[Talk-us] Updating unchanged TIGER imports to TIGER 2013

[Eric Fischer]

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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