[josm-dev] Validator

[Dermot McNally]

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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