[OSM-newbies] Ungluing in Potlatch

[Dave Stubbs]

On Tue, Jan 12, 2010 at 11:38 AM, Steve Bennett <stevagewp at gmail.com> wrote:
> On Tue, Jan 12, 2010 at 6:49 PM, Mike Harris <mikh43 at googlemail.com> wrote:
>> ... And when there is a hedge or fence alongside the road with a stile or
>> gate through the hedge giving access to the footpath? The stile is neither
>> in the road, or at the footpath / road junction node, nor in the field
>> adjacent to the road ... I don't think it is such a clear-cut situation as
>> you (rather vigorously IMHO (;>) imply ...
>
> I can't quite picture what you mean. There is a footpath perpendicular
> to the road, which crosses a hedge which is parallel and next to the
> road? If so, wouldn't you have two parallel ways, one tagged
> barrier=hedge, one highway=road, crossed by a highway=footway, with a
> barrier=stile at the junction of the hedge and the footway? And
> meanwhile, have a landuse=farm polygon sharing a way with the road, or
> with the hedge, as you prefer?

Yes, exactly: "or with the hedge". Except if you haven't tagged the
hedge then you just stopped the farm short of the road.

Both are completely justifiable and "right". The problem is, as you
allude to, a breakdown in the different abstraction levels being
applied.
We map roads as (roughly) centre lines because doing anything else
with just GPS is too hard (and then we get routing for free), but
we're happy drawing areas exactly from imagery or known shape. We also
tend to stick points of interest such as restaurants and post boxes
next to the road, not within it (the post box is usually on the
pavement, so could be argued that is should be in it, but putting it
next to the road tells us the correct side).

Joining a foot path to a road makes sense because it's the same
abstraction, joining an area to the road is a bit more complicated. If
you wish to maintain the connectedness then you join nodes, but if you
wish to maintain positional accuracy then you do it separate. The more
detailed you make the map the more important the positional part
becomes. I tend to do them as separated items, and the main reason is
post boxes. If you have a post box on the pavement by the road, we put
it by the road, and if you join a park to that road then the post box
ends up in the park, which it isn't :-)

It also makes stuff easier when someone comes along to put the road
areas in.. which I'm sure someone will start doing at some point.

Dave