[Gdal-dev] OGR: TIGER/Line polygons

[Curt Mills]

On Wed, 20 Oct 2004, Schuyler Erle wrote:

> * On 20-Oct-2004 at  2:33PM PDT, Curt, WE7U said:
> >
> > I end up with a LOT of polygons.  Upon drawing that shapefile
> > polygon file to my display it looks very similar to what it would
> > look like if I had drawn all of the individual line features from
> > multiple layers of the original raw tiger file.
>
> Yes, that is what you get - TIGER/Line, frankly, contains a lot of
> polygons! If you do a topological cleanup - removing spurs and bridges
> and so on - you get the actual polygons, one per census block - which
> is typically a pretty small area.  Like I said earlier, I use GRASS
> for this.

And I'm trying to do it in straight C.  It's looking pretty good so
far, except for the "hole" polygon thing I just posted about.  The
maps look very good on the screen anyway.


> > So far I'm no closer to getting a Shapefile with just the lake
> > polygons in it.  I'll keep studying the TIGER docs and the Python
> > script and will learn more about it.
>
> The one thing tigerpoly.py doesn't do is connect area landmarks with
> the polygons - I've been pondering how to do this. However, if hydro
> features are all you're after, you can try selecting and merging the
> polygons from TIGER/Line that have a ZCTA5 attribute ending in 'HH' -
> this seems to select all of the water polygons in my vector layers.

I've got all of the polygon pieces connected together now (via
C-code), including the Landmarks/AreaLandmarks stuff.  It's a bit of
a pain.  One of our other developers tweaked tigerpoly.py so that it
does this as well.

-- 
Curt, WE7U.				archer at eskimo dot com
http://www.eskimo.com/~archer
  Lotto:  A tax on people who are bad at math. - unknown
Windows:  Microsoft's tax on computer illiterates. - WE7U.
The world DOES revolve around me:  I picked the coordinate system!"