CST Level 1 Land Surveyor Certification Practice

What does a Zenith Angle measure?

1. An angle measured counterclockwise from North

2. An angle measured clockwise from the vertical line

3. A horizontal angle measurement

4. An angle measured directly above the horizontal plane

The correct answer is: An angle measured clockwise from the vertical line

A zenith angle is defined as the angle measured from the vertical line directed straight up toward the zenith (the point in the sky directly above an observer) to the line of sight to an object. This angle effectively provides a measure of how far an object is away from the vertical line, which is why it is specifically characterized as being measured clockwise from that vertical line. Understanding this context helps clarify the nature of a zenith angle. When you visualize the concept, consider that if you are looking straight up (which is the zenith), any angle to a point below the zenith would represent a deviation from this vertical line down toward the horizontal plane. Thus, the measurement originates from the vertical and goes downward rather than across the horizontal plane, ruling out other options based on how angles are typically defined. The other choices describe different types of angular measurements that do not relate to the zenith angle. For instance, an angle measured counterclockwise from North typically refers to azimuth angles, which impact navigation and direction rather than vertical measurements. Horizontal angles, on the other hand, pertain to angles measured parallel to the ground, further distinguishing them from the concept of zenith angles, which operate in a three-dimensional space above and below the horizontal