[Talk-GB] Sorting out layering in East Anglia, Essex, London and Kent

Ed Avis eda at waniasset.com
Wed Apr 20 14:05:45 BST 2011

Peter Miller <peter.miller at ...> writes:

>It it is in a cutting the the 'cutting' tag would be appropriate. because the
>layer tag saying nothing about relative height to a parallel way, only about
>the z ordering at crossing points.

This is the problem - there are two different conventions for the layer tag which
most of the time co-exist, but make it hard to interpret or clean up the data.
It can be considered as applying only at crossing points - in which case it makes
little difference whether you tag the roads as layers 0 and 1 or -1 and 0, and it
makes little difference if the layer=1 extends further along the way than the
crossing (in other words you need not carefully split a way into sections, you
can just tag layer for a nice long stretch until you get near the next crossing).

Or you can think of it as height relative to any *nearby* object, even if not
touching.  I think we have a mixture of both conventions.

Above all, the wiki is not to be trusted - it's worth checking on this list.

Ed Avis <eda at waniasset.com>

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