[OSM-talk] tagging trailblazes / marked paths

[Alex Mauer]

Andy Allan wrote:
> highway=footway + foot=no is simply garbage, 

I agree.

> People in charge of renderers being asked why highway=path,
> cycleway=designated doesn't show up when highway=cycleway does, when
> they could spend time on more useful things which add value to the
> maps.

The renderers need to accommodate this sort of thing anyway, because of
multi-use paths like
http://wiki.openstreetmap.org/index.php/Image:Designatedsigns.jpeg --
even if that were to be tagged as footway/cycleway/bridleway renderers
would still need to  understand the bicycle=*, horse=*, ski=*,
snowmobile=*, foot=* tags in order to render the other access methods.

In fact, highway=path makes it easier on renderers.

Without using highway=path, renderers need to understand every single
specialized way.  snowmobileway, skiway, nordicskiway, telemarkskiway,
alpineskiway, elephantway, etc.  When someone introduces a new
specialized way, the renderers need to be updated to understand it.

*With* highway=path, the renderers only need to understand highway=path.
 Most renderers can render all paths generically.  If a new access
method is added, no change is needed.  Specialized maps like cyclemap
only need to add special rendering for their area of interest.  For
example, a cycle map can render any highway=path the same, and only
highlight those which are for bicycles.

> I'm not obliged to spend my time patiently explaining the
> counterarguments to every proposal on the wiki - the obligation to
> research alternative options (rather than just campaigning for one)
> surely lies with the proposers.

I did consider several alternatives, and I wouldn't have proposed one if
I'd found that another was clearly superior.  I'll go over the ones I
considered, and their problems and benefits:

1. highway=[anything]way.  Renderers need to know about every type of
[thing]way. Impossible to tag a multiple-use way (or ridiculously
complex anyway -- highway=bicyclefoothorseskisnowmobileway?  I hope
everyone uses those in the same order.).  No good way to tag a "generic"
path where the intended/primary use is unknown or unclear.  Requires a
change to the renderer for every new type of way and a new value for
every permutation of access methods.

2. highway=[anything]way plus access tags.  This makes it possible to
tag the multi-use way, but prioritizes one access mode over the others.
 Renderers still need to know about every [thing]way.  Renderers which
don't understand the access tags are likely to render incorrectly. Still
no good way to tag a generic path.  Still requires a change to the
renderer for every new type of way, but no new value for every permutation.

3. highway=path + access tags + existing footway/cycleway/bridleway.  No
changes required to existing data.  Easy to render without knowing about
every variation (only four are needed).  Easy to tag a single-use way.
Easy to tag a multi-use way, and doesn't prioritize one use of the way.
 Easy to tag a generic path.  Renderers which don't understand the
access tags can still identify all paths and render with a generic
style. Only specialized renderers need to care about the access tags.
Requires a one-time change to the renderers to understand highway=path.

Clearly the first is a terrible idea.

You seem to prefer the second method.  It is definitely better than the
first.  I don't know if you weren't aware of its flaws, or just don't
think they're important enough -- or if you have some preferred fourth
alternative which I didn't consider and you've never mentioned.

I don't see any flaws in the third, and 22 others didn't either, or at
least approved it without mentioning them.  There were some objections
which you can find on the proposal page.  In my opinion they're
outweighed by the benefits above.

Perhaps there's a fourth method which is far superior to the other
three.  I didn't encounter it though.

-Alex Mauer "hawke"