How to Read a Topographical Map

Learning how to read a topographic map can be rather cumbersome depending on the complexity of the map, therefore we normally ignore it and revert to our typical road-map or GPS devise which is normally sufficient for most purposes. However, there are instances where ignorance of a topographical map could ultimately cost you your life.

What is a Topographic Map? The map is a representation of the Earth, or section of it. The distinctive characteristic of a topographic map is that the shape of the Earth’s surface is shown by contour lines. Unlike a road-map or GPS devise, which shows you where you are on earth, possibly to the exact spot your two feet occupy in the dirt, a topographic map is a representation of the earth looks like where your two feet are standing.

Let’s back up and look at an example of where knowing how to read a topographical map could save your life:

You are stranded in what appears to be a vast prairie. You’re not actually lost because your GPS devise has pinpointed your exact location and you have plotted your map, which shows if you travel 20 miles in any direction, you will run into one of several major highways that crisscross the area. So where does the importance of a topographical map come into play?

Had you been able to read it, the map would have told you there was actually only one direction you should take in order to be rescued, North.

Beyond the horizon of the flat prairie a Southern direction takes you into a massive number of rolling hills, some rather high and difficult to climb, all exhausting and time consuming. Depending on your resources or weather, the delay and unexpected over exertion could pose a deadly threat.

The Western direction slopes into deep ravines and barriers carved from the meandering path of an ancient river. Climbing down into a ravine in order to cross it may end up being your grave if you can’t climb back out.

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The Eastern direction appears quite promising as it contains gentle prairie, easy to transverse, until suddenly two miles from reaching your destination, the highway, mountains erupt into the sky blocking any access past them and requiring you to turn completely around and return to your original position.

Three of the four directions could result in injury or even the possibility of death, while only the fourth, Northern direction maintains the gentle prairie landscape all the way to the highway. What’s the chances you’ll randomly pick the right direction? That’s when a topographical map can save your life.

MAP SYMBOLS

First lets recognize that map symbols are color coded. Symbols in green indicate vegetation, symbols in blue represent water, brown is used for topographic symbols, man made features are shown in black or red.

Contour Lines

Contour lines are lines that indicate elevation. These are the lines that show the topography on the map. Contour lines are shown in brown. Two types of contour lines are normally shown. Regular contour lines are the thinner brown lines, index contour lines are the thicker brown lines. The numbers written in brown along the contour lines indicate elevation of the line. Most map elevation is in feet above sea level.

Forests and Clearings

Forested areas are represented by areas shaded green; Areas that are not forested are left nun-shaded (white). Note that not all topographic maps show forests. Also note that this information is not always up to date or accurate. I have struggled to walk across densely wooded areas in places that have been mapped as “clearings” as well as indicated densely wooded areas that had been deforested by clear cut logging.

Streams

Streams and other water features are shown in blue.

Roads and Trails

Man made features are shown in black or red. Trails are represented as thin single dashed lines. Roads are represented as double lines or thicker red lines. A series of symbols are used roads to indicate road quality from double dashed lines for dirt roads to thick red lines for major highways.

Buildings

Like other man made features buildings are shown in black. Solid squares usually indicate buildings that would be inhabited by people (a house), hollow shapes usually indicate uninhabited buildings (for example, a barn) (Note this may not hold for maps in the future because it is not possible to determine what a building is used for from the aerial photos used to make the maps). Larger buildings, like factories, are shown by larger shapes that outline shape of the building, and cities with closely spaced houses are shaded pink instead of showing individual houses.

Boundaries

Even though these are not physical features you can see on the ground, boundaries are shown on topographic maps by black or red lines. Boundaries are usually represented by broken lines (combinations of dots and dashes of different sizes). Different patterns are used for different types of boundaries (state, county, city, etc).

Bench Marks

Bench marks indicate places where the elevation has actually been surveyed. These locations are indicated on the map by a triangle if a marker has been placed in the ground, or an “x” if not marker was left behind. Near either symbol are the letters “BM” and a number which represents the elevation of that particular location. Bench marks are shown in black on topographic maps.

University of Mount Union Geology provided the Map Symbols information

How to read a topographical map is no easy task. I’m not suggesting you take a college course to learn, but you need to familiarize yourself with a few of the basics so you at least know where to begin looking for dangerous terrain if nothing else.

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