Step-by-Step: Generating Garmin Maps from OpenStreetMap DataCreating Garmin-compatible maps from OpenStreetMap (OSM) data lets you build custom navigation maps for hiking, cycling, off-road driving, or specialized routing. This guide walks through the process from choosing data to installing maps on your Garmin device — with practical tips, common pitfalls, and alternative tools.
What you’ll need
- A computer running Windows, macOS, or Linux.
- OpenStreetMap data (planet extract, country extract, or custom region).
- Tools to convert OSM to Garmin’s .img format (eg. mkgmap, garmin-tool, or other converters).
- Optional: QGIS or JOSM for editing and inspection.
- A Garmin device or Garmin-compatible app (BaseCamp, MapSource, or an SD card slot device).
Overview of the workflow
- Obtain OSM data for the area you want.
- Prepare and optionally edit the data (filter, correct, enhance).
- Convert OSM data to Garmin .img using mkgmap (or alternatives).
- Test the generated map on PC software (MapSource/BaseCamp) or a Garmin device.
- Install the map on your device or SD card and verify routing and appearance.
1) Obtain OSM data
Options:
- Download a regional extract from Geofabrik (easy for countries/regions).
- Use BBBike for custom bounding boxes.
- Download the full planet file (planet.osm.pbf) if you need large-scale processing.
- Use Overpass API for very specific queries (e.g., only trails and waterways).
Tips:
- Use .pbf format when possible — it’s much smaller and faster than XML .osm files.
- Keep your area extract as small as needed to reduce processing time.
2) Prepare and edit the data
Why prepare?
- Remove unnecessary data (large POI dumps, building details) to speed conversion.
- Correct or add tags if you need specific features to appear or route correctly.
- Split very large extracts into smaller tiles to avoid memory/time issues.
Tools:
- JOSM (OpenStreetMap editor) — for manual edits and local cleaning.
- Osmosis — for filtering, extracting, and converting between formats.
- osmconvert/osmium-tool — fast command-line tools to cut and convert extracts.
Common tasks:
- Filter by feature type (e.g., keep only highways, waterways, contours).
- Merge multiple extracts if your area crosses boundaries.
- Add custom POIs or trail data if you want them visible and routable.
3) Convert OSM to Garmin .img with mkgmap
mkgmap is the most widely used open-source tool to convert OSM data into Garmin’s IMG format.
Install mkgmap:
- Requires Java (OpenJDK or Oracle JDK).
- Download mkgmap from its repository or package manager.
Basic command:
java -jar mkgmap.jar --output-dir=output --mapname="My_OSM_Map" myarea.osm.pbf Important options:
- –gmapsupp to name output file suitable for gmapsupp.img placement.
- –family-id to set the Garmin family ID (avoid conflicts with other maps).
- –series-name and –product-id for proper map identification on device.
- –route to enable routing data, and –tdbfile for precompiled tile database.
- –no-separate or –split-file to control how mkgmap splits the output into tiles.
Styling:
- mkgmap uses a style file (rendering style) to control which features are visible and their symbols. You can supply a custom .mapcss or use default styles. For more advanced visual control, use mkgmap’s style map features or postprocess with Mapnik/Maperitive for rasterized overlays.
Speed and memory:
- For large areas, increase Java heap: java -Xmx4G -jar mkgmap.jar …
- Consider splitting input into chunks and processing in parallel.
4) Enable routing and elevation (optional)
Routing:
- mkgmap can create routable maps if the OSM data contains appropriate highway tags. Use options like –route and ensure highway tagging is correct (motorway, trunk, primary, secondary, tertiary, residential, track, path, cycleway, footway, etc.).
- For advanced routing (bicycle, foot, car), mkgmap supports profiles and custom routing rules via tag remapping and preferences.
Elevation and contours:
- Garmin maps can display contour lines if you include contour data. Sources:
- Generate contours from SRTM/DEM data (using GDAL or QGIS) and convert to OSM or include as separate layers.
- Use tools like Tangram or other converters to transform DEM into contour OSM features.
- mkgmap supports contour lines included in the OSM input — ensure contours are properly tagged and included in conversion.
5) Test the generated map
On PC:
- Place gmapsupp.img into Garmin/MapSource or BaseCamp’s map folder and open BaseCamp to inspect map tiles, labels, POIs, and routing.
- Use Garmin’s MapSource or MapInstall to preview and transfer maps.
On device:
- Copy gmapsupp.img to the Garmin device’s /Garmin/ folder or to the root of an SD card. Rename to gmapsupp.img if necessary.
- Eject properly and power on the device. Activate the map in Settings > Map > Map Information (or similar). Verify appearance and routing behavior on the device.
Common issues:
- Map not visible: check file name (gmapsupp.img), placement (Garmin folder), and map activation in device settings.
- Routing errors: verify highway tags and mkgmap routing options; inspect log output for warnings.
- Labels or icons missing: adjust style file and rebuild.
6) Distribute and license considerations
Licensing:
- OSM data is licensed under the ODbL (Open Database License). You can distribute derived maps but must:
- Attribute OpenStreetMap and contributors.
- Share any public-domain-like data changes under compatible terms.
- Provide access to the underlying OSM data if you produce a “Produced Work” that uses OSM data in a way requiring share-alike (consult ODbL specifics for complex cases).
Attribution:
- Include an attribution file (e.g., in the map package README) mentioning OpenStreetMap contributors and a link to osm.org.
Distribution formats:
- Share the .img file for direct device use.
- Provide installer packages for MapInstall/BaseCamp or zipped files with install instructions.
Alternatives and additional tools
- Garmin’s MapConverter (older proprietary tools) — less commonly used now.
- mkgmap front-ends: PyMapTool, MapSetToolkit for Windows to merge, split, and manage Garmin maps.
- OsmAnd and MapsForge — for mobile devices (not Garmin IMG, but useful alternatives).
- QGIS with OSM plugins — for visualization and advanced editing before conversion.
Troubleshooting quick reference
- Slow conversion: increase Java heap, split input, use .pbf input.
- Missing map: check filename and folder, enable map in device settings.
- Routing incorrect: review highway tags and mkgmap routing options.
- Licensing questions: attribute OSM and check ODbL requirements.
Example: minimal mkgmap workflow
- Download region.pbf from Geofabrik.
- Edit/filter with osmconvert: osmconvert region.pbf -o=region.osm.pbf –drop-author –drop-version
- Run mkgmap:
java -Xmx2G -jar mkgmap.jar --output-dir=out --gmapsupp --mapname="My_OSM_Map" region.osm.pbf - Copy out/gmapsupp.img to /Garmin/ on the device or SD card.
Generating Garmin maps from OpenStreetMap data is a powerful way to create tailored maps for specific activities and regions. With mkgmap and the OSM toolchain you can control appearance, routing, and included features — just mind processing limits and ODbL licensing.
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