15 PRINCIPAL CHARACTERISTICS OF CONTOUR LINE

A contour line is an imaginary line which connects points of equal elevation. Such lines are drawn on the plan of an area after establishing reduced levels of several points in the area. The contour lines in an area are drawn keeping difference in elevation of between two consecutive lines constant.

Characteristics of Contours

The principal characteristics of contour lines which help in plotting or reading a contour map are as follows:

  1. Contour lines must close, not necessarily in the limits of the plan.
  2. The horizontal distance between any two contour lines indicates the amount of slope and varies inversely on the amount of slope.
  3. Widely spaced contour indicates flat surface.
  4. Closely spaced contour indicates steep slope ground.

    contour showing steep slope terrain
    contour showing steep slope terrain
  5. Equally spaced contour indicates uniform slope.

    contour showing uniform slope terrain
    contour showing uniform slope terrain
  6. Irregular contours indicate uneven surface.
  7. Approximately concentric closed contours with decreasing values towards centre indicate a pond.

    Pond and its contour
    Pond and its contour
  8. Approximately concentric closed contours with increasing values towards centre indicate hills.

    Hill and its contour
    Hill and its contour
  9. Contour lines with U-shape with convexity towards lower ground indicate ridge.
  10. Contour lines with V-shaped with convexity towards higher ground indicate valley.

    contour showing ridge line and valley line
    contour showing ridge line and valley line
  11. Contour lines generally do not meet or intersect each other. If contour lines are meeting in some portion, it shows existence of a vertical cliff.

    Vertical cliff and its contour
    Vertical cliff and its contour
  12. Contours of different elevations cannot cross each other. If contour lines cross each other, it shows existence of overhanging cliffs or a cave.

    overhanging cliff and its contour
    overhanging cliff and its contour
  13. The steepest slope of terrain at any point on a contour is represented along the normal of the contour at that point.
  14. Contours do not pass through permanent structures such as buildings.

    contour across a permanent structure
    contour across a permanent structure
  15. A contour line must close itself but need not be necessarily within the limits of the map.

 

 

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