[josm-dev] Validator

Pieren pieren3 at gmail.com
Wed Aug 20 10:42:15 BST 2008


I think the layer=-1 is a good trick in urban zones where you have
many bridges. But is it necessary to add a layer -1 in the countryside
even in sections where you have no crossing at all ?
Anyway, is that the correct ML to discuss mapping rules ?
Pieren

On Wed, Aug 20, 2008 at 11:24 AM, Dermot McNally <dermotm at gmail.com> wrote:
> 2008/8/20 Gervase Markham <gerv at gerv.net>:
>
>> I think that both waterways and roads are layer 0, "the ground", and
>> when one crosses another, the upper one should have layer=1 - because
>> there's air between it and the actual surface of the earth. I would
>> apply this to any ground-based physical features, not just roads and rivers.
>
> That articulates my view pretty well. Once again, consider that
> "layer" isn't the same as "level". We don't care whether a bridge
> rises up above the "level" of the road either side of it. The
> important thing is that at the point where it crosses the river, the
> road must be on a higher "layer" than the river. So along the length
> of a way, it is acceptable (and unavoidable) to have "jumps" in layer
> that may not reflect actual changes in elevation. Layers exist to
> determine the drawing order of overlapping elements, nothing more.
>
> Dermot
>
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