Convert between coordinates and cells

a5_lonlat_to_cell() maps longitude/latitude coordinates to the cell containing each point at a resolution. a5_cell_to_lonlat() returns the centre point of each cell. Indexing a cell's centre at the cell's own resolution returns the cell.

Usage

a5_lonlat_to_cell(lon, lat, resolution)

a5_cell_to_lonlat(cell, as_dataframe = FALSE)

Arguments

lon

Numeric vector of longitudes in degrees.

lat

Numeric vector of latitudes in degrees, between -90 and 90. Non-finite coordinates (NA, NaN, Inf) give NA cells.

resolution

Integer scalar or vector of resolutions (0–30), recycled against lon and lat.

cell

An a5_cell vector (or character coercible to one).

as_dataframe

Logical scalar controlling the return container. When FALSE (default), centres are returned as a wk::xy() vector with WGS 84 CRS, the geographic-typed form that plugs into wk/sf pipelines. When TRUE, centres are returned as a base data.frame with columns lon and lat.

Value

• a5_lonlat_to_cell(): an a5_cell vector.

• a5_cell_to_lonlat(): a wk::xy() vector, or a data.frame with columns lon and lat when as_dataframe = TRUE.

See also

a5_cell_to_boundary() for full cell polygons, a5_polygon_to_cells() for areas.

Examples

cell <- a5_lonlat_to_cell(-3.19, 55.95, resolution = 5)
a5_cell_to_lonlat(cell)
#> <wk_xy[1] with CRS=OGC:CRS84>
#> [1] (-3.280745 56.43135)
a5_cell_to_lonlat(cell, as_dataframe = TRUE)
#>         lon      lat
#> 1 -3.280745 56.43135

# a cell's centre indexes back to the cell
ll <- a5_cell_to_lonlat(cell, as_dataframe = TRUE)
a5_lonlat_to_cell(ll$lon, ll$lat, resolution = 5) == cell
#> [1] TRUE