DGGS projections with PostGIS or pgLatLon

Question

Important DGGS projections (like ISEA4T, ISEA4D or ISEA7H variants of ISEA) are free at https://github.com/sahrk/DGGRID , the DGGRID Software Project, but I not see how to use it with PostGIS. Only maybe drawing and exporting each hierarchical level of the (big data) grid.

Ideal is a function pair like ST_GeoHash / ST_GeomFromGeoHash that encode/decode cell identifiers of the grid.

Some clue or workaround to "plug" DGGRID into PostgreSQL? It can be a plug for PostGIS or pgLatLon extensions.

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NOTES FOR CURIOUS READERS:

• Discrete Global Grid Systems (DGGS) are the trend in GIS, and since 2017 has an standard OGC Abstract Specification.

• pgLatLon extension is a lightweight alternative for PostGIS, see https://www.public-software-group.org/pgLatLon

• DGGRID (and ISEA4T, ISEA4D, ISEA7H grids) documentation is at git/sahrk/DGGRID/dggridManualV71.pdf. About first levels of the grid, they are analog to ISEA3H, described here with general conventions for orientation here. See also DGGRID use case examples.

Answer 1

PostGIS use PROJ.org, and recent PROJ versions has implemented some projections, used in DGGS candidates:

• PROJ v8.2+ added S2 Geometry's projection.

• PROJ v??+ added QSC projection.

• PROJ v??+ added partial ISEA, without inverse.

• PROJ v4.8+ added rHEALPix. See urn:doi:10.1088/1755-1315/34/1/012012 for "rHEALPix is DGGS" demonstration.

• ...

You can check your PostGIS's PROJ version by SELECT postgis_full_version().