FUNDAMENTAL SURVEYING Leveling & Differential Leveling 1 — Questions and Answers
Question 1: What is a benchmark (BM) in surveying?
- A temporary point used only during a single survey day
- A permanent point of known elevation used as a reference (Correct answer)
- The highest point on a survey route
- A control point established by GPS only
Correct answer: A permanent point of known elevation used as a reference
A benchmark is a permanent, stable point of known elevation set by a government agency (like NGS) or established through precise leveling.
Question 2: In differential leveling, what is a 'backsight' (BS)?
- A reading taken toward the previous station
- A rod reading taken on a point of known elevation (Correct answer)
- A reading taken in the direction of magnetic north
- The closing reading taken at the final benchmark
Correct answer: A rod reading taken on a point of known elevation
A backsight is a rod reading taken on a point of known elevation (like a BM or turning point) to establish the instrument's height of instrument (HI).
Question 3: Height of Instrument (HI) in leveling is calculated as:
- Known elevation minus backsight reading
- Known elevation plus backsight reading (Correct answer)
- Foresight reading minus backsight reading
- Backsight reading times foresight reading
Correct answer: Known elevation plus backsight reading
HI = elevation of the backsight point + backsight rod reading, giving the elevation of the line of sight.
Question 4: What is a 'turning point' (TP) in differential leveling?
- The point where the survey changes direction horizontally
- A temporary point used to carry elevation forward (Correct answer)
- The highest rod reading in a level run
- A permanent monument marking a property corner
Correct answer: A temporary point used to carry elevation forward
A turning point is a temporary, solid point where both a foresight and backsight are taken, used to advance the level run when the instrument must be moved.
Question 5: If HI = 512.34 ft and the foresight rod reading is 3.21 ft, what is the elevation of the foresight point?
- 515.55 ft
- 509.13 ft (Correct answer)
- 512.34 ft
- 3.21 ft
Correct answer: 509.13 ft
Elevation = HI minus foresight = 512.34 minus 3.21 = 509.13 ft.
Question 6: Which type of level uses a pendulum compensator to automatically maintain a horizontal line of sight?
- Dumpy level
- Builder's level
- Automatic level (Correct answer)
- Hand level
Correct answer: Automatic level
An automatic level uses a magnetic-damped or gravity-driven compensator to self-level the line of sight within a limited range.
FUNDAMENTAL SURVEYING Leveling & Differential Leveling 1
What is a benchmark (BM) in surveying?