The OSM wiki contains links to various downloads for Garmin maps, as well as some information about creating your own from OSM data.

For many years now I’ve used maps on Garmin devices that I’ve created myself. I’ve done this so that I show things like England and Wales public footpaths and bridleways that I’m not aware that other maps can show. Until now, I’ve never quite got around to making the mechanism publicly available, or indeed the maps themselves. I’ve finally got around to fixing that.

The “readme” here explains how to run the script yourself, if you want to do that. If you don’t, you can download the latest files for Great Britain. New maps should appear there about weekly.

Differences between these maps and other maps for Garmin devices include:

• They’re routable. Many maps for Garmin devices are, but not all.
• Public Footpaths have “(FF)” added to the end of the name, or used instead of the name if there was none.
• Public Bridleways, Restricted Byways and Byways Open to All Taffic similarly add “(FB)”, “(RB)” or “(BY)”.
• Members of foot and hiking routes have the name of the routes in brackets after the road name, if any.
• Ways inaccessible on foot (private tracks etc.) are removed from the map.
• Pubs and bars selling real ale have “PQR” appending to the name

Some of these mirror how things are represented on maps at map.atownsend.org.uk. Those maps use osm2pgsql, osmium, osm-tags-transform and lua scripts to determine what is shown on the map.

These Garmin maps currently only use mkgmap style files such as this one, which isn’t quite as flexible. Eventually I may get a chance to change that and do more of the transformations in lua which should and also allow more precise changes to be made, and also reduce the size of the style files,