Identify neighbouring grid squares — bng

Find BNG references which share a grid cell edge with a target BNG reference.

Usage

bng_neighbours(bng_ref, ...)

bng_is_neighbour(bng_ref1, bng_ref2, ...)

Arguments

bng_ref: target object of type BNGReference
...: additional parameters. Not currently used
bng_ref1, bng_ref2: BNGReference objects for comparison when assessing neighbour relationships.

Value

A list containing a set of up to four BNGReference objects that border the target reference.

a boolean identifying if the grid references share a border

Details

Grid references are "neighbours" when they share a contiguous edge (i.e. corners do not define neighbours). In the event that a target reference is along the edge or corner of the valid BNG area, then 3 or 2 references, respectively, will be returned bng_is_neighbour only compares references of equal resolution.

If bng_ref1 exactly matches bng_ref2 then bng_is_neighbour returns FALSE.

Examples

bng_neighbours(as_bng_reference("SU1234"))
#> [[1]]
#> <BNGReference[4] with Resolution=1km>
#> [1] <SU 12 33> <SU 11 34> <SU 13 34> <SU 12 35>
#> 

bng_is_neighbour(as_bng_reference("SE1921"), as_bng_reference("SE1821"))
#> [1] TRUE

bng_is_neighbour(as_bng_reference("SE1922"), as_bng_reference("SE1821"))
#> [1] FALSE

bng_is_neighbour(as_bng_reference("SU1234"), as_bng_reference("SU1234"))
#> [1] FALSE