How to Read Contour Lines and Calculate Contour Interval? Major contour lines are recommended to show with prominent colour along with texts showing the contour interval value. To make it easy to read drawings, it is recommended to show minor contour lines with less prominent colour and without any text for contour intervals. By doing this it would be very easy to read and review the topography of the surface. It is recommended to generate contour maps at 25mm intervals. Therefore, it is very important to design the cross-fall at the interface location precisely and contour maps assist designers to eliminate uneven surfaces and make them like a smooth surface. Over the urban junction, the road cross-fall of the primary road joins the cross-fall of the secondary road. So, contour maps are used to check the steep slopes of proposed surfaces.ĥ. It is not recommended to provide a footway cross-fall of more than 3.3%. Steep slopes or sub-standard cross-falls along the footways would not be comfortable for wheelchair and pushchairs users. If they are then it would be recommended to eliminate those low points.Ĥ. It also helps designers to review if the low points are coming across the pedestrian crossing points (at road junction) or not. Flow arrow helps drainage designers to identify low points and propose drainage gully pots and kerbs drainage systems accordingly. If flat spots are found within the contour map, it means those locations could create ponding and need to redesign to eliminate flat spots.ģ. In Rural Highways or Urban Road Projects, contour maps assist designers to check the flat spots, flow arrows, steep slopes, uneven surfaces over the junction.Ģ. Contour Maps are created to check the design proposals. Design organisations use this information’s plan new infrastructure projects in such a way that further damage or further flooding can be avoided.ġ. Meteorological Departments use Contour Maps to inform the public about flood-prone locations. Low-lying areas (close to rivers or canals) are prone to flooding.So generating a contour map of existing ground helps designers to plan the proposed drainage network accordingly. In an urban or rural setting, low-lying locations are commonly used for drainage outfalls and connect to existing rivers or ponds or canals.This will help designers to design the levels of the proposed road or railway lines in a similar manner to minimise extensive cuttings or embankments. In order to design a new physical infrastructure, it is very important to know where are the low points or high points across the project area.Purpose of Contour Maps of Existing Ground: It assists designers to understand highpoints, low points, hilly terrain, valleys and flat spot locations. What is the Purpose of Contour Maps?Ĭontour Map explains the topography of the ground surface. When the contour lines are drawn underwater, they are termed as submarine contours.
In simple words when we analyse a 3D surface and observe some equally elevated points and draw a line joining those equal elevation points, the line is called a contour line. What is Contour?Ĭontours are imaginary lines passing through equal elevation points on the ground surface, normally created by using the triangulation surface model. What are the factors affecting Contour Interval?Īs a Civil Engineer, you must have seen Contour Maps, but do you know what is Contour maps and Contour intervals? Purpose of Contour Maps for Proposed Surface: If you have any queries regarding the subject or you want to add something from your side please write it in the comment section provided below.Purpose of Contour Maps of Existing Ground:
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I hope you got complete information about Contouring in this article. For steep slopes, the horizontal equivalent is narrow while for flatter slopes it is wide. It is not constant and varies according to the steepness of the ground. The horizontal equivalent is the horizontal distance between any two continuous contour lines. The interval in the contour line generally depends upon (i) The nature of the ground surface, (ii) The scale of the map prepared, and (iii) the purpose of the survey. The contour interval for the contour lines will be 3 m here. Suppose a map having contour lines of 100 m, 97 m, 94 m, and so on. Similarly, for the contour of 99 m, all the points will have a reduced level of 99 m, and so on.Ĭontour Interval is the vertical distance between any two consecutive contours as shown in the figure above. For example, the contour of 98 m indicates that all the points on this line have a reduced level of 98 m.
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