How To Find Vertical Exaggeration On A Topographic Map

How practice I construct a topographic contour?
Connecting points to make a smooth curve

Other parts of this resource on graphing have you through plotting points and constructing a straight line through data points. If you aren't sure how to plot points on a graph, please make sure you lot visit and piece of work through the plotting points tutorial before moving on with this part of the graphing pages. This page is geared toward thinking about the shape of landscapes and pretty unique to geoscience courses. There are other instances in mathematics and graphing where a smoothen curve is necessary (eastward.g., exponential curves, sine waves, etc.); this page is focused on a specific instance when you volition construct a topographic contour from a two dimensional map.

When working data with topographic maps, topographic profiles and their construction, we frequently inquire you to connect data points with a smooth curve. In such instances, you will exist asked to plot some points and connect them with a shine line. This is different from the plotting of a best fit line because it involves extrapolation of information from spatial data. In the example of constructing a topographic map, y'all must extrapolate the placement of the appropriate tiptop profile. For topographic profiles, you must extrapolate the contour of the landscape (that is, whether it goes upwards or down) when faced with repeating elevation contours.

When should I construct a contour?

In introductory geoscience courses, a contour is appropriate when you are asked to construct a cross-section or profile. Topographic profiles are used to empathize what a topographic map is telling you lot in a specific area (or, yous can call up near information technology similar it is giving y'all a "side view" of the landscape along a specific line on the map). Interestingly, many geologists are quite visual and like to take visual representations of data. Considering maps are two-dimensional simply represent three dimensions (that is, topgraphic maps are flat with lines that stand for hills and valleys). Professional geologists use exercises such equally the ones yous volition practice with below to aid you (and us) visualize a two dimensional cross-department of what the land surface looks similar (from the side) - giving you a slice of the 3rd dimension. In other words, profiles aid you lot to empathise what a topographic map is telling us about hills and valleys forth a particular line.

How do I construct a topographic contour?

Examine the topographic map image to the left (y'all tin click on the image to make it larger or you tin download the map and a profile (Acrobat (PDF) 2.3MB Jul18 xi) to attempt the steps below on your own). Before you start, you might desire to review some of the rules about topographic maps before standing (you can notice rules at Idaho State U.'southward field exercise, U. of Montana labs and U. of Memphis Topo Lab).

To construct a topographic profile, you need to find a line on a map that is interesting. In many cases, this line is given to y'all (often labeled something like A-A' or A-B). The line should go through some part of the map that you are interested in, and then that you lot go useful information. The following list provides some guidelines for effectively constructing a topographic profile and uses the topographic map and profile line provided to the left (y'all can download a pdf of the map and profile to work from (Acrobat (PDF) ii.3MB Jul18 11)):

1. Sketch in the line on the map or locate the line that is provided.
   
2. Place the edge of a blank slice of paper forth the line and marker the starting and ending points of the line (characterization them with A and A', or whatever the given line is labeled).
   
3. Beginning at one cease (perhaps information technology'south the A finish) and move along the edge of the paper, making a mark on the newspaper every time a contour line touches the edge of the newspaper. Make certain you label each mark with the right summit so that you can transfer that point to the correct height on your profile. (If you get tired of marking every elevation contour, you can just characterization the index (darker) contours and the places where a profile line repeats). You may as well want to mark where rivers or streams occur.
   
4. Take note of the highest and lowest tiptop you tape for after.
   
5. In this case, we have marked the graph paper with the appropriate lines, but you lot can also find a random slice of paper and marker the distances betwixt contours on a line that you've drawn. If this is the case, yous will need to detect a piece of graph paper (or a paper with all horizontal lines) that is at least as long every bit your contour line (you lot tin can paste more than i piece together but make certain you line up the grid lines).
   
6. Draw a horizontal line on the graph paper that is the length of your profile line. Draw vertical lines above your starting and ending points. Label the y-axis (vertical lines) with elevations making sure that your scale goes from highest to everyman on your cross-section (see pace 3). For example, if your lowest elevation is 4200 feet and your highest acme is 7600 feet, you lot might want to label your axis going from 4000 to 8000 feet.
   
7. Line upwardly your tick marked paper with the bottom of the graph (or utilise your marked graph paper) and, beginning with the tiptop on the left hand side of the paper, get directly upwardly from that tic marker to make a small dot at the corresponding tiptop. Note that the point does not need to exist on a vertical line on the graph paper.
   
8. Once you have transferred all of your tick marks to your graph, connect the dots with a smooth curve.

   If you aren't sure why it should be a smooth curve, here are some pointers most how to think about this profile.

   

Where are smooth curves used in the geosciences?

Topographic profiles are used in many applications in the Geosciences. Some of the topics where you will need to recognize and draw a topographic contour are:

• topographic maps
• earthquakes
• structural geology (and geologic cross-sections)
• glacial geology
• coastal geology
• geomorphology

Adjacent steps

You have completed the steps for constructing a topographic profile! Now y'all can move on and practice with some other information on the sample issues page.

If you would like to know more than almost smooth curves and topographic profiles, you can use the links beneath.

References and resource

Several universities have tutorials for how to construct a topographic profile. Here are just a few:

• Academy of Wisconsin Stevens Signal has a flash animation to walk you through the construction of a contour.
• Idaho State University has step-by-pace instructions for constructing a topographic profile.
• University of Texas at Austin has stride-by step instructions and an caption of vertical exaggeration

Source: https://serc.carleton.edu/mathyouneed/slope/topoprofile.html

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