duck_dggs

Appearance

Hierarchical Index Conversions ​

These functions convert between the sequential cell index (SEQNUM) and alternative hierarchical indexing schemes. Hierarchical indices encode spatial locality, which can improve range queries and spatial sorting.

Z-Order (Morton Code) ​

Available for aperture 3 and aperture 4 grids.

seqnum_to_zorder ​

sql
UBIGINT seqnum_to_zorder (seqnum UBIGINT, res INTEGER)
UBIGINT seqnum_to_zorder (seqnum UBIGINT, res INTEGER, params STRUCT)

Converts a sequential cell index to its Z-order (Morton code) index.

sql
SELECT seqnum_to_zorder(2380::UBIGINT, 5);
-- → 3688448094816436224

zorder_to_seqnum ​

sql
UBIGINT zorder_to_seqnum (value UBIGINT, res INTEGER)
UBIGINT zorder_to_seqnum (value UBIGINT, res INTEGER, params STRUCT)

Converts a Z-order index back to a sequential cell index.

sql
SELECT zorder_to_seqnum(3688448094816436224::UBIGINT, 5);
-- → 2380

Z3 Index ​

Only available for aperture 3 hexagon grids. Requires passing a dggs_params struct with aperture = 3.

seqnum_to_z3 ​

sql
UBIGINT seqnum_to_z3 (seqnum UBIGINT, res INTEGER)
UBIGINT seqnum_to_z3 (seqnum UBIGINT, res INTEGER, params STRUCT)

Converts a sequential cell index to its Z3 hierarchical index.

sql
SELECT seqnum_to_z3(100::UBIGINT, 4,
    dggs_params('ISEA', 3, 'HEXAGON', 0.0, 58.28252559, 11.25));
-- → 2994893752201379839

z3_to_seqnum ​

sql
UBIGINT z3_to_seqnum (value UBIGINT, res INTEGER)
UBIGINT z3_to_seqnum (value UBIGINT, res INTEGER, params STRUCT)

Converts a Z3 index back to a sequential cell index.

sql
SELECT z3_to_seqnum(2994893752201379839::UBIGINT, 4,
    dggs_params('ISEA', 3, 'HEXAGON', 0.0, 58.28252559, 11.25));
-- → 100

Z7 Index ​

Only available for aperture 7 hexagon grids. Requires passing a dggs_params struct with aperture = 7.

seqnum_to_z7 ​

sql
UBIGINT seqnum_to_z7 (seqnum UBIGINT, res INTEGER)
UBIGINT seqnum_to_z7 (seqnum UBIGINT, res INTEGER, params STRUCT)

Converts a sequential cell index to its Z7 hierarchical index.

sql
SELECT seqnum_to_z7(100::UBIGINT, 4,
    dggs_params('ISEA', 7, 'HEXAGON', 0.0, 58.28252559, 11.25));
-- → 1162491653815009279

z7_to_seqnum ​

sql
UBIGINT z7_to_seqnum (value UBIGINT, res INTEGER)
UBIGINT z7_to_seqnum (value UBIGINT, res INTEGER, params STRUCT)

Converts a Z7 index back to a sequential cell index.

sql
SELECT z7_to_seqnum(1162491653815009279::UBIGINT, 4,
    dggs_params('ISEA', 7, 'HEXAGON', 0.0, 58.28252559, 11.25));
-- → 100

Vertex 2DD ​

Vertex-based 2D coordinates with triangle metadata. Available for all grid configurations.

seqnum_to_vertex2dd ​

sql
STRUCT seqnum_to_vertex2dd (seqnum UBIGINT, res INTEGER)
STRUCT seqnum_to_vertex2dd (seqnum UBIGINT, res INTEGER, params STRUCT)

Return type: STRUCT(keep BOOLEAN, vert_num INTEGER, tri_num INTEGER, x DOUBLE, y DOUBLE)

Converts a sequential cell index to its VERTEX2DD representation.

sql
SELECT seqnum_to_vertex2dd(2380::UBIGINT, 5);
┌─────────────────────────────────────────────────────────────────────────────────────┐
│                   seqnum_to_vertex2dd(CAST(2380 AS "UBIGINT"), 5)                   │
│     struct(keep boolean, vert_num integer, tri_num integer, x double, y double)     │
├─────────────────────────────────────────────────────────────────────────────────────┤
│ {'keep': true, 'vert_num': 3, 'tri_num': 1, 'x': 0.15625, 'y': 0.27063293868263705} │
└─────────────────────────────────────────────────────────────────────────────────────┘

vertex2dd_to_seqnum ​

sql
UBIGINT vertex2dd_to_seqnum (keep BOOLEAN, vert_num INTEGER, tri_num INTEGER,
                             x DOUBLE, y DOUBLE, res INTEGER)
UBIGINT vertex2dd_to_seqnum (keep BOOLEAN, vert_num INTEGER, tri_num INTEGER,
                             x DOUBLE, y DOUBLE, res INTEGER, params STRUCT)

Converts VERTEX2DD coordinates back to a sequential cell index.

sql
SELECT vertex2dd_to_seqnum(true, 3, 1, 0.15625, 0.27063293868263705, 5);
-- → 2380