An electronic distance measurement instrument determines distance mainly by measuring the:
Correct answer: B. Travel time or phase change of electromagnetic waves
- A. Weight of a suspended measuring tape
- B. Travel time or phase change of electromagnetic waves
- C. Difference between two staff readings
- D. Deflection of a magnetic needle
Explanation
EDM instruments send electromagnetic waves to a target and determine distance from their travel time or phase difference. Staff readings belong to levelling, while magnetic deflection is used in compass surveying.
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About Surveying
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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