OpenStreetMap is a collaborative, free map of the world. The data behind the map either comes from contributors' GPS tracks or from public domain data. The map above is displaying OpenStreetMap as rendered by Mapnik.
I wrote a python script that exports a line or polygon feature class to the .osm XML format used by JOSM. I used it to export features for Rowan University (see map above) and am in the process of taking public data currently in shapefiles or geodatabases and adding it to OpenStreetMap.
The script will preserve topology, in that if you export lines or polygons that share vertices, only one set of vertices will be created, but multiple ways will use them. Your data must be clean and planar in ArcGIS for this to work properly.
Multipart polygons are exported as multipolygon relations.
If any fields in the feature class begin with an underscore ("_") or "osm_", they will be converted into keys for that way. For example, if you have a polygon feature class with a field of "osm_landuse", each polygon in the resultant .OSM file will have "landuse=attribute data".
The script will also reproject your data from your current projection to WGS 1984. Your current projection must be defined for this to work.
• ExportToOSM.py (python 6kb)
This code is licensed using the GNU GPLv3 license. This is free software. Use at your own risk. I welcome any and all feedback. Please let me know if you've found this software to be useful.
I go by johnjreiser on OSM. You can see what I've added or updated here. Here's what I've edited on the OSM wiki. If you're interested in collaborating on a mapping project with me, please let me know.