Short answer:

Think of open source maps as the “Wikipedia of maps”.

Created through literally millions of contributors, open source maps are completely free, cover the entire world, and often more accurate and up-to-date than any map you could buy from a commercial company or government agency. You can find open source maps and a great interface for printing them at Caltopo.com, and on the Gaia GPS navigation phone app.

Check out the real thing at OpenStreetMap.org.

Long answer:

Historically, maps were typically made by a government agency within a country. For example, in the United States, the 7 1/2 minute US Geological Survey (USGS) topographic map series. These maps were pretty much the only ones available for many decades, and they definitely have their shortcomings. There was no shaded relief, newer roads and trails were often not accurate, and the maps were often not updated for many decades, if at all.

And, of course, the maps stopped at the borders of the country that made them. Want to go on a motorcycle tour in Bolivia? Finding maps for a Big Trip could be a hit or miss project, because who knows if the Bolivian government has a good cartography department.

The answer is Open Street Map. Inspired by the success of Wikipedia, this visionary product was founded in 2004 in the UK. It now has over 2 million users, many of whom regularly add features and improvements, to collectively create a single, free, open sourced map of the entire world.

(Note that map heights and contours are in meters, which might only pose a problem to the three countries in the world that do not use the metric system: Liberia, Myanmar, and the United States. )

What does this mean for you, the recreational user? It means that roads and trails are probably going to be more current and accurate than you’ll find on any other map, and that the entire world is mapped with a consistent look, legend, and standard. This makes the maps especially useful for international travel.

Open source maps come in several flavors, so let's look at a few examples.

The maps below are from the main visitor area for Mount Rainier National Park, and are screen grabs taken from Gaia GPS, our favorite backcountry navigation GPS app.

Open Street map example

USGS topo map example

Above on the left is the standard US Geological Survey topographic map. Note the contours are great, but the roads are rather hard to see, and trails are sadly nonexistent. No trails, LAME! Not too helpful for the backcountry.

Above on the right is Open Street map for the same area. Notice we have nice road for driving, a bit of vegetation shading and even some trails, but no contours.

Open Cycle map example

Open Topo map example

Above on the left we see Open Cycle. This is often a great choice for hiking, because it shows shaded relief (which makes gullies and ridges much easier to see), labeled contours, and hiking trails in easy-to-see red, along with well marked roads.

And finally, above on the right we see what is often my go-to layer, Open Topo, which has shaded relief, labeled contours, some vegetation coverage such as rock, snow, or forest, more detailed streams, human made structures, and current roads and trails. The trails are printed in black and are a bit hard to see, and the text is tiny, which are small drawbacks.

So, next time you’re looking for a good map source in your favorite mapping software, be sure and have a look at any map layer with the word “Open” in the title.

Becoming a contributor is easy. You can be out on a hike or bike ride, in the woods or even on a little trail in your neighborhood. You may notice that the trail you are walking on is not on your open source map on your phone. Time to record a track of your own and add it!

Record a GPS track, upload that track when you get home, trace right over the top of it with various line symbols, and boom, in a minute or so you’ve made your own small contribution to a single map of the world. You may find doing this feels surprisingly rewarding.