Consider the following statements regarding horizontal equivalent and contour interval. i.Horizontal equivalent between two contour lines is always constant. ii.Horizontal equivalent may be zero for a vertical cliff. iii.Contour interval should be inversely proportional to the scale. iv.For detailed design work, large contour interval is taken. Which of the given statements are correct?
- Aii and iiiCorrect
- Bi and iii
- Cii and iv
- Di and iv
Solution
Concept
Horizontal equivalent depends on ground slope. Contour interval is small for large-scale maps and detailed work.
Formula
Horizontal equivalent = Contour interval / tan θ
Step-by-step solution
1. Statement i: Horizontal equivalent changes with ground slope, so it is not always constant. False. 2. Statement ii: At a vertical cliff, contours meet or overlap, so the horizontal equivalent is zero. True. 3. Statement iii: A larger scale map uses a smaller contour interval, so the interval is inversely proportional to scale. True. 4. Statement iv: Detailed design needs a small contour interval, not a large one. False. 5. The correct statements are ii and iii, so the answer is A.
Explanation
Horizontal equivalent is the horizontal distance between two contours. It is small on steep ground and zero at a vertical cliff. A large-scale map and detailed design work need a small contour interval.
Why the other options are wrong
B: Statement i is false because HE changes with slope. C: Statement iv is false because detailed work needs a small interval. D: Both i and iv are false.
Shortcut
Steep slope means small HE, and a vertical cliff means HE = 0. Detailed work means a small interval.
Common mistake
Confusing contour interval (vertical distance, constant on a map) with horizontal equivalent (horizontal distance, varies with slope).
Correct answer: A) ii and iii