[OSM-talk] highway=* + area=yes vs area:highway=*

[Lester Caine]

On 08/08/18 11:49, Tomasz Wójcik wrote:
> As highway=footway etc. tags are set to "should not be used on areas" on 
> Wiki, and mapping them in combination with area=yes is not documented at 
> all and considered as wrong tagging by part of users, there is a key 
> "area:highway=*" (133k uses at the moment). Part of users still map 
> footway areas as a combination anyway, propably because it's rendered by 
> default style. Due to our rules, that we shouldn't have 2 active tagging 
> schemes for the same feature, so we should discuss this topic.
> 
> I vote for area:highway=* key, because it's simpler, and it gives a 
> possibility to show also street areas with crossings in the future.
> 
> * Wiki with specyfications of a:h=* for certain keys: 
> https://wiki.openstreetmap.org/wiki/Key:area:highway
> * TagInfo: https://taginfo.openstreetmap.org/keys/area:highway
> * area:highway=* visualisation: http://osmapa.pl/w/area

As more and more detail is added to the data, the switch from 
'macro-mapping' to 'micro-mapping' needs to be considered. There has 
been some discussion on park areas being 'footpaths where you can walk 
anywhere', so rather than creating multiple ways covering all 
combinations of access points, a pedestrian router would understand that 
they can enter and exit the area at any valid gateway. I don't know if 
any routing software actually does use this approach. Boats on lakes 
have a similar problem ... so at a macro-mapping level a waterway or 
highway can have a sensible reason for being an area.

Switching to micro-mapping which is starting to expand, one has areas 
for each facet of a route. Footpaths, grass verges, roadway, private 
drives off the roadway across verge and path and so on. There is however 
no current method of converting all of these area elements into 'ways', 
so one needs additional highway=xxx ways to provide the routing 
information that provides the macro level view. So you do not want an 
'area:highway=footpath' if there is a highway='road with footpaths' way 
that covers the same object ...

-- 
Lester Caine - G8HFL
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