[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) ;-)

cheers,
Martin
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