Convert longitude/latitude to Quad IJ coordinates

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

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

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

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

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