"invalid" geometries in shape data
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.
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