Question

The contour interval depends on: (A) time and expanse of field and office work, (B) purpose and extent of survey, (C) scale of plan and nature of country, (D) contour characteristics, (E) interpolation of contours. Choose the correct answer from the options given below:

• A. (B), (C) and (D) only
• B. (A), (B) and (C) only
• C. (C), (D) and (E) only
• D. (A), (C) and (D) only

Hint:

Remember that contour interval is inversely proportional to the map scale and directly proportional to the flatness of the terrain.
Flat land needs a small interval (e.g., \(0.25\text{ m}\)), while steep mountains need a large interval (e.g., \(5\text{ m}\)).

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
The contour interval is the constant vertical distance maintained between any two consecutive contour lines on a topographical map.
Selecting the correct contour interval is critical to ensure the map shows topographic features clearly without becoming cluttered or requiring excessive field survey time.

Step 2: Detailed Explanation:
The selection of a contour interval depends on several practical factors:
- (A) Time and expense of field and office work: A smaller contour interval requires more detailed field measurements and longer plotting times, which increases the total cost of the project.
If time or funds are limited, a larger contour interval is chosen.
- (B) Purpose and extent of survey: If the map is intended for detailed engineering designs (such as dams, canals, or roads), a very small contour interval is necessary to show fine elevation changes.
For general geographic mapping of large regions, a larger interval is sufficient.
- (C) Scale of the plan and nature of the country: The contour interval is inversely proportional to the scale of the map.
If the map scale is small, a large contour interval is used to prevent the lines from overlapping.
Additionally, the nature of the terrain (flat, rolling, or mountainous) dictates the interval; flat terrain requires a small interval to show features, whereas steep terrain requires a large interval to keep the lines legible.
- Factors (D) and (E) are characteristics of the contour plotting process itself and do not dictate the choice of the contour interval.
Therefore, the contour interval depends primarily on (A), (B), and (C).

Step 3: Final Answer:
The contour interval depends on (A), (B), and (C) only.