RPLS Surveying Principles and Methods 2 — Questions and Answers
Question 1: When using a total station, what is the purpose of 'face left' and 'face right' observations?
- To measure horizontal angles twice for redundancy
- To eliminate systematic instrumental errors by averaging both face readings (Correct answer)
- To check that the tribrach is level
- To calibrate the EDM distance measurement
Correct answer: To eliminate systematic instrumental errors by averaging both face readings
Observing on both faces (direct and reverse) cancels out collimation, horizontal axis, and other systematic errors in the instrument.
Question 2: A survey crew measures a traverse leg as 452.78 ft. The EDM has a constant error of +0.005 m and a scale error of 5 ppm. What type of error is the ppm component?
- Constant error
- Systematic proportional error (Correct answer)
- Random error
- Blunder
Correct answer: Systematic proportional error
PPM (parts per million) errors grow proportionally with distance, making them systematic proportional (scale-dependent) errors.
Question 3: In a closed traverse, what does the term 'closure error' refer to?
- The difference between the measured and theoretical bearing
- The vector difference between the computed final position and the starting point (Correct answer)
- The sum of all interior angles minus the theoretical sum
- The difference in elevation between first and last benchmark
Correct answer: The vector difference between the computed final position and the starting point
Closure error is the linear distance between the computed ending position and the known starting point after traversing the loop.
Question 4: What is the primary purpose of establishing control points in a large survey project?
- To mark property corners permanently
- To provide a network of accurately known positions from which detail surveys are referenced (Correct answer)
- To document historical land use
- To set benchmarks for construction staking only
Correct answer: To provide a network of accurately known positions from which detail surveys are referenced
Control points provide a framework of accurate horizontal and vertical positions that ensure all subsequent survey work ties to a common datum.
Question 5: A surveyor observes a vertical angle of +3°15'30" to a target. If the instrument height is 5.25 ft and the target height is 6.00 ft, what additional data is needed to compute the elevation difference?
- The magnetic declination
- The horizontal distance between instrument and target (Correct answer)
- The atmospheric pressure at each point
- The GPS coordinate of the instrument
Correct answer: The horizontal distance between instrument and target
The elevation difference via trigonometric leveling requires the slope or horizontal distance along with the vertical angle and height corrections.
Question 6: In differential leveling, which type of rod reading provides a check on instrument settlement?
- Backsight reading
- Foresight reading
- Turning point reading taken twice (check rod) (Correct answer)
- Intermediate sight
Correct answer: Turning point reading taken twice (check rod)
Taking a second rod reading at the turning point before moving the instrument detects any settlement or disturbance between the foresight and backsight.
Question 7: A surveyor is running a level line and the sum of backsights is 42.316 m while the sum of foresights is 41.884 m. What is the total change in elevation?
- -0.432 m
- +0.432 m (Correct answer)
- -84.200 m
- +84.200 m
Correct answer: +0.432 m
Total change in elevation equals sum of backsights minus sum of foresights: 42.316 − 41.884 = +0.432 m.
RPLS Surveying Principles and Methods 2
When using a total station, what is the purpose of 'face left' and 'face right' observations?