[R-sig-Geo] "invalid" geometries in shape data

[Edzer Pebesma]

The Delft group has done a lot of work on this; I could find these two
references:

http://www.springer.com/%3FSGWID%3D5-102-45-124048-p32597622
http://www.sciencedirect.com/science/article/pii/S009830041400020X
https://3d.bk.tudelft.nl/hledoux/pdfs/12_agile.pdf

I guess you will like the last two in particular; they point to
https://github.com/tudelft3d/prepair which also contains data.

There should also be some simple feature for sql compliance suite,
http://www.opengeospatial.org/compliance/downloads

When working with GEOS, it might be worth looking into the precision -
both rgeos and sf allow you to do so.

On 07/02/17 22:46, Michael Sumner wrote:
> Hi,
> 
> I'm interested in exploring the details of kinds of errors and warnings
> that are seen from the underlying geometry lib (GEOS) for spatial data in
> R.
> 
> I would like to also have a collection of  examples with actual data and
> reproducible code.
> 
> (The underlying theory and definitions and source code are all open and
> available, I'm looking for examples).
> 
> The kinds of errors I'm talking about come from the GEOS library under the
> hood, and this is more or less the same in the sp/rgdal as well as the new
> sf family.
> 
> Here's one example, this data set is not valid because of at least one
> "polygon self intersection", basically the ring winds back on itself:
> 
> library(maptools)
> data(wrld_simpl)
> rgeos::gIsValid(wrld_simpl)
> [1] FALSE
> Warning message:
> In RGEOSUnaryPredFunc(spgeom, byid, "rgeos_isvalid") :
>   Ring Self-intersection at or near point -95.902496339999999
> 66.946641920000005
> 
> I'd appreciate if you could send me similar examples, preferably
> reproducible with code but links to existing emails and online posts are
> welcome too. Feel free to construct examples from scratch that reproduce a
> particular warning/error.
> 
> If you like, you can use the Github Issues mechanism here, or just email
> them in reply.
> 
> https://github.com/r-gris/toposhop/issues
> 
> Cheers, Mike.
> 
> 

-- 
Edzer Pebesma
Institute for Geoinformatics  (ifgi),  University of Münster
Heisenbergstraße 2, 48149 Münster, Germany; +49 251 83 33081
Journal of Statistical Software:   http://www.jstatsoft.org/
Computers & Geosciences:   http://elsevier.com/locate/cageo/

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