Theodolite terminology and faces: Choose the correct set of statements regarding a transit theodolite and the definitions of left face and right face during observation.

Introduction / Context:

Correct nomenclature for theodolite parts and observation faces is essential for angle measurement protocols (e.g., double centering). A transit theodolite permits full rotation of the telescope about the horizontal axis, while ‘‘face left’’ and ‘‘face right’’ define the position of the vertical circle relative to the observer.

Given Data / Assumptions:

• A standard transit theodolite is used.
• Observer identifies the side on which the vertical circle (vernier/plate) lies.
• No special instrument peculiarities are implied.

Concept / Approach:

A theodolite capable of reversing (transiting) the telescope in the vertical plane is called a transit. During any pointing, if the vertical circle is on the left of the telescope (as seen by the observer), the instrument is in face left; if on the right, it is in face right. Observations are commonly repeated on both faces to eliminate certain systematic errors.

Step-by-Step Solution:

Verification / Alternative check:

Field procedures for horizontal and vertical angles specify ‘‘FL’’ and ‘‘FR’’ sets to average out index errors, confirming the definitions’ importance.

Why Other Options Are Wrong:

• ‘‘None of these’’ contradicts standard surveying terminology.

Common Pitfalls:

• Mistaking the face definition by looking from the wrong side; always judge as viewed during observation.

Final Answer:

all the above