How to Read a Topographic Map.

One of the important essentials that are commonly overlooked is how to read a topographic map. Most are content with a trail map, but topo maps provide far more detailed information that can be extremely valuable in the wilderness. The major thing they provide is something called contour lines, you know, those squiggly circles and numbers that many may not pay much regard to. Well, those days are over, because we are diving in to how to interpret them and it may benefit you on your next adventure.

Even before you understand them, your brain is drawn to maps. – Ken Jennings

If you visit a national or state park, you will undoutedly run into a trail map. They are useful for trip planning but do not provide the in depth perspective of what you will be navigating through if you decide to venture away from the general population. Topographic maps take things a step further and introduce contour lines which provide you with a three dimensional view of what is ahead. This allows you to visualize more and determine what will be the best route.

So how do counter lines work?

For perspective, lets take a look at a topographic profile for a volcano.

  • Gradual slopes – On the ride hand side you can see the contour lines have more space between them. This lets you know that the right side of the volcano is a gradual slope and will be easier than the left side to travel up.
  • Steep slopes – The left hand of this profile tells a different story. The contour lines are very close together and indicate steep elevation changes which may be tricky to traverse.
  • Peaks – If you are trying to get a high vantage point, are a summit bagger, or want to avoid steep ascents, peaks are indicated by small closed circles. You can see a few on the top of the page. They are also accompanied by tighter contour lines signaling the incline.
  • Shape – Contour lines also show you the character of the terrain. You can easily visualize the shape of the land and visualize the aspects to navigate effectively.
  • Passes – The area between the two peaks in the center is called a pass. The elevation would be 6,000 feet in that area as it plateaus before the steep incline to the two summits.
  • Contour intervals – the numbers on the lines provide you with the elevation above sea level. The legend of your map will provide you with the specific intervals. This example here has each contour line being 1,000 feet higher than the prior.
  • Contour Loops – The best way to think about a contour line is as a closed loop. If you were to hike on a contour line, you would not hike uphill or downhill, and would eventually make it back to the starting point.

 

A map, it is said, organizes wonder. – Ellen Meloy

A Few Other Useful Map Details

Look closely at the map legend. It’s loaded with map-reading clues and navigational data. Start by studying what each line, symbol and color means. Generally, darker colors mean denser vegetation, while light or colorless areas suggest open terrain. And, as you’d expect, streams and lakes are shown in blue.

REI Expert Advice: How to Use a Topo Map - detail of a topo map legend

The legend also lists key data like the map’s scale, contour- and index-line intervals, grid systems (used for more advanced navigation) and magnetic declination (needed to set up your compass).

REI Expert Advice: How to Use a Topo Map - practice reading features from a map

Practice reading features from a map of a familiar area. Visualize how the terrain on the major landmarks relates to the contour lines on your map. Pick out features like peaks and passes. Identify subtler features like valleys: They’ll have a series of U- or V-shaped contour lines pointing toward a higher elevation. This is easier to spot if a valley has a stream because its blue line bisects those contour lines.

Hone your map-reading skills on every trip. Pull it out at the trailhead, orient it correctly (see How to Use a Compass for details) and mentally check off landmarks as you hike. Regular map readers rarely get lost.

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