LSIT Surveying Fundamentals 4 — Questions and Answers
Question 1: In a road curve, the 'degree of curve' using the chord definition is defined as the central angle subtended by a chord of:
- 50 ft
- 100 ft (Correct answer)
- 200 ft
- 1 station (100 ft arc)
Correct answer: 100 ft
Under the chord definition, the degree of curve is the central angle subtended by a 100-ft chord; this definition is commonly used in railroad surveying.
Question 2: Which instrument measures both horizontal and vertical angles and is used for electronic distance measurement (EDM)?
- Level
- Total station (Correct answer)
- Planimeter
- Theodolite only
Correct answer: Total station
A total station integrates an electronic theodolite with an EDM, allowing simultaneous measurement of horizontal angles, vertical angles, and slope distances.
Question 3: The geodetic datum NAD 83 is referenced to which ellipsoid?
- Clarke 1866
- WGS 84
- GRS 80 (Correct answer)
- Bessel 1841
Correct answer: GRS 80
NAD 83 is based on the Geodetic Reference System 1980 (GRS 80) ellipsoid, though it is nearly identical to the WGS 84 ellipsoid used by GPS.
Question 4: A 'foresight' in leveling operations is a rod reading taken on:
- A benchmark with known elevation
- A turning point or new point whose elevation is to be determined (Correct answer)
- The instrument setup point
- A reference object used for orientation
Correct answer: A turning point or new point whose elevation is to be determined
A foresight rod reading is taken on a turning point or a new point to determine its elevation using the established height of instrument.
Question 5: When using a total station, 'face left' and 'face right' observations are averaged primarily to eliminate:
- Collimation error and vertical axis tilt (Correct answer)
- Instrument leveling errors
- Scale factor errors in the EDM
- Atmospheric refraction effects
Correct answer: Collimation error and vertical axis tilt
Observing in both face-left and face-right positions and averaging the results cancels out systematic errors such as collimation error and horizontal axis tilt.
Question 6: The 'tangent length' (T) of a simple horizontal curve is calculated as:
- T = R × sin(Δ/2)
- T = R × tan(Δ/2) (Correct answer)
- T = R × cos(Δ/2)
- T = R × (1 - cos(Δ/2))
Correct answer: T = R × tan(Δ/2)
The tangent length T = R × tan(Δ/2), where R is the radius and Δ is the central (deflection) angle of the curve.
Question 7: In GPS surveying, 'PDOP' (Position Dilution of Precision) is a measure of:
- Signal-to-noise ratio of satellite signals
- The effect of satellite geometry on positional accuracy (Correct answer)
- The multipath error at the receiver
- Atmospheric delay corrections applied
Correct answer: The effect of satellite geometry on positional accuracy
PDOP quantifies how satellite geometry affects positional accuracy; a lower PDOP value indicates better geometry and potentially more accurate positions.
LSIT Surveying Fundamentals 4
In a road curve, the 'degree of curve' using the chord definition is defined as the central angle subtended by a chord of: