[OSM-talk] tagging roads

Blaž Lorger blaz.lorger at triera.net
Sun Aug 2 10:49:11 BST 2009


On Sunday 02 August 2009 10:59:08 John Smith wrote:
> --- On Sun, 2/8/09, Blaž Lorger <blaz.lorger at triera.net> wrote:
> > I also propose extending instructions for road
> > classification to use width tag
>
> I agree with everything else you wrote except width since I really don't
> want to get a tape measure out and measure widths of roads, using lanes=*
> to estimate widths would be more sensible and is already in use.

Unfortunately lanes only specifies number of lanes. In general every road that 
is not one way has at least 2 lanes, even if it is narrow, say 3.5 meters.

But you are right. Actually measuring road width is cumbersome and dangerous. 
We really don't want any OSM mapper to be nominated for Darwin award.  :-)

Still, you must get width data somehow. But, since width is more important in 
case of narrow road, you can limit gathering of width data only on narrow 
roads. Which has additional benefit that width for narrow road is easier to 
estimate than for wide road.
Obviously  it would be a good idea to add recommendation that only width of 
narrow roads should be estimated to tagging instructions. Some good practices 
on how to accurately estimate road width could also came handy.

Which leaves us with problem how accurate is width data. Wiki suggest using 
tag est_width. But this means that software needs to check two tags: width and 
est_width. Maybe additional tag (width_estimated=yes|no) could solve this 
problem. Default value for tag would be yes, since we can assume that someone 
that did not bother to acquire accurate data won't bother to add the tag to 
record such fact.





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