Getting Started

Installation

INSTALL duck_dggs FROM community;
LOAD duck_dggs;

Quick Examples

Geographic point to cell ID

Convert a geographic point to a cell ID at resolution 5 (default ISEA4H grid):

SELECT geo_to_seqnum('POINT(0.0 0.0)'::GEOMETRY, 5);
-- → 2380

Cell ID to cell centre

SELECT seqnum_to_geo(2380, 5);
-- → POINT (-0.902 -0.000)

Cell boundary polygon

Requires the spatial extension:

LOAD spatial;
SELECT seqnum_to_boundary(2380, 5);
-- → POLYGON ((...))

Grid statistics

SELECT dggs_n_cells(5);
-- → 10242

SELECT dggs_res_info(5);
-- → {res: 5, cells: 10242, area_km: 49811.1, spacing_km: 220.4, cls_km: 251.8}

Neighbors

SELECT seqnum_neighbors(2380::UBIGINT, 5);
-- → [2412, 2413, 2381, 2348, 2347, 2379]

Parent / Child

SELECT seqnum_parent(2380::UBIGINT, 5);
-- → 599

SELECT seqnum_children(599::UBIGINT, 4);
-- → [2380, 2412, 2413, 2381, 2348, 2347, 2379]

Custom grid configuration

SELECT geo_to_seqnum('POINT(0.0 0.0)'::GEOMETRY, 5,
    dggs_params('ISEA', 3, 'HEXAGON', 0.0, 58.28252559, 11.25));
-- → 572

Coordinate Systems

Symbol	Type	Description
GEO	GEOMETRY (POINT)	Geographic lon/lat as a WKB point.
SEQNUM	UBIGINT	Global sequential cell index.
Q2DI	STRUCT(quad UBIGINT, i BIGINT, j BIGINT)	Quad number + integer cell indices.
Q2DD	STRUCT(quad UBIGINT, x DOUBLE, y DOUBLE)	Quad number + continuous coordinates.
PROJTRI	STRUCT(tnum UBIGINT, x DOUBLE, y DOUBLE)	Icosahedron triangle + projected coordinates.
PLANE	STRUCT(x DOUBLE, y DOUBLE)	Unfolded icosahedron plane coordinates.
VERTEX2DD	STRUCT(keep BOOLEAN, vert_num INTEGER, tri_num INTEGER, x DOUBLE, y DOUBLE)	Vertex-based 2D coordinate.