On Thu, 2009-02-26 at 19:27 +0100, Nop wrote:
> Hi!
>
> Osm2pgsql calculates some sort of z_order.
>
> Does anybody know how it does that? What input does it evaluate?
z_order is used to control the rendering order for objects of a given
type.
For highways, unimportant roads like unclassified and residential are
rendered first and the motorways are drawn on top. This ensures that
motorways are not obscured by more minor roads.
In addition, the presence of a layer, tunnel or bridge tag also effects
the z_order. This ensures objects on one layer render on top of objects
on a lower layer.
The are details which I have glossed over in the description above, you
will have to read the source to see the exact calculations. Or ask some
more specific questions.
Jon
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