RPLS Equipment and Tools Knowledge 3 — Questions and Answers
Question 1: In GPS/GNSS surveying, what does 'multipath error' refer to?
- Signals received from satellites below the horizon
- GPS signals arriving at the antenna via reflections from nearby surfaces (Correct answer)
- The delay caused by the ionosphere on signal transmission
- Errors introduced by incorrect datum transformation parameters
Correct answer: GPS signals arriving at the antenna via reflections from nearby surfaces
Multipath error occurs when GPS signals reflect off buildings, vehicles, or terrain before reaching the antenna, creating false path lengths and degrading positional accuracy.
Question 2: A 'robotic total station' differs from a conventional total station primarily in that it:
- Uses laser plummet instead of optical plummet
- Can automatically track a prism and be operated by a single surveyor (Correct answer)
- Computes coordinates without a data collector
- Requires no backsight orientation
Correct answer: Can automatically track a prism and be operated by a single surveyor
A robotic total station uses motorized drives and automated target recognition to follow a moving prism, allowing one person to simultaneously operate the rod and instrument.
Question 3: The 'C-factor' in differential leveling refers to:
- The collimation error of the level instrument (Correct answer)
- The correction for Earth curvature
- The rod scale error determined during calibration
- The atmospheric refraction index
Correct answer: The collimation error of the level instrument
The C-factor (or collimation error) is the angular deviation of the line of sight from a truly horizontal plane in a level instrument, corrected by the peg test.
Question 4: Which GNSS constellation is operated by the European Union?
- GLONASS
- BeiDou
- Galileo (Correct answer)
- NavIC
Correct answer: Galileo
Galileo is the global navigation satellite system operated by the European Union and the European Space Agency, designed to provide independent positioning capability.
Question 5: What is the function of a 'data collector' (field computer) in modern total station surveying?
- It powers the EDM laser in the total station
- It stores observations, runs coordinate geometry calculations, and controls robotic instruments (Correct answer)
- It transmits data via satellite to the office in real time
- It calibrates the instrument's vertical index error
Correct answer: It stores observations, runs coordinate geometry calculations, and controls robotic instruments
A data collector records field observations, performs on-the-fly coordinate geometry, guides instrument operation, and transfers data to office software for processing.
Question 6: A surveyor uses a hand level to perform a rough check of a proposed grade. The hand level is held at eye height and a rod is read 150 ft away. What is this instrument's primary limitation?
- It cannot be used beyond 100 ft
- It provides only approximate elevations due to lack of precise bubble magnification and fixed line of sight (Correct answer)
- It requires a calibrated rod to function properly
- It only works on level terrain
Correct answer: It provides only approximate elevations due to lack of precise bubble magnification and fixed line of sight
A hand level provides only rough elevation differences because the small bubble vial cannot be precisely centered while holding the instrument freehand, limiting accuracy.
Question 7: In terrestrial laser scanning (TLS), what does 'point cloud density' refer to?
- The total weight of the scanner hardware
- The number of measured points per unit area on a scanned surface (Correct answer)
- The maximum range capability of the scanner
- The accuracy of the GPS position recorded with the scan
Correct answer: The number of measured points per unit area on a scanned surface
Point cloud density describes how many 3D measurement points are captured per square meter or unit area, which directly affects the level of detail in the resulting model.
RPLS Equipment and Tools Knowledge 3
In GPS/GNSS surveying, what does 'multipath error' refer to?