Sunday, January 8, 2012

License Change Mapping

So far I have avoided saying anything about the OpenStreetMap license change on this blog. It is a very sensitive subject for a lot of people for a million different reasons. This is not a post about how right/wrong the license change is. I personally have agreed to the new terms but then again I don't really care what license my data gets redistributed under. While I prefer (in most situations) a share-alike clause, if we were switching to public domain instead of ODbL, I would probably still agree. Whatever.

But the license change is happening and we must prepare the map for it, ahead of the April 1 cutover date set by the license working group. Today I decided to take a look at what it would take to get I-70 in Kansas cleaned up, license-wise, and thought I'd share my findings. Note that this particular process may or may not apply to other areas. The interstate system is kind of special in that it was imported from a public domain source and has very long stretches that are identical except for tags that don't really matter. This means that there isn't really very much unique or unrecoverable information present. If there is a small section of road (say a bridge) that is dirty, it can just be removed and replaced from clean data that surrounds it plus imagery to verify that it is indeed a bridge. However whenever possible it is preferred to maintain the history of objects in OSM so I don't want to just nuke and replace large sections of I-70. Plus, deleting and recreating ways gets more complicated because of the route relations that they may be a part of.

A majority of I-70 in Kansas is already clean but there is still a noticeable fraction of dirty objects. The goal is to end up with all objects being "clean" to re-license under ODbL. First task: find dirty objects. For this I use the "License Change" view in the OSM inspector tool created by Geofabrik: