Grid Configuration

All transform functions use the default ISEA4H grid (ISEA projection, aperture 4, hexagon topology) when no explicit configuration is provided. Pass a dggs_params struct as the last argument to override this.

dggs_params

Signatures

STRUCT dggs_params (projection VARCHAR, aperture INTEGER, topology VARCHAR,
                   azimuth_deg DOUBLE, pole_lat_deg DOUBLE, pole_lon_deg DOUBLE)

STRUCT dggs_params (projection VARCHAR, aperture INTEGER, topology VARCHAR,
                   azimuth_deg DOUBLE, pole_lat_deg DOUBLE, pole_lon_deg DOUBLE,
                   is_aperture_sequence BOOLEAN, aperture_sequence VARCHAR)

Parameters

Parameter	Type	Description
projection	VARCHAR	'ISEA' (Icosahedral Snyder Equal Area) or 'FULLER'.
aperture	INTEGER	Cell aperture: 3, 4, or 7.
topology	VARCHAR	'HEXAGON', 'TRIANGLE', or 'DIAMOND'.
azimuth_deg	DOUBLE	Rotation of the icosahedron around the pole axis (degrees).
pole_lat_deg	DOUBLE	Latitude of the icosahedron pole (degrees). Default ISEA: 58.28252559.
pole_lon_deg	DOUBLE	Longitude of the icosahedron pole (degrees). Default ISEA: 11.25.
is_aperture_sequence	BOOLEAN	Use a mixed-aperture sequence instead of a fixed aperture. Default: false.
aperture_sequence	VARCHAR	Aperture at each resolution as a digit string (e.g. '3437'). Only used when is_aperture_sequence is true.

TIP

The resolution is not part of dggs_params — it is always passed as a separate INTEGER argument.

Examples

Standard ISEA3H grid:

SELECT dggs_params('ISEA', 3, 'HEXAGON', 0.0, 58.28252559, 11.25);

Mixed-aperture grid (aperture 3, then 4, then 3, then 7):

SELECT dggs_params('ISEA', 3, 'HEXAGON', 0.0, 58.28252559, 11.25, true, '3437');

Using with a transform:

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

Aperture Sequences

Aperture sequences allow different apertures at each resolution level. This is useful for creating grids where the refinement ratio varies — for example, coarse levels with aperture 7 and fine levels with aperture 3.

Constraints:

• Only supported for HEXAGON topology
• The sequence string must only contain '3', '4', and '7'
• Resolution must not exceed the sequence length

-- 4 levels: aperture 3, 4, 3, 4
SELECT dggs_n_cells(3,
    dggs_params('ISEA', 3, 'HEXAGON', 0.0, 58.28252559, 11.25, true, '3434'));
-- → 362