How Do You Make a Contour Map?
Contour maps are brilliant in their innate storage of information. Learn to read them and they quickly become a decipherable visual metaphor for the natural features of a landscape. It is this surprising ability that makes knowing how to plot your own contour lines such a useful skill. There is no better description of a landscape's features than a full understanding of its topography.
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Instructions
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Pick an existing map to build contours on to---preferably a small plot of land you will have constant and easy access to. While the piece of land to be mapped can be of any shape or size, developing contours for a rectangular plot would likely be the most instructive.
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Beginning at the property's corner, mark out a 9 by 9 foot square. Place stakes down in each corner and create a border of string.
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Measure the total change of elevation within the square. Begin at the highest spot. Place one corner of a bubble level at the highest point, then point the other end of the level toward the lowest point in your plot. Raise the level until the bubble indicates levelness. Measure the distance to the ground using the yardstick. Once again point the level toward the lowest elevation, except using where your yardstick touched the ground as the new origin point. The total of all measurements should be the total elevation change from the plot's highest to lowest point.
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Divide your total height change by the number of contour lines intended per nine feet to produce your contour interval. A reasonable number for a 9 by 9 foot square could be four different contour lines. If your total elevation difference was 20 inches, divide this by five (not the number of lines, but the number of segments or strips that would exist if you were to apply those lines) to reach a contour interval of four inches. This number, the contour interval, will guide the plotting of your contour map. No matter how great or small the difference between two contour lines, it will represent an elevation change of four inches.
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Plot your contour lines, beginning at the highest corner. Begin by measuring down the vertical border into what you have measured four inches of elevation change. Put down a stake. Return to your origin corner and do the same measurement for the horizontal border. You will now have the points where your first contour line enters and exits the plot.
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Return to your origin corner and measure out straight lines until four inches of elevation change has been achieved. The more lines you measure radiating from the origin point, the more points you will be able to plot along the contour line between the two markers made in the last step. This is where you determine how precise your contour lines will be shaped on the final map.
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Use any point on the first contour line as an origin point for plotting a point on the second contour line. If you have ten different plotted points from the first contour line, measure out four inches of elevation change from each plot point and plot an equivalent point on your second contour line.
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Tips & Warnings
You can also use contour lines to plot other phenomena such as weather.
