Custom Garmin GPS Maps

Garmin makes, what are in my opinion, some of the best GPS receivers on the market. While the company sells a world map that provides a bit more international detail than the default base map that comes with one of their GPS units, the detail is still typically lacking for humanitarian field use (you can purchase detailed street and topographic maps for Europe, Canada and the US, which aren't that much use if you're off the beaten track in Asia or Africa).

Garmin's GPS maps are proprietary. They make money selling their maps, and don't want just anyone creating them. A couple of years ago some Polish hackers figured out Garmin's internal map format and wrote some software that allows you to create your own GPS maps. Over the years, a growing number of free Garmin maps have been produced for some fairly remote parts of the world. Check out this database, where people freely contribute maps they've produced. You might find something useful.