Meridian-wrap artefacts in shapefile reprojected with sf::st_transform()

[geotheory]

I'm getting 180° meridian-related artefacts when projecting a shapefile to Robinson - see horizontal red lines in the map below. Any suggestions why this is occuring or how to resolve?

require(sf)
require(ggplot2)

m = read_sf('https://gist.githubusercontent.com/geotheory/b75a60e1659daa484e0f513a6350be79/raw/3838e475af1cdfa73bd94f68fd0807ed3e9c956f/robinson-artefacts.geojson')
m = st_transform(m, crs = '+proj=robin +ellps=WGS84 +datum=WGS84 +no_defs')

ggplot(m, aes(fill = value)) + 
  geom_sf(col = 'red', size=.5) +
  theme_light() + theme(panel.border = element_blank())

[edzer]

Right after reading the geojson, I see

> st_bbox(m)
      xmin       ymin       xmax       ymax 
-179.99958  -55.98125  180.00042   83.62792 

so there seems to be a problem with your input data.

[geotheory]

Good spot @edzer. Do you know the best practice way to rectify this? I find that the (hacky)

for(i in 1:length(m$geometry)) m$geometry[[i]] = m$geometry[[i]] + st_point(c(-0.00042,0))` 

does in practice move the polygons, but st_bbox(m) does not update.

[mdsumner]

Try crop the input to -180/180 after also zero-buffering (that decomposes the shapes to segments and forces a degeneracy fix for some problems, and appears to work with your data).

Hacky? Sure, but balance that with what you need to do ;)

library(sf)
#> Linking to GEOS 3.8.0, GDAL 3.0.4, PROJ 6.3.1
library(ggplot2)

m = read_sf('https://gist.githubusercontent.com/geotheory/b75a60e1659daa484e0f513a6350be79/raw/3838e475af1cdfa73bd94f68fd0807ed3e9c956f/robinson-artefacts.geojson')
m = st_buffer(m, 0)  ## fixes some issues
#> Warning in st_buffer.sfc(st_geometry(x), dist, nQuadSegs, endCapStyle =
#> endCapStyle, : st_buffer does not correctly buffer longitude/latitude data
#> dist is assumed to be in decimal degrees (arc_degrees).
m = st_transform(st_crop(m, st_bbox(c(xmin = -180, xmax = 180, ymin = -90, ymax = 90))),  crs = '+proj=robin +ellps=WGS84 +datum=WGS84 +no_defs')
#> although coordinates are longitude/latitude, st_intersection assumes that they are planar
#> Warning: attribute variables are assumed to be spatially constant throughout all
#> geometries

ggplot(m, aes(fill = value)) + 
  geom_sf(col = 'red', size=.5) +
  theme_light() + theme(panel.border = element_blank())

^{Created on 2020-10-21 by the reprex package (v0.3.0)}