[Talk-GB] Mass edits of landuse /natural tags

Chris Hill osm at raggedred.net
Fri Apr 26 13:45:32 UTC 2013

I'd like to respond to Tom's points:

On 26/04/13 10:12, Tom Chance wrote:
> I worry a bit about the view put across by Chris Hill, among others, 
> that we should always assume every tag has been put in place with the 
> greatest of care and so shouldn't be changed; that little-used tags 
> are probably valuable, rather than being accidental or unknowing 
> variations on a more appropriate tag.

My point is not that every tag is carefully chosen, but that some are 
and a mess edit will not differentiate . Indeed Jerry started this 
thread with the very concern that a tag key being changed reduced the 
value of the tagging. A wide-scale or mass edit will blunder through 
these with little regard and hence the reason for discussion first. 
Contacting editors and discussing mass edits first will throw up these 
> Such a position shows little regard for data users, who have to deal 
> with the resulting mess and inconsistency. As with the wood/forest 
> example, it means you really can't rely on the difference so you just 
> have to treat them as interchangeable, all meaning "some trees here". 
> The building key is treated by most, at the moment, as a catch-all. 
> There are so many pointless variations on similar meanings that people 
> treat it as "everything under the building key is basically a 
> building". Without a lengthy translation matrix drawn up from manually 
> inspecting TagInfo you can't say much more.

I am sure you, like me, are a data consumer Tom, but I'm surprised at 
this attitude. Whenever data is consumed it must be processed and 
identified, how else do you tell between a wood and a lake? If you 
choose to treat two things as equivalent, such as natural=meadow and 
landuse=meadow, the lines of code to use both in the same way are 
insignificant compared to the effort to mass edit or manually change 
them. Once you have written that few lines of code you have solved the 
problem once and for all, no matter how many other occurances get added 
to the database. You can deal with this as you load the data, extract 
the data, render or otherwise process the data, it doesn't matter, but 
as someone who uses OSM data I know this is easy, repeatable, reusable 
and provides a permanent solution. Mass editing doesn't; someone may 
revert your edit or add a new object with that tag at any time in the 
future, making the editing solution fragile to say the least. I don't 
have a lengthy translation matrix, I have a few extra lines of code I 
can copy to my next project.
> I routinely change tagging I find that looks inappropriate in an 
> effort to make the data more useful. I'm happy to see John Baker 
> trying to do this. I only wish he had discussed his plans on this list 
> first, as doing otherwise always raises hackles, and that he took care 
> to inspect each individual case rather than processing batches of 
> objects en masse.
You make the data more useful to you, but are you sure you are not 
destroying someone else's detail? Would you alter the geometry of an 
object just so it looks tidier on your map, even though it does not 
reflect its real shape? Why is that different to altering tagging? If 
you know the area or survey it and actively decide to add or change tags 
to reflect more accurately what is there then that is great, but just 
homogenising data is awful and potentially reduces the value of other 
contributors' work.

I am fully in favour of editing the data in our database and I actively 
encourage it by assisting new mappers as and when I can. I want to see 
all kinds of edits of any object type, but those edits should add value 
and detail, not reduce it.

Cheers, Chris
user: chillly

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