[OSM-newbies] Ungluing in Potlatch

[Dave F.]

Steve Bennett 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? 

The problem here is that the hedge is the edge of, lets say, a field 
polygon.
it can be mapped as another way joined to the edge of the field, or 
added directly to the polygon tags.
 
The way you map it, that hedge, is joined to the centreline of the road.

(The mapped way for a highway represents the centreline of a road/river 
etc not the edge.
The width of these is usually left up to the renderer or designated with 
the width=* tag).

Therefore you've got the hedge running parallel down the middle of the road.

As has been pointed out, if you had an access to that field, such as a 
gate through the hedge, that tag would appear as if the barrier was 
blocking the main highway. Not accurate at any level of detail.

Leave a gap between the field & the centreline of the road to allow for 
the estimated width of the way & that was any barriers will be shown 
going just through the hedge.

> 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?
>
> As you pointed out, at the micro level, you'll probably want something
> more precise than setting the boundary of the landuse polygon to be a
> road way, but it's a pretty good approximation for higher levels.
>
> What's interesting is that the landuse tags (and possibly others) seem
> to have subtly different meanings depending on the level of detail. A
> big block of landuse=residential would mean "this area is mostly
> houses". Whereas a smaller block with a detailed outline would mean
> "this is one house". 

I would use building=* for individual err.. buildings within a polygon 
of landuse=*

> It's hard to know how much extraneous stuff you
> can include in the area you're demarcating.
>   

Don't know why you call it extraneous. If it's physical, it's mappable.
How detailed you want to go depends on time & patience.

Cheers
Dave F.