A map view looks at the surface of the earth from overhead.
Contour maps use the contour lines to represent the third
dimension of elevation. In a previous lesson we examined geologic
maps. We also looked at geologic cross sections that cut through
the earth and showed the rocks beneath the surface. The top line
on the cross section represented the surface of the earth. We can
apply this same alteration of perspective to contour maps. From
the information provided by the contour map, we can produce a cut
across this surface into the earth and, thus, show a side view
like a silhouette or skyline. This illustration is called a
A topographic profile is a diagram that shows the change of
elevation of the land surface along a given line. As indicated
above, it represents graphically the skyline viewed from a
distance. The VERTICAL scale is the scale used to plot the
elevation. It is usually larger than the horizontal or map scale,
EXAGERATED, in order to emphasize the difference in the relief.
The MAXIMUM RELIEF is the difference in elevation between the
highest and lowest points.
Following are the steps for drawing a topographic profile.
1. Lay the edge of a strip of paper along the line between the
starting and ending points for the profile.
2. Mark on the edge of the strip the EXACT places where each
CONTOUR, STREAM, and HILLTOP crosses this line.
3. Label these marks with the elevation and correct
4. Mark any important other features such as bottoms of
depressions or landmarks to be included.
5. If a graph is not provided, construct the horizontal line for
your profile of the SAME LENGTH as your profile (unless a
different horizontal scale is to be used for the profile.)
Generally, the same horizontal scale is used. Prepare the
VERTICAL SCALE by lightly drawing lines parallel to your
horizontal base line on the proper scale for each of the
elevations to be represented. Label these lines with the correct
elevations starting one or two intervals below the lowest
elevation that will be plotted (lowest elevation on the profile).
Thus, the side represents a kind of graphic scale.
6. Place the edge of the strip of paper with the labeled contour
lines at the bottom of the profile base line and project each
contour and feature to the horizontal line of the same elevation.
Put a small dot at the intersection of these two lines.
7. Connect all of the points with a smooth line being careful to
show all hilltops at the proper height and all valleys and
depressions at their correct approximate values.
Continue with the lesson