Hi everyone. At the time OpenStreetMap imported the US Census TIGER map data, the Census was in the middle of their "Accuracy Improvement Program" that greatly improved the alignment of TIGER features in many areas for the 2010 census. Many of the TIGER corrections have since also been applied to OpenStreetMap, particularly in major metro areas, but not generally not systematically, and many others, particularly in rural areas, have not been applied.
I would like to update OpenStreetMap with as many of the corrections that have been made to TIGER as can be applied to Open StreetMap without altering anything that has been edited directly in OSM. In most cases this just means moving unedited OSM nodes that came from TIGER to the positions that TIGER currently indicates, although in some cases TIGER edges have had nodes added or removed, so the corresponding OSM ways must also have nodes added or removed. I don't propose to delete or move any intermediate points that have been linked to other OSM ways, or to move any nodes that have been moved in OSM since the TIGER import. I also don't propose to change any tags other than an addition to indicate the source of the new location data. Although this process will never change the topology of the network, there can occasionally be some odd-looking results where someone has moved (but not to the correct location) an OSM node that connects to an updated TIGER node, sometimes causing streets to have abrupt turns or to cross over themselves. I'm not sure what to do about these cases other than call them out and fix them manually. There are also many cases where TIGER 2013 knows about streets that were not built or not mapped in TIGER 2006. Some of these have also been added by OSM contributors but many others have not been. I think the right thing to do for these is to generate speculative OSM equivalents, but rather than checking any of them in directly, use something like MapRoulette to review each of them to see whether or not it ought to be adopted. The code I've been writing to generate the XML for these changes, mostly only tested so far on a few Indiana counties, is at https://github.com/ericfischer/osm-tiger-update A rendering of what the changes look like in those counties is at http://www.flickr.com/photos/walkingsf/8549176793/ Please let me know what you think of the idea and if there is a better way to do it. Thanks, Eric
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