[gdal-dev] ogr2ogr to convert one CSV row of MULTIPOLYGON to many CSV rows of POLYGON

[Simon Eves]

Thanks for that, Jukka, and sorry for the vagueness of my original post...
I was under a very tight deadline to finish something on Thursday before
being away for a long weekend.

I got the same result as you without the -lco option. The output file just
contained the same MULTIPOLYGONS, although the file was not identical (I
presume due to precision of some of the numbers).

Adding that option, however, still doesn't create a third column, at least
not with my file, which I also neglected to say is very wide (hundreds of
thousands of small POLYGONs in each MULTIPOLYGON).

The file is private data, so I can't post it, I'm afraid.

In the end, I wrote a script to just read in the file as text and chop up
the lines, basically splitting on ")),((".

I'll have a play with geopandas too.

SE


On Fri, Oct 11, 2019 at 6:09 AM jratike80 <
jukka.rahkonen at maanmittauslaitos.fi> wrote:

> Here is a partial solution or workaround
>
> Take this as input
>
> id,wkt
> 1,"MULTIPOLYGON ((( 296 643, 623 660, 531 484, 349 507, 296 643 )), (( 681
> 635, 895 588, 632 432, 681 635 )))"
>
> Run this
> ogr2ogr -f csv -lco geometry=as_wkt -explodecollections wkt_expl.csv
> wkt.csv
>
> Get this result
>
> WKT,id,wkt
> "POLYGON ((296 643,623 660,531 484,349 507,296 643))","1","MULTIPOLYGON (((
> 296 643, 623 660, 531 484, 349 507, 296 643 )), (( 681 635, 895 588, 632
> 432, 681 635 )))"
> "POLYGON ((681 635,895 588,632 432,681 635))","1","MULTIPOLYGON ((( 296
> 643,
> 623 660, 531 484, 349 507, 296 643 )), (( 681 635, 895 588, 632 432, 681
> 635
> )))"
>
> So, the original multigeometry is included in both lines but an additional
> WKT columns contains the exploded polygons. Without -lco geometry=as_wkt
> just the the multipolygon geometry is written into both lines.
>
> id,wkt
> "1","MULTIPOLYGON ((( 296 643, 623 660, 531 484, 349 507, 296 643 )), ((
> 681
> 635, 895 588, 632 432, 681 635 )))"
> "1","MULTIPOLYGON ((( 296 643, 623 660, 531 484, 349 507, 296 643 )), ((
> 681
> 635, 895 588, 632 432, 681 635 )))"
>
>
> So something happened but not exactly what I would have guessed. Use case
> is
> a bit special but perhaps this is buggy behavior.
>
> -Jukka Rahkonen-
>
>
>
> jratike80 wrote
> > Hi,
> >
> > Please provide some test data and explain in details what did you try.
> > Spending some time for making an answerable question would certainly be
> > the
> > best way for getting fast and usable help.
> >
> > -Jukka Rahkonen-
>
>
>
>
>
> --
> Sent from: http://osgeo-org.1560.x6.nabble.com/GDAL-Dev-f3742093.html
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-- 
<http://www.omnisci.com/>
Simon Eves
Senior Graphics Engineer, Rendering Group
100 Montgomery St (5th Floor), San Francisco, CA 94104, USA


Email: simon.eves at omnisci.com | Cell:  415.902.1996
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