Azimuth vs Bearing

The word azimuth came from a word of Arabic origins, ‘as-sumut’, which is the plural of ‘as-samt’. It means – ‘the way or direction’.

When one refers to azimuth, it is a determination of a direction with the use of a compass. The reference is North, which is 0 or 360 degrees. The compass user’s direction is then measured in degrees, clockwise from zero or North. So in effect, East is considered as 90 degrees, 180 degrees for South, and 270 degrees for West. It is essentially an angular measurement from a horizontal reference. It is a part of the angular coordinate system used for locating a point in the sky. Typically, azimuth uses True North as the reference, but may sometimes use the North base line (meridian) for land navigation.

When used to express a position of a particular star, the azimuth is found in this way:

Making the star as the point of interest, in a horizontal plane, face True North and consider it as your reference vector. The azimuth will be the angle found between the reference vector (North) and the perpendicularly projected position of the star down on the horizon. It is naturally and usually expressed in degrees, and used in various practical applications, e.g. astronomy, navigation, artillery, mining, and mapping.

Azimuth, technically, is a type of bearing, because by definition in terms of land navigation, it is an expression of an angle between points. Basically, azimuth is the bearing of a point in reference to the horizontal True North. However, bearing holds many definitions depending on its application (e.g. marine navigation and aircraft navigation), and can be a bit different, but it still describes distance and direction. There are two ways to express bearings ‘“ mils and degrees, with the latter being the more common.

Perhaps the most notable difference between the two is the way they are expressed. Their standards in expression will surely make you recognize whether it is azimuth or bearing. Bearing is described either from the South or the North (which does not necessarily mean True North, as it could be North-based on the observer’s perspective or meridian), and the angle is described either going East or West.

Examples:

– An azimuth of 45 degrees is the same as the bearing 45 degrees East of North (N 45 E).
– An azimuth of 135 degrees is the same as the bearing 45 degrees East of South (S 45 E).
– An azimuth of 225 degrees is the same as the bearing 45 degrees West of South (S 45 W).
– An azimuth of 315 degrees is the same as the bearing 45 degrees West of North (N 45 W).

In astronomy, Azimuth is sometimes called bearing, and it is nearly always measured from the North.

Summary:

1. The direction or expression given by the compass is what you call Azimuth.
2. Azimuth is typically in reference to the True North, especially in astronomy, and in this field of study, it is sometimes referred to as bearing.
3. Bearing is considerably general, and encompasses many meanings and uses, which are mainly based on its application. Azimuth is somewhat more specific.
4. Bearing is general because it is defined as an angle of separation between two points, while azimuth is always in respect to a horizontal plane.
5. Bearing can be expressed in mils or degrees, while azimuth is often, if not always, in degrees.
6. An expression of bearing can be in reference to either North or South, with the description of the angle going towards the East or West.

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