In order to find out where they are going, mushers need a map. A special kind of map called a topographic map, which contains the towns and check points, rivers, and mountains also gives more information about the flat surface on the trail.
The closer the contour lines are the higher the slope is. The farther the lines are the flatter the ground is.
The mushers do not only use the topographic maps to find the next check point. They can also try to figure out what kind of terrain they will be traveling on and make a plan.