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Description
I think I found abug in GEOS, but I am not 100% sure. I use the GEOS library via the R programming language using the terra, sf or geos packages which all rely on GEOS. With all of these three, I had issues with buffers around some lines. Starting from a certain buffer size, the buffer intersects the line it was supposed to buffer. These issues don't arise when the buffer is smaller, e.g. 1m instead of 2m.
I already opend two other issues for this in the respective packages: r-spatial/sf#1986, rspatial/terra#765. Someone suggested the issue would be at the GEOS package, so I wanted to let someone know although I use GEOS only via the R API.
Here is some example code and output in R:
# input data
ch_crd <- structure(
c(1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3.50850510439515, 3.34156954142671,
2.87898194958676, 2.72374630132234, 2.2922345396554, 2.29312419890067,
2.32261681738335, 2.49720251348322, 3.19886481773371, 3.50850510439515,
1.62424111363924, 1.64507013529592, 1.71055495856562, 1.8867890234822,
2.38801074041958, 2.91005134572971, 3.22939872710867, 3.25684154033292,
2.97375702861173, 1.62424111363924), dim = c(10L, 3L), dimnames = list(
NULL, c("id", "x", "y")))
# printed data frame with coordinates
> ch_crd
id x y
[1,] 1 3.508505 1.624241
[2,] 1 3.341570 1.645070
[3,] 1 2.878982 1.710555
[4,] 1 2.723746 1.886789
[5,] 1 2.292235 2.388011
[6,] 1 2.293124 2.910051
[7,] 1 2.322617 3.229399
[8,] 1 2.497203 3.256842
[9,] 1 3.198865 2.973757
[10,] 1 3.508505 1.624241
library(terra)
# create line object
ch_lin <- vect(ch_crd, "lines", crs = CRS("EPSG:25832")@projargs)
# create 2m buffer around object
ch_buff <- buffer(ch_lin, 2)
# plot buffer per section
plot(ch_buff, col = "lightblue")
plot(ch_lin, add = T)
library(sf)
# create line & buffer
ch_lin = st_linestring(ch_crd[, 2:3])
ch_lin = st_sfc(ch_lin, crs = "epsg:25832")
ch_buff = st_buffer(ch_lin, 2)
# plot line & buffer
plot(ch_buff, col = "lightblue")
plot(ch_lin, add = T)