[OSM-talk] Key:layer update

Martin Koppenhoefer dieterdreist at gmail.com
Tue Mar 11 14:56:42 UTC 2014

2014-03-11 15:52 GMT+01:00 Dave F. <davefox at 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) ;-)

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