On 13 May 2008, at 14:06, Ulf Mehlig wrote: > Please excuse me if this is a FAQ, I just didn't find an answer in the > wiki (possibly because it is obvious) ... > > In topological GISses like grass, borders are shared between adjacent > (vector) areas. However, I wonder how adjacent areas should be > digitized > in OSM (let's say, forests and farmland, or riverbanks and the > associated wetlands). Am I right in assuming that OSM ways always > belong > to one single area? If this is so, do I have to duplicate ways along > the > common border? JOSM informs about double ways when it validates data > so > I had the slight impression that they are not really wanted. > > I see a similar problem with line data (e.g. roads, streams) which may > happen to be an area border. From reading > > http://wiki.openstreetmap.org/index.php/Editing_Standards_and_Conventions#Tagging_Areas > > I think that using a street as a border of a plaza (or a block of > buildings) is not wanted. Does one digitize double ways, leading along > the same nodes, or does one make a separate area in a small distance > to > the existing line (street/stream), which might be topologically > incorrect and is more difficult to maintain? >
If you have a road and stream running parallel they would be entered as 2 ways that are parallel. The same happens for the carriageways of a motorway that are separated by a barrier. The way that I look at it, is if there is a barrier, such as a fence of wall, then the node in the way should not be shared. Otherwise the sharing of nodes isn't a problem, and can produce better results, especially for routing. Shaun _______________________________________________ talk mailing list [email protected] http://lists.openstreetmap.org/cgi-bin/mailman/listinfo/talk
