Solar azimuth angle

The solar azimuth angle is the azimuth angle of the sun. It is most often defined as the angle from due north in a clockwise direction.

It can be calculated in various way. In different times, it has been explained in different ways. It can be calculated, to a good approximation, using the following formula, however angles should be interpreted with care due to the inverse sine, i.e. x = sin−1(y) has more than one solution, only one of which will be correct.

\, \sin \phi_\mathrm{s} = \frac{-\sin h \cos \delta}{\cos \theta_\mathrm{s}}

The following two formulas can also be used to approximate the solar azimuth angle, however because these formulas utilize cosine, the azimuth angle will always be positive, and therefore, should be interpreted as the angle less than 180 degrees when the hour angle, h, is negative (morning) and the angle greater than 180 degrees when the hour angle, h, is positive (afternoon).

\, \cos \phi_\mathrm{s} = \frac{\sin \delta \cos \Phi - \cos h \cos \delta \sin \Phi} {\cos \theta_\mathrm{s}}
\, \cos \phi_\mathrm{s} = \frac{\sin \delta - \sin \theta_\mathrm{s}\sin \Phi} {cos \theta_\mathrm{s}\cos \Phi}

The previous formulas use the following terminology:

Contents

Solar elevation angle

Main article: Solar elevation angle

Sun height, height angle, solar altitude angle or elevation (gS) is the angle between a line that points from the site towards the centre of the sun, and the horizon. The zenith angle is the opposite angle to the sun height (90° – gS). At a sun height of 90°, the sun is at the zenith and the zenith angle is therefore zero.[2]

See also

References

  1. ^ The formula is based on geocentric latitude, which differs from geographic latitude by less than 12 minutes of arc.
  2. ^ http://www.volker-quaschning.de/articles/fundamentals1/index_e.html

External links