Contour lines and Profiles

Contour lines are used to signify a three-dimensional image of a flat surfaces. They are commonly used on topographic maps. Here contour lines connect continuous points of equal elevation. There is a connection between the change of height and the relative change of distance. If you move from one contour line to another then there is a change of height. The closer the lines are the 'faster' the height changes, and thus the 'steeper' the terrain. The further apart the contour lines are, the greater distance over which height changes, the slope is gentler.
Figure 1 shows Profile A - B drawn at a Baseline 10 m. Usually students need to draw profiles at the lot boundaries as shown in Figure 2. The rise & fall method is used to convert instrument readings at all grid points into reduced levels (RL's).

The RL's at the boundaries are then used to draw the profiles at a predetermined horizontal scale. The vertical scale is generally exaggerated to give a clearer indication of the profile.


Contour lines are abstract, they do not exist in reality but some relvant. information can be obtained from them, like the shape and slope of the ground and the location of hills, ridge lines and valleys.


 
 In the previous figures the contours in the upper right corner illustrate the shape of the hill at various heights. If all soil above 10 metres would be removed then the shape of the hill would no longer exist.

Figure 3 gives you an idea about its final outline.

Figure 3