The zenith angle is the angle between a point of interest and the zenith, the point directly above the head. In a three-dimensional coordinate system, the zenith is the axis perpendicular to the horizontal plane.
The zenith angles is measured from a local zenith, which means that it changes depending on the location of the person or device taking the measurement. The solar zenith angle, the angle between the zenith and the sun, is useful for determining whether the sun is rising or setting and for predicting solar effects on radio communications.
A zenith angles can specify the location of a satellite.
Mathematically, the zenith corresponds to the z axis in a set of spherical coordinates. This type of three-dimensional coordinate system describes positions on a sphere. The x and y axes, which are horizontally perpendicular to each other, form a plane.
The third axis, or z-axis, is vertically perpendicular to this plane in the third dimension. If the Earth were drawn in spherical coordinates with the center of the Earth as the point of origin, the z-axis would traverse the center of the Earth from the north pole to the south.
The position of the sun can help predict the level of interference from solar flares.
When the zenith angles is measured, the origin point is defined based on the location where the measurement is made. For example, a person standing on the ground creates a vertical axis that runs from the center of the Earth through his head to the sky.
This line is the local zenith. If that person were to observe the sun and measure the angles between his position in the sky and the local zenith, he would have found the angle of the solar zenith.
This measurement can be useful to determine position, since it can be measured from any celestial object. Satellites and stars, as well as the sun, can be marked with the zenith angle.
The angle between the local zenith and a point such as a satellite is sometimes referred to as the zenith angles of view.
The smaller the solar zenith angles, the higher the sun is in the sky. As the sun rises, the angle gradually decreases until noon. The position of the sun can be important in both navigation and radio communications, where it is used to predict the level of interference from solar flares.
When the angles is low and the sun is high in the sky, radio signals are more likely to be attenuated or lost due to the activity of solar flares.