[Gdal-dev] tigerpoly.py - how to use it?

[Jack Twilley]

>>>>> "Frank" == Frank Warmerdam <warmerdam at pobox.com> writes:

Jack> shpdump tells me that this shapefile is of type polygon and
Jack> contains 14293 shapes.  When I examined the output with the
Jack> rendering tool I normally use for shapefiles, it appears to have
Jack> all the possible layers jammed together.  I see water polygons,
Jack> land boundaries, major roads, minor roads, water features,
Jack> everything all together.  Is there a way to generate individual
Jack> shapefiles for each layer instead of one shapefile containing
Jack> everything?  I read through the script and didn't see any way to
Jack> set options to only output a single layer per file or anything.
Jack> If I'm missing something. please let me know as this would be
Jack> terribly useful.

Frank> Jack,

Frank> I am somewhat embarrassed to admit I don't know enough about
Frank> the meaning of the various fields in the tiger dataset to
Frank> really figure out which boundaries are for things like water
Frank> boundaries.  Basically, in TIGER/Line all the lines are in one
Frank> big heap, and if you want to split it into layers you need to
Frank> do so based on the various attributes on the edges and/or
Frank> polygons.

Okay.  So the sample script just connects all the dots without regard
to what they mean.  That's cool.

Frank> I have successfully work out country and stateboundaries before
Frank> mostly by only extracting edges for which the left and right
Frank> county or state id were different.

Frank> I would encourage you to download and review the TIGER/Line
Frank> manual to understand the data model better.  However, you might
Frank> find it easier to utilize one of the "predigested" tiger
Frank> datasets from folks like ESRI (shapefile format) or Manifold
Frank> (in their own format).

It's easier to download files from ESRI if only a few files are
desired.  It's pretty frustrating to get, say, all of California.

I'll look over the model and see if I can figure out how to do this.
I just wish someone else had done the hard part already. :-)

Jack.
-- 
Jack Twilley
jmt at twilley dot org
http colon slash slash www dot twilley dot org slash tilde jmt slash
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