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Build an analysis grid from a lon/lat bounding box.

grid_from_bbox.Rd

Picks a projected CRS for the area of interest (centred on the bbox), reprojects the extent into it, snaps the extent out to whole multiples of res, and returns a ready GridSpec.

Usage

grid_from_bbox(
  bbox,
  res,
  projection = c("laea", "aeqd", "utm", "pconic", "eqdc"),
  ellps = "WGS84",
  buffer = 0,
  dtype = "f32"
)

Arguments

bbox

Length-4 numeric lon/lat bbox (xmin, ymin, xmax, ymax), EPSG:4326.

res

Target resolution in the projected CRS units (metres for the supported projections); a scalar, or c(xres, yres).

projection

Projection family; the first is the default (see Details).

ellps

Ellipsoid for the centred projections.

buffer

Extent padding in projected units, applied before snapping.

dtype

Grid dtype.

Value

A GridSpec.

Details

The default projection is Lambert azimuthal equal-area ("laea") centred on the AOI: analysis wants an equal-area basis, so areas, fractions and densities are correct and there are no zone seams. "utm" is available when you want storage-oriented zone alignment (it is not equal-area). "aeqd" is azimuthal equidistant (true distances from the centre); "pconic"/"eqdc" are conics using the bbox's north/south edges as standard parallels. Centred projections are bespoke (no EPSG code), so a grid's CRS may print as its projection name rather than an EPSG code.

See also

grid_from_src() to build a grid from a raster or vector source; grid_spec() to build one from an explicit extent.

Examples

# An equal-area 30 m grid over a small AOI.
g <- grid_from_bbox(c(144.13, -7.725, 144.47, -7.475), res = 30)