2012/9/30 Lester Caine <[email protected]>: > The problem *I* am seeing with the cadastre data I have looked at is that a > building is not simply one or two profiles, but several seemingly unrelated > elements all strange shapes and not relating to the imagery. Since there is > no explanation of the detail my feeling was that these SHOULD all have been > combined into a single element in the raw processing until such time as real > detail of a difference was available?
We provided explanations many times... Separate polygons can come from: - different ownership of building parts - different building but same looking roof on the aerials - different building type: porchs, garages, hangar, without wall tagged as "wall=no" It is not data errors, but much more detailed geometry compared to what you can do by simply surveying or trace on aerials. Some may think its too much details, some don't. > I'd EVEN be happy with a 'bot' going > around the current data and combining adjacent or overlapping buildings into > one where there IS no other tagging? This would at least give a better > representation of what is known and I believe would substantially reduce the > number of building elements? > This would not work in most cases like we explained already several times. Is cities this would make a whole block looking as one building. My own house would be merged with all the neighborhood houses. pnorman wrote: > The cadastre imports are more complicated. I'm not aware of any > comprehensive studies on the quality of the imports, but I did some > analysis[1] previously. Based on this, about 75% of the buildings are > building=yes wall=yes and 25% are building=yes with no wall tag. building=* + wall=no should be more in the 25% zone and building=* without wall=* tag in the 75% (we do not use wall=yes). Many wall=no polygons are porch, garages in France usually have walls... and locks ;) -- Christian Quest - OpenStreetMap France - http://openstreetmap.fr/u/cquest _______________________________________________ talk mailing list [email protected] http://lists.openstreetmap.org/listinfo/talk
