On Tue, Jan 22, 2019 at 10:18:51PM +0100, Tobias Zwick wrote: > On 22/01/2019 10:47, Lionel Giard wrote: > > So, i'm really in favor of the level=* for a "data user friendly" tag > > (that could correspond to local numbering, but not always) and a special > > tag for the local levels. At this moment i would see a *local level tag > > *like "level:ref=*" or "loc_level=*" (like we have for name and loc_name > > ?) but _*on each object*_, as it would not be realistic to use an > > outline in the cases i present). > > > > PS: i hope my example is not too confusing, or badly explained. :-) > > I understand it. (To recap - ) you are giving a real-life example of > what Roland described: Using the level tag outside of (a single) > building but in a wider scope. > To be able to show on indoor maps what is really on the same level on a > scope that exceeds single buildings, you need to use the level-tag also > in a scope that exceeds single buildings, making it important that the > level indices of (neighbouring) buildings match. > > So, basically, your example is like a situation where two malls are > connected by a footbridge, but one mall labels its level there as "UG" > and the other as "M".[1] > If the level tag was allowed to be non-numerical and required to always > follow the building operator's denomination even if they are letters and > not numbers, the information on what buildings (and non-buildings like > footbridges, train stops, tunnels etc.) connect to each other is lost.
I think "level" in adjacent buidlings can never be relied upon. In some cases key:ele would help. > So, though, this means that (already now), the level tag enjoys somewhat > of a dual-usage: > - On the one hand, it should follow the building operator's denomination > as long as it is numeric, thus, is or comes close to how the level is > really named "on the ground" > - On the other hand, in a wider context, it is used similarly to the > layer tag: An arbitrary ("programmer's") value to arrange a Z-order. > > I think this dual usage may come back to bite us. correct and it is tempting to do it so. If and when it bites us I think we will find "rescues". > Second, why can not the layer tag be used to arrange the global z-order > of things? layer is too weak as ordering operator. 2 ways layer=-1 + layer=2 can meet in a node and (depending on node type if any) - will usually be assumed to meet exact level. Also there are loads of historical baggage associated with layer limiting its usability. Because of widespread errors/abuse data consumers will/have to ignore layer in many combinations. Richard _______________________________________________ Tagging mailing list Tagging@openstreetmap.org https://lists.openstreetmap.org/listinfo/tagging