Facts About Topographic Maps

by Ethan Shaw

Topographic maps, two-dimensional depictions of terrain, are invaluable tools for outdoors enthusiasts--and beautiful pieces of art.

Scale

A topographic map’s scale fraction or ratio refers to any measurement unit. On a map with a scale of 1:12,000, one inch on the map equals 12,000 inches in the actual depicted terrain, just as one map foot, one map centimeter, and so on would equal 12,000 feet, centimeters, and so forth on the ground.

Contours

Contour lines are the foundation of the topographic map. Along the length of any given line, the elevation remains the same. Some contour lines will be labeled (in feet or meters) as references. Closed contours represent summits, and ones with hatch marks represent depressions.

Intervals

The map will provide a contour interval, which refers to the vertical difference between two adjoining lines. A smaller contour interval--one of 500 feet, say, instead of 2,000--will show greater detail.

Maps and Geology

You can make an educated guess about an area’s underlying geology simply from the contours of a topographic map. For example, a highland with a very steep scarp on one edge and a gradual slope on the other might suggest terrain dominated by faulting.

Navigation

Topographic maps, when used with a compass, are essential for backpackers, hunters, and others navigating in roadless wilderness.

References

  • "Interpretation of Topographic Maps"; Victor C. Miller, Mary E. Westerback; 1989.

About the Author

Ethan Shaw is a writer and naturalist living in Oregon. He has written extensively on outdoor recreation, ecology and earth science for outlets such as Backpacker Magazine, the Bureau of Land Management and Atlas Obscura. Shaw holds a Bachelor of Science in wildlife ecology and a graduate certificate in geographic information systems from the University of Wisconsin.