CST Field Procedures & Data Collection 2 — Questions and Answers
Question 1: What is the primary purpose of performing a two-peg test on a level?
- To check the rod for wear at the base
- To determine the collimation (line-of-sight) error of the instrument (Correct answer)
- To calibrate the EDM distance constant
- To verify the compensator's battery level
Correct answer: To determine the collimation (line-of-sight) error of the instrument
The two-peg test compares readings from two setups to reveal whether the line of sight is truly horizontal.
Question 2: A steel tape standardized at 68°F is used at 88°F to measure 100.00 ft. Using a coefficient of 0.00000645/°F, what is the temperature correction?
- -0.013 ft
- +0.006 ft
- +0.013 ft (Correct answer)
- +0.129 ft
Correct answer: +0.013 ft
Ct = 0.00000645 × (88 − 68) × 100 = +0.013 ft, positive because the tape expanded.
Question 3: A crew member records a wrong number in the field book. What is the accepted way to correct it?
- Erase it and write the correct value
- Cover it with correction fluid
- Tear out the page and recopy the notes
- Draw a single line through it and write the correct value nearby (Correct answer)
Correct answer: Draw a single line through it and write the correct value nearby
Field notes are legal records, so original entries must stay legible and never be erased.
Question 4: Why do surveyors try to keep backsight and foresight distances about equal in differential leveling?
- To cancel collimation error and curvature/refraction effects (Correct answer)
- To reduce the number of turning points
- To make rod readings easier to read
- To eliminate rod-plumbness error
Correct answer: To cancel collimation error and curvature/refraction effects
Equal sight lengths make systematic errors equal on both sights, so they cancel in the elevation difference.
Question 5: A backsight of 4.52 ft is taken on a benchmark with elevation 100.00 ft, then a foresight of 3.17 ft on a turning point. What is the elevation of the turning point?
- 98.65 ft
- 101.35 ft (Correct answer)
- 104.52 ft
- 107.69 ft
Correct answer: 101.35 ft
HI = 100.00 + 4.52 = 104.52; elevation = 104.52 − 3.17 = 101.35 ft.
Question 6: What device helps a rod person hold a leveling rod plumb during readings?
- Plumb bob
- Tribrach
- Rod level (bull's-eye) (Correct answer)
- Hand level
Correct answer: Rod level (bull's-eye)
A circular rod level attached to the rod shows when the rod is vertical.
Question 7: When taping down a steep slope, what technique keeps measurements horizontal?
- Laying the tape on the ground and applying a slope correction only
- Holding the tape at full tension with no plumbing
- Using a longer tape to reduce the number of segments
- Breaking tape into shorter horizontal segments and plumbing down at each end (Correct answer)
Correct answer: Breaking tape into shorter horizontal segments and plumbing down at each end
Breaking tape lets the crew hold short horizontal sections and transfer points with a plumb bob.
CST Field Procedures & Data Collection 2
What is the primary purpose of performing a two-peg test on a level?