FUNDAMENTAL SURVEYING Measurement and Data Collection 2 — Questions and Answers
Question 1: A steel tape calibrated at 68°F is used at 95°F. If the tape is 100 ft long, what is the temperature correction?
- +0.018 ft (Correct answer)
- −0.018 ft
- +0.180 ft
- −0.180 ft
Correct answer: +0.018 ft
Temperature correction = 0.0000065 × (95−68) × 100 = 0.0000065 × 27 × 100 ≈ +0.018 ft.
Question 2: Which of the following best describes a GPS carrier-phase measurement?
- Measuring the time delay of a code signal
- Counting the number of complete wavelengths between satellite and receiver (Correct answer)
- Measuring Doppler shift of the signal
- Timing the signal strength drop
Correct answer: Counting the number of complete wavelengths between satellite and receiver
Carrier-phase measurement counts the number of full and fractional wavelengths of the carrier signal between satellite and receiver.
Question 3: What is the purpose of a plumb bob or optical plummet in surveying?
- To measure vertical angles
- To center the instrument over a ground point (Correct answer)
- To level the instrument
- To measure magnetic declination
Correct answer: To center the instrument over a ground point
A plumb bob or optical plummet is used to align the instrument's vertical axis directly over the survey point on the ground.
Question 4: What is the term for the error caused by the line of sight not being perpendicular to the horizontal axis of a theodolite?
- Index error
- Vertical axis error
- Collimation error (Correct answer)
- Trunnion axis error
Correct answer: Collimation error
Collimation error occurs when the line of sight (collimation axis) is not perpendicular to the horizontal (trunnion) axis.
Question 5: In total station surveying, what does 'PPM' correction refer to?
- Parts per million atmospheric correction applied to EDM measurements (Correct answer)
- Pulses per minute of the laser
- Pixels per measurement in digital leveling
- Precision per measurement
Correct answer: Parts per million atmospheric correction applied to EDM measurements
PPM (parts per million) corrections are applied to EDM distance measurements to account for atmospheric temperature and pressure effects.
Question 6: What is the typical accuracy of a survey-grade GNSS receiver in static mode after post-processing?
- ±1–5 cm (Correct answer)
- ±1–5 m
- ±0.1–0.5 mm
- ±10–50 cm
Correct answer: ±1–5 cm
Survey-grade GNSS in static mode with post-processing typically achieves ±1–5 cm horizontal accuracy.
FUNDAMENTAL SURVEYING Measurement and Data Collection 2
A steel tape calibrated at 68°F is used at 95°F.
If the tape is 100 ft long, what is the temperature correction?