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

[Markus Metz]

first replying to your initial post:

> I'm working in EPSG:3413 and  gdalsrsinfo reports "PROJ.4 :
'+proj=longlat +datum=WGS84 +no_defs '" for this shapefile.

The corresponding PROJ.4 term for EPSG:3413 should be
+proj=stere +lat_0=90 +lat_ts=70 +lon_0=-45 +k=1 +x_0=0 +y_0=0 +datum=WGS84
+units=m +no_defs

> When I v.import it in GRASS, it takes ~2 hours, and there are many
boundaries that appear incorrect. If I set "snap=-1" it only takes a few
minutes, but there are more errors.

this is because v.import snaps by default with snap=1e-13. A fixed snapping
threshold does not make sense, it depends on the actual input data.
Therefore I have changed v.import in trunk and relbr72 (r71577,8) to not
snap by default.

On Sat, Oct 21, 2017 at 10:42 AM, Ken Mankoff <mankoff at gmail.com> wrote:
>
>
> On 2017-10-20 at 18:22, Helmut Kudrnovsky <hellik at web.de> wrote:
> > try to use v.in.ogr instead in a location with the original projection
> > and then reproject it.
>
> If I import into its native projection with ~v.in.ogr~ it displays fine.
If I then reproject with ~v.proj~, data is once again dropped.

Can you post the error message of v.proj, why data are dropped?

>
> ~v.in.ogr~ complained about overlaps, which I don't think should exist,
even if they are valid in theory.

Overlapping polygons can be ok, depending on what kind of information
should be in the input.

> I am currently re-importing with ~snap=1E-13~ as suggested by ~v.in.ogr~,
but that is taking a few hours. Anyway, it seems likely the reprojection
won't work in this case either.
>
> I find it strange that QGIS handles this both instantly and correctly (at
least correctly based on a cursory visual examination).

Can you post a link to the problematic shapefile? Then we can 1) try to
find out what exactly is causing these problems, 2) fix these problems.

Markus M
>
>   -k.
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