[Talk-GB] Vandalism in London

SomeoneElse lists at mail.atownsend.org.uk
Sat Oct 4 10:12:54 UTC 2014

On 04/10/2014 10:14, David Woolley wrote:
> ... it is probably a mistaken attempt at personal mapping.

That's what it looked like to me, certainly.

> The big problem with relations is that they tend to be subject to 
> frequent edits, so reverts may fail, because they would take out a 
> subsequent legitimate change.  In this particular case, the same 
> person probably damaged relations in multiple edits, making only their 
> very last change affecting the relation revertable. 

The usual JOSM revert approach is to start at the latest problematic 
changeset in a series and work backwards to the start; the problem is 
that it can take out valid edits to the same data as "collateral damage" 
on the way.  Depending on how large the problem and the 
non-problematical edits were this can be difficult to achieve perfectly 
- sometimes there has to be a manual tidying-up exercise.

> Maybe there should be some super revert tool that takes a list of 
> changesets, and will revert objects that were last changed by any of them.

That's pretty much what the JOSM revert plugin does (in fact the way 
that it manages to do what it does as well as it does is actually 
extremely impressive).  There are other revert options as well of course 
(the wiki's got details).

I suspect that the problem with London is that it's a "target" for a 
couple of reasons.  One is that it's a "known name" - a target for 
actual vandals (of which there are few, thankfully).  The other is that 
there are a lot of people there who are just learning to map stuff, or 
(like this person, probably) wanted a personal map of something, thought 
that that is what they were creating, and did a lot of damage in the 

Because London is densely populated and there's a lot of detail, it 
doesn't take long for other people to modify the affected data, making 
reverts more difficult - the sooner this stuff is spotted the better 
(within minutes if possible).  If any Londoners don't already, I'd 
strongly suggest subscribing to a "WhoDidIt" feed for the area (see the 
links from http://wiki.openstreetmap.org/wiki/Quality_assurance ) and a 
new mappers feed (such as 
).  If something is spotted reporting it on IRC (there are usually 
people in the #osm-gb channel, failing that there are _always_ people in 
#osm) is probably the quickest way at getting stuff resolved.



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