[OSGeo-Discuss] Command line tool for dissolving polygon boundaries

[Simon Cropper]

On 02/03/11 12:41, Noli Sicad wrote:
> Dan,
>
> I am using Spatialite CLI for to this job.
>
> 1. Import shapefile into Spatialite
> 2. Create CSV.file for the counties
> 3. Use Vitual table for counties.csv
> 4. Use ST_UNION to create a new table with dissolved boundaries
> 5. Dump the new spatialite table to Shapefile file
>
> Noli
>
>
> On 3/2/11, Simon Cropper<scropper at botanicusaustralia.com.au>  wrote:
>> On 02/03/11 08:37, Dan Putler wrote:
>>> All,
>>>
>>> Is there a FOSS command line tool that runs under Linux for dissolving
>>> polygon boundaries based on a field in an attribute table that (ideally)
>>> works directly with shapefiles? There are a number of non-cli tools out
>>> there, but I'm working with all US counties on a county by county basis,
>>> and wanted to avoid importing each individual county into another product.
>>>
>>> Dan
>>> _______________________________________________
>>> Discuss mailing list
>>> Discuss at lists.osgeo.org
>>> http://lists.osgeo.org/mailman/listinfo/discuss
>>>
>>>
>>
>> Dan,
>>
>> My understanding is that SAGA can be accessed using the command line.
>> Check out this page...
>> http://sourceforge.net/apps/trac/saga-gis/wiki/Executing%20Modules%20with%20SAGA%20CMD
>>
>> If you intend to create a bash script to dissolve your shapefiles, it
>> would be just as easy I presume to write a script that opens the
>> shapefile, dissolves the polygons, then closes it; progressively working
>> through the list of counties. Remember most packages have the ability to
>> run script. gvSIG uses Jpython, QGIS python, etc. I fact from what I can
>> tell you can actually import QGIS modules into python.
>> http://desktopgisbook.com/Creating_a_Standalone_GIS_Application_1
>>
>>
>>
>> --
>> Cheers Simon
>>
>>      Simon Cropper
>>      Principal Consultant
>>      Botanicus Australia Pty Ltd
>>      PO Box 160, Sunshine, VIC
>>      W: www.botanicusaustralia.com.au
>> _______________________________________________
>> Discuss mailing list
>> Discuss at lists.osgeo.org
>> http://lists.osgeo.org/mailman/listinfo/discuss
>>
> _______________________________________________
> Discuss mailing list
> Discuss at lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/discuss
>
>
Noli,

That sounds great.

I thought I remembered having read somewhere that Spatialite could 
accept commands in this way but could not find a link to the webpage 
when putting together my reply.

Can you provide a step by step outline of the code necessary to do this?

Why is it necessary to create a CSV? Can't Spatialite manipulate 
shapefiles directly in a virtual table?

-- 
Cheers Simon

    Simon Cropper
    Principal Consultant
    Botanicus Australia Pty Ltd
    PO Box 160, Sunshine, VIC
    W: www.botanicusaustralia.com.au