Here's a decent equ-distant logic for segmentizing tiles. Underneath is a segment-decomposition of an extent, so this could be applied generally in silicate as well.
ll_extent <- function(ext, ndiscr = 24, mindist = 1e5) {
## technically we don't need meridionally segmentation, but this is general enough
## for any set of segments assumed to be rhumb lines so it also works for graticules and
## will be fun for silicate
dat2 <- matrix(c(spex::xlim(ext),
spex::ylim(ext))[c(1, 2, 2, 2, 2, 1, 1, 1,
3, 3, 3, 4, 4, 4, 4, 3)],
ncol = 2)
l <- purrr::map(seq(1, nrow(dat2), by = 2),
~{
xy <- dat2[c(.x, .x + 1), ]
dst <- geosphere::distRhumb(xy[1, ], xy[2, ])
nn <- if (is.null(mindist)) ndiscr else round(dst/mindist)
nn <- max(c(nn, 3)) ## there's got to be a limit
cbind(approx(xy[,1], n = nn)$y, approx(xy[,2], n = nn)$y)
})
do.call(rbind, lapply(l, head, -1))
}
## segmentized with respect to distance for longlat segments (rhumb lines)
ext <- raster::extent(-40, 40, -60, -40)
## if we specify
pts <- ll_extent(ext)
bind_1 <- function(x) rbind(x, x[1, , drop = FALSE])
library(sf)
prj <- "+proj=laea +lat_0=-50 +lon_0=0 +x_0=0 +y_0=0 +datum=WGS84 +units=m +no_defs"
#prj <- "+proj=stere +lat_0=-90 +lon_0=0 +lat_ts=-70 +datum=WGS84"
sx <- st_transform(st_sfc(st_polygon(list(bind_1(pts))), crs = 4326),
prj)
plot(sx, reset = FALSE)
plot(st_cast(sx, "MULTIPOINT"), add = TRUE)
The more general silicate approach can be started with
sc <- silicate::SC0(spex::spex(ext))
idx <- do.call(rbind, lapply(sc$object$topology_, as.matrix))
dat2 <- as.matrix(sc$vertex[c("x_", "y_")])[t(idx), ]
Here's a decent equ-distant logic for segmentizing tiles. Underneath is a segment-decomposition of an extent, so this could be applied generally in silicate as well.
The more general silicate approach can be started with