[OSM-talk] Ditches

[John Smith]

2009/12/15 Peter Childs <pchilds at bcs.org>:

> If you have a bridge or a tunnel you don't need a layer tag a bridge
> infers it "goes over" a tunnel that it "goes over"

Let's start with the basics, we're talking about a water way and a
road way, what if neither is tagged with layer or tunnel or bridge
tags and there is no connecting nodes for the 2 ways,

> If there is neither a tunnel, or a bridge and no layer either then it
> must be a ford.

Only if there is a connecting node, otherwise you are just guessing as
what it should be.

> If you mark bridge=yes, layer=1 you are repeating your self. which is
> where problems start, see database normalisation.

That's making the assumption that all redundency is a bad thing, some
times it helps reduce guesswork.