With the 2012 move to the Open Database Licence a small number of users did not agree to the new licence conditions in order that their their contributions could continue within OSM under the new licence. Though we would of course have preferred to retain this data, we do respect the original contributors’ decision, and we thank them for their past involvement in the project.
We asked everyone to help remap the affected areas ahead of the redaction process to reduce the impact and help ensure OpenStreetMap remains the best map in the world. This was a somewhat tricky process involving using various tools to locate data elements which were likely to be affected, removing those elements and then replacing them with new, preferably improved, map content.
The redaction process was run across the whole world. More than 99% of the data was retained, and in most places, the difference was barely noticeable. There were, however, some areas of our map where the redaction was concentrated, in particular Poland and Australia. These areas were left with large amount of missing data, and an extensive remapping was undertaken, with large amounts of data recreated from aerial imagery. There are still some artifacts of large scale remapping from imagery around this time.