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

[Barry Rowlingson]

Searching GIS StackExchange for [r] and TopologyException might find you a few:

http://gis.stackexchange.com/search?q=%5Br%5D+topologyexception

[answered one of these just today:
http://gis.stackexchange.com/questions/227569/r-error-fortifying-dataframe-from-shapefile]

Barry

On Tue, Feb 7, 2017 at 9:46 PM, Michael Sumner <mdsumner at gmail.com> 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.
>
>
> --
> Dr. Michael Sumner
> Software and Database Engineer
> Australian Antarctic Division
> 203 Channel Highway
> Kingston Tasmania 7050 Australia
>
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>
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