equi7grid

The goal of equi7grid is … currently a barebones get equi7 and plot it.

The Equi7Grid is a project that aims to define 7 global zones that are better than the current UTM and MGRS grid for classifying high resolution satellite imagery. Here we provide a single simple endpoint Geopackage url with the 7 zones in it with straightforward layer names:

"/vsicurl/https://github.com/mdsumner/equi7grid/raw/main/data-raw/equi7grid.gpkg"

The layers are these (note ‘NA’ is slightly unfortunate in R, but oh well).

"AF", "AN", "AS", "EU", "NA", "OC", "SA"

Example

This plots each zone with its local centre in native Azimuthal Equidistant projection, the orange point shows the poles when they are in the frame.

Note that we have a single vector source Geopackage, with the 7 zones in it, each in their own native projection.

library(equi7grid)
dsn <- "/vsicurl/https://github.com/mdsumner/equi7grid/raw/main/data-raw/equi7grid.gpkg"


m <- do.call(cbind, maps::map(plot = F)[1:2])
library(terra)
#> terra 1.7.71
layers <- vector_layers(dsn)
par(mfrow = n2mfrow(length(layers)), mar = rep(0, 4))
for (i in seq_along(layers)) {
  v <- vect(dsn, layers[i])
  ex <- as.vector(ext(v))
  m1 <- project(m, to = crs(v), from = "EPSG:4326")
  m1 <- m1[m1[,1] >= ex[1] & m1[,1] <= ex[2] & m1[,2] >= ex[3] & m1[,2] <= ex[4], ]
  plot(NA, axes = FALSE, xlim = ex[1:2], ylim = ex[3:4], asp = 1, xlab = "", ylab = "")
  plot(v, axes = F, border = "firebrick", add = TRUE)
  lines(m1, col = rgb(0, 0, 0, .5))
  pt <- cbind(0, c(-90, 90))
  p0 <- project(pt, to = crs(v), from = "EPSG:4326")
points(p0, pch = "+", cex = 2, col = "orange")
box(col = "lightgrey")

}
#> Warning: [project] 1972 failed transformations

#> Warning: [project] 1972 failed transformations

#> Warning: [project] 1972 failed transformations

#> Warning: [project] 1972 failed transformations

#> Warning: [project] 1972 failed transformations

#> Warning: [project] 1972 failed transformations

#> Warning: [project] 1972 failed transformations

In the package we can read the entire set from a single FlatGeobuf, but you’ll need to use them locally as they don’t make sense in one single CRS.

The crs is recorded on each, but obviously we can craft our own scene and projection, here we just focus on the south in LAEA.

library(equi7grid)
fgb <- system.file("extdata/equi7_longlat.fgb", package = "equi7grid", mustWork = TRUE)
library(terra)
x <- vect(fgb)
m <- do.call(cbind, maps::map(plot = F)[1:2])
crs <- "+proj=laea +lat_0=-90"
plot(project(x[-(3:5), ], crs), col = hcl.colors(4))
lines(project(m, to = crs, from = "EPSG:4326"))
#> Warning: [project] 1972 failed transformations

Code of Conduct

Please note that the equi7grid project is released with a Contributor Code of Conduct. By contributing to this project, you agree to abide by its terms.