Topo maps use concentric “contour lines” to show elevation changes, and help people navigate mountains and wilderness areas. The denser the contour lines appear, the steeper the terrain. Topographic maps also tend to show a wealth of natural information, like markings for trails, springs, forests, and swamps, though they tend to include roads as well.
In this post, you’ll learn how to read a topo map, as well as how to use topos to plan outdoor adventures. We touch on a variety of topo maps, including United States Geological Survey (USGS), U.S. Forest Service (USFS), and OpenStreetMap (OSM) topos.
Comparing Topo Maps
| Overview | Features | Coverage & Units |
|---|---|---|
USGS Topos (Classic)
The industry standard for topographic information. Possibly still the best topo for hiking. |
MayContours are toned down compared to newer USTopos, making other features easier to see. |
Feet* Covers the US |
USGS Topos (USTopo)
“Born digital,” next-generation USGS topo maps published since 2009. Based on seamless digital data, but presented in a familiar quad format. These often have fewer features and less detail than legacy USGS topos. Revised every 3 years. |
Can be missing trails, remote roads, campgrounds, survey markers, and boundaries. |
Feet* Covers the US |
FSTopo
USFS-based topos with forest-related enhancements. Often more detailed and up-to-date than USGS topos. Only available for quads containing National Forests or Grasslands. |
|
Feet* Covers US National Forests |
The National Map
MayService provides a seamless view of USTopos for use in apps and on the Web. |
May be missing trails, remote roads, campgrounds, survey markers, and boundaries. |
Feet* Covers the US |
OpenLandscapeMap
MayStyles OSM data to accentuate natural features. Good for rural and backcountry areas. |
|
Meters Global |
OpenCycleMap
Styles OSM data to enhance cycling features. |
|
Meters Global |
OpenHikingMap
Styled OSM map for hikers. |
|
Meters Global |
Gaia Vector Topo
Worldwide topo map based on OSM data, styled like USGS topo maps. |
|
Feet Global |
*Meters in Puerto Rico
What are Topo Maps Used For?
Topo maps provide a bird’s-eye view of a particular area and help you orient yourself in the landscape based on local landmarks. An essential tool for backpacking, hikers use topos to avoid very steep ascents, figure out how to split up multi-day hikes, and determine the right amount of supplies. Topos can also indicate the need to ford a stream, as well as warn you away from dangerous areas like mines, depressions, bogs, and submerged rocks in lakes and streams.
More than just a tool for recreation, topo maps serve conservationists, firefighters, and other professionals who either study the environment or work outdoors. Architects and planners also use them to assess potential build sites.
How to Read Elevation Contour Lines
Contour lines indicate changes in elevation—they act as a 2D tool for visualizing landscapes in 3D. Contour lines show the shape of the terrain, including its hills, slopes, and depressions, by connecting points of equal elevation. If you follow a line, you’ll stay at the same elevation. When you cross a line, elevation either goes up or down.
Think of contour lines as imaginary horizontal planes sliced through the terrain surface. It may be helpful to visualize them as stacked “layers” of the landscape, similar to a layer cake. Lots of contour lines clumped together mean a lot of elevation change, or a steep slope. A large mountain appears as a dense group of lines with a small circle in the center that represents the peak—just picture looking down at a wedding cake from above. Areas with few contours appear relatively flat—more like a 2-tier birthday cake.
Cartographers often use brown hues for contour lines, and they label every fourth or fifth line with the elevation it represents to serve as an “index contour.” They often style index contours thicker or bolder, to make them easier to see. The non-index contour lines give more detail about the landscape, but lack labels usually.
The contour interval, or amount of elevation change between each line, varies from map to map. To figure out the interval, look at the labels for two consecutive index lines and subtract the lower number from the higher number. If the map labels every 5th line, divide by five. For index lines occurring every 4th line, divide the difference of the two numbers by 4.
In addition to contour lines, some modern topos like OpenCycleMap add hill shading, which makes it easier to visualize the terrain in 3D.
Features on Topo Maps
Best known for emphasizing naturally occurring features such as mountains, streams, springs, and land covers, topographic maps also show administrative boundaries, roads, churches, cemeteries, rail lines, and campgrounds.
Topos utilize colors, patterns, and symbols to indicate different features. USGS maps, for example, use light green for parks, light blue for water, brown for contour lines, bright red for major highways, and dashed black or gray lines to represent trails. Typically these features have labels of the same color.
To learn more, check out our post about USGS and other U.S. government topos.
Classic 7.5 minute USGS topographic map for Manitou Springs, Colorado, 1961. Credit: U.S. Geological Survey.
OpenStreetMap-Based Topos
OpenStreetMap (OSM) crowdsources detailed maps of the world. Many apps and websites stylize OSM-based data to accentuate specific features specialized for a particular audience.
Drawn in a modern style, OSM-based maps offer a higher resolution that increases zoom potential. OSM-based sources often have more details and more feature types than newer USGS topos, such as improved trail coverage. Note that while USGS typically labels elevations on the 1:24,000 scale maps in feet, OSM-based maps are labeled in meters.
To learn more, read our post on OpenStreetMap-based Topo Maps.
Gaia Vector Topo
Gaia GPS develops a worldwide topo vector source based on OSM, styled like the USGS topos. Unlike other tiles-based sources, vector maps get styled and drawn directly to the device. Because the map gets rendered locally, it appears crisper when zooming, and provides better text readability—the smaller download size doesn’t hurt, either.
Now that You Know How to Read a Topo Map
We encourage you experiment with all of these sources in Gaia GPS as you plan your next adventure. Follow the iOS and Android links throughout this email to view our Knowledge Base articles about adding these map sources in the app.
If you have any questions about using topos in Gaia, just email us at support@gaiagps.com.
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