Azimuth
Horizontal angle from north used in navigation and astronomy.
Azimuth is a horizontal angle measured from a cardinal direction, most commonly north, in a local or observer-centric spherical coordinate system. It is a fundamental concept used in navigation, astronomy, engineering, mapping, geodesy, mining, and ballistics.
- field
- Navigation, Astronomy, Geodesy, Engineering
- known_for
- Horizontal angle from north used for celestial and terrestrial positioning
Lore & Background
The word azimuth originates from medieval Arabic السموت (al-sumūt), meaning 'the directions', and entered late Medieval Latin in an astronomical context, particularly with the astrolabe. Its first recorded use in English is in the 1390s in Geoffrey Chaucer's A Treatise on the Astrolabe. The first known record in any Western language is in Spanish in the 1270s in an astronomy book derived from Arabic sources, the Libros del saber de astronomía, commissioned by King Alfonso X of Castile.
Reader's Guide
Azimuth is a key coordinate in the horizontal coordinate system used in celestial navigation, where it is paired with altitude. In modern astronomy, azimuth is nearly always measured from the north. In land navigation, azimuth is usually denoted alpha (α) and defined as a horizontal angle measured clockwise from a north base line or meridian. However, some systems use south as the reference vector, and bearings may be stated in systems where north or south is zero, with angles measured clockwise or anticlockwise. In geodesy, azimuth can be calculated for a spherical Earth using a formula involving latitude and longitude, while for an oblate spheroid, normal-section azimuth and geodetic azimuth differ slightly, with the difference usually negligible for distances under 100 km.
Did You Know?
- The word azimuth comes from medieval Arabic السموت (al-sumūt), meaning 'the directions'.
- Its first recorded use in English is in the 1390s in Geoffrey Chaucer's A Treatise on the Astrolabe.
- In navigation, a bearing might be described as 'S30°E', meaning 30 degrees eastward from south.
Frequently Asked Questions
What is Azimuth in cartography and navigation?
Azimuth is the horizontal angle you measure away from a cardinal direction—most often true north—to pinpoint a target relative to where the observer is standing. It operates within a local, observer-centric spherical coordinate framework rather than a global grid.
Which fields rely on Azimuth as a core measurement?
Navigation, astronomy, geodesy, engineering, mining, and ballistics all treat it as a foundational quantity for locating celestial bodies or terrestrial targets. In map projection work, it helps anchor local direction before any distortion model is applied.
What reference point does Azimuth measure from?
The angle is taken from a chosen cardinal direction, with true north being the most common starting reference. This makes it inherently observer-centric: the same target will carry different azimuth values from different vantage points.
Why do cartography fans keep bringing up Azimuth in projection discussions?
Because every azimuthal equidistant or azimuthal equal-area projection is literally named for this angle—it defines the radial direction from the projection's center point. Understanding the concept clarifies why those projections preserve true bearing from the center while distorting distance elsewhere.
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