Hi,
although I'm late - I want to present some "hard numbers" on the effect
of split ways.
I've written a script that is based on the (imprecise) assumption that a
way has resulted from a split if its version 1 has 2 or more nodes that
another way from the same changeset has had before. Also such ways are
discovered only if a way (pre-split) has lost at least 3 nodes from one
version to another. So naturally the actual number of splits might
differ from the number of splits the script detects.
Then if a pre-split way is found to be the ancestor of another way, all
versions that were created before the split are appended before the new
way's version 1, with version numbers (-n ... 0), carrying original
nodes and tags. On these extended history objects the licence status was
evaluated with conventional WTFE logic.
Input data was a small (city-sized) history extract, dated
2011-11-19.[1] Agreed users data and WTFE code were from 2012-01-16.[2]
Total number of ways: 17273
Number of ways created by denier
- without split detection: 1129 (incl. 227 deleted)
- with split detection: 1274 (incl. 234 deleted)
Number of ways modified by denier[4]
- without split detection: 381 (incl. 8 deleted)
- with split detection: 441 (incl. 10 deleted)
There's still lots of work to be done to make it read larger data chunks
(currently the script reads and writes XML and is really, really slow)...
I'll make the scripts available if anyone is interested in taking up the
work. I'm not going to have much time for this during the next weeks.
cheers
ant
[1]
http://ftp5.gwdg.de/pub/misc/openstreetmap/osm-full-history-extracts/110919/xml/europe/germany/rheinland-pfalz/mainz.osh.bz2
[2] http://planet.openstreetmap.org/users_agreed/users_agreed.txt
http://planet.openstreetmap.org/users_agreed/anon_changesets_agreed.txt
http://wtfe.gryph.de/report.tgz
(no user or changeset overrides)
[4] Ways affected only by harmless edits are not counted.
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