[Tagging] sidewalks

Tobias Knerr osm at tobias-knerr.de
Thu Aug 26 22:52:25 BST 2010

On 26.08.2010 22:25, Peter Wendorff wrote:
> My approach would be - and I would like to get your opinions on that:
> - a sidewalk is tagged like every other footway
>    highway=footway|path
>    (foot=yes)
>    (segregated=yes|no)
>    footway=sidewalk
>    name=NAME-OF-STREET

I understand why you like this approach: The mappers will essentially
draw the routing graph for you. ;-)

Generally, individual ways for sidewalks and cycleways make it easier to
use the data for navigation, while adding tags (or relations) to the
roads themselves appears somewhat easier for renderers.

I happen to write a (3D) renderer at the moment, so I assume this will
create some challenges for me. Simply drawing the footways and roads
independently will certainly look bad - there will either be gaps
between the sidewalk and the road or they will overlap. Unless, of
course, the distance between the sidewalk way and the road way is
exactly half the sum of their respective width tags' values ... which is
unlikely, to say the least. *g*

So I will need to associate sidewalks with road sections. And therefore

> - no geometric analysis necessary (finding parallel streets to unnamed
> footways)

... I *will* need to do geometric analysis.

It's still possible, though (or so I hope, at least...), so your
proposed solution would be acceptable for me. It's actually nice that it
works well with today's editors, while other approaches require editor
or even API improvements. This will probably lead to fast adoption by

> 2) dedicated sidewalks make it a lot more simple to tag crossing details
> like islands etc.

Could you describe crossing layouts in more detail? I assume you would
model them like this

A  B  C

|  |  |
|  |  |
|  |  |
|  |  |

where A and C are sidewalks, B is a road, and *o are junction nodes.
If we use the existing tagging for crossings, then node o should be
tagged highway=crossing + crossing=island/...

So how would you tag the horizontal way? May I suggest that it is tagged
differently from A and C to make it easier to distinguish in software?

Tobias Knerr

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