In reviewing this forum, one of the things that has surprised me is how little mention OpenStreetMap
gets. For those not familiar with it, it's an open map that can be edited and used by anyone. On the web, it's like the other mapping sites, except you can say "Wait, that's wrong," and then fix it on the spot.
In GPS applications seem to have three advantages over manufacturer's maps. Firstly, it's free, so if you're buying a cheap GPS, you don't end up paying a significant percentage more to get usable maps. Secondly, it updates all the time. You can notice an error on your GPS one day, edit in a fix on the site, and have a corrected, routable map on your GPS the next day. Thirdly, there are many ways to massage the data, and there are at least a few bicycle specific treatments of the data, that optimize the maps and the routings for bikes (optionally giving preference to bikeways or tertiary roads).
While this may work with other GPS units, the focus of my reading and experimenting has been on Garmin units, which most here seem to use, as well. The easiest way to play with OpenStreetMap maps on a Garmin (or the Garmin software on your computer) is to pull a section of the Lambertus maps
, where you select the region you want maps for on their site, and they'll mail you a link to the downloads. These maps seem optimized for car routing, making them an analogue to the City Navigator maps. There are a couple cycle specific versions, including Cyclemap and VeloMaps, but those require rather more effort to build on your own. I've just gotten a mostly working build for the Northeastern US using the VeloMaps encoding, and it mostly seems pretty neat, though some of the routings are a bit unexpected.
Have others played around with this? Are the pitfalls to these maps that I haven't hit yet? It seems the more cyclists we get using these, the better the data will get.