There are quite a few options on the interwebs for free open source GPS maps, especially for Central and South America. If you don’t own a GPS unit yet read this article for some advice.
A Word (or 60) on Paper Maps: This article is specific to electronic GPS maps, but it is my opinion that nothing replaces a good paper map. Hands down the best on the planet are from Reise Know How. You can buy through US distributors, but to get the most up-to-date versions we recommend that you contact Reise directly. (The shipping from Germany isn’t that much!)
The most popular free GPS maps are from OpenStreetMap (OSM). This is the largest open source map ever created. It 150 GB or uncompressed XML data. (Gigs people, Gigs!) OSM is always the best place to start when looking for free GPS maps. There are a few things you need to know.
The easiest way to download OSM is to visit garmin.openstreetmap.nl. Just select the region you want, enter your email address, and then wait for your maps to be compiled. You will recieve an email when your maps are ready for download. In the email will be a link to a page that will list several different file types. You decide if you want an .exe file (to install in MapSource), a GMAPSUPP.IMG file (to transfer directly to your GPS), or several other options. There is a good forum post with instructions over on Horizons Unlimited.
Alternately, you can download the entire map set via osm2garmin.com. The compressed planet.osm file is currently 22 GB. Yes, even on speedy internet, it will take hours. It is possible to download only one continent or region at a time. See the OSM wiki download page for more info.
Because anyone can contribute to or alter the OSM map file, updates happen constantly. You’ll be surprised at the differences in maps over just a few months. With osm2garmin you can easily download updates when it is most convenient for you. Usually they are a few hundred megs. If you download only selected maps through another site, be sure to revisit every few months and get a new version. You will be surprised at the changes.
If you want to contribute your routes or waypoints download JOSM. This program imports the tracks from your GPS and lets you compare them to the OSM maps. You can decide how to classify the road and what to change or upload.
Note that these listings are accurate as of the date of publishing but as time goes on some maps are updated and others are not. Particularly OSM maps continue to improve as more and more travelers add their routes and waypoints. Please leave a comment (and read others comments!) to help keep us up-to-date.
Contrary to popular belief, OSM isn’t the only free GPS mapping project out there. Frequently, when looking for that tiny dirt road to that one-horse town, you’ll need to consult more than one map. Here is a list of other free maps for Central and South America. Sometimes they are better than OSM, other times not.
CENRUT (Central America)
This is a great open source map collection specific to Central America. It covers everywhere south of Mexico through Panama. In some places it is more accurate than OSM, in other places it is lacking. I would download with OSM and check your destination on MapSource.
These maps are for Colombia only. They are excellent in the north, on the Caribbean side of Colombia, but as soon as you move East or South it's probably better to switch to OSM.
Excellent maps for Peru. These GPS maps are far better than OSM. Highly recommended!
Proyetcto Mapear (Argentina, Chile, Paraguay & Uruguay)
Incredible maps for Chile and Argentina. On par with OSM in terms of major highways. Excellent for finding campgrounds especially in Argentina. Waypoints aren't as frequent in Chile, where OSM is usually better.
ConoSur (Bolivia, Argentina, Chile, Peru, Paraguay, Uruguay)
A good second set for Chile and Argentina. Reportedly better in Chilean Patagonia than Proyetcto Mapear. Not very useful in Peru or Bolivia. Stick with Perut.org and OSM in those countries.
The highest recommended free maps for Brazil. They actually mark every single speedbump in these maps. Much better than OSM for southern Brazil, up to Rio. Can't comment on the rest of the country, because we didn't visit.
Another set for Brazil. TrackSource seemed to be better in cities and the southern and coastal areas. But these are mentioned frequently enough they are worth installing as a backup.
The only maps of Venezuela aside from OSM. They are routable and seem to be updated frequently. Sorry, I haven't been to Venezuela so I can't comment further.
Proyecto Ecuador (Ecuador)
These maps for Ecuador are pretty freakin’ terrible. I’ve added it to the list here in hopes that a new version is released soon! Until then, stick with OSM.
Bolmap Geogroup (Bolivia)
A very difficult map to find on the web. The link above requires forum registration to download. And it is only a GMAPSUPP.IMG files so it will NOT install to MapSource, only directly to your device. It does seem to be more accurate than both OSM and Viajeros Mapas.
Viajeros Mapas (Bolivia)
At the time of writing all GPS maps for Bolivia are less than great. These are good for a second reference in some remote areas, but usually OSM is better. Also these maps are not routable.
The easiest way to work with multiple GPS maps is to download Garmin’s MapSource program, or BaseCamp for Macs. You can download MapSource and BaseCamp on Garmin's website, or alternately check the software that came with your GPS. I generally refer to MapSource throughout this article, but note that the functionality is practically the same in BaseCamp, I just have less experience with it.
MapSource easily allow you to:
Most of the maps I listed above are meant to be installed via MapSource, meaning you must install MapSource first. Then install the maps. After the maps are installed you can open MapSource, preview the maps and send to your GPS device.
You cannot send most open source maps directly to your GPS. Garmin requires a specific file name and type (called gmapsupp.img). MapSource compiles the data from your installed maps and creates a gmapsupp.img file that your GPS can read.
If you have a gmapsupp.img file and want to convert it into something that can be read on MapSource, follow the instructions here. I have had mixed experiences using this method.
OSM to BaseCamp (on a Mac):
In some cases, when you download the Mac install file from OSM , you will need two free additional programs. Garmin MapManager is needed to install the map from OSM onto BaseCamp and Garmin MapInstall is needed to transfer the maps from BaseCamp to your GPS device. Whether you need these extra programs or not seems to depend on the ages of your GPS. Huge thanks to Bryan at Southern Tip Trip for this info!
Help us Stay Up-to-Date
Know of other maps not listed here? Links broken or incorrect? Leave a comment and we’ll do our best to keep this up to date.