[Tagging] highway=footway - Advanced definition: Distinction footway vs path
ilpo.jarvinen at helsinki.fi
Thu Aug 6 23:15:36 UTC 2015
On Wed, 5 Aug 2015, Greg Troxel wrote:
> Martin Koppenhoefer <dieterdreist at gmail.com> writes:
> >> Then what is the point of having path and all these other tags that
> >> overlap?
> > because path and bicycle=designated is the same as highway =cycleway
> > path with horse=designated is the same as highway =bridleway
> > and you can also make combinations without having to decide for
> > footway, cycleway or bridleway. Also, without any further access tags,
> > path is neutral and open to all unmotorized means of transport (unlike
> > footway, cycleway etc.)
> I agree with what Martin said. I also agree with previous commenters
> that redefining semantics of path or adding footpath would cause a lot
> of problems. A few problems and random comments.
> There's no clear default for path, footway or every cycleway about
> surface. The obvious answer is that surface tags should be used.
> Similarly, a width tag should be used. Or perhaps some tag that
> indicates a forest trail. But this shoudl be extra, so that data
> consumers that don't know about it will still know that
> foot/bike/etc. traffic works.
But that's actually exactly the dangerous approach. There's no guarantee
that such forest trails will even be safe to use (especially on
mountaneous terrain). It would be much more conservative approach to not
render nor use them without intention. In theory sac_scale and various
other tags could be used to distinguish them but it would be much better
to have a highway type which has built-in expectation that various
hazards/obstacles to use are more likely to exists compared to what is
likely to occur on man-made highway=footway/path (I suppose somebody comes
up a counterexample from a signposted footway which is why I used
"likely". It's enough to understand that no matter what, hazards will
always be possible and we should not try to entirely remove map user
brains from the loop like GPS driving instructions occassionally tend to
do to some people :-)).
In addition, giving equal prominance to forest trails and other footways
depending on surface alone as proposed is significantly less useful to
both map users and also to mappers (no hiking map or like is magically
going to fix this as it's not the main source of mapper visual feedback).
The map user (I refer to a human here, not to somebody using the data)
perspective should be pretty obvious, if both look the same there's no way
to know that one of the equal looking "unpaved paths" is actually built-up
recretional route whereas the others are just tiny, some even faintly
visible, forest trails. In theory this prominance problem might be solved
by informal=yes but in practice I expect at least the mapnik stylesheet
guys to stonewall on this because of the extra data column that will be
needed to make them less prominant (however, I don't endorse informal as
solution as I think a new highway=* value or =trail would be much better
for this but one the same time some solution would be better than no
solution). Pointing map users to "hiking maps" is not going to work since
those people who want to use the non-trail ways are not going to identify
themselves to need such alternative presentation when they only want to
identify the safe routes, not the serious hiking information.
>From the mapper point of view the default stylesheets are supposed to
help mapping (the visual feedback thing) and therefore IMHO it should try
to provide means to distinguish details we are highly interested in, that
is, access and surface at minimum. I don't know if such style becomes too
messy to be implementable, however, I think that the lack of visual
feedback on all these currently both in default mapnik and editors is one
of the major reasons why people are not realizing where they need to
be added. In addition, the forest/informal trails should be somehow given
less prominance to help both mappers and map users to identify them
visually (the former need this information to spot mistakes in order to
I know that there will be some (rather vocal) people who oppose any idea
that there's need to such prominance distinction (or even that it
would/should matter to anyone) but it's hard to understand as those people
tend to describe their point of view as that only access tags matter which
(to me) implies that shouldn't matter at all what the highway=* value is.
> The default rendering is problematic in two ways;
> path is much heavier than footway/cycleway/bridleway, which are
> similar except for color.
On this I agree, especially if many forest trails are mapped, see eg.:
> I believe that a lot of the footway/path angst would go away if path
> stopped looking like a higher class of road.
Also less prominance to forest/informal trails are needed, as they are
more messy when mapped with high density and the distinction is
meaningful to many map users (regardless of some people admiting it or
> For all of these, some notion of hierarchy is needed. For roads, we
> have primary/secondary/etc., which has its own issues. For footways
> as an example, we have sidewalks that are not particularly interesting
> except at high zoom levels. But a foot path that goes 3 km through a
> forest is interesting when you can see the whole forest, just like a
> through road. This is not easily determinable automatically, because
> the 10 km through path that junctions with a sidewalk does not make
> the sidewalk important. Importance is determined by the way being
> useful for a long hiking route. So probably some sort of importance
> tag is needed. One approach would be a tag distance=X, where X is a
> distance that one could reasonably travel where that way would be
> naturally a component. Perhaps X should be rounded to 1/2/5 x 10^k m.
> I don't really like this suggestion, but I think we need something
> like it.
You seem to admit that there's need for some hierarchy, however, on the
same time you seem to oppose the idea that such hierarcy would exists
based on physical properties (man-made vs informal). I find it strange
since it shouldn't be that hard to come up use cases where excluding or
warning the user about informal paths is very useful thing. In order to
make mappers to tag that differentiation, I think that the default
stylesheet should visualize this difference somehow.
IIRC, attempt to define tags for hierarcy for bicycle network didn't go
that well on tagging@, so I except any usage related hierarcy similar to
what we already have with motor vehicle networks to be shot down for some
strange reason as if such thing wouldn't exists at all for other than
Last but not least, why I consider forest trails and other informal paths
so important: They're great way engage mappers to do real surveys as they
tend to be such that imagery won't let drawing them fully or even
correctly. Also, OSM tends to be only source in quite many places where
the trail data has a chance to be even remotely trustable/matching what's
on the ground.
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