hexify_lonlat_to_quad_ij: Convert longitude/latitude to Quad IJ coordinates

In hexify: Equal-Area Hex Grids on the 'Snyder' 'ISEA' 'Icosahedron'

Convert longitude/latitude to Quad IJ coordinates

Description

Converts geographic coordinates to the intermediate Quad IJ representation used internally by ISEA DGGS. Returns the quad number (0-11) and integer cell indices (i, j) within that quad.

Usage

hexify_lonlat_to_quad_ij(lon, lat, resolution, aperture = 3L)

Arguments

lon	Longitude in degrees (-180 to 180)
lat	Latitude in degrees (-90 to 90)
resolution	Grid resolution level (0-30)
aperture	Grid aperture: 3, 4, or 7

Details

The 20 icosahedral triangle faces are grouped into 12 quads:

• Quad 0: North polar region

• Quads 1-5: Upper hemisphere rhombi

• Quads 6-10: Lower hemisphere rhombi

• Quad 11: South polar region

Value

List with components:

quad	Quad number (0-11)
i	Integer cell index along first axis
j	Integer cell index along second axis
icosa_triangle_face	Source icosahedral face (0-19)
icosa_triangle_x	X coordinate on triangle face
icosa_triangle_y	Y coordinate on triangle face

See Also

Other coordinate conversion: hexify_cell_id_to_quad_ij(), hexify_cell_to_icosa_tri(), hexify_cell_to_lonlat(), hexify_cell_to_plane(), hexify_cell_to_quad_ij(), hexify_cell_to_quad_xy(), hexify_grid_cell_to_lonlat(), hexify_grid_to_cell(), hexify_icosa_tri_to_plane(), hexify_icosa_tri_to_quad_ij(), hexify_icosa_tri_to_quad_xy(), hexify_lonlat_to_cell(), hexify_lonlat_to_plane(), hexify_quad_ij_to_cell(), hexify_quad_ij_to_icosa_tri(), hexify_quad_ij_to_xy(), hexify_quad_xy_to_cell(), hexify_quad_xy_to_icosa_tri(), hexify_roundtrip_test()

Examples

# Get Quad IJ coordinates for Paris
result <- hexify_lonlat_to_quad_ij(lon = 2.35, lat = 48.86,
                                    resolution = 10, aperture = 3)
print(result)

hexify documentation built on March 1, 2026, 1:07 a.m.