Believe it or not, travelers weren’t always blessed with the convenience of global positioning systems to help guide the way. Especially before this land was truly developed, it was up to surveyors and cartographers to develop the very first maps detailing our nation’s landscape to those wanting to build everything from railroads to the towns that surrounded them. And in a more leisurely fashion, these maps were then used by hikers, campers, and all-around explorers with the sole purpose of navigating through unfamiliar terrain. We’re talking of course about topographic maps.
For those who aren’t aware, topography maps are a two-dimensional means of viewing three-dimensional landscapes. Thanks to the useful tools and symbols used to designate land formations, river, lakes, and streams. However, the ubiquitous nature of smartphones and GPS systems has taken the challenge and – to be honest – the fun out of exploring your local backcountry landscape. To the untrained eye, these maps look about as confusing as they come. But to the experienced hiker, these brilliant maps come alive through their mind’s eye, revealing what lies ahead, and how to navigate that seemingly impossible rock formation. Want to learn the basics? Not a problem. We’re here to help.
Your New Best Friend
Before you begin to dissect what a topographic map is showing you, there is one very important feature that you must understand. We’re talking of course about a map’s contour lines. These are the thin lines that make a topographic map so special and their job is to convert a three-dimensional landscape into a two-dimensional map. That is to say, contour lines represent certain elevations on the earth’s surface.
To make this easy, it’s important to remember that there are several rules surrounding contour lines that we must follow. First, all points along the contour line will be of equal elevation. Next, that each contour line will form a circle (albeit an imperfect one most of the time). Also, contour lines will never intersect on a topographic map. And finally, the steepness of the terrain is dictated by how tight contour lines are to one another. In this instance, a gentle slope is represented by contour lines that are spaced out while a steep mountain or cliff face will have a bunch of contour lines stacked next to each other in a tight manner.
It’s also important to understand the types of contour lines you’re reading for not all lines are considered equal. For example, typically every fifth contour line will be bolded with the elevation depicted somewhere along the line. These are called indexed lines and are used to reference the elevation of the surrounding lines. Lines in between these indexed lines are referred to as intermediate contour lines. Also, if the terrain is quite flat like you’d find in a coastal plain or in our nation’s midsection, cartographers will develop supplementary contour lines. These are dashed lines that represent the terrain that is half the elevation between the contour lines surrounding them.
Again, here’s a brief example of the types of contour lines you’ll see across at topographic map. Notice how the only lines depicting elevation are the Index and Depression Index lines.
More Than Just Aesthetics
In addition to contour lines, topographic maps will feature specific map colors to denote surface features across a specific landscape. These, naturally, will be a bit more self-explanatory than the contour lines since cartographers aren’t out to reinvent the wheel in common color association. With that in mind, you’ll notice that the color green is used to denote vegetation such a forest and blue will naturally represent water features like lakes and rivers.
Also, for mountainous regions that may be snow capped year round, contour lines are drawn in blue as opposed to the widely accepted and utilized brown. Also, in accordance with human influenced landscapes, black will represent man-made objects such as trails while red denotes man-made features like roads and state boundaries.
It’s also important to pay attention to your maps legend. These handy little sections often located at the bottom of your map will ascribe meaning to all sorts of symbols and lines on the topographic map that might not currently make sense. Also, here is where you’ll find the scale, which is a very important feature to understand when mapping out a hike. Here, most scales will be in inches. That is a scale of 1:64,000 means that every inch on the map represents 64,000 inches in reality. Naturally, the smaller the scale the more detailed each map becomes.
Fairly self-explanatory, we should emphasize the importance of understanding some of the universally accepted symbols for bodies of water and partially submerged ecosystems in the form of wetlands. Otherwise, that 2-hour hike could easily double thanks to unforeseen obstacles.
Know What's Out There
In addition to map colors, you’ll find various shadings placed sporadically on the map face. And while this may appear random in nature, we can assure you they aren’t. Understanding the shadings outlined on each topographic map is crucial for gaining an idea of what landscape lies ahead. For instance, certain shadings will represent a marsh or swamp, wooden marsh, or submerged swamp for starters. However, there are a handful of other important shadings that are outlined in USGS Topographic Map Symbols document that we suggest you keep on your person at all times in addition to whatever topographic map you’re carrying.
Knowing these three basic will then get you properly introduced to utilizing a topographic map correctly. However, there’s no better way to become comfortable with these handy tools than real world application. Bring them alongside a GPS to start and see if you can navigate without the use of technology, knowing that safety net is there if you need it. Understand the surrounding terrain and how the map depicts changes in elevation and landscape by finding your position on the map and correlating the maps interpretation of the land to your surroundings. Soon enough, the map will come alive, allowing you to visualize a top-down three-dimensional landscape from a piece of paper. It’s what makes these navigation tools so useful.
For a brief summary, outdoor gear powerhouse REI put together this fantastic video covering all the basics you should know when reading a topographic map.
Survival Skills For When The Going Gets Rough
Sometimes even a Topographic map isn’t enough to get you out of a hairy situation. Best brush up on some basic survival skills ahead of time.