[Tagging] Layer=* tags disappearing

[Andrew Errington]

On Tue, October 12, 2010 14:39, Peter Budny wrote:
> I've noticed that some bridges and tunnels I've edited previously no
> longer have layer=* tags on them.  I could swear they did before.  Is there
> some bot (or person) going through and removing them?

If there was, there would be an entry in the object's history.  I looked
at one bridge there and it looks like a Tiger import, with no layer=* tag.

<http://www.openstreetmap.org/browse/way/42269006/history>

It was changed today (I'm guessing by you) and now has a layer tag.  There
is no intermediate stage when it did then did not have a tag.

> I thought that setting bridge=yes or tunnel=yes didn't imply anything
> about the layer.  The wiki says, "it is better to explicitly state the
> layer".  It definitely appears that the renderers don't get the layering
> right without explicit tagging.

True.  I always explicitly tag layer=* on every bridge, even if it doesn't
appear to cross anything.

> For reference, I'm looking at http://www.openstreetmap.org/?lat=33.89221&
>  lon=-84.45676&zoom=17&layers=O (which I just fixed) --

Looks like there are many layers there!  I would suggest you used layer 1,
2 *and* 3.

I think that the swooping curve on top (Way 41644292) should be layer 3.

These should all be layer 2:
Way 41644319
Way 41644287
I-285 bridges

These should be layer 1:
Larry McDonald Memorial Highway
Way 41644312

And there is an obvious 'ground' layer.

My point is, to make the structure more obvious you could consider a road
to be on the same layer as its bridge, and therefore any other bridge that
crosses that road would be on the layer above, even if it doesn't actually
cross another bridge.

Best wishes,

Andrew