PS Surveying Equipment & Technology 2 — Questions and Answers
Question 1: What is the primary advantage of a robotic total station over a conventional total station?
- It measures angles more accurately
- It can be operated by a single person without a rodman (Correct answer)
- It requires no calibration
- It stores data in cloud format automatically
Correct answer: It can be operated by a single person without a rodman
Robotic total stations use servo motors and remote control so one surveyor can operate the instrument and hold the prism simultaneously.
Question 2: In GNSS surveying, what does the term 'multipath error' refer to?
- Signals arriving from too many satellites
- Satellite signals reflecting off surfaces before reaching the antenna (Correct answer)
- Errors caused by using multiple constellations
- Phase ambiguity in carrier wave resolution
Correct answer: Satellite signals reflecting off surfaces before reaching the antenna
Multipath error occurs when GNSS signals bounce off buildings, terrain, or other surfaces and arrive at the antenna via indirect paths, degrading position accuracy.
Question 3: Which component of a digital level is responsible for converting the bar-code rod image into a height reading?
- CCD or CMOS image sensor (Correct answer)
- Compensator pendulum
- Electrolevel bubble
- Phase detection circuit
Correct answer: CCD or CMOS image sensor
Digital levels use a CCD or CMOS sensor to capture the bar-code pattern on the rod and correlate it to a stored reference pattern to compute the reading.
Question 4: A surveyor notes that EDM distances measured on a hot summer day are consistently shorter than expected. Which error source is most likely responsible?
- Scale error in the EDM crystal
- Higher air temperature reducing the refractive index and shortening the measured path (Correct answer)
- Prism constant mismatch
- Incorrect atmospheric pressure correction
Correct answer: Higher air temperature reducing the refractive index and shortening the measured path
High temperature lowers air density, reducing the refractive index; the EDM applies a velocity correction, but unaccounted temperature gradients can cause systematic short readings.
Question 5: What is the purpose of the 'tilt sensor' integrated into modern total stations?
- To measure the slope of the terrain
- To compensate for small residual vertical axis errors (Correct answer)
- To detect movement of the tripod
- To calibrate the EDM distance
Correct answer: To compensate for small residual vertical axis errors
The dual-axis tilt compensator measures and electronically corrects for any residual tilt of the vertical axis that remains after rough leveling.
Question 6: When selecting a GNSS antenna for high-accuracy geodetic work, why is the Phase Center Variation (PCV) important?
- It determines battery life during field sessions
- It describes how the electrical phase center shifts with satellite elevation and azimuth, affecting position accuracy (Correct answer)
- It controls the frequency of signal reception
- It sets the baseline length for RTK operations
Correct answer: It describes how the electrical phase center shifts with satellite elevation and azimuth, affecting position accuracy
PCV corrections account for the fact that the antenna's effective phase center moves as satellite geometry changes, and ignoring them introduces systematic errors in precise positioning.
Question 7: A surveyor uses a drone-based LiDAR system to produce a point cloud. What post-processing step is essential to derive a bare-earth Digital Elevation Model (DEM)?
- Applying color correction to the RGB imagery
- Classifying and removing non-ground returns such as vegetation and structures (Correct answer)
- Converting UTM coordinates to state plane
- Merging overlapping flight strips with photogrammetry software
Correct answer: Classifying and removing non-ground returns such as vegetation and structures
Ground filtering (classification) separates ground-level returns from above-ground features, allowing creation of a true bare-earth DEM from the LiDAR point cloud.
PS Surveying Equipment & Technology 2
What is the primary advantage of a robotic total station over a conventional total station?