[Talk-GB] Cliff editing

[Russ Garrett]

It's worth noting that orthorectification will struggle with cliffs at the
best of times (i.e. the accuracy of the aerial imagery will be lower where
gradient is steeper), so I wouldn't expect great accuracy when mapping them
from aerial imagery. Cliffs mapped in the "middle" may well have been
mapped at the top in older imagery.

Cheers,

Russ

On Mon, 22 Aug 2022 at 12:18, Tom Crocker <tomcrockermail at gmail.com> wrote:

> Hi Keith.
>
> My understanding (and practice) is to map the top of the cliff edge. You
> can then add an area of natural=bare_rock if the cliff is a slab and
> extends out 'beneath' the top edge (of course, there may also be flat bare
> rock along the top edge and perhaps at the bottom).
> The wiki recommends path=climbing_access for dedicated crag access, used
> 1188 times apparently without additional tags (e.g. highway=path):
> https://taginfo.openstreetmap.org/tags/path=climbing_access#overview
> Personally I would just add them as footways if their placement seems
> reasonably stable (with additional tags as appropriate).
> You can add the starting point of each route with climbing_route=bottom
> https://wiki.openstreetmap.org/wiki/Climbing although I haven't done this
> as I am unsure about the appropriateness of any source of names.
>
> P.S. I know of no good way of dealing with overhangs regarding natural=*
> or paths (possibly use of covered for paths, or later?)
>
> Cheers
>
> Tom Crocker
>
> On Mon, 22 Aug 2022, 11:51 Keith, <keith at fachwen.org> wrote:
>
>> I’m interested in adding missing rock-climbing cliffs here in Snowdonia.
>> There are lots 🙂
>>
>> Mostly obscure little ones, that can be quite a challenge to find when
>> walking to visit for the first time due to bracken, no real path, etc.
>>
>> Just checking … should the line of the cliff be at the top of the edge of
>> the cliff, or at the bottom where rock-climbers naturally want to be
>> setting up kit, etc.
>>
>> As a climber, the need is to know where to walk to, best place for
>> setting-up, etc.
>>
>> As an OSM mapper, maybe the issue is ‘where is the crag edge?’ ie the
>> dangerous bit for walkers, general public, etc.
>>
>> Most existing crags seem to be mapped somewhere in ’the middle’ of the
>> cliff, as a line of nodes, or the actual top edge.
>>
>> One ‘best practice’ might be to map the top edge of the actual cliff, and
>> survey the path to where climbers mostly go to park their rucksacks, etc
>>
>> Thanks.
>>
>>
>> _________________________________________________________________________
>>
>> Keith Robertson, Tyn y Pwll, Fachwen, Caernarfon, Gwynedd, North Wales,
>> UK LL55 3HD
>>
>> keith at fachwen.org - www.fachwen.org
>>
>> Text or Voice: 07515 966 558
>> twitter: @keithrobertson
>> www.flickr.com/photos/fachwen/sets
>>
>>
>> BE GREEN! Read from the screen.
>>
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-- 
Russ Garrett
russ at garrett.co.uk
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