Solar altitude and azimuth gs & as--Algorithm 1.14

Solar altitude is defined as ¼/2-solar zenith angle (the angle between the centre of the sun and the zenith). It is only approximately the angle of the centre of the sun above the horizon, because near the horizon the apparent position of the sun is affected by refraction in the atmosphere.

Solar azimuth is sometimes given as an angle from north, measured 0 to 2¼ clockwise; alternatively, it may be given as an angle from south, positive towards the east, negative towards the west. The following formula gives the solar azimuth as an angle from north. The angles are in radians.

Solar declination, ds radians (algorithm 1.11)
Solar hour angle, x radians (algorithm 1.13)
Latitude of site, j radians (positive north of equator)


CIE (1)


  1. Commission Internationale de lÕEclairage Guide to daylighting of building interiors, draft 1990. Editor Nancy C Ruck. (Paris: to be published by Commission Internationale de lÕEclairage).

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