Unlike a road atlas, a topographic map includes contour lines to portray the shape and elevation of the land. Hence, a topographic map defines the topography or lay of the land. Maps come with in a variety of scales. On some, one inch represents one mile or on a more defined map one inch may represent only a quarter of a mile. At the bottom of the map, there is usually a scale that you can use as a reference. Depending on the scale of the map the contour lines represent varying distances from 100 feet to maybe 40 feet or less. As an easy rule of thumb, the closer the lines, the steeper the terrain.
Once you have the correct map, the first step is to orient it to the terrain. This is where your compass comes in. A good compass can be very simple with a magnetic needle and a bezel (the dial with markings for 360-degree increments). We recommend a compass with at least one flat or right angle to line it up on the map. The compass can be used for many navigational reasons, but primarily it helps you to align the map or “orient” it in the appropriate direction, i.e., the top of the map to North. A map does little good if you have it slightly off, let alone upside down. Here is where the compass gets a bit complicated. The needle in the compass does point North, however, it points to magnetic North. The map however is drawn to true North. This difference is called declination. Because of a variety of issues declination can be off 10 degrees or more depending on where you are in the world. For example, Eagle, Colorado is nearly plus 10 degrees from magnetic north. As you might imagine, this small oversight can lead to big navigational mistakes.
Although the terrain may be very rugged, maps are drawn to right angles for a reason. Step one is to align the compass so that it is parallel to the grid lines drawn on the map. In western Colorado, you must then turn the map so that the needle on the compass points to +10 degrees in the compass bezel. Your map is now adjusted for declination to true North. When you finally look up from the map to the field, or the terrain around you, features such as rivers, mountains and gullies will be directly in line to how the map is laid out.
For more information and a more detailed description of navigation, check out REI’s navigation basics.
Additionally, an introductory course at a local outdoor shop will really help to improve your understanding of maps and navigation.