[Tagging] Subject: Feature Proposal - RFC - highway=social_path

Andy Townsend ajt1047 at gmail.com
Wed Jun 15 13:36:04 UTC 2016

On 15/06/2016 13:10, John Willis wrote:
> So SAC scale and being outside a park polygon/relation is good enough 
> to allow a data consumer and the folks over in -carto to render a 
> "footway" and a "trail" differently and reliably enough? What happens 
> when I have a strong mix of =pedestrian, =footway, and ="trail"? In 
> the same park area?

Before answering that, let's take a step back and have a think about 
what we're trying to do here:

o People tag stuff so that the essential nature of what's on the ground 
is capture.  That might be "is mainly designed for use by foot traffic" 
(highway=footway), "has a gravel surface" (surface=gravel) or "is part 
of some sort of route relation" (appropriate relation membership).  Data 
consumers occasionally grumble about specific tagging choices, but 
usually if the data's there, they can somehow deal with it.

o Renderers have a limited number of ways that they can render stuff 
without things becoming _way_ too complicated.  If you look at osm-carto 
you can see that for linear features such as roads and tracks it uses:

1) feature width
2) feature colour
3) casing width
4) casing colour
5) How it's actually rendered (continuous line, dots, dashes, whatever)
6) Some text printed alongside the feature

Those are basically the degrees of freedom you've got.

"osm-carto" uses 6 for names, and chooses to use just lines for 
footpaths and tracks (we'll leave highway=pedestrian out as it's 
rendered - correctly in my view - as a road), which basically leaves you 
with 1, 2 and 5.  Of those, the combination of 1 and 2 need to be 
carefully adjusted together so that a particular feature has the right 
level of "importance" in a particular rendering at a particular zoom 
level.  "osm-carto" de-emphasises footways at the expense of other 
features; other styles (see the two examples below) emphasise them more.

Of the available choices "osm-carto" currently uses 1 and 2 to 
distinguish between footway, bridleway, cycleway and track (and I 
believe puts "path" in one of the first two buckets based on other 
tags).  It uses 5 to show paved vs unpaved (see 
http://www.openstreetmap.org/#map=18/53.21858/-1.49726 ).  It doesn't 
show relation membership.

Other styles do things slightly differently.  Thunderforest Outdoor 
doesn't show the surface difference, de-emphasises roads but does show 
relation membership:


I use a style based on OSM-carto that doesn't show surface explicitly on 
these features (or relation membership) but does show England and Wales 
legal status (using colour) and track width (using dashes instead of dots):


So data consumers have choices, and there's a limit to the differences 
in the data that they can render.  If someone asked me 'to render a 
"footway" and a "trail" differently' my first question would be, apart 
from tags that I already understand such as surface, tracktype, 
smoothness, etc., what's the difference?  In my view if there's a muddy 
flat 1m-wide path in a city centre and a muddy flat 1m-wide path miles 
away, then they should be rendered the same - apart from relationship 
membership of course, if a style renders that.

> It seems to me -  as a person who is a Kountry Kilometer away from 
> being data consumer - that using a subtag or similar to let mappers 
> tag trails and other rough footways (the "track" end of footway) is a 
> much more straightforward and direct solution to get trails to render 
> differently than more casual and easily traversed footways found in a 
> city park or rose garden.
> I am really having trouble understanding the reasoning behind the 
> resistance when it removes uncertainty and confusion while tagging.

Clearly there is confusion about tagging these sorts of features (this 
disussion wouldn't exist if there wasn't) but I'm really struggling to 
see any difference between a "footway" and a "trail" that can't be 
expressed in other, more frequently used tags.  To take a random 
example, what should I infer about 
http://www.openstreetmap.org/way/372458198 ?  How wide is it?  What 
surface does it have?  What are the access rights for various sorts of 



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