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Hello OSM Community! New here and wanting to tag green roofs and green walls (separately - particularly in Berlin, Germany). There does not seem to be tags for these elements yet - how do I go about creating a new tag for this? Should also distinguish between public/private areas... Best, Samie |
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I'll divide this answer into three parts, related to roof material, façade material, and individual rooftop plants, respectively. Roof materialWhen we look at the usage numbers of tags related to plants on roofs, the most common example is An important detail in this context is that the roof:material key itself is defined as the "outer material for the building roof". So when there are multiple materials involved (which is commonly the case, such as with shingles on top of a wooden frame, a plaster coating on concrete etc.), we tag the outermost layer. There are two main reasons why this definition was chosen:
As such, tagging a plant-covered roof using roof:material is appropriate, even though there is likely a supporting structure made from some other material. Façade materialThe However, this is not applicable to buildings only partially overgrown with plants (such as vines), as the material below is still visible in that case. As far as I know, there is no tag for this particular situation. Rooftop plantsRoof gardens and other "green roofs" are not limited to grass, but can consist of many other plants, up to and including trees. You can map those normally, with tags such as |
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Assuming the "roof/wall with plants growing on them" definition. I'd be tempted to go with wall:cover:material and roof:cover:material except that there's hardly any existing value that matches on taginfo. There's roof:material=grass/plants with decent usage numbers, but green walls are usually covered by plants, not made from them. 1
Even though the walls are only covered by plants, the existing keys building:material and roof:material still fit. They were intentionally defined as the outermost material when the tag was created, thus plaster (the second-most common value) or plants are right at home there. I've tried to elaborate a bit with my answer.
(05 Dec '16, 20:58)
Tordanik
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I think Tordanik has covered the basic tagging issues. However using roof:material and building:material keys do not unambiguously identify any given structure as being a green roof or wall. Indeed I can think of at least one building where the outer material of the roof is grass, but this is not a green roof. To avoid this I would suggest the use of one of:
In practice green roofs and green walls usually only cover part of a roof or a single façade. Thus at least green roof tagging is often best combined with building:part As I have stated elsewhere these are usually distinct structures from the building proper, but Tordanik clarifies that point. In most cases roof:material=grass for a green roof will be wrong, but it is difficult to ascertain the actual composition of the plants used in the green roof. Many green roofs will have different mixes of plants in zones across the roof:
(my own image from Geograph) Incidentally the famous green wall at Caixa Forum, Madrid is mapped as a garden: http://www.geograph.org.uk/photo/5151779. |
Do you mean "roofs coloured green" or "roofs with plants growing on them"?
So it looks liek there is no consensus at all on how to map/tag green roofs or façades.... how does one get an consensus on these things within the OSM community?
For now, I think I like:
roof:cover=plants wall:cover=plants
as I think it describes what we are looking for best. If I go with the above tag, where/how do I use it? (such a newbie, sorry for the basics...)
THANKS
xx Samie
@essgame There's no precise definition for "consensus" in the OSM community, but looking at the wiki documentation and checking the popularity among mappers and developers (e.g. using Taginfo statistics) gets you pretty close.
The keys building:material and roof:material, which I mentioned in my answer, have together been used over a million times, and are supported by numerous data consumers. This is as close to established consensus as you will ever get in OSM.
The exact values to use for green roofs and walls (such as "grass" or "plants") are not really established yet, but introducing new keys won't help with that at all.
Indeed follow @Tordanik's advice (& if you feel inclined also additionally add one of the tags I suggest). These two approaches are compatible & synergistic: roof:material & building:material are widely used for 3D rendering, and values can be refined if actual composition of the plants is known, the green_roof tag allows one to find objects specifically known to be green roofs, whereas roof:material=plants may cover a wider range of roofs.