2014-03-11 15:52 GMT+01:00 Dave F. <dave...@madasafish.com>: > I agree it does say which object is above another. For the benefit of the > renderer. Who else needs that data? Certainly not routers. >
well, everybody who tries to understand what this specific part of the map represents will have to have this information in the case of objects that overlap in 2D. > > > >> For instance if you had an area tagged 'park' & another area within it >>> tagged 'lake' you could add a 'layer' tag to 'lake' to ensure the render >>> displayed it. >>> >> -1, you should not add any layer in this case (tagging for the renderer) >> > > The correct expression is 'don't tag incorrectly for the renderer'. >> There's /nothing/ wrong in making OSM data clearer & more accurate. > > > > +1, but adding a layer=1 to a lake in a park isn't clearer or more > accurate, they are both on the same layer, the lake is in the park, not > above (usually). > > > Which confirms my point perfectly. You're are correct: The lake & park > /are/ at the same level, which is why the layer tag is needed. It's used > purely to let the renderer know which entity to put on top of the pile show > it display properly. > no, it would be wrong to use the layer tag here, as it would move the lake out of the park and above. OK, this sounds unprobable to a human, and he might still understand what was the intention (by interpretation and common sense), but the modelling remains "wrong" (IMHO). Btw.: a lake is a physical object, while a park is an abstract object, so they aren't on the same level anyway (but on the same layer) ;-) cheers, Martin
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