[OSM-talk] Abuse of natural=cliff tag

Yves yvecai at mailbox.org
Wed Sep 11 18:21:59 UTC 2019

Vladimir, I see around https://www.openstreetmap.org/#map=15/50.9610/14.0724 an incredible work of micromapping, it can also look ugly in other context.
But OSM is glad to have climbing enthusiast in its ranks too! 
Probably worth opening an issue at https://github.com/gravitystorm/openstreetmap-carto the cliff pattern really looks messy.

Le 11 septembre 2019 19:26:42 GMT+02:00, Vladimir Vyskocil <vladimir.vyskocil at gmail.com> a écrit :
>Hi ! 
>> On 11 Sep 2019, at 15:33, Vladimir Vyskocil
><vladimir.vyskocil at gmail.com> wrote:
>> A even crazier area regarding the abuse of the cliff tag ! 
>> https://www.openstreetmap.org/#map=15/50.9610/14.0724
>What I see there is far from reasonable and far for common sens, it is
>just wrong and mad...
>All this bad information about cliffs in that area ie what common sens
>think is a real cliff and what is explained in the openstreetmap wiki
>page about this tag impact the usability of the data and I even don’t
>talk about the rendering, we are not tagging for the renderer but we
>easily could see that this tag was not designed for this mess !
>Now have a look please at the Grand Canyon in USA, for example :
>This is useful information ! How do you think It had looked if every
>little stones or slopes were mapped as a cliff like it is in the area
>we are talking about ?
>> Vladimir.
>>> Le 11 sept. 2019 à 15:27, Vladimir Vyskocil
><vladimir.vyskocil at gmail.com <mailto:vladimir.vyskocil at gmail.com>> a
>écrit :
>>> 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
>that is not too far from there and where the terrain is similar in many
>>> 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
>>> «  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/Tag:natural%3Darete> instead. Also
>do not usenatural
><https://wiki.openstreetmap.org/wiki/Key:natural>=cliff <> just for
>mapping an inclined bare rock surface, use natural
><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
>>> 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
>>> 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
><mailto: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>> 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
>>>>> A cliff <http://en.wikipedia.org/wiki/en: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:
>>>> 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 :
>>>>> 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
>>>> 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
>>>> Sarah
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