Which of the following statements is INCORRECT about the contour interval of a contour map?

Explanation:

• A contour interval is the vertical distance or elevation difference between two adjacent contour lines on a topographic or contour map. It is used to represent the terrain's elevation and slope accurately in a two-dimensional format.
• While the contour interval is a fixed value on a map, the spacing between contour lines indicates the slope of the ground. Closer lines suggest a steep slope, while wider spacing indicates a gentle slope.
• Common contour intervals include 0.2 m, 0.5 m, 1 m, 2 m, 5 m, 10 m, etc., depending on terrain and required detail. These values are selected to be easy to read and scale-friendly.

Factors Affecting Contour Interval Selection

• The scale of the map: Larger-scale maps (showing smaller areas in more detail) use smaller contour intervals.

• The nature of terrain: Flat areas require smaller intervals to depict subtle elevation changes, while hilly or mountainous regions use larger intervals to avoid clutter.

• Time and resources: In time-constrained projects or rough surveys, larger contour intervals may be chosen to reduce effort.

• Purpose of the map: Engineering or construction projects require more precise elevation data, hence smaller intervals.

 Additional Information Plane Table Survey

• Plane table surveying is a graphical method of surveying in which field observations and plotting are done simultaneously using a drawing board (plane table) mounted on a tripod.

Main Instruments Used

• Plane table: The drawing board for field plotting

• Alidade: A sighting device for taking observations

• Spirit level: To ensure the board is horizontal

• Plumbing fork and plumb bob: To center the table over the survey station