Claude-skill-registry h3-pg

PostgreSQL bindings for H3 hexagonal grid system. Use when working with H3 cells in Postgres, including spatial indexing, geometry/geography integration, and raster analysis.

install

source · Clone the upstream repo

git clone https://github.com/majiayu000/claude-skill-registry

Claude Code · Install into ~/.claude/skills/

T=$(mktemp -d) && git clone --depth=1 https://github.com/majiayu000/claude-skill-registry "$T" && mkdir -p ~/.claude/skills && cp -r "$T/skills/data/h3-pg" ~/.claude/skills/majiayu000-claude-skill-registry-h3-pg && rm -rf "$T"

manifest: skills/data/h3-pg/SKILL.md

h3-pg PostgreSQL Extension

Extension Architecture

Two extensions:

```
CREATE EXTENSION h3
```
— Core H3 bindings (indexing, traversal, hierarchy, inspection,
```
<->
```
operator). No PostGIS dependency.
```
CREATE EXTENSION h3_postgis
```
— PostGIS integration (geometry/geography casts,
```
@
```
operator, polygon fill, raster helpers). Requires
```
postgis
```
and optionally
```
postgis_raster
```
.

Postgres-Specific H3 Features

These exist only in h3-pg, not other H3 language bindings.

Direct casts (

h3_postgis

```
h3index::geometry
```
→ cell centroid as POINT, SRID 4326
```
h3index::geography
```
→ cell centroid as POINT, SRID 4326

Operators:

```
a <-> b
```
— grid distance in cells between two h3index values (
```
h3
```
)
```
geom @ resolution
```
— index geometry/geography at resolution (
```
h3_postgis
```
)

Operator classes for

h3index

: BTREE, HASH, BRIN, SP-GIST (

h3

)

Boundary helpers (

h3_postgis

```
h3_cell_to_boundary_geometry(h3index)
```
→ polygon with SRID 4326, splits at antimeridian
```
h3_cell_to_boundary_geography(h3index)
```
→ geography polygon, splits at antimeridian

Polygon fill (

h3_postgis

h3_polygon_to_cells(geometry, resolution)

→ SETOF h3index

h3_polygon_to_cells(geography, resolution)

→ SETOF h3index

Raster integration (

h3_postgis

, requires

postgis_raster

```
h3_raster_summary(raster, resolution, [band])
```
— per-cell stats (count, sum, mean, stddev, min, max)
```
h3_raster_summary_clip(...)
```
— clips raster by cell boundaries
```
h3_raster_summary_centroids(...)
```
— uses cell centroids, avoids pentagon edge cases
```
h3_raster_summary_subpixel(...)
```
— for cells smaller than pixels
```
h3_raster_class_summary*(...)
```
— discrete class counts per cell

Tile helper (

h3_postgis

h3_get_resolution_from_tile_zoom(z, [max_h3_resolution=15], [min_h3_resolution], [hex_edge_pixels=44], [tile_size=512])

— returns optimal H3 resolution for XYZ tile zoom level

, targeting hexagons approximately

hex_edge_pixels

wide on screen

Common Pattern Fixes

Pattern	DO NOT	DO
Get centroid	`ST_Centroid(h3_cell_to_boundary_geometry(h3))`	`h3::geometry`
Get boundary with SRID	`h3_cell_to_boundary(h3)::geometry`	`h3_cell_to_boundary_geometry(h3)`
Distance check (meters)	`ST_Distance(a.h3::geography, b.h3::geography) <= N`	`ST_DWithin(a.h3::geography, b.h3::geography, N)`
Grid distance (cells)	`h3_distance(a, b)`	`a <-> b`

Antimeridian gotcha: Cells crossing 180° are split into valid polygons.

ST_Centroid

of a split polygon may fall outside the cell — use

h3::geometry

for centroids instead.

Critical v3 → v4 Renames

v3 Name (DO NOT USE)	v4 Replacement
`h3_geo_to_h3`	`h3_latlng_to_cell`
`h3_to_geo`	`h3_cell_to_latlng`
`h3_to_geo_boundary`	`h3_cell_to_boundary`
`h3_k_ring`	`h3_grid_disk`
`h3_k_ring_distances`	`h3_grid_disk_distances`
`h3_hex_ring`	`h3_grid_ring_unsafe`
`h3_line`	`h3_grid_path_cells`
`h3_distance`	`h3_grid_distance`
`h3_to_parent`	`h3_cell_to_parent`
`h3_to_children`	`h3_cell_to_children`
`h3_compact`	`h3_compact_cells`
`h3_uncompact`	`h3_uncompact_cells`
`h3_polyfill`	`h3_polygon_to_cells`
`h3_indexes_are_neighbors`	`h3_are_neighbor_cells`
`h3_hex_area`	`h3_get_hexagon_area_avg`
`h3_hex_area_km2` / `h3_hex_area_m2`	`h3_get_hexagon_area_avg(res, unit)`
`h3_edge_length_km` / `h3_edge_length_m`	`h3_get_hexagon_edge_length_avg(res, unit)`

Unit parameters (v4): Area and length functions now take a

unit

text parameter:

h3_get_hexagon_area_avg(resolution, [unit = 'km^2'])

— use

'km^2'

'm^2'

h3_get_hexagon_edge_length_avg(resolution, [unit = 'km'])

— use

'km'

'm'

```
h3_cell_area(cell, [unit = 'km^2'])
```
— exact area for specific cell
```
h3_edge_length(edge, [unit = 'km'])
```
— exact length for specific edge

Spelling change (v4.2.3+): Prefer

h3_latlng_to_cell

over

h3_lat_lng_to_cell

(underscore version deprecated). Same for

h3_cell_to_latlng

h3_vertex_to_latlng

Documentation

API reference: https://github.com/zachasme/h3-pg/blob/main/docs/api.md
v3→v4 migration: https://h3geo.org/docs/library/migration-3.x/functions