Ever wonder how to read a topographic map? Our video has the answers or check out the text version below.
What are all those wiggling random lines doing on your map? Those are contour lines and you are looking at a topographic map commonly shortened to just a topo map. These lines provide a way to show elevation, a third dimension, on a flat two dimensional map. This is possible because each contour line represents a specific elevation. Darkened contour lines have their elevation labeled on the map itself. The lines between them are set apart at intervals defined by the key at the bottom of the map. The easiest way to understand how these work is to look at some hill tops or mountain peaks. I’ll use Sugar Loaf Mountain since it’s general cone shape makes it pretty easy figure out contour lines. When you are looking at a topo map, down on a hill top, you can see the smaller circles represent the hill getting taller and taller and you can imagine what the hill actually looks like. Notice that the closer together the contour lines, the steeper the hill. So now you should be able to look at any topo map and point out the hill tops and summits, but there are other terrain features that you’ll need to know to complete the picture.
The first is a ridge. A ridge is a long narrow section of higher ground with lower ground sloping away. On a topo map look for contour lines that form a “U” shape. The bottom of the U will be pointing downhill. Ridges may connect several hilltops or they may slope gradually down in one direction. Smaller ridges are also called spurs or fingers. The next terrain feature is the drainage. A drainage is the path that water follows when it falls on the ground. A drainage can be called a valley, draw or a canyon depending on the amount of water flowing through it and the steepness of its sides. On a topo map look for a blue line that marks the path of the water. That is the first giveaway. But many seasonal streams may not have a blue line, so also look for the “V” shape in the contour lines. The bottom of the V will point uphill. The next terrain feature to learn is the saddle. A saddle is nothing more than the low ground between two higher points. On a map look for two hill tops or just two pieces of higher ground with a low point between them. A saddle is sometimes called a pass since it is usually the easiest way to get over a mountain. The final terrain feature I’ll talk about is the cliff. On the map, look for a place where contour lines become very close together to the point where you can’t tell one from the next. This indicates an extremely steep slope and is the tell tale sign of a cliff. Knowing how to read a topographic map will help you plan your routes to avoid going up and down hills all day and it will also help you figure out or confirm where you are at any given time. Check out more from our Navigation Skills series here.