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Elevation angle
The elevation angle is used interchangeably with altitude angle and is the
angular height of the sun in the sky measured from the horizontal. Both altitude
and elevation are used for description of the height in meters above the sea level.
The elevation is 0 degrees at sunrise and 90 degrees when the sun is directly
overhead. The angle of elevation varies throughout
the day and depends on
latitude of the particular location and the day of the year.
Zenith angle
This is the angle between the sun and the vertical. It is similar to the angle
of elevation but is measured from the vertical rather than from the horizontal.
Therefore, the zenith angle = 90 degrees – elevation angle as in the figure2.4 [5].
Figure 2.4 Angle of elevation and zenith angle
Azimuth angle
This is the compass direction from which the sunlight is coming. At solar
noon, the sun is directly south in the northern hemisphere and directly north in
the southern hemisphere. The azimuth angle varies throughout the day. At the
equinoxes, the sun rises directly east and sets directly
west regardless of the
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latitude. Therefore, the azimuth angles are 90 degrees at sunrise and 270 degrees
at sunset [5].
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