ST_AsMVTGeom for converting a geographic grid to a geometry in a tile coordinate system - ApsaraDB RDS

Converts a geographic grid object (geomgrid or H3) into a geometry in the tile coordinate system, ready for use in Mapbox Vector Tile (MVT) output.

Syntax

geometry ST_AsMVTGeom(geomgrid grid, geometry bounds, int4 extent, int4 buffer, boolean clip_geom);
geometry ST_AsMVTGeom(h3grid grid, geometry bounds, int4 extent, int4 buffer, boolean clip_geom);

Return value

Returns a geometry object in the tile coordinate system.

Parameters

Parameter	Type	Description	Default
`grid`	geomgrid \| h3grid	The geographic grid object to convert for MVT output.	—
`bounds`	geometry	The rectangular boundary of the tile, excluding the buffer. Unlike the standard `ST_AsMVTGeom` (which takes a `Box2D`), this variant accepts a `geometry`.	—
`extent`	int4	The tile size in the tile coordinate system.	`4096`
`buffer`	int4	The buffer size in the tile coordinate system.	`256`
`clip_geom`	boolean	Specifies whether to clip the grid geometry at the tile boundary.	`true`

Usage notes

The output coordinate system is determined by the bounds parameter. Use ST_TileEnvelope to generate bounds.
If you generate bounds by another method, specify the Spatial Reference Identifier (SRID) explicitly (see examples 2 and 5 below).

Examples

Example 1: Convert a geomgrid object using ST_TileEnvelope as bounds.

SELECT st_asmvtgeom('010200040000'::geomgrid, st_tileenvelope(0, 0, 0));

Output:

0103000020110F000001000000050000000000000000D8A2400000000000FC99400000000000D8A240000000000000A040000000000000A040000000000000A040000000000000A0400000000000FC99400000000000D8A2400000000000FC9940

Example 2: Convert a geomgrid object with bounds transformed to SRID 4326.

SELECT st_asmvtgeom('010200040000'::geomgrid, st_transform(st_tileenvelope(0, 0, 0), 4326));

Output:

0103000020E610000001000000050000000000000000D8A2400000000000F493400000000000D8A240000000000000A040000000000000A040000000000000A040000000000000A0400000000000F493400000000000D8A2400000000000F49340

Example 3: Convert a geomgrid object with custom extent, buffer, and clipping disabled.

SELECT st_asmvtgeom('010200040000'::geomgrid, st_transform(st_tileenvelope(0, 0, 0), 4326), 1024, 128, false);

Output:

0103000020E610000001000000050000000000000000D882400000000000F073400000000000D8824000000000000080400000000000008040000000000000804000000000000080400000000000F073400000000000D882400000000000F07340

Example 4: Convert an H3 grid object using ST_TileEnvelope as bounds.

SELECT st_asmvtgeom(st_h3fromlatlng(20.5, 128.2, 5), st_tileenvelope(0, 0, 0));

Output:

0103000020110F00000100000006000000000000000064AB400000000000449C40000000000066AB400000000000489C40000000000066AB4000000000004C9C40000000000062AB4000000000004C9C40000000000062AB400000000000489C40000000000064AB400000000000449C40

Example 5: Convert an H3 grid object with an explicit SRID polygon as bounds.

SELECT st_asmvtgeom(st_h3fromlatlng(20.5, 128.2, 5), 'SRID=4326;POLYGON((-180 -85,-180 85, 180 85, 180 -85, -180 -85))');

Output:

0103000020E61000000100000007000000000000000064AB400000000000449840000000000066AB400000000000489840000000000066AB400000000000509840000000000064AB400000000000549840000000000062AB400000000000549840000000000062AB4000000000004C9840000000000064AB400000000044984