[GRASS-user] OpenFileGDB input error

[Even Rouault]

On lundi 25 septembre 2017 22:24:21 CEST Markus Metz wrote:
> On Mon, Sep 25, 2017 at 8:23 PM, Even Rouault <even.rouault at spatialys.com>
> 
> wrote:
> > On lundi 25 septembre 2017 11:04:35 CEST Rich Shepard wrote:
> > > On Mon, 25 Sep 2017, Markus Metz wrote:
> > > > these multi-surfaces are in the layer with multi-polygons. OGR calls
> 
> these
> 
> > > > geometries multi-surfaces. Investigating a bit more, I found
> > > > 
> > > > curve-polygons within these multi-surfaces. Curve-polygons are in
> 
> turn not
> 
> > > > ordinary polygons, but defined by curves, and v.in.ogr (most GIS
> 
> software
> 
> > > > in general) does not support curves.
> > > 
> > > Markus,
> > > 
> > > 
> > > 
> > > Thanks for exploring the data files. Please suggest how I could extract
> > > 
> > > the useful polygons and attribute data. I know that agencies assume
> 
> everyone
> 
> > > buys ESRI's software and they're not concerned with accommodating those
> 
> of
> 
> > > us who do not. In the mid-1990s everyone used ESRI's export format
> 
> (.e00)
> 
> > > and it was easy to write input filters for grass back then.
> > 
> > You could for example use ogr2ogr to convert the curve geometries to
> 
> linear ones with
> 
> > ogr2ogr -f sqlite out.db in.gdb -nlt CONVERT_TO_LINEAR
> 
> Thanks a lot for this suggestion! How are these curves converted to linear
> features, i.e. how does ogr2ogr decide on reasonable conversion parameters
> such as distance between vertices?

It uses (actually OGR_G_ForceTo() which I mentionned and underlying functions) a 4 degree 
step for circular portions. This can be tuned by setting the OGR_ARC_STEPSIZE configuration 
option/env variable to a value in degree.

-- 
Spatialys - Geospatial professional services
http://www.spatialys.com
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