On Fri, Apr 04, 2008 at 08:29:56AM +0000, Jonathan W. Lowe wrote: > When overlaying OSM with the recently available TIGER 2007 shapefile > data for Census Blocks in Alameda County (California), I'm encountering > both an offset and difference in relative position of the linework. In > short, OSM's data looks a lot more accurate and consistent -- streets > that should be straight actually look straight in OSM, but often zig-zag > in the TIGER 2007 edges and tabblock shapefiles. For a visual, visit: > http://www.giswebsite.com/demos/tiger_overlays.html
Um, isn't this the whole point of OSM? The TIGER data was imported so that it could be improved manually by users. This doesn't include just the geometry either: attributes have been changed as well. (See http://crschmidt.net/osm/history.html?type=way&id=21456366) > Any observations or ideas about where the misalignment might come from? This misalignment is common in TIGER: It's designed for 1:100000 accuracy. Anything more than that (you're at about 1:7500 there) is not going to be accurate. (Or at least likely to not be.) > Though it smells partially like a datum problem, that path hasn't > yielded any solutions yet. Doubtful. You'd have a more significant shift. This is the real power of OSM at work. See it, and marvel in its glory. :) Regards, -- Christopher Schmidt MetaCarta _______________________________________________ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/cgi-bin/mailman/listinfo/talk