Comments (6)
I am not sure why CGAL throws an error there, we'll investigate.
But the problem is that the last polygon in the SHP is invalid, it's WKT is:
POLYGON((29.59067730619167236 -28.787288587651922,29.58994774533908156 -28.78723217025416403,29.58932547284739201 -28.78683724761136276,29.58878903104476521 -28.78627306981286793,29.58881048871658592 -28.78557724632377557,29.58891777707746584 -28.78414797270364645,29.58951859189644296 -28.78358378035597198,29.59033398343718702 -28.78364019972809018,29.59084896756798599 -28.78373423194659253,29.59091334058433986 -28.78373423194659253,29.59087042524070554 -28.78373423194659253,29.59087042524070554 -28.78379065123732516,29.59087042524070554 -28.78377184481073314,29.59082750989617949 -28.78386587691133514,29.59082750989617949 -28.78384707049752933,29.5907631368799855 -28.78558664937470724,29.59067730619167236 -28.787288587651922))
If you use prepair we have newer/better code to repair single polygons and there it works, the result is:
MULTIPOLYGON (((29.590677306191672 -28.787288587651922,29.590763136879985 -28.785586649374707,29.590827509896179 -28.783847070497529,29.590827509896179 -28.783865876911335,29.590870425240706 -28.783771844810733,29.590870425240706 -28.783734231946593,29.590848967567986 -28.783734231946593,29.590333983437187 -28.78364019972809,29.589518591896443 -28.783583780355972,29.588917777077466 -28.784147972703646,29.588810488716586 -28.785577246323776,29.588789031044765 -28.786273069812868,29.589325472847392 -28.786837247611363,29.589947745339082 -28.787232170254164,29.590677306191672 -28.787288587651922)))
So that's your solution for the time being, cheers for reporting that bug.
from pprepair.
Hi Hugo,
Many thanks for your response, and thanks for the prepair solution. If I could follow up to get your advice, we are using pprepair to clean anything from individual polygons to several polygons. We call pprepair out of R using two functions:
library(rgdal)
library(rgeos)
callPprepair <- function(dirnm, spdfinname, spdfoutname, crs = crs) {
Function to make system call to polygon cleaning program pprepair
Args:
dirnm: directory where the shapefiles will go
spdfinname: Name of the ESRI shapefile written to disk that needs cleaning, without the .shp extension
spdfoutname: Name of shapefile that pprepair should write to, without the .shp extension
Returns:
spdf of cleaned polygons, pointing to a temporary shapefile written to disk
inname <- paste(dirnm, "/", spdfinname, ".shp", sep = "")
outname <- paste(dirnm, "/", spdfoutname, ".shp", sep = "")
ppcall <- paste("/usr/local/bin/pprepair -i", inname, "-o", outname, "-fix")
ctch <- system(ppcall, intern = TRUE)
polyfixed <- readOGR(dsn = dirnm, layer = spdfoutname, verbose = FALSE)
polyfixed@proj4string <- crs
return(polyfixed)
}
createCleanTempPolyfromWKT <- function(geom.tab, crs) {
Function for reading in a spatial geometry from PostGIS and creating a temporary shapefile out of it
Args:
geom.tab: Dataframe with geometry and identifiers in it. Identifier must be 1st column, geometries 2nd col
crs: Coordinate reference system
Returns:
A SpatialPolygonsDataFrame
Notes:
Uses callPprepair function to clean up read in polygons and write them to a temporary location
polys <- tst <- sapply(1:nrow(geom.tab), function(x) {
poly <- as(readWKT(geom.tab[x, 2], p4s = crs), "SpatialPolygonsDataFrame")
poly@data$ID <- geom.tab[x, 1]
newid <- paste(x)
poly <- spChFIDs(poly, newid)
return(poly)
})
polyspdf <- do.call("rbind", polys)
polys.count <- nrow(polyspdf)
td <- tempdir()
tmpnmin <- strsplit(tempfile("poly", tmpdir = ""), "/")[[1]][2]
tmpnmout <- strsplit(tempfile("poly", tmpdir = ""), "/")[[1]][2]
writeOGR(polyspdf, dsn = td, layer = tmpnmin, driver = "ESRI Shapefile")
polyfixed <- callPprepair(td, spdfinname = tmpnmin, spdfoutname = tmpnmout, crs = polyspdf@proj4string)
valid.string <- as.character(gIsValid(polyfixed))
return(list("polygons" = polyfixed, "polygoncount" = polys.count, "validity" = valid.string))
}
Would you suggest a workflow that uses prepair first to fix individual polygons, followed by pprepair to clean up overlaps, etc, or if the validity issue we found something that pprepair is likely to be able to clean up?
Following from this, is there a way to use pprepair to read WKT directly, as I see prepair does?
Thanks!
from pprepair.
At this moment I would suggest that workflow yes. First it's less likely to crash (although I was surprised, it very rarely happens) and second, prepair gives you more control over the repair. You should perhaps check the "--isr" option that performs snap rounding and permits you to eliminate "spikes" (there were a few, probably unwanted, in the dataset you linked to). "--minarea" could also be useful.
We plan to integrate the prepair code in pprepair in the near future, not sure when we'll have the time though.
pprepair doesn't read directly WKT, although a GeoJSON file should work, or anything OGR.
from pprepair.
I agree with Hugo here. At this moment it's probably a good idea to call prepair for individual polygons before using pprepair. We do have the intention of incorporating the code that solves this problem (I think it's related to #12) into pprepair, but we need to put some more thought into the consequences before doing so.
from pprepair.
Great, thanks for your responses on that. I will look at revising our code to do this. Thanks for the rapid responses...
from pprepair.
This will definitely be solved by #12, so I'll close this issue.
from pprepair.
Related Issues (20)
- pprepair output: invalid polygons returns points HOT 6
- poygons disapear after pprepair HOT 9
- Fails to build with GDAL 2.0
- --outerrors option doesn't work HOT 2
- pprepair for self-intersection increases the number of features HOT 1
- pprepair triangulation (--outtr option) contains invalid polygons HOT 2
- in the triangulation output, record an array with the original polygon IDs
- (p)prepair fails on it`s own output polygons (.shp) HOT 6
- pprepair generates lots of spikes (dangling edges) HOT 12
- In case of ties in the "r -LB" , RN choice should only be between the LB neighbors, not all neighbors
- Segmentation fault: 11 when working with empty properties in a geojson input file HOT 3
- segfault when reading features with no geometry HOT 4
- pprepair hangs HOT 3
- Tagging error with triangles? HOT 5
- Forced region splitting HOT 1
- Specifying SHP-file output doesn't work as advertised HOT 1
- Crash on first run HOT 1
- pprepair creates duplicate vertex
- pprepair hangs on this geometry HOT 2
- CGAL 5.0 support HOT 1
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from pprepair.