Statement A: Latitude is the coordinate length measured perpendicular to the meridian. Statement B: Taking levels at right angles to a main line for vertical cross-section is called differential levelling. Identify the correct answer.
Correct Answer: D. Both statements are incorrect
📚 Detailed Explanation: Both Statements Are Incorrect
Why D (Both statements are incorrect) is correct: Both definitions in the statements are wrong. Each uses the incorrect direction (perpendicular vs. parallel) or the wrong term for a surveying concept.
Analysis of Statement A
Statement A: “Latitude is the coordinate length measured perpendicular to the meridian.” — FALSE
The CORRECT definition: Latitude of a survey line is its projection parallel to the reference meridian (the North-South component). The projection perpendicular to the meridian is called the Departure (the East-West component).
The CORRECT definition: Latitude of a survey line is its projection parallel to the reference meridian (the North-South component). The projection perpendicular to the meridian is called the Departure (the East-West component).
| Term | Direction | Component |
|---|---|---|
| Latitude (L) | Parallel to meridian (N-S) | L = length × cos(bearing) |
| Departure (D) | Perpendicular to meridian (E-W) | D = length × sin(bearing) |
Analysis of Statement B
Statement B: “Taking levels at right angles to a baseline for vertical cross-section is called differential levelling.” — FALSE
The CORRECT term: This method is called Cross-Sectioning (or Cross-section levelling), which is a form of profile levelling. Differential levelling is used to determine the difference in elevation between two distant points using multiple change points.
The CORRECT term: This method is called Cross-Sectioning (or Cross-section levelling), which is a form of profile levelling. Differential levelling is used to determine the difference in elevation between two distant points using multiple change points.
| Method | What It Does | How Wrongly Described in Statement B |
|---|---|---|
| Cross-Sectioning | Takes levels at right angles to a main line to plot transverse profile | Statement B incorrectly calls this “differential levelling” |
| Differential Levelling | Determines elevation difference between two distant points using change points | Has nothing to do with cross-sections or right-angle lines |
- Statement A WRONG: Latitude = parallel to meridian (N-S); Departure = perpendicular.
- Statement B WRONG: Right-angle offsets = Cross-Sectioning, not Differential levelling.
- Both statements are incorrect → Answer is D.