[OSM-talk] Unrepentant Vandal

Sun Nov 8 09:29:56 UTC 2015

Thanks everyone.  I'll double-check the resurrected railway line and
keep an eye on it.  I am not impressed by that mapper's work, and I
expect more problems in the future.  The other problems I have seen
are, in many cases, caused by misguided QA tools.  I have had one guy
remove all highway=steps because of a reported routing error.

Presumably the price of free maps is eternal vigilance?  Oh well, best crack on.

Andrew

On 07/11/2015, Andy Townsend <ajt1047 at gmail.com> wrote:
> On 07/11/2015 10:36, Andrew Errington wrote:
>> Hi all,
>>
>> Here is a link to a random point on a light rail system:
>> http://osm.org/go/546Jvddtd--?m=
>>
>> Soon after it opened I travelled on it from end to end, collecting gps
>> data and photos of all the station signs.  There are two railway
>> lines, one in each direction, and I mapped them both carefully.
>>
>> Recently I discovered that someone had helpfully deleted one of the
>> lines and tagged the other with tracks=2.  I really don't think this
>> is acceptable.
>>
>> I found the changeset and asked the user who did it why they destroyed
>> my work.  They replied:
>> "The OSM wiki implies that a single way with tracks=2 is the preferred
>> way of showing rail lines with two tracks. This was the method used
>> most in S. Korea, I was attempting to create consistency."
>>
>> This is not actually true (and I double-checked the wiki, just in
>> case).  I pointed this out but the user did not acknowledge this was a
>> mistake, or offer an apology.
>
> I'd definitely suggest that changeset discussions are the best place to
> have this sort of conversation.  That way, it's visible, so that other
> people can be aware of the problem (and also discussions in public
> tended to be conducted with more politeness).  I'm sure that they
> generally believed that they were doing the right thing, but didn't
> think through the implications of what they were doing on data
> consumers* and other mappers.
>
>  From looking at their edit history, which appears to be wide-ranging, I
> suspect that they're a non-surveying mapper who may not actually have
> been to all of the places that they've edited.
>
>>
>> So, my question is, am I being unreasonable, or am I right to think
>> this is unacceptable?  How can I guard against this?
>
> There are a bunch of "who's been editing where" tools - one that's
> especially worth mentioning is
> http://wiki.openstreetmap.org/wiki/Quality_assurance#WhoDidIt which
> looks for changes in an area and can provide an RSS feed.  I also use
> ITO's OSM Mapper http://wiki.openstreetmap.org/wiki/ITO_World#OSM_Mapper
> .  That works a few days in arrears, but is very useful at helping you
> to visualise what has changed.
>
>> I have no
>> problem with people improving the map by improving the data, but I am
>> starting to see a lot of deletions, incorrect tagging, and generally
>> shoddy work appearing, especially in Korea where I have done a lot of
>> original work.
>
> There might be a couple of issues here.  One possibility is people using
> "QA tools" to identify "problems" and "fixing" them.  We've had a lot of
> issues in GB with this - people changing the tagging on oneway roads in
> carparks incorrectly when the _real_ problem was that not all of the
> roads had been mapped is one example that springs to mind.  Where a QA
> tool identifies a problem, it should really be a prompt to carry out a
> local survey rather than apply a "remote guess" of what might be wrong.
> If I spot a problem like that I'd usually add to the changeset
> discussion of the original mapper, or add an OSM note or a fixme, to try
> and get it looked at properly.  Sometimes not of this works and there
> really are no local mappers, and the problem is bad enough that a remote
> fix really is needed (perhaps a newbie has broken a major road by
> mistake), but it's surely best that edits are done by people who either
> actually are there, or at least have been there.  Previous OSM tags +
> imagery don't always give a full sense of what something actually is.
>
> Related to this is people "correcting" tags that are "wrong".  Often a
> "wrong" tag is a really useful indicator that an inexperienced mapper
> has been active, there are other things besides the "wrong" tag that
> might been checking, and the QA report is a useful indicator of this.
> Fixing the "wrong" tag removes the QA report but leaves the other data
> that doesn't match the real world in OSM.
>
> The other possibility to people causing problems using QA tools is
> actually good news - lots of new mappers!  People new to OSM will get
> things wrong, whichever editor they're using, and any attempt to get
> them to trudge through the mire that is the current "beginners' guide"
> in the wiki will cause many to stop mapping before they've even
> started.**.  New mappers need help and understanding rather than "you've
> done it wrong!".  Often asking "what are you trying to map - how can I
> help?" is a good way of getting to the root of the problem.  I'd also
> give new mappers a week or more to "find their feet" - I suspect that
> the feeling of being watched would put some off too.
>
>> Do I have to set up some kind of watch on all of my
>> contributions and check them if someone edits them?
>
> I did actually used to do this - I postprocess OSM data before using
> mkgmap to create a Garmin map, and one of the things that that did was
> to enable a list of "things edited since I last edited them" to be
> produced.  It's not something I've looked at of late though, since most
> edits are perfectly valid and there are plenty of other ways of
> identifying problems introduced by new (and old) mappers.
>
> One other thing worth mentioning is whenever I've gone back to resurvey
> something that has been "questionably edited" I've almost always missed
> something that's either changed or that I missed the first time.  I can
> think of more than one example of someone changing "my" X to "their" Y,
> and after I had gone and had a look I found that Y was actually correct now.
>
> Cheers,
>
> Andy (SomeoneElse)
>
>
> * as a data consumer I don't really care what you're changing to what as
> long as I know it's changing, no information is lost, and it doesn't
> make it impossible to extract the information in the future.
>
> ** Compare http://wiki.openstreetmap.org/wiki/Beginners'_guide with
> http://wiki.openstreetmap.org/w/index.php?title=Beginners%27_guide&oldid=1140764
> to see the problem.  Thankfully the person responsible for those changes
> is no longer editing the wiki.
>
>
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