[OSM-talk] Ditches

[Mike Harris]

Mike Harris
 

> -----Original Message-----
> From: Steve Bennett [mailto:stevagewp at gmail.com] 
> Sent: 15 December 2009 03:38
> To: John Smith
> Cc: openstreetmap
> Subject: Re: [OSM-talk] Ditches
> 
> On Tue, Dec 15, 2009 at 2:36 PM, John Smith 
> <deltafoxtrot256 at gmail.com> wrote:
> > I tend to mark bridges as layer=1 and anything at ground 
> level I don't 
> > set a layer tag, which seems the most logical to me since ditches 
> > aren't under the ground etc.
> 
> The one benefit of marking waterways layer=-1 (particularly for long
> ones) is that it's protection against anyone else forgetting 
> to set layer=1. That is, someone else might draw a bridge 
> over it somewhere and not set the layer. Well, if the 
> waterway itself is -1, that will still behave the same.
> 
> (And there's no downside)

I think there are two quite serious downsides:

1. When the waterway (e.g. ditch or stream) eventually links into other,
bigger downstream waterways (probably mapped by different people at
different times) these are very likely to be tagged (or assumed) as level=0.
But there is not usually a reverse waterfall at the junction! (this would be
water flowing uphill - as we go upstream the level  changes from 0 to -1
!!!).

2. Forgetting to draw a bridge - and give it a layer higher than what is
underneath - is naughty (:<) - but surely two wrongs don't make a right?
 
> Steve
> 
> 
>