Defining The Position Of The Sun

Defining The Position Of The Sun

The location of the sun is specified by two angles:

• Altitude (γ) the angle between the sun and the horizon (in degree).
• Azimuth (α) the angle between north and the sun's position. Similar to using a compass where the direction being faced is measured as a number of degrees from north. The altitude and azimuth of the sun are constantly changing throughout the day and year as the Earth rotates on its axis (day/night) and around the sun (seasonal variation).

Altitude

Altitude refers to the angle between the sun and horizontal (or ground), and is always an angle between 0 degree and 90 degree. The sun is higher in the sky in summer and lower in the sky in winter due to the neutral tilt of the earth with respect to the sun as the Earth orbits the sun throughout the year.

Azimuth 

The sun moves from east to west across the sky through the day. The angle between north and the point of the compass where the sin is position is called the  azimuth angle. In general, the azimuth is measured clockwise going from 0 degree (true north) to 359 degree. East is 90 degree, South is 180 degree and West is 270 degree.

In the diagram, altitude and azimuth are shown with points of the compass.

Variation in the altitude and azimuth are shown in the table along with time of days and time of years for Delhi. The table provides the time for solar noon, when the sun is at the highest altitude for the day, midway between sunrise and sunset. In India this is typically between 12 pm an 1 pm.