Surveying Equipment & GPS/GNSS Flashcards
6 cards from real FUNDAMENTAL SURVEYING practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 6 Surveying Equipment & GPS/GNSS flashcards as text
What is 'DOP' (Dilution of Precision) in GPS surveying?
Answer: A dimensionless number indicating the geometric strength of the satellite configuration
DOP values indicate how satellite geometry affects position accuracy — a low PDOP (such as less than 4) means good geometry and better accuracy.
Which type of GPS error is largely eliminated by differential techniques (DGPS or RTK)?
Answer: Common-mode atmospheric errors that affect both base and rover
Differential GPS cancels errors common to both the base and rover (atmospheric delays, clock biases) as they cancel in the differencing process.
What is 'geodetic height' (ellipsoidal height) in GPS terminology?
Answer: The height above the reference ellipsoid (GRS 80 or WGS 84)
Geodetic (ellipsoidal) height is the distance above the mathematical reference ellipsoid, not sea level; it must be corrected by the geoid undulation to get orthometric height.
What is a 'tribrach' in surveying instrumentation?
Answer: A leveling base with three foot screws that mounts instruments on a tripod head
A tribrach is a leveling base with three leveling screws and a forced-centering plate that attaches to a tripod and accepts interchangeable survey instruments.
What is 'forced centering' in surveying?
Answer: A system allowing interchangeable instruments to be swapped onto a tribrach without re-centering over the point
Forced centering uses matched tribrachs and adapters so that a total station, prism, or target can be interchanged at the same setup point without disturbing the centered, leveled base.
What is the purpose of atmospheric corrections applied to EDM measurements?
Answer: To adjust the velocity of electromagnetic waves for actual air temperature, pressure, and humidity
EDMs assume a standard atmosphere; corrections for actual temperature, pressure, and humidity adjust the wave propagation speed to give the true distance.