Understanding contour line formations and also how to check out topographic maps.Updated: November 6th, 2020


What space Contour Lines and Topographic Maps?

Ever i found it those squiggly lines all over your long walking map? other than the noticeable trails and also rivers, this squiggly lines room contour lines. 

Put simply, contour lines note points of same elevation top top a map. If you trace the length of a line v your finger, each suggest you touch is the very same height over sea level. If you to be to to walk the path of a contour line in real life, girlfriend would continue to be at the very same elevation the whole hike, never ever traveling increase or down.

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Contour currently are an important to understanding the key profile of your terrain or a particular land formation. This information deserve to be beneficial when picking a long walking route... Or lifesaving in a desperate survive situation. Past backpacking and hiking, numerous other professions use them - land surveyors, foresters, engineers, miners, geologists, hunters, to surname a few.

Topography is the research of geographical functions on a landscape. A map with contour lines on the is dubbed a topographic map. Topographic maps use a combination of colors, shading and also contour lines to represent alters in elevation and also terrain shape. Essentially, topographic maps represent the three-dimensional see of planet within the two-dimensional space of a map.

The first known maps to encompass geographical attributes were found in old Rome. It would certainly be thousands of years prior to cartographers (map makers) might chart huge areas of terrain with any real accuracy. Contour lines, as we know them today, came into popular use in the mid-1800s together with the rise of source extraction sectors like mining and logging.


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How To review Contour Lines

A quick glance at a topographic map will provide you a general idea that the landscape. Is it flat or mountainous?

If each line to represent an equal allude of elevation, climate any change in key would bring about inconsistent heat spacing, right? because that example, numerous contour currently spaced close with each other would suggest steep terrain, when lines spaced far apart would show a gentler slope.

Let"s destruction deeper. There are 3 kinds of contour lines you’ll view on a map: intermediate, index, and also supplementary.

1. Table of contents lines room the thickest contour lines and also are usually labeled through a number in ~ one suggest along the line. This tells you the elevation over sea level.

2. Intermediate lines are the thinner, more common, lines in between the table of contents lines. They typically don"t have a number label. Typically one index line occurs because that every five intermediate lines.

3. Supplementary lines appear as dotted lines, indicating flatter terrain.


If you looking in ~ an index line, it"s straightforward to review the elevation since it is clearly labeled. However, interval lines are rather trickier. To determine their elevation, you’ll require to know the edge intervals. Contour intervals tell friend the change in elevation between any kind of two contour lines. Friend can discover the contour interval in the map key, usually located underneath the scale of the map in ~ the bottom center. To recognize all map symbols, watch the US Gov document.

Example: The edge interval is 50 feet follow to the map key. You desire to find out the elevation of one intermediate line 3 lines over an index heat labeled 1,000. For each line above this table of contents line, elevation rises 50 feet. Therefore, the interval heat in question is at 1,150 feet over sea level.

Understanding line Formations

After reading contour lines on a map for a while, you’ll notice that a few distinct forms pop again and again. Discovering to identify usual contour heat formations will aid you read topo maps quickly, and recognize the various terrain features they represent on a map. Let"s dig right into "em.

A. Top Ring. The innermost ring at the facility of several contour loops nearly always represents a optimal (highest elevation). Periodically the optimal will be stood for with a small X and also number denoting elevation.

B. Depression Ring. Occasionally, however, an inner ring indicates a depression (lowest elevation), which the map will present with a series of little tick clues pointing towards the center (called hachures).

Closed loops without hachures are always uphill ~ above the inside and downhill ~ above the outside. This is well-known as the “Rule of O’s”. This way hills and mountains will show up on the map as a swarm of concentric O shapes.

C. Cliff. If friend see 2 or more lines converge till they appear as a solitary line, this to represent a cliff. Usage caution, but - part cliffs may not appear on the map. If your contour interval was 50 feet, a cliff that 40 feet might not show up on the map, since the key doesn’t readjust enough come warrant a brand-new contour line.

D. Valley. when contour lines overcome a sink or a stream, they do a spicy pointed V or U-shape. Rivers, of course, are represented by blue lines that will certainly run with the center of the V-shape. Sometimes referred to as draws, the V-shape that this feature always points in the direction of their peak. Friend can also use a topographic map to recognize the direction the river is flowing. Since water flows downhill, the V-shape constantly points in opposing direction that the water is flowing. This is dubbed the “Rule the V’s”.

E. Ridgeline. Think that a ridgeline choose an elongated peak, no coming come a fine point. Rather of a closed within circle, a ridgeline can look prefer a large oval.

F. Saddle. A saddle is a short lying area in between two higher points the elevation. Identifying saddles can display you the quickest route through hilly areas. They appear as hourglass shapes between two concentric circles.

G. Ledge. Ledges or flat locations on the side of a mountain show up as protruding U-shapes that point away native the peak.


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Topographic Map Tools

Of course, file maps no the just topographic device out there. Smartphone apps and also computers can administer any topographic map you might need quickly and accurately, even past the with of wifi and cell signals.

Google Maps. You deserve to turn their topographic check out (complete with contour lines) by choosing the “Terrain” layer from the choices menu. 

Gaia. iPhone users deserve to use Gaia GPS. It is an elegantly designed map regimen with topographic maps obtainable for download. You can download the maps as soon as you have actually data or wifi prior to you venture off-grid. The app itself is free, but membership (which is required for offline topo maps) is $9.99. The app is also available to purchase on Android.

Backcountry Navigator. fear not, Android users. The app Backcountry Navigator offers the exact same service, with a similar setup. The demo version of the application is free. But, again, the ability to download maps because that offline usage is $11.99.

Caltopo. My favorite. The is a free, browser-based map device that allows you to print out practice topo maps... Or carry them to your general practitioners device. Initially designed for search-and-rescue, Caltopo provides a the majority of customization. You can free-draw routes and switch in between different varieties of topography favor shading, contours and satellite images. It also enables collaboration with various other users and also online sharing of your tradition maps. 


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comparable to Caltopo, but mostly focuses on the US and Canada. They administer detailed practice maps, consisting of topo maps, satellite images and also public land searching maps of any an ar in the US. Super professional quality maps, which you deserve to view online for free or have shipped as high-quality prints for a tiny fee.


By kris CageChris released dearteassociazione.org Meals in 2014 after ~ thru-hiking the Appalachian Trail for 6 months. Due to the fact that then, dearteassociazione.org has actually been composed up by anyone from Backpacker magazine to rapid Company. That wrote How come Hike the Appalachian Trail and also currently works from his laptop all over the globe. Instagram: