[Tagging] Highway property proposal "covered=yes"

Randy rwtnospam-newsgp at yahoo.com
Sat Oct 31 05:18:20 GMT 2009


Ed Hillsman wrote:

>I would welcome any suggestions you have on how to deal with the open- 
>building situations, the student center, or shade. Yes, in a way,  these 
>are minor, even trivial situations, but they contribute to the  quality of 
>the local environment, and it would be good to be able to  record that in 
>OSM.
>
>Ed

Ed - Regarding your 2nd, 3rd paragraphs, and last part of your 4th 
paragraph, yes, that's exactly what I'm dealing with. In my current case 
it is auto ways, but I was also thinking toward your situation.

For me, at least, tunnel, whether footpath, road or waterway implies no 
side access, unless you map entry ports along the tunnel. A "covered" way, 
on the other hand, implies (or would imply) that there may be ad hoc or 
unmapped access to it, such from parking, or from most points to a 
sidewalk, even when the sign says "Keep off the grass". Of course, others 
may see it differently. For example, if I mapped a covered street and a 
covered sidewalk in parallel, I would assume I could get in or out of a 
car from the sidewalk, if it were tagged "covered" but that I could not do 
that if each was a tunnel, unless I mapped a connecting tunnel.

It seems that most of your other issues have more to do with shade 
covering rather than weather elements. Things such a "portico" can better 
be described as building attributes rather than shelter or shading 
attributes on the way. The only (unlikely) exception would be if their is 
a meaningful height restriction, which should be tagged on the way as 
"maxheight=*". This by the way, is a precedence of for tagging the way 
rather than what is above it with the information. We don't tag a bridge 
with its height, we tag the underpassing way with maxheight.

Depending on how sophisticated you want to get, shade can be a very 
complex issue, as I'm sure you recognize. If the trees are deciduous then 
shaded may need a seasonal qualification. (or, it may not be important 
during those months when the trees are bare) If a path is next to a 
building, possibly a seasonal (as in your example), or maybe an hourly 
restriction, depending on the side of the building. Do you want to route 
based on morning vs. afternoon classes? An hourly restriction can even 
apply to a building overhang or an awning, depending on how far out it 
extends. I think that "shaded" would be a valid attribute for ways, and 
you may have to come up with your own qualifiers to associate with the 
shaded attribute, such as "seasonal=[months] and time=[daylight hours] 
that will work for your specific purpose, but will be ignored by more 
general renderers and routers. "covered" would imply total shade, unless 
the way was also tagged with "shaded".

In the case of the path next to the building, you have a situation where 
the building attributes might be important. Depending on how sophisticated 
you want to make it, the routing software could be made smart enough to 
determine how close, and in what direction a building is, from the 
sidewalk, so it could estimate shade as a function of time and/or month. 
The building can be tagged with a physical attribute, height, which could 
aid in determining when a pedestrian way is shaded by the building.  There 
is a whole page on proposed building attribute tags, including 
building:height=*.

There are those who would argue that there is a node/way/area tag for 
tree(s) that can be used to map the areas of a path that are shaded by 
trees, and that this is the preferred method of mapping trees. I 
personally believe that you have to look at the purpose of the mapping. If 
it is just to show that there are some trees around an area then that is 
adequate. If you are mapping for a different purpose that is more related 
to using a way, then, in my opinion, a method, that while on the surface 
is redundant, is more functional to your purpose, is not only valid, but 
preferred.

As you see, my tendency at times is to ramble.

-- 
Randy





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