Theodolite MCQ with answer and solution

Concept

The vertical circle of a theodolite is used to measure vertical angles (angles of elevation or depression). Its graduations are designed to show 0° when the telescope is horizontal.

Step-by-step solution

1. A theodolite has two main circles: horizontal and vertical. 2. The horizontal circle is usually graduated from 0° to 360° (Whole Circle Bearing system). 3. The vertical circle is fixed to the telescope and rotates with it. 4. In a standard transit theodolite, the vertical circle is graduated in four quadrants. 5. Each quadrant is numbered from 0° to 90°. 6. The 0°-0° line is horizontal, and the 90°-90° line is vertical. 7. This allows the user to read the angle of elevation (upward) or depression (downward) directly. Answer: (A) the quadrantal system from 0 to 90° in the four quadrants

Explanation

The vertical circle measures angles above or below the horizontal line. Because these angles never exceed 90 degrees in normal surveying, the circle is divided into four quadrants of 90 degrees each. The zero marks are placed on the horizontal axis.

Why the other options are wrong

B: This system is used for the horizontal circle to measure bearings. C: Semi-circle systems are not standard for theodolite vertical circles. D: A prismatic compass uses a 0-360 degree system, which is different from the vertical circle's 0-90 degree system.

Shortcut

Vertical = Quadrants (0-90); Horizontal = Whole Circle (0-360).

Common mistake

Students often confuse the vertical circle with the horizontal circle, which uses the 0-360 degree system.