On 17 April 2012 02:50, Alan Mintz <[email protected]> wrote:
> At 2012-04-16 11:46, Sam Kuper wrote: > > On 16 April 2012 02:15, Serge Wroclawski <[email protected]> wrote: > On Sun, Apr 15, 2012 at 8:57 PM, James Ewen <[email protected]> wrote: > > > My personal feeling is that if you're going to map landuse to the > > physical edge of the road, then you should create the road as a > polygon > to show the edge of the road sharing the edge of the landuse. > > Roads as polygons is really poorly supported in OSM, and by poorly supported, > I mean that for the most part, they're not at all, and should be avoided. > > While you might be able to render them, the renderer already has support > for rendering road size based on road type- using areas will mess that > up. In addition, AFAIK, none of the routing engines in OSM support roads > as areas, so using them would be a problem for both renderers and routers. > In my view, OSM's lack of support for roads (which are polygons, not > lines) as polygons is a bug in dire need of fixing. > > Technically, everything is a polygon, since a line cannot exist in the > physical world. Boundaries are lines. > So, proper tools (including OSM) either add a width property to them or > assume a width based on other criteria (like road class). This works fine > for most purposes, and avoids the performance penalties of unnecessary > detail. I don't think it works fine at all. Lots of sections of road aren't symmetrical, for a start. Centreline plus width strikes me as misleading in these cases. Map roads as polygons, I say! And any of us finds that the tools don't > facilitate that, then (s)he should stop tagging for the moment and turn > her/his attention to improving the tools. > > If we get this right, then eventually we'll be able to use OSM to look up > the dimensions of roads, pavements, traffic islands, central reservations, > etc, which has the potential to be very useful in support of open planning. > > > I disagree. Even professionals see no need for this. Professionals at which aspects of which professions? > County road databases (all that I've seen) are all based on centerlines, > with traffic classes, widths, etc. well-used for necessary traffic > planning. The details of particular curb, lane, and island placements are > all available in the various map books, which are often available online by > links. I'd be genuinely interested to see examples showing how to correlate the data from such country road databases and map books. Please could you provide some? > This isn't because of lack of capability - all current tools have support > for polygons - it's simply a matter of using the right feature for the job. > There's no reason to overload one map layer with all that detail that is of > no importance to the vast majority of consumers. > Are you proposing that OSM should use one layer for roads as lines, and another layer for roads as polygons? > In the OSM world, I believe it's not presumptive to say that the vast > majority of mappers are unwilling to go out there with a survey crew and > measure the type of details your talking about, nor to (probably manually) > import them from engineering drawings, nor to want to support the > performance penalty caused by having to render all that detail, Not yet. Give it time. > for no real benefit to them or anyone they can think of. > Yet :-) Sam
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