[GRASS-user] large shapefile not importing properly with v.import

[Helmut Kudrnovsky]

Markus Metz-3 wrote
> On to the next one:
> 
> On Fri, Oct 20, 2017 at 10:07 PM, Helmut Kudrnovsky <

> hellik@

> > wrote:
>>
> [...]
>>
>> o World database of protected areas (~ 1 GB):
>>
>> https://www.protectedplanet.net/
> 
> First problems: lots of warnings like
> WARNING: Degenerate island (1 vertices)
> WARNING: Feature (cat 
> <XY>
> ): degenerated polygon (1 vertices)
> 
> These are invalid geometries in the input
>>
>> >The real cleaning happens only if the snap option is set to > 0.
> 
> From the WDPA manual:
> "There are many overlapping protected areas in the WDPA. These can be
> overlapping areas with
> different IUCN categories or the overlap of national protected areas with
> designations under
> regional or international conventions and agreements."
> 
> Thus I would not regard all overlapping areas as errors. I used a spatial
> subset for testing:
> v.in.ogr spatial=5.467,43.842,14.3,50.558
> that's the Alps and a bit around.
> 
> v.in.ogr suggests a snapping value in the range 1e-5, 1e-13. I started
> with
> 1e-9 and got rid of the warnings like
> WARNING: Unable to calculate area centroid
> 
> but some incorrect boundaries remained in the output. With snap=1e-8,
> these
> incorrect boundaries disappeared.
> 
> The output contains lots of small areas. According to GIS_AREA in the
> attribute table, the smallest areas in the input are larger than 100
> square
> meters, so I cleaned with v.clean tool=rmarea thresh=100, getting rid of
> 60% of all areas in the output.
> 
> In earlier years, the WDPA was separated into different shapefiles: one
> for
> marine areas, one for IUCN I-VI, one for all other areas. Now everything
> is
> in one shapefile / GDB. When importing these data, a spatial and an
> attribute filter should be set for v.in.ogr.

thanks for also testing this data set. I'll add some notes in the wiki about
importing these datasets.

thanks.




-----
best regards
Helmut
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