[GRASS-user] Help: Completely confused about multi-layered vectors trying to import TIGER/Line files

[Dylan Beaudette]

On Thursday 28 February 2008, Tom Russo wrote:
> On Thu, Feb 28, 2008 at 07:57:48AM -0800, we recorded a bogon-computron 
collision of the <dylan.beaudette at gmail.com> flavor, containing:
> > TIGER data (in its current format) is a beast to work with-- in any
> > GIS. I have found that the simplest way to get "normal" looking data
> > out of the TIGER files was with the tutorial on processing these data
> > using PostGIS [1]. There are excellent instructions on the GeoServer
> > page [1] that make use of basic PostGIS functionality, along with some
> > self-contained java utilities. Following those instructions I was able
> > to get *most* of the point, line, and polygon data (with meaningful
> > attributes) extracted to simple tables in PostGIS. It would be a
> > simple matter to export to GRASS from there.
>
> I will take a look at that.
>
> I can also do some of this processing using OGR and Python (I once had the
> displeasure of working on such a script to make polygon shapefiles out
> of TIGER/Line files), but my goal here is not so much "what tools external
> to GRASS can I use to recast the problem" but "how can I learn GRASS tools
> better?"

Understandable-- although I would look for a better data set from which to 
learn about layers. That TIGER data is a beast.

> > I think that you can get 2000 TIGER data, by county, from our favorite
> > 'leading GIS vendor' for free [2]. That format should be simpler to
> > use.
>
> Yeah, but that won't teach me anything about layers in GRASS.

Understandably.

> > There is also tiger2shp [3] which is now distributed for free (Windows).
> >
> > Finally, it looks like the US Census will be moving away from the
> > current data format, and will be henceforth distributing their data as
> > shapefiles [4]. Hurray!
>
> Yeah, saw that some time ago.  I had concerns about the initial set of
> attributes they said they would be distributing in the data, but they have
> changed that and it looks usable.  Those will be available in March,
> according to http://www.census.gov/geo/www/tiger/tgrshp.html
>
> > I cannot offer any insight into the GRASS vector/layers system right
> > now, but there are several good threads from a couple of months ago on
> > this very topic (vector/layers/confusion).
>
> I'll see if I can search the archives and find those.

Here is a good starting point:

http://www.nabble.com/forum/Search.jtp?forum=1200&local=y&query=layer

If there aren't any good examples, it might be nice to work up something for 
the new NC sample dataset -- so that there is a common framework for 
teaching/learning about vector layers. In the last 5 years I have seen the 
topic come up several times.


Cheers,
Dylan

-- 
Dylan Beaudette
Soil Resource Laboratory
http://casoilresource.lawr.ucdavis.edu/
University of California at Davis
530.754.7341