A contour line is an imaginary line that connects points of equal height. Such lines are drawn on the plan of a region after establishing the decreasing levels of several points in a region. The contour lines of a field are drawn keeping the difference in height between two consecutive lines constant.
features of outline
The salient features of contour lines that help in plotting or reading a contour map are as follows:
- Contour lines should be close, not necessarily within the boundaries of the plan.
- The horizontal distance between any two contour lines indicates the amount of slope and is inversely proportional to the amount of slope.
- A widely spaced contour indicates a flat surface.
- Nearby contours indicate steeply sloping land.
- A uniformly spaced contour shows uniform slope.
- An irregular shape indicates an uneven surface.
- A nearly concentric closed figure indicates a pond with values decreasing towards the center.
- Closely concentric contours indicate hills, with values moving toward the center.
- U-shaped contour lines denote the ridge with convexity towards the lower ground.
- V-shaped contour lines mark the valley with convexity towards the higher ground.
- Contour lines generally do not meet or intersect. If the contour lines are meeting in a part, it indicates the existence of a vertical rock.
- Figures of different heights cannot cross each other. If the contour lines intersect, it indicates the existence of hanging rocks or a cave.
- The steepest slope of the terrain at any point on a contour is represented along the normal to the contour at that point.
- Contours do not pass through permanent structures such as buildings.
- A contour line should be closed on its own but not necessarily within the bounds of the map.