Using a Topographic Map
Use the resources below to gain a better understanding on how to read and use topographic maps.
- Learn how to identify common topographic symbols with this feature-by-feature visual guide
Use the resources below to gain a better understanding on how to read and use topographic maps.
The surface of the earth is not flat, but a two-dimensional map is. The strategy for converting the planet's hills and valleys to a flat piece of paper involves all the little brown contour lines on a topographic map. They indicate topography – the shape of the land.
A contour line joins all the places of equal elevation. The value of a contour interval depends on the map. Every fifth line is usually an index contour line. It is heavier and has an elevation reading along it. By subtracting two elevations and dividing by the number of intermediate contour lines between them, you can determine the vertical distance between two adjacent lines. In flat landscapes that may be 10 feet. In mountainous areas it may be 100 feet.
The way the lines are drawn indicate the shape of the land. Ridges and valleys, peaks and flat land, saddles (the low part between two hills), and depressions (noted by hatch marks inside a contour line) can be interpreted from the lines on a map.
You can practice converting shapes to topographic lines. Imagine a basketball. Cut it in half. Place the cut side on the floor. If you were to connect all the points on the half-sphere that are the same distance above the floor, you would draw concentric circles around the outside of the ball. If you put all those circles on a piece of paper, what would it look like?
If you turn a wastebasket upside down and did the same thing, what would it look like? Which drawing looks more like an upside down kitchen funnel?
When the shape is steep, the lines are closer together. When the increase is very gradual, the lines are farther apart. When the shape is flat, there are no lines. Why?
Each topographic map has a legend that indicates the correlation between inches on the map and inches in the real world. A 7.5 minute map (indicating the latitudinal distance covered in one map) usually has a scale of 1:24,000, or 1 inch on the map equals 24,000 inches on the ground (24,000 inches equals 2,000 feet).
The legend also provides a scale (which resembles a ruler) that shows miles, feet, kilometers, and meters. You can use this scale as you would a ruler to determine the straight line distance between points on a map.
The Air and Waste Management Association created a number of delightful classroom exercises to teach some basic concepts. This activity - called Watershed Woes - helps learners understand topographic maps, to identify a watershed. Many of their explanations are useful for teaching youth to read the topographic lines in a map.
This worksheet is a useful quiz to help learners review map symbols. It comes from the Air and Waste Management Association’s Watershed Woes activity.