How is a topographic profile useful

For example, the first elevation from left to right is feet - on a vertical line, just above your tick mark for feet, place a dot on the line that represents feet. Then feet, and so on. If you need a reminder of how to plot points, visit the plotting points page but don't forget to come back and finish this module!!

The finished product should look like this:. Show show me the smooth curve constructed from these points. Remember that we're thinking about how the landscape looks. So, the tops of hills should go up above the contours that surround them and valleys go just below the contour elevations on either side. Valleys aren't flat and in most cases neither are hilltops. Steep sided hills have contour lines that are close together and gentle slopes have contours that are far apart - your profile should reflect these ideas.

Here's the profile connected from the dots plotted in step Show pointers. Remember that this is a profile or slice of the landscape; therefore, we do not connect the dots with straight line segments.

Think about hills you have seen from a distance - do they go straight across at the top yes there are some hills - called mesas - that do this but most do not, right?

Although the hill tops have two repeating contour lines, we do not connect the hill tops or valleys with straight lines across at the same elevation. Because there is space between them the land surface must go up or down. How much? Well, depending on the contour interval, we can make an estimation. The top of the hill cannot be higher than the next elevation marked by a topographic line.

For example, on the figure above, the 40 ft contour is repeated at the top of the left hill, the profile shows the elevation going above 40 ft but not all the way to 50 ft.

Note the minimum and maximum elevations along the line you've recorded. Label the graph's y-axis with elevation values ensuring that they encompass the minimum and maximum values recorded previously. Therefore the x-axis corresponds to the horizontal distance of the line on map.

The y-axis represents the elevation of points along the line. On the graph paper, plot the corresponding elevation above each tick mark. By connecting the dots, the elevation profile along the line of interest is drawn. In some cases topographic relief of the terrain is modest, such as the case of small hills and other subtle features as opposed to mountainous terrain, or the profile of interest is extended over a large horizontal distance relative to vertical relief.

In such situations the elevation profile may only show small variations in elevation without much detail of the topography.

For this reason some amount of vertical exaggeration VE is used in order to get a clearer picture of the subtle changes in topography and emphasize vertical relief and slope steepness. In order to calculate vertical exaggeration, divide the real world units of horizontal scale by the real world units of vertical scale. Make sure same units are used in numerator and denominator of the division. By using a ruler, you can transfer these elevation points from your topographic map straight down onto your graph paper such as shown in Figure 3.

Be sure to only plot those elevations that are at the intersection of the contour line with line A-B. Once your points are plotted on the graph paper, you simply connect the dots. As a rule, hilltops will be slightly rounded to show a slight increase in elevation to represent the crest of the hill, but be careful not to draw the hilltop too high on your graph paper. For example, the first hill on the left has a top contour line of 50ft. The elevation interval between the contour lines is dependent on the level of detail provided by the map and the kind of topography present.

For example, regions with significant topographic variation might require contour lines separated by ft. To an experienced user of such maps, the patterns made by the topographic lines are representative of various landform patterns, such as ridges, valleys, hills, and plateaus. Although modern three-dimensional imagery e. In contrast, a topographic map can provide a distortion-free source of information regarding altitudes for discrete points over the entire map area.

The ability to extract dependable elevation data for any point on the topographic map allows for the construction of topographic profiles. These are cross-sectional views perpendicular to the standard plan-view or map-view that define a continuous series of elevations along a line, connecting two points on the map. The topographic profile is a graph of elevation y-axis versus distance x-axis between the two defined points on the topographic map. This graphical profile allows one to effectively see the land surface from an "edge-on" view that shows how the land surface rises and falls along a hypothetical line, joining two points on the map.

The perspective of the topographic profile is very useful; it provides a starting point for making geologic cross-sections that project rock structures or layers into the subsurface. Subscription Required. Please recommend JoVE to your librarian. Topographic maps are a standard map view that provides aerial perspective and three-dimensional representation of the Earth's surface.

These can be used to generate side-on views of the land, also known as topographic profiles. When planning roads, railroads, pipelines, or hiking trails, topographic profiles can be a valuable tool to inform the professional or recreational user of the terrain in a target area. Among the defining features of topographic maps are the contour lines, which notate elevation. These lines convey three-dimensional information, and can inform the map user of various landform patterns, such as ridges, valleys, hills, or plateaus.

In topographic mapping, maps produced can vary in detail and scale, often dependent on the subject terrain. The elevation interval between the contour lines is one aspect that may vary. For example, in regions with significant topographic variation, maps may use contour lines of 40 to feet. In generally flat-lying areas with little variation, maps may use more broadly separated 10 to 20 foot contours. The precise composition and ability to extract dependable elevation data for any point on the topographic map allows for construction of topographic profiles.

These "side-on" cross-sectional views are constructed using a line established between points, and recording contours crossing this line. The subsequent data is plotted as a graph of elevation, with elevation plotted on the Y-axis, and the contour crossings along the X-axis. When these points are joined, this allows the user to see how the surface rises and falls along this hypothetical line.

Depending on the intended use of the map, vertical exaggeration can be applied to the Y-axis. This can be beneficial in scenarios where the topographic profile is being utilized to show the ruggedness of the terrain. In scenarios where the primary use of the topographic profile is to project geologic features or cross-sections, vertical exaggeration is best avoided.

Topographic profiles can be extremely useful, and provide a starting point for making geologic cross-sections that project rock structures or layers into the subsurface.

In a very general sense, we find that ridges are composed of resistant rocks and valleys are composed of less-resistant, easily eroded rocks. Now that we are familiar with topographic maps and making topographic profiles, let's take a look at how this is carried out.

The first step in making a topographic profile is to obtain a topographic map. These can be generated by the scientist, or gathered from a geological survey agency. Once an appropriate map has been selected, topographic profiling can be started. Establish a line between two points that intersects the region of interest on the map. These should be labeled as A-A'. Take a strip of paper, and lay it along the cross section line between the two points.