[OSM-talk] Abuse of natural=cliff tag

Vladimir Vyskocil vladimir.vyskocil at gmail.com
Wed Sep 11 13:27:22 UTC 2019


Hello Sarah,

I read carefully your response and looked at the picture. I didn't travelled exactly at this place but will go there in October ! However I've already been in Český ráj <http://www.cesky-raj.info/en/contacts/bohemian-paradise-association/> that is not too far from there and where the terrain is similar in many aspects.
I still think that the usage of the tag is abused in this area…
You may read the description of this tag here :

https://wiki.openstreetmap.org/wiki/Tag:natural%3Dcliff <https://wiki.openstreetmap.org/wiki/Tag:natural=cliff>

«  A cliff <http://en.wikipedia.org/wiki/en:cliff> is a vertical or almost vertical natural drop in terrain topography as it occurs for example in form of coastal cliffs or escarpments. The face of the cliff usually consists of bare solid rock but can occasionally also consist of clay, compacted sand, ice or other solid materials.» 


« 
When not to use
natural <https://wiki.openstreetmap.org/wiki/Key:natural>=cliff <> should not be used for ridges, i.e. crests where there is a significant drop in terrain to both sides and neither of them is close to vertical. Use natural <https://wiki.openstreetmap.org/wiki/Key:natural>=ridge <https://wiki.openstreetmap.org/wiki/Tag:natural%3Dridge> or natural <https://wiki.openstreetmap.org/wiki/Key:natural>=arete <https://wiki.openstreetmap.org/wiki/Tag:natural%3Darete> instead. Also do not use natural <https://wiki.openstreetmap.org/wiki/Key:natural>=cliff <> just for mapping an inclined bare rock surface, use natural <https://wiki.openstreetmap.org/wiki/Key:natural>=bare_rock <https://wiki.openstreetmap.org/wiki/Tag:natural%3Dbare_rock> instead.

" 

This is not what I see when I look at this mapped area, I agree that some mapped cliffs here are really what should be considered a cliff but they are lost in lots of wrongly mapped and not relevant ones. 

You might look at this as a example in many many more :

https://www.openstreetmap.org/#map=19/50.89893/14.28319 <https://www.openstreetmap.org/#map=19/50.89893/14.28319>

We are seeing it at level 19 and the density of cliffs is still crazy ! 

Or here : https://www.openstreetmap.org/#map=15/50.8791/14.3647 <https://www.openstreetmap.org/#map=15/50.8791/14.3647>

Could you tell me that all theses mapped cliffs really exists ? Or aren’t they just « a significant drop in terrain and neither of them are close to vertical » mapped as cliffs only looking at terrain model and that are completely disconnected from the reality of the terrain ?

Regards,
Vladimir



> Le 11 sept. 2019 à 00:17, Sarah Hoffmann <lonvia at denofr.de> a écrit :
> 
> Hi,
> 
> On Fri, Sep 06, 2019 at 02:42:06PM +0200, Vladimir Vyskocil wrote:
>> Around this area : https://www.openstreetmap.org/#map=16/50.9034/14.2763 <https://www.openstreetmap.org/#map=16/50.9034/14.2763> there is a flagrant misuse and abuse of the usage of the natural=cliff tag. It is used to map the iso altitude lines and not real cliff as stated in the WIKI :
>> 
>> A cliff <http://en.wikipedia.org/wiki/en:cliff> is a vertical or almost vertical natural drop in terrain topography as it occurs for example in form of coastal cliffs or escarpments. The face of the cliff usually consists of bare solid rock but can occasionally also consist of clay, compacted sand, ice or other solid materials.  
> 
> I know that area very well and I can assure you, that natural=cliff is no misuse
> under this definition. The area is full of rock towers like those:
> https://commons.wikimedia.org/wiki/File:20171124195DR_Lohmen_Basteiaussicht_zum_Sieberturm.jpg
> 
> That's what you see on the map.
> 
>> I already removed the natural=cliff ways mapped by MichaOSM after asking him to fix this but without response the changeset comment was : 
>> 
>> "Felsen, Riffe, Topografie nach GeoSachsen digitale Geländemodellhoehenlinien 2.5m, digitales Geländereliefmodell, DTK10, topografische Karte”
>> 
>> For example this changeset : https://www.openstreetmap.org/changeset/66373825#map=15/50.9016/14.3093 <https://www.openstreetmap.org/changeset/66373825#map=15/50.9016/14.3093>
>> 
>> It say that it used a 2.5m topographic map to map all these false cliffs in this area, he was mapping the topography (MNT) and this is forbidden in OSM.
> 
> You missunderstood, he was mapping rock edges. A terrain model is more helpful
> for that task than arial imagery. We have permission to use the terrain model
> for OSM as far as I know.
> 
> I would kindly request that you reinstate deleted natural=cliffs for
> the moment. If you are still not convinced from the photo above that the
> tagging is correct then we need to have a fundamental discussion first about
> how to tag these kind of rock towers. But that would rather be something for
> the tagging mailing list (or talk-de if you want to get the locals involved).
> 
> Sarah

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