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Hi Charles,<br>
<br>
I could reply from the perspective of developing a routing system
(we are developing <a class="moz-txt-link-freetext" href="http://openrouteservice.org">http://openrouteservice.org</a> that currently
contains a beta version of a wheelchair routing profile):<br>
<br>
For implementing routing algorithms it is generally easier, if the
sidewalks are separate geometries, since then the routing algorithm
can directly handle them as separate features. <br>
<br>
However, since there is a considerable share of sidewalks that is
only attached to the respective streets as metainformation, we have
to deal with these situations anyway and derive "virtual" lines
within the routing engine. There is a good article about the concept
how to derive these virtual lines from the sidewalk tags in the OSM
Wiki:
<a class="moz-txt-link-freetext" href="http://wiki.openstreetmap.org/wiki/User:Maxbe/B%C3%BCrgersteigrouting">http://wiki.openstreetmap.org/wiki/User:Maxbe/B%C3%BCrgersteigrouting</a><br>
Unfortunately, this is only available in German language, but since
there are lots of illustrations, I think the concept gets a little
bit clear even without reading the text.<br>
<br>
When to use separate lines and when to use metainformation attached
to the roads to me seems to be very idiosyncratic, i.e. it depends
on the preferences of the local mappers, if not even of the
individual mappers.<br>
<br>
Nevertheless, the distinctions criterion that you describe (whether
sidewalks are *directly* attached to the road or whether there is
any separating feature) makes sense to me.<br>
<br>
For the key incline - I think, it is reasonable to assume that an
attached sidewalk has basically the same incline like the road (at
least within the accuracy needed 1% difference is not important
here). However, this does not hold true for surface and smoothess,
which can be very different between road and sidewalk. There it
makes sense to specify them for the sidewalks separately. Tagging
schemes like described here:
<a class="moz-txt-link-freetext" href="http://wiki.openstreetmap.org/wiki/Wheelchair_routing#Sidewalks">http://wiki.openstreetmap.org/wiki/Wheelchair_routing#Sidewalks</a> may
be perceived as very complicated by potential mappers. My personal
feeling that it would be little bit easier to attach sidewalk
relatied information (e.g. surface/smooth) to a separate lines,
since complicate constructs, such as <tt
style="background:#DDE;white-space:nowrap" dir="ltr"><a
href="http://wiki.openstreetmap.org/w/index.php?title=Key:sidewalk:left:surface&action=edit&redlink=1"
class="new" title="Key:sidewalk:left:surface (Seite nicht
vorhanden)">sidewalk:left:surface </a></tt> could be avoided.<br>
<br>
Best,<br>
Stefan.<br>
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