_______ is a parameter that a total station usually does NOT measure.
- AHorizontal distanceCorrect
- BHorizontal angle
- CVertical angle
- DSlope distance
Solution
Concept
A total station directly measures horizontal angle, vertical angle and slope distance. Horizontal distance is calculated from these.
Formula
HD = SD × sin(Z) = SD × cos(α)
Step-by-step solution
1. The EDM in a total station measures slope distance (SD) directly. 2. The angle encoders measure the horizontal angle and the vertical (zenith) angle directly. 3. The microprocessor computes horizontal distance as HD = SD × sin(Z). 4. So horizontal distance is not directly measured. Answer is A.
Explanation
A total station has an EDM to measure slope distance and electronic encoders to measure angles. Horizontal distance is worked out by the built-in computer from slope distance and the vertical angle. So it is a computed value, not a measured one.
Why the other options are wrong
B: Horizontal angle is measured directly by the horizontal encoder. C: Vertical angle is measured directly by the vertical encoder. D: Slope distance is measured directly by the EDM.
Shortcut
Measured = 2 angles + slope distance. Everything else (HD, VD, coordinates) is computed.
Common mistake
Thinking horizontal distance is measured because the screen shows it. It is only computed.
Correct answer: A) Horizontal distance