Question

The instruments required for contour survey are: (A) dumpy level, (B) levelling staff, (C) chains and tapes, (D) odometer, (E) prismatic compass. Choose the correct answer from the options given below:

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

Hint:

Every contouring method requires vertical control (measured using a level and staff) and horizontal control (measured using chains, tapes, or tacheometers) to map the elevation points accurately.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
A contour survey involves determining both the vertical elevations (vertical control) and the horizontal positions (horizontal control) of various points on a terrain to plot lines of equal elevation.

Step 2: Detailed Explanation:
To perform a standard contour survey, surveyors must establish both horizontal and vertical reference grids:
- Vertical Control: A dumpy level (A) is a high-precision optical leveling instrument used to establish a horizontal line of sight.
In combination with a graduated levelling staff (B), the surveyor measures the vertical distance from the instrument line of sight to the ground points, calculating the reduced levels (elevations) of the terrain.
- Horizontal Control: To plot these surveyed points accurately on a map sheet, their planimetric coordinates (horizontal distances) must be measured.
Chains and tapes (C) are the standard instruments used to measure linear ground distances from reference grid lines.
- Odometers (D) provide only approximate, low-precision distance measurements, and prismatic compasses (E) are used for angular bearings rather than standard grid leveling elevation measurements.
Thus, the primary instruments required for a standard, reliable contour survey are the dumpy level, levelling staff, and chains and tapes.

Step 3: Final Answer:
The instruments required are (A), (B) and (C) only.