[Talk-us] What to do about horrifically bad TIGER data

[Karl Newman]

On Thu, Aug 28, 2008 at 6:07 PM, Chris Lawrence <lordsutch at gmail.com> wrote:

> The existing data in OSM (imported from TIGER) for Webb County, Texas
> is really, really awful - if you want to see for yourself, visit
> http://www.openstreetmap.org/?lat=27.553&lon=-99.476&zoom=12&layers=B00FTF
> .
>  Centerlines of streets are off by dozens of meters, bits and pieces
> of streets are missing, etc. (And that ignores the fact that all three
> borders - US, Texas, or Webb County - are misaligned with each other
> and none of them is actually right.)
>
> Ideally it seems to me the best solution would just be to blow away
> the import and replace it with data from the TIGER Accuracy
> Improvement Project, but that hasn't reached Webb County yet in the
> public data.  The TIGER 2007 shapefiles seem to be somewhat better
> than what's in OSM now, but still not as accurate as the existing
> commercial coverage and possibly still offset from reality - I haven't
> tried an overlay of the 2007 data with GPS tracks yet, but my guess is
> that it's not much better aligned.
>
> So the question is: should I (we?) just hold off on trying to fix
> things until the AIP data is available, and then just blow away the
> data and replace it?  I know the TIGER import was a "one-off" but I'd
> imagine there are a lot of places like Webb County where nobody's
> touched the local data yet and the AIP data will be a much better
> baseline for future work (and also allow us to pull in the address
> data for geocoding, municipal boundaries, water features, etc. which
> didn't come in before).
>
>
> Chris
>

The problems you're seeing are the same for most of the US (the parts not
touched by the accuracy improvement project anyway). Generally we're all
trying to realign the streets using GPS tracks (preferred) or Yahoo aerial
photos. If you're really interested in improving the data of Webb County,
you might be better off seeing if you can locate a county street centerline
GIS data set, which is likely more accurate and up-to-date than even an
improved TIGER. Even then, you might want to use it as a background for
realignment instead of a wholesale delete + replace. As far as the address
data, it wasn't imported because there wasn't (and still isn't) an agreed
format for such a basic feature as address numbers. As far as water
features, Ian Dees was working on importing the NHD stuff, which to my
knowledge is the best available source, but I don't know what the status is
there.

Karl
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