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Rule files
GroundTruth software generates maps for Garmin GPS units using OpenStreetMap data and NASA's SRTM digital elevation model. It's being maintained by User:Breki.

For other meanings of "Ground truth" see Ground truth

Who Is GroundTruth For?

  • OSM mappers who use Garmin units for mapping and who want their maps to contain as much useful information as possible.
  • Non-OSM users who want to have free (and often better quality) maps of the world.

Warning: Distribution Of OSM Maps

This warning is for anyone who wishes to distribute maps generated using GroundTruth from OSM data: GroundTruth uses 3rd party cgpsmapper software to generate the actual .IMG files for Garmin units. Unfortunately the license for the free version of cgpsmapper states that the produced maps cannot be distributed for commercial purposes. This is in conflict with the OSM license.

The bottom line is: you cannot distribute Garmin maps made with the free / shareware or personal version of cgpsmapper if they contain OSM data. You can, however, distribute contour maps, since the original SRTM3 data is in public domain.

I (User:Breki) don't know what the situation is with the commercial versions of cgpsmapper.

Main Features

  • Support for custom line and area styles - you specify how the feature should look like
  • Support for custom icons for POI
  • Map rules can be shared among mappers by publishing them on this Wiki.
  • Automatic generation of TYP files
  • Generating relief contours using NASA's SRTM data
    • Generating OSM files with contours (a successor to Srtm2Osm)
  • Downloading of OSM vector data
  • Support for additional map features (like map transparency) available through cgpsmapper
  • Conversion of national characters into the ones supported by Garmin units
  • Generation of Mapsource preview files
  • Registration of generated maps into Mapsource
  • Automatic uploading of generated maps onto a GPS unit
  • Command-line interface


You can download the latest package (or older ones) from You need to have Microsoft .NET 3.5 SP1 (available here) installed on your computer in order to run GroundTruth.

How To Use

For a brief introduction please visit GroundTruth For Dummies.

For detailed instructions and FAQ please visit GroundTruth Manual.

See also