How To Draw A Topographic Profile
Dr. Marian Mustoe
University of Texas, Odessa, TX



A topographic profile is just what it sounds like it is....a side view, a profile, of a topographically depicted or mapped piece of land. Essentially you draw a line on the map between two points and you look at it sideways by taking elevations along the line and then presenting these on a graph show the vertical (usually distorted) aspect of the topography between the two points.

What you will need:
1. A topo map.
2. A straight edge of paper to draw a line on the map.
3. Two points selected on the map with a straight line drawn across between the two lines.
4. A piece of standard graph paper to plot the profile on.
5. A vertical axis on the graph which corresponds to the elevation of the selected points.
6. A horizontal axis on the graph paper which corresponds to the distance between the points.

Here's how you do it.

1. On the map, place the edge of a sheet of paper along an imaginary line that connects the top of Castle Rock and Old Butte. Place the corner of the paper at the starting point or highest point. (See diagram below).

     
      
                                                                                    Figure 1.

2. Starting from the top of the mountain, make marks along the edge of the paper where very dark contour line (also known as index lines) intersects the paper. (See fig. 1) (There are four little lines between each dark contour line, this distance represents 4 times 20 feet (the contour interval of the map =20 feet) So the distance between two of the dark lines represents 100' of elevation. Remember, the distance between these lines is set at 20'. The contours represent the distance of vertical rise over that horizontal distance.

3. Look at the elevations you plotted on the piece of paper and determine how high and low they go. Now on the vertical (Y) axis of the graph paper develop a scale that represents the vertical distance you covered on your plot. Next Place the edge of the paper that you marked on at the base (X axis) or bottom of the graph paper. Use the direct reading of the horizontal distance you covered on the map to represent the base scale. Your graph will be set up so that the bottom of graph (X) will show horizontal distance between the two points on the map. The vertical (Y) axis will be set up to show the vertical axis of the map. Make sure you give enough vertical distance to incorporate the highest point on the cross section.

4. With the paper that you plotted with at the base of the graph, (see fig. 2) for every mark you made on the paper place a point on the graph directly above that point corresponding to the correct elevation. Remember you are reading elevation along the Y axis of the graph paper.                  

             
                Figure 2 .

5. After you have put in all the points, connect the points (like connect the dots! Is this not fun!) to show the contour profile. This is the contour profile, a sideways view of the landscape between two points.

6. Make sure you label and title the profile. Show the scale on the graph paper you use...for example, 5 Squares = 100 Feet of vertical elevation.Remember, The contour interval shows the standard change between contour. The interval can be found stated at the bottom of the map. The more contour lines over a given area the steeper the area is.

ABOUT MAP SCALE Like all topographic maps, North is on the top, West is on the left side of the map and East is on the right side. When you give relative locations for things on these maps use the compass directions. This map uses a scale of 1:24000. This is a relative fraction scale (RF), which is discussed in the textbook. Briefly a relative fraction scale can be simply described like this:

ONE OF ANYTHING ON THE MAP IS (:) EQUAL TO 24,000 OF THE SAME IN REALITY
That means that if you took a ruler and measured 1 inch on the map between two points on the map.......if you found those two points in reality (on the ground) there would be 24,000 inches between them. If you then convert the 24000 inches to feet you would divide them by 12 (12 inches in a foot), and you would get 2000 feet. So in a scale of 1:24000 One inch equals 2000 feet.
Remember, you can substitute anything you like with an RF scale just as long as you use the same units on both sides. You could measure 3 inches on the map between two points and that would mean 24,000 times 3 inches in reality or on the ground, or converted to feet, 6,000 feet. You could measure 2 mm on the map and in reality it would be 24000 times 2 or 48,000 mm. in reality or on the ground. The height or depth of a landform is not the elevation, it is the measured vertical distance between two measured elevations. Assume a crater has a measured (control point) elevation at the bottom of the crater to be 5227 Feet and a measured control point along the NE rim of the crater of 5619 Feet. On the map you will find a triangle with a that dot means there was actually a measurement made on the ground at that point. To find the depth of the crater subtract the smaller from the larger. If you do not have any graph paper please copy or use the next sheet for your cross sectional diagram.