I'd like to use my Garmin 20 to go biking. Since I do not want to buy one of microSD card from garmin, I'd like to build one myself.

For this I went to:


  • "Routable Bicycle (Openfietsmap Lite)"


  • "Enable manual tile selection: "

And then simply selected region north of Toulouse, France:

Toulouse North

This seems to be the direct link:

After a couple of minutes, I received an email containing a direct link to the GMAPSUPP.IMG. If I extract this file and copy it:

$ unzip openfietsmap_lite_gmapsupp.zip
$ cp gmapsupp.img /media/malat/GARMIN/GARMIN/GMAPSUPP.IMG

Then everything works as expected, except one tiny detail: accented characters. My Garmin 20 does not display some city names properly.

Some cities contains odd characters for example:

  • Bruguières is stored as "BRUGUI?RES"
  • Saint-Geniès-Bellevue is stored as "SAINT-GENI.S-BELLEVUE"
  • Villeneuve-lès-Bouloc is stored as "VILLENEUVE-L.S-BOULOC"

Is there a way to export/re-create this particular map using proper Latin1 encoding to fix all the invalid encodings ?

Update: I can fix the binary file directly using hexedit, for example I can generate the correct name for "Bruguières" using:

$ file input
input: UTF-8 Unicode text
$ cat input
$ iconv -o output -f utf8 -t latin1 input
$ file output
output: ISO-8859 text

Then I simply replace the original '3F' into 'C8' and then everything works as expected. While this is obviously not a proper solution (I would need to fix hundreds of binary strings) this demonstrate that a proper conversion is possible.

It seems the original 'img' file:

Already contains the invalid character encoding. So I need to generate the img file myself.


It looks like I need to recreate the map myself. I followed instructions from:

So this means I went to:

Because I was getting an error, I followed the advices on the left panel, and went instead to:

I renamed the 'map' file into 'map.osm'. On my Debian system I did:

$ sudo apt-get install mkgmap
$ mkgmap --latin1 --gmapsupp map.osm

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