FUNDAMENTAL SURVEYING Surveying Equipment & GPS/GNSS 1 — Questions and Answers
Question 1: What is the purpose of a 'prism constant' when using a total station with a prism?
- To adjust for the magnetic deviation of the prism pole
- To correct for the optical offset between the prism face and its mechanical center (Correct answer)
- To convert slope distance to horizontal distance
- To account for atmospheric temperature at the prism
Correct answer: To correct for the optical offset between the prism face and its mechanical center
The prism constant offsets the EDM measurement to account for the distance from the prism's optical reflective plane to the pole's plumb point.
Question 2: What is 'stadia' in surveying?
- A stadium-shaped survey control network
- An optical distance measurement method using the rod intercept between stadia crosshairs (Correct answer)
- A unit of horizontal angle measurement
- A type of photogrammetric target
Correct answer: An optical distance measurement method using the rod intercept between stadia crosshairs
Stadia measures distance by reading the rod intercept between the upper and lower stadia hairs of a transit/level and multiplying by the stadia factor (usually 100).
Question 3: What is the function of an optical plummet on a total station?
- To sight the sun for astronomic azimuth
- To accurately center the instrument over a ground point (Correct answer)
- To level the circular bubble for rough leveling
- To measure vertical angles without a target
Correct answer: To accurately center the instrument over a ground point
The optical plummet (or laser plummet) allows the surveyor to precisely center the instrument over a ground monument by looking straight down through a prism or laser.
Question 4: Which component of a total station measures the horizontal circle reading electronically?
- The EDM module
- The absolute encoder on the horizontal circle (Correct answer)
- The servo motor drive system
- The tilt sensor compensator
Correct answer: The absolute encoder on the horizontal circle
An absolute encoder on the horizontal circle reads the angular position directly in any orientation, eliminating the need to set a reference zero during setup.
Question 5: What does 'GNSS' stand for in modern surveying?
- Geographic Navigation and Satellite Survey
- Global Navigation Satellite System (Correct answer)
- Grid Network Survey System
- Geodetic North Standard System
Correct answer: Global Navigation Satellite System
GNSS refers to all global satellite positioning systems collectively, including GPS (US), GLONASS (Russia), Galileo (EU), and BeiDou (China).
Question 6: What is 'RTK GPS' in surveying?
- A static GPS method requiring 24 or more hours of data collection
- Real-Time Kinematic GPS providing cm-accuracy positions in real time via a base station correction link (Correct answer)
- A GPS receiver that works only on road networks
- A retroreflective target used with GPS surveys
Correct answer: Real-Time Kinematic GPS providing cm-accuracy positions in real time via a base station correction link
RTK (Real-Time Kinematic) GPS uses a fixed base station transmitting carrier-phase corrections to a rover, achieving centimeter-level accuracy in real time.
FUNDAMENTAL SURVEYING Surveying Equipment & GPS/GNSS 1
What is the purpose of a 'prism constant' when using a total station with a prism?