Which of the following options represents the methods that can be used effectively to locate the routes of highways or railways from a contour map?
- ATracing of contour gradient method and the method of horizontal plane
- BMethod of cross-section and the equal depth contours method
- CTracing of contour gradient method and the equal depth contours method
- DMethod of cross-section and the tracing of contour gradient methodCorrect
Solution
Concept
Routes of roads and railways are located on contour maps by tracing a contour gradient and by drawing cross-sections.
Formula
Horizontal distance between contours = Contour interval × (1/gradient)
Step-by-step solution
1. To find a route with a fixed gradient, set the divider to the horizontal distance for that gradient between two contours. 2. Step this distance from contour to contour. This is the tracing of contour gradient method. 3. Draw longitudinal and cross-sections along the trial route from the contour map. Use them to check cutting and filling. 4. Equal depth contours and the horizontal plane method are mainly used to find earthwork volume for levelling a site, not to locate routes. 5. So the answer is: method of cross-section and tracing of contour gradient.
Explanation
A contour gradient is traced on the map to get a route with a fixed slope. Cross-sections drawn from the contour map help check the earthwork along that route. Together, these two methods are used to fix highway and railway alignments.
Why the other options are wrong
A: The horizontal plane method is for site levelling and earthwork, not route location. B: Equal depth contours are for earthwork volume, not route location. C: Equal depth contours are not a route location method.
Shortcut
Route location = contour gradient + cross-sections. Equal depth and horizontal plane = earthwork volume.
Common mistake
Mixing up methods for earthwork volume calculation with methods for route location.
Correct answer: D) Method of cross-section and the tracing of contour gradient method