- Create a bounds file for a certain area for geobase2osm.py.
- Execute geobase2osm.py.
- Download OSM data for this area from JOSM.
- Open the resulting OSM file in JOSM.
- Copy over the features which do not exist.
- Make sure you connect the new roads to the existing roads in OSM.
- Depending on the density of the data, it is generally better to work in multiple iterations.
- Upload the data to OSM.
- Indicate in the description of the changeset that you imported data from Geobase for tile 999x00.
- Perform cleanup.
For historical reference only: previously the import involved also loading Geobase shape data into PostGIS, extract it, and use it in OpenJump with the RoadMatcher plugin. This process hardly offers any benefits. The time saved by letting OpenJump exclude certain roads automatically doesn't weigh against having to execute extra steps, as well as making sure that the right roads are excluded by OpenJump.
In October 2009 we settled down to use the above process on talk-ca.