Question

Which of the following is the first operation of Total station when it is sighted to the target?

• A. Rotation of optical axis.
• B. Rotation of vertical axis
• C. Rotation of horizontal axis
• D. Rotation of line of collimation

Hint:

A Total Station's primary functions are:
1. Angle Measurement (like a theodolite).
2. Distance Measurement (EDM).
When you sight a target and press the measure button, the first key automated step is the EDM sending a signal along the line of sight to measure the distance.

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
The question asks about the initial action performed by a Total Station after it is aimed (sighted) at a target prism.

Step 2: Detailed Explanation:
A Total Station is an electronic instrument that combines an electronic theodolite (for measuring angles) with an electronic distance meter (EDM).
The process of measuring a point is as follows:
1. The operator manually aims the telescope's crosshairs precisely at the center of the target prism. This process is called "sighting" or "collimation".
2. The operator then initiates the measurement. The first automated action the instrument takes is to measure the distance to the target. It does this by sending out an infrared signal from the EDM. This signal travels along the

optical axis of the telescope, reflects off the prism, and returns to the instrument. The instrument measures the phase shift or time of flight of this signal to calculate the slope distance.
3. Simultaneously or sequentially, the instrument reads the horizontal and vertical angles from its internal encoders.
The options are somewhat ambiguously phrased:
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(A) Rotation of optical axis: This is not a standard term. However, the first measurement (EDM) happens along the optical axis.
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(B) Rotation of vertical axis: This happens when the instrument is turned horizontally to sight a new target.
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(C) Rotation of horizontal axis: This happens when the telescope is moved up or down to sight a target at a different elevation.
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(D) Rotation of line of collimation: The line of collimation is the line of sight. Rotating it is part of the manual aiming process, not the first automated operation.
The question is poorly worded. However, the most fundamental operation that a Total Station performs, which an older theodolite cannot, is the electronic distance measurement, which happens along the optical path. If we interpret "first operation" as the first electronic measurement, it is the EDM measurement along the optical axis. The provided answer key states (A) as correct, which likely refers to the internal processes related to the optical path for the EDM.

Step 3: Final Answer:
Given the options, the most plausible interpretation is that the first operation refers to the functioning of the EDM along the optical path of the instrument. Therefore, "Rotation of optical axis" is chosen as the best fit, despite its non-standard terminology.