[Tagging] layer=-1, rivers, bridges and tunnels

Richard Z. ricoz.osm at gmail.com
Mon Apr 21 18:48:43 UTC 2014

On Mon, Apr 21, 2014 at 11:42:34AM +0200, Pieren wrote:
> On Sat, Apr 19, 2014 at 1:46 AM, Andrew Errington <erringtona at gmail.com> wrote:
> > I am using OSMAND for navigation, so it's important to have clear maps.  Now
> > that I have downloaded the latest data for this area (which includes my
> > updates) I am much happier with the map I see.
> Without any additional tags like "tunnel=*" or "covered=*", a
> "layer=-1" river shouldn't be rendered differently than a "layer=1" or
> even in the absence of any "layer" tag. This is a bug in OsmAnd. You

except for the the very frequent case when the river with a layer=-1
goes through a landuse=* area with a layer=0.
There is no general agreement that the renderer is supposed to override
the layer and render the river on top of the landuse in this case and
last time I looked the renderers were evenly split about how to render 
this. This is clearly undefined behavior and asking for trouble.

> You clearly admit that you tag for the renderer.

Tagging for the renderer is good as long as it is correct tagging. It is
only wrong when it mean "deliberately tagging contrary to best practice" 
for the purpose of achieving a certain effect (not limited to rendering btw).

His changes (as he explained them) were certainly correct and most likely 
an improvement over the previous state.


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