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Maps: are something you’re going to need when travelling or Geocaching. You can either use good old paper maps (which you should always take as a backup anyway), borrow a copy of an online map (France / UK) using a screen capture program, or purchase a map for your GPS. Most GPS vendors charge a substantial price for suitable walking maps on GPS, especially with topographic details includes (contour lines).  Perhaps it isn’t that much when you consider the cost of buying the same data on paper, or the cost of creating the information in the first place, but it always feels like a lot.  

I think OpenStreetMap has now become an excellent resource - as evidenced by the above animation and the fact that I haven’t bought an overpriced Garmin map for years.  In combination with the NASA SRTM data, it has becoming practical to roll your own topo maps. There’s a great blog and podcast covering OSM over at OpenGeoData.org.

Once you have the data in Garmin img format, then if you’ve got a recent Garmin device that can take img files over USB - it’s a simple matter of drag and drop.  

If you’ve got an older device, you’ll need to use cgpsmapper and sendmap.  It is possible to take the map data, and get Garmin’s mapsource to read it, but it is a more involved process.  

Creating maps from the OSM data:  There are a number of programs that will allow you to create your own maps from the data.  For each of these, you need to:-

  • First grab the OSM data (typically .osm).  I’ve found 2 ways  to do this successfully
    • For small areas, and the most up-to-date data - grab josm, register an openstreetmap account and enter your username in the settings; then download the data for the area you’re interested in, and save it to an OSM file.
    • For larger areas (whole countries), download the osm.bz2 file from cloudmade or geofabrik and extract it with something like 7zip
  • Then convert it to an img file for sending to your GPS (assuming you have a recent USB device that supports img files).  I’ve had the best luck using mkgmap, with a command line as below.  If you’re loading multiple maps onto your GPS, be sure to give your maps a unique mapname (8 digit number) - otherwise you’ll only be able to see one of them.
    • java -Xmx1024m -jar mkgmap.jar —mapname=63241234 —code-page=1252 —tdbfile —gmapsupp —latin1 —generate-sea=multipolygon —country-abbr=MC1 —country-name=MOROCCO —road-name-pois —route —product-id=99 —family-id=99 —family-name=”OSM Maps” —description=”OSM Casa” casablanca.osm
    • I haven’t quite worked out how to get the —generate-sea command working at the moment. My last attempt for Lisbon seemed to have catastrophically flooded most of the city. You may find more job and less frustration by using the pre-packaged img files described below.

Pre-packaged Garmin .img files: Alternatively you can look at one of the existing resources for pre-packaged OSM data, although none of these offer live, up-to-the minute data (mind you - some services are now running autobuild services - so the data you grab here if often no more than a week old).

Other map data options: In addition to data sourced from OSM, there are a number of other options:-

  • GPS Map Search appears to offer open-source maps, including some with topo data, but I’ve not had much luck getting these to work.  
  • I haven’t tested them - but mapstor seems to be offering a collection of topo maps created by the military agencies of Russia and some East European countries.
  • In the US - GPS File Depot is apparently the best source for US topo maps, and has a limited selection of international maps (ref GPS TrackLog).
  • In New Zealand - there’s an excellent resource at the NZ Open GPS project.  It isn’t OSM, but it is ready to roll for Garmin devices.

Contributing: Of course if you’re using OpenStreetMap data - and find something that’s not on the map - then you’ll be keen to fix the map and make the correction!

There are several ways to contribute to OSM - the easiest being simply to upload the tracklogs from your gps unit. This is really easy, and allows anyone who is working on the map in that area to make updates. Just make sure that as you’re walking you have the GPS set to save your movements to a track. Once you get back to a PC - you’ll be able to grab the GPX file that represents that track and upload it to openstreetmap.org (after you’ve created yourself an account).

As far as I can tell, there are 2 main-stream editing packages - which you can use to map the GPX file you captured on your GPS, and/or fill in details using satellite images from Bing (details of the Microsoft Bing OSM license)

  • Potlatch2 - which is built into openstreetmap.org (under the edit tab screenshot), and probably the simplest place to start contributing, however I actually found v1 hard to use. v2 should be better.
  • JOSM - which seems to be the most powerful package - although it does have a learning curve - so it is well worth doing one of the tutorial videos or looking for one on YouTube.

Once you’re up to speed, you’ll be able to start contributing to the world’s biggest open map!