intermediate points between these main directions.

Windrose en
Windrose en

These diagrams are essential tools for navigation. You can find them on magnetic compasses, nautical charts, and monuments. Modern technology still uses these concepts in satellite navigation devices, known as GPS. They also appear in non-directional beacons (NDB) and VHF omnidirectional range (VOR) systems.

Most human communities use four cardinal points for orientation. Anthropological studies show that the names for these directions vary by culture. Some groups use local geographic features, such as "towards the sea." Others use celestial bodies like the sun or atmospheric features like the wind. Mobile populations often use the sunrise for East and the sunset for West. They may also use the direction of specific winds to define North and South.

The history of the compass rose involves many different systems. The ancient Greeks originally kept wind names and celestial points separate. Aristotle identified ten distinct winds for his meteorological studies. These included two north-south winds and four sets of east-west winds. These sets were based on different latitudes and solar horizons. Timosthenes of Rhodes later added two winds to create a 12-wind rose.

Roman 12-wind rose
Roman 12-wind rose

This allowed the winds to represent geographical directions for navigation. Eratosthenes later reduced this to an eight-wind rose. The Romans adopted the 12-wind system but used Latin names. Later, Germanic names replaced Latin terms for north, south, east, and west.

Some navigators used stars instead of winds to find their way. This is called a sidereal compass rose. Arab navigators in the Red Sea and Indian Ocean used a 32-point sidereal rose before the end of the 10th century. In the Northern Hemisphere, they used the Pole Star, or Polaris, for the north-south axis. Navigators in the Southern Hemisphere used the Southern Cross.

Compass rose in 1753, from Ari Atoll 1753 (cropped)
Compass rose in 1753, from Ari Atoll 1753 (cropped)

The other thirty points on this rose were determined by fifteen bright stars. These stars were identified by their rising and setting positions. This method was also used by Polynesian and Micronesian navigators in the Pacific Ocean.

European mariners developed a distinct eight-wind system in the Mediterranean. This system used names from a Mediterranean lingua franca. This language was a mix of Venetian, Sicilian, Greek, and Arabic terms. The exact origin of this rose is not fully known. However, two names, Scirocco and Garbino, have Arabic roots. This suggests southern Italian seafarers may have acquired the system from Norman Sicily.

32-point compass (traditional winds)
32-point compass (traditional winds)

By the 14th century, Mediterranean navigators used a 32-point compass. This version had increments of 11 degrees between points. Sailors were expected to master "boxing the compass," which meant naming all 32 winds.

Compass roses have also changed how maps look. Early medieval portolan charts used color-coded lines to show directions. Black lines represented the eight main winds. Green lines showed the eight half-winds. Red lines were used for the sixteen quarter-winds.

Compass rose in 1753, from Ari Atoll 1753 (cropped)
Compass rose in 1753, from Ari Atoll 1753 (cropped)

In 1375, the cartographer Cresques Abraham drew the first ornate compass rose. By the 15th century, Portuguese cartographers drew many ornate roses on their charts. They used specific symbols to mark north. Some used an arrowhead, while others used a stylized Pole Star. Pedro Reinel introduced the fleur-de-lis as a north mark, which is still common today. Some roses even used a Christian cross to point toward Jerusalem.

Modern compass roses often feature two rings to show different types of north. The outer ring shows true north, which is the geographic North Pole. The inner ring shows magnetic north, which is where a magnetic needle points.

Modern nautical compass rose
Modern nautical compass rose

The difference between these two points is called variation. There is also a difference called deviation, which depends on the specific vessel. Today, these diagrams remain vital for both scientific study and public art.

BownLibrary!CompassRose
BownLibrary!CompassRose

They help us connect our physical location to the wider world.

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🖼️ Images & Media (7)
File:Modern nautical compass rose.svg
Modern nautical compass rose.svg
File:Windrose en.svg
Windrose en.svg
File:Roman 12-wind rose.svg
Roman 12-wind rose.svg
File:32-point compass (traditional winds).svg
32-point compass (traditional winds).svg
File:BownLibrary!CompassRose.jpg
BownLibrary!CompassRose.jpg
File:Rosadelosvientos2.png
Rosadelosvientos2.png
File:Compass rose in 1753, from Ari Atoll 1753 (cropped).jpg
Compass rose in 1753, from Ari Atoll 1753...
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