[OSM-talk] US County and State Borders Was: Re: TIGER, which states next?

[Dave Hansen]

On Wed, 2007-10-24 at 13:14 -0400, Ted Mielczarek wrote:
> On 10/24/07, Dave Hansen <dave at sr71.net> wrote:
> > On Wed, 2007-10-24 at 10:31 -0400, Ted Mielczarek wrote:
> > >
> > > Yep, they're all TIGER data, provided as shapefiles by the Census
> > > bureau.  I've already imported the state boundaries for the northeast
> > > of the US, you can see them in mapnik as dashed red lines.  I didn't
> > > just throw them all in willy-nilly, I split the borders into sections
> > > so I could label them left:state and right:state, and I deleted
> > > overlapping border sections.
> >
> > Manually, or programatically?
> >
> > We'll probably have to automate it to get county boundaries.  There are
> > just too many of them to do manually.
> 
> Manually.  It's not so bad for states since they have nice large
> borders and large overlapping areas.  It would be tedious for
> counties.  There's probably an algorithm you could use to find the
> common borders, but I haven't looked at all.

This ruby code:

https://www.sr71.net/~dave/osm/tiger/tiger-to-osm-v0.7.tar.gz

has stuff to coalesce points that are close to each other and ways that
have common endpoints.  It might need some education about the
left/right tags, but you might find it useful.

-- Dave