Knowing how to correctly read a topographic trail map can help keep you safe in the wilderness. Before you embark on that wilderness adventure, learn the basics.
Practice. Take time to familiarize yourself with topographic maps before you head into the wilderness. Reading a topographic or trail map is not the same as reading a standard road map. A road map lists major streets, highways and important geographical features. In addition to representing the features of a standard road map, a topographic trail map uses contour lines to show elevation, trails and other significant man-made or natural landmarks of interest to a wilderness camper, hiker or adventurer.
Learn the symbols. Each map should have a legend that explains what each symbol represents:
- Colors. Colors play an important role in reading a topographic map. Green is used for vegetation. Blue is used for bodies of water. Red or black are used for man-made features. Brown is used for topographic symbols. Always look at the individual map legend to confirm what each color represents.
- Contour lines. The United States Geological Society (USGS) defines contour lines as “lines that join points of equal elevation,” making it “possible to measure the height of mountains, depths of the ocean bottom, and steepness of slopes.” There are two types of contour lines: regular lines and index lines. Index lines are dark brown and are accompanied by elevation numbers. Regular lines are light brown.
- Roads and trails. Trails are normally indicated by a light red dashed line. Roads are normally in the form of thicker red lines or double lines. Road quality also is represented by the type of line. Look at the map legend for details.
- Buildings. Inhabited buildings are indicated with a black, solid square. Uninhabited buildings are indicated by a hollow black square.
Learn the basics. The Geospatial Training and Analysis Cooperative (GTAC) explains the basics of how to read a topographic trail map:
- Every point on a contour line represents the same elevation.
- Because each line represents a different elevation, contour lines never cross.
- Contour lines may merge, indicating cliff faces.
- Moving from one contour line to another represents a change in elevation. Use the map index to determine if the elevation increases or decreases.
- Contour lines that are close together represent steep slopes.
- Consistently spaced contour lines represent a steady slope.
The importance of familiarizing yourself with the map legend cannot be stressed enough. In addition, no matter how good you are at reading a topographic trail map, it may be of little use if you’re not carrying — and capable of using — a compass.