I've been playing with mkgmap over the last week, with the aim of creating a Garmin map of the National Cycle Network from OSM data. It's effectively a new version of the one I did the other year, but with better styling (via a .TYP file), contours, and so on.

NCN mapping on OSM is coming on in leaps and bounds this year, not least due to Gregory Williams' Three Corners Cycle Ride. So I figured this was a great opportunity to make it available for GPS, and so tackle the familiar "now which way do I go here...?" problem. The screenshot above would have helped Gregory find his way out of Gloucester. :)

You can now download a prerelease version (UK-only, 240Mb file):

http://richard.dev.openstreetmap.org/garmin/gmapsupp.img

The installation procedure is the same as any such map: connect your Garmin via USB, go into Mass Storage Mode (Setup->Interface), open the Garmin folder (creating one at the top level if there's not one already) and copy gmapsupp.img in.

I'd very much like to hear comments on what could be improved, in particular with the styling, and the choice of what's rendered at each zoom level. I've not as yet paid a lot of attention to POIs and would particularly welcome suggestions and comments on that. (I think I might remove the bus-stops before NAPTAN drowns us all.)

Routing is enabled but does not consistently choose the quiet routes I'd like it to. If anyone knows how to make it suck less, let me know; the eTrex's routing algorithm is famously impenetrable. Caveat emptor. Source will be available when I get round to uploading it to svn.

Regional and Local routes are both rendered in the same blue. I'm anticipating the abolition of Regional Routes in favour of three-digit National Routes. ;) The National Byway is shown in brown (let joy be unconfined).

Many thanks to Andy Gates for his Garmin cycling map, which has been a great inspiration and especially helpful in figuring out what goes where; and also for having the generosity to release the source. Several of the icons and some colouring are taken from his work. Thanks to the Scottish Mountaineering Club for the contour files. Thanks to Andy Allan whose fault all this open cycle mapping is, and yes, you're right, taking a photo of an eTrex screen is a PITA. And thanks, of course, to Steve Radcliffe and the mkgmap community for a superb, ever-improving program - for example, shield support has just been added, which really lifts the appearance of the map - and for being consistently helpful.

Update: The source is now in svn here, and full instructions are on the wiki.