[GRASSLIST:922] Re: GMT / GRASS use / shp2gmt

[Trevor Wiens]

On Wed, 26 Apr 2006 11:30:59 -0700 (PDT)
Allan Hollander <adh at ice.ucdavis.edu> wrote:

> Trevor,
> 
> I'm sorry that was a bit terse. Basically, both the use of shp2gmt and the
> awk script are preprocessing steps before you run psxy. The processing
> flow is like this:
> 
> 1) Run the shp2gmt script over the shapefile to produce a 
> preliminary input file for psxy. In a bash shell, this would be something 
> like:
> 
> % shp2gmt usstates > usstates0.xy
> 
> 2) Run the awk script over the preliminary input file to produce the final
> version of the input file for psxy which is tagged for polygon-by-polygon
> symbology. Assuming the awk script below is in a file named alaska.awk,
> the command line here would be:
> 
> % awk -f alaska.awk usstates0.xy > usstates.xy
> 
> 3) You can then plot this input file using psxy, as follows:
> 
> % psxy usstates.xy [other GMT parameters go here...] >> outputplot.ps
> 
> By the way, there's nothing magical about using awk -- most any scripting 
> language can be used for this sort of processing (a lot of people would 
> use perl, for instance).
> 
> Hope this helps,

Hmm...

OK, now I understand. I think however that probably for my needs having
the ability to select objects by attribute values using SQL is
important so I will probably load my base information into PostGIS and
export my themes as different layers. I will keep this option in mind
however because this way would be faster than going PostGIS to shape
and then shape to xy.

Thanks again.

T
-- 
Trevor Wiens 
twiens at interbaun.com

The significant problems that we face cannot be solved at the same 
level of thinking we were at when we created them. 
(Albert Einstein)