Contour map provides useful information for locating a route at a given gradient such as highway, canal, sewer line etc.

Let it be required to locate a route from P to Q at an upward gradient of 1 in 100. The contour map of the area is available at a contour interval of 5 meter at a scale of 1:10000. The horizontal equivalent will therefore be equal to 100 meter. Then with centre at P with a radius of 2 cm draw an arc to cut the next higher contour, say at q. With q as centre, mark the next higher contour by an arc of radius 2 cm say at r. Similarly, other points such as s,t,u…. etc are obtained and joining the points provides the location of route. (Figure 18.2)

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