cosazimuth

Cosazimuth, or the cosine of the azimuth, is a term used to describe the horizontal component of a direction in polar or spherical coordinate systems. The azimuth is the angle between a reference direction and the projection of a vector onto the horizontal plane. In many geospatial and navigational conventions, azimuth is measured clockwise from north, though alternative conventions (such as from the east) also exist. The cosine of the azimuth, cosazimuth, thus encodes how strongly the direction aligns with the reference axis in the horizontal plane.

In a standard convention where azimuth is measured from north, the northward component of a unit horizontal direction equals cosazimuth, while the eastward component equals sinazimuth. Therefore, cosazimuth serves as a convenient factor for decomposing a direction into axis-aligned components without computing the full vector if only the projection on the reference axis is needed. This makes cosazimuth useful in a range of applications, including geographic information systems (GIS), navigation, solar position calculations, remote sensing, and computer graphics.

Practically, cosazimuth is sensitive to the chosen convention for azimuth (whether the reference axis is north or east, and whether angles are given in degrees or radians). When applying cosazimuth in calculations, it is important to maintain consistent angular units and axis definitions to ensure correct projection results. See also azimuth, sine of azimuth, and spherical coordinate systems for related concepts.