In the video, tThe vertical angle is measured by first setting the theodolite at 90˚ and then measure the vertical angle. True False

The statement is False.

Explanation:

In the process of measuring angles with a theodolite, the vertical angle is measured directly from the position of the instrument, not by first setting it to 90 degrees. The theodolite is a precision instrument used for measuring horizontal and vertical angles.

1. Vertical Angle Measurement: To measure a vertical angle, the observer typically aims the theodolite at a target point and reads the angle off the vertical circle of the instrument, starting from the horizontal line (which is generally considered as 0 degrees).

2. Initial Position: Setting the theodolite to 90 degrees initially would not provide the correct reference point for vertical angle measurement, as the angles measured should be relative to the horizontal line rather than a preset angle.

3. Understanding Vertical Angles: The vertical angle can go above or below the horizontal line (also known as zenith angle). Orientation of the instrument is crucial for accurate readings.

In conclusion, the measurement process does not involve setting the instrument to 90 degrees for vertical angle measurement; instead, the observer should focus on aligning the theodolite with the target of interest to capture accurate vertical angle readings.