The two-peg test of a levelling instrument is mainly used to determine whether the:
Correct answer: C. Line of collimation is truly horizontal
- A. Bubble tube is correctly graduated
- B. Staff is held exactly vertical
- C. Line of collimation is truly horizontal
- D. Tripod legs have equal lengths
Explanation
The two-peg test checks whether the line of collimation is horizontal when the bubble is centred. Unequal sight lengths help reveal collimation error because its effect does not cancel in that arrangement.
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Surveying covers measurement of distances, angles and elevations, traversing, levelling, contouring, plane table work, theodolites, total stations and basic photogrammetry. It includes error adjustment, coordinate calculations, area and volume determination, and the distinction between accuracy and precision, as well as between temporary and permanent adjustments.
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