Which of the following statements is/are true for trigonometric levelling? i. It is a process of determining the elevations of stations from observed vertical angles only ii. Vertical angles are measured with a theodolite
- AOnly (i)
- BOnly (ii)Correct
- CBoth (i) and (ii)
- DNeither (i) nor (ii)
Solution
Concept
Principles and features of trigonometric levelling
Formula
NONE
Step-by-step solution
1. Trigonometric leveling determines elevation differences using vertical angles along with measured horizontal or direct distances. 2. Vertical angles are measured using a theodolite, but distance measurements are also necessary alongside vertical angles. Answer: B
Explanation
Trigonometric levelling determines relative elevations by combining measured vertical angles with known or measured horizontal or geodetic distances between stations, not from vertical angles alone. The vertical angles required for these trigonometric calculations are accurately measured using a theodolite. Thus, statement i is false because horizontal distance is also required, and statement ii is true, making option B the correct answer.
Why the other options are wrong
A) Statement (i) is false because trigonometric levelling requires measured distances in addition to vertical angles.
Shortcut
Trigonometric levelling uses a theodolite to measure vertical angles for elevation calculations.
Common mistake
Selecting option C instead of B by assuming trigonometric levelling relies solely on observed vertical angles without requiring distance measurement.
Correct answer: B) Only (ii)