H3_CELL_TO_LAT

Return the WGS 84 latitude of the center of an H3 cell.

Category: h3Returns: DOUBLEDialect: Standard

Syntax

H3_CELL_TO_LAT(cell)

Description

## Overview Returns the WGS 84 latitude in decimal degrees of the geometric center of an H3 cell. Every H3 cell has a well-defined center point located at the centroid of its hexagonal (or pentagonal) boundary. This function extracts just the latitude component; pair it with H3_CELL_TO_LNG when you need both coordinates. Use it to project cells back to point coordinates for distance calculations, geocoding, rendering, or serialization to downstream systems that operate on lat/lng pairs rather than cell IDs. ## Behavior - Returns a DOUBLE in the range [-90, 90]. - Returns NULL if the input is NULL or not a valid H3 cell index. - Cell centers are deterministic; the same cell always returns the same latitude. - The returned latitude is not guaranteed to equal the input of H3_LATLNG_TO_CELL because any point within a cell maps to the same cell; round-trip precision is bounded by the cell half-width at the given resolution. - Coordinates are on the WGS 84 ellipsoid; no SRID is involved. - Precision is limited only by DOUBLE floating-point (approximately 15 significant digits). ## H3 resolution reference | Res | Average edge length | Cell half-width (approx) | | --- | --- | --- | | 0 | 1,107 km | 1,000 km | | 7 | 1.22 km | 1 km | | 9 | 174 m | 150 m | | 12 | 9.4 m | 8 m | | 15 | 0.5 m | 0.4 m | ## Compatibility - Follows the standard H3 hierarchical hex grid specification for cell centroids.

Parameters

Name	Type	Description
`cell`		Specifies the H3 cell index whose center latitude to return. Must be a valid H3 cell.

Examples

-- Round-trip a known point: the cell center is close to the input latitude, within the cell half-width.
SELECT H3_CELL_TO_LAT(H3_LATLNG_TO_CELL(51.5074, -0.1278, 9)) AS lat;

SELECT
  H3_CELL_TO_LAT(c) AS center_lat,
  H3_CELL_TO_LNG(c) AS center_lng
FROM (SELECT H3_LATLNG_TO_CELL(-33.8688, 151.2093, 8) AS c);

-- Combine with Haversine to rank cells by distance from a reference point.
SELECT
  h3_cell,
  ST_DISTANCE_HAVERSINE(H3_CELL_TO_LAT(h3_cell), H3_CELL_TO_LNG(h3_cell), 40.7128, -74.0060) AS distance_m
FROM analytics.curated.geo_events_h3
ORDER BY distance_m
LIMIT 20;

-- Derive a 1-degree latitude band from a cell center.
SELECT FLOOR(H3_CELL_TO_LAT(h3_cell)) AS lat_band
FROM analytics.curated.geo_events_h3;

Pitfalls

The cell center latitude differs from the input latitude in a round trip H3_LATLNG_TO_CELL -> H3_CELL_TO_LAT by up to the cell half-width at the resolution. At resolution 7 that is about 1 km, at resolution 9 about 150 m.
Do not compare two cell centers at different resolutions and expect them to match. A cell at resolution 7 and its center child at resolution 10 have different center latitudes.
Pentagon cell centers are defined and returned, but the geometry around pentagon cells is distorted. Use H3_IS_PENTAGON to flag pentagon cells if the downstream consumer expects uniform neighborhoods.
NULL or invalid cells return NULL silently. Validate input with H3_IS_VALID_CELL for external data sources.
The output is a scalar latitude, not a point geometry. To build a geometry, combine with H3_CELL_TO_LNG or use H3_CELL_TO_BOUNDARY for the full hex shape.