[Talk-GB] Advice please: Goat tracks in mountain areas

[Andy Townsend]

On 08/02/2022 14:47, Phil Endecott via Talk-GB wrote:
> Andy Townsend wrote:
>>   * If you find maps and apps that misrepresent the path, or show it to
>>     a readership that probably shouldn't be encouraged to use it, then
>>     perhaps let OSM's Data Working Group know via email to
>>     data at openstreetmap.org
>
> As someone who is potentially "misrepresenting" this path,
> what advice would the DWG offer me? 

To be honest, Gruff who started this thread is better placed than me to 
answer that.  I'd suggest that it's going to depend on who your maps are 
targetted at - if it's the "determined mountain hiker", and people 
understand what they might find, then it makes perfect sense to show 
it.  If it's the "person on Snowdon in flip=flops" mentioned in another 
post, I wouldn't show it.


>> ** Currently the tags that you've added to 
>> https://www.openstreetmap.org/way/982094029 have made it disappear 
>> from 
>> https://map.atownsend.org.uk/maps/map/map.html#zoom=16&lat=53.07435&lon=-4.07194 
>> (disclaimer - my site) which is entirely correct.
>
> Andy, could you share exactly what rules you are using to achieve that?
> Are you using trail_visibility? Is that in combination with something
> else?
>
It's a combination of things.  The map style has a lua file that changes 
OSM tags into a smaller subset that are rendered, and then a regular 
"carto" map style, which evolved from OSM Carto starting around 2014*

Firstly there's a round-up for trail_visibility values at 
https://github.com/SomeoneElseOSM/SomeoneElse-style/blob/master/style.lua#L363 
.  Very poor visibilty paths that aren't designated are removed at 
https://github.com/SomeoneElseOSM/SomeoneElse-style/blob/master/style.lua#L391 
.

At 
https://github.com/SomeoneElseOSM/SomeoneElse-style/blob/master/style.lua#L383 
informal and overgrown paths are assumed to have intermediate visibility.

Then at 
https://github.com/SomeoneElseOSM/SomeoneElse-style/blob/master/style.lua#L411 
some intermediate visibility paths are retagged as such so that the 
stylesheet can handle them.

Some high-sac_scale paths are removed at 
https://github.com/SomeoneElseOSM/SomeoneElse-style/blob/master/style.lua#L475

Finally there's a caveat on the about page 
https://github.com/SomeoneElseOSM/SomeoneElse-map/blob/master/about.md 
that says: "Also note that a particular route may be safe to travel 
along at some times but not others (e.g. when a river is in spate), or 
only with suitable equipment." with a link to Gordale Scar near Malham - 
https://www.openstreetmap.org/way/43324000/history .


> I've just done an overpass turbo query to look for 
> trail_visibility=horrible
> and it includes the main path from the summit of Scafell Pike to
> Mickledoor. It's not shown on your map. 
Funny you mention that - I actually queried the sac_scale there with the 
mapper who added that tag 3 years ago:

https://www.openstreetmap.org/changeset/59901184

I haven't updated it myself because I haven't been there for ages.  If 
it's wrong, please change it!  It also appears to be an untagged 
designation=public_footpath according to the PRoW overlay that Richard 
created based on local authority data via rowmaps, but I can't comment 
whether there's any on-the-ground signage.  I also can't comment on the 
trail_visibility there because I really can't remember what it was like, 
but if it is wrong please correct that too.

> Even if that path were difficult
> to see on the ground (which I don't think it is), I believe it should
> still be shown on the map; in fact, a route that's difficult to see on
> the ground is exactly the situation where a map showing where the correct
> route goes is most useful.

That's a very good point - when people need to get somewhere in an 
emergency, it's helpful to see what might be available that isn't a 
cliff edge, but isn't that  just "different maps for different 
audiences" again?

One way of handling that with raster tiles might be via an overlay layer 
- the simple map style at https://github.com/SomeoneElseOSM/floodedmap 
is a very simple example of that (see 
https://www.openstreetmap.org/user/SomeoneElse/diary/398374 for 
context).  Overlays aren't a magic bullet - you can't easily guarantee 
you won't get text or icon clashes for example - but used for something 
simple like this would do the job.

Best Regards,

Andy

* when OSM Carto opted for a better rendering of central European 
graveyards rather then the paths on the other 99.9999996% of the planet.