Cells within a great-circle radius

Returns, for each centre cell, the cells whose centres fall within a great-circle distance of its centre, as an a5_covering.

Usage

a5_spherical_cap(cell, radius, units = "m")

Arguments

cell

An a5_cell vector of centre cells.

radius

Non-negative numeric scalar, great-circle radius in units, or a units object of length. It is measured on the sphere A5 uses internally, so membership can differ by a fraction of a percent of radius from distances given by a5_cell_distance().

units

Character scalar, the length unit of a plain numeric radius: "m" (the default) or any unit convertible from metres, such as "km".

Value

An a5_covering vector the same length as cell, at the resolution of each centre cell. NA where cell is NA. Use a5_uncompact() for the cells.

See also

a5_grid_disk() for hop-based selection.

Examples

cell <- a5_lonlat_to_cell(-3.19, 55.95, resolution = 8)
cap <- a5_spherical_cap(cell, radius = 1000)
cap
#> <a5_covering[1]>
#> [1] res 8: 1 cell (1 stored)
a5_uncompact(cap)
#> <a5_cell[1]>
#> [1] 63bb980000000000