Background
I’ve started importing Sherbrooke addresses into OSM, simple cases first. So far, I’ve added about 40,000 address tags to OSM buildings.
I’m currently working on the case of multiple addresses on the same building, which represents about 6,900 cases with 2+ addresses. In one case, I even have 112 distinct addresses for the same shopping center. According to the wiki, I can do this in three different ways:
Using comma-separated values for building tags. This option is easy to implement, but the rendering is not attractive when there are more than two or three addresses.
Proposal
In the case of multiple addresses on the same building, minimum and maximum house numbers can be assigned by adding two new nodes along the building way, a few meters apart, on the street side. An addr:interpolation way is added between these nodes when there are 3+ addresses. The interpolation way must overlap the building footprint.
Comments/objections?
If most agree, without major objections, I will add the (revised) proposal to the Canadian tagging guidelines.
Personally, I’d rather avoid having them on the building way. A few reasons:
If the shape of the building changes (rare, but happens with renovations over time), future mappers will have more complicated geometry to deal with
If housenumbers are added or removed, future mappers may have to reposition each node while still maintaining the building’s geometry
If someone tries to actually map the entrances using a tool like StreetComplete, they will have a much harder time placing and moving entrance nodes if the addresses are already at arbitrary points on the same way (I don’t know about Sherbrooke, but within the greater Montreal area you will sometimes find buildings with two or more addresses per-entrance and multiple entrances splitting these up)
More minor, but I’m not fond of the way this visually results in ‘fake entrances’, making it kinda look like there’s extra data that doesn’t really exist.
I believe it’s valid to simply place the address nodes within the building–this would basically avoid the above issues.
I also wouldn’t attach the addresses to the building way either, precisely for the reasons Hugues elaborated.
For buildings with a small number of addresses, e.g. your CSV example above with only three addresses on what looks to me like a semi-detached or townhouse, I would definitely just add separate nodes within the building way. However, ideally I try to map townhouses as separate ways entirely, if I can intuit the geometry of the units, and barring that I like to add the addresses to the front entrance door (with associated entrance=home and access=private tags). Although that’s predicated on knowing where the entrances are…
I do not have the geometries nice yet. Each ⌟ ⌞ ⌜ ⌝ of each + should be the identical shape and size, all nice right angles. I also have not yet added the sidewalks to connect each entrance to the greater sidewalk network.
, I missed this option (maybe because I don’t like seeing address nodes randomly positioned in building footprints), but it’s a valid one !
