This function converts a geographic grid object into a geometric object in a tile coordinate system.
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 values
This function returns a geometric object in a coordinate system.
Parameters
Parameter | Description |
grid | The geomgrid or H3 geographic grid object that you want to output to MVT. |
bounds | The rectangular boundaries of the tile, excluding the buffer. |
extent | The size of the tile in the tile coordinate system. Default value: 4096. |
buffer | The size of the buffer in the tile coordinate system. Default value: 256. |
clip_geom | Specifies whether the geometry corresponding to the grid is clipped by the tile boundary. Default value: true. |
Usage notes
This function converts the geometry corresponding to a geographic grid object into a geometry in a tile coordinate system.
Unlike the ST_AsMVTGeom function whose input parameter is Geometry, the rectangular boundary type of the tile is Geometry instead of Box2D.
The output coordinate system is determined by the value of the bounds parameter. We recommend that you use the ST_TileEnvelope function to generate the value of the bounds parameter.
If you use a method other than the ST_TileEnvelope function to generate the value of the bounds parameter, specify the Spatial Reference Identifier (SRID).
Examples
select st_asmvtgeom('010200040000'::geomgrid, st_tileenvelope(0, 0, 0));
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0103000020110F000001000000050000000000000000D8A2400000000000FC99400000000000D8A240000000000000A040000000000000A040000000000000A040000000000000A0400000000000FC99400000000000D8A2400000000000FC9940
select st_asmvtgeom('010200040000'::geomgrid, st_transform(st_tileenvelope(0, 0, 0), 4326));
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0103000020E610000001000000050000000000000000D8A2400000000000F493400000000000D8A240000000000000A040000000000000A040000000000000A040000000000000A0400000000000F493400000000000D8A2400000000000F49340
select st_asmvtgeom('010200040000'::geomgrid, st_transform(st_tileenvelope(0, 0, 0), 4326), 1024, 128, false);
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0103000020E610000001000000050000000000000000D882400000000000F073400000000000D8824000000000000080400000000000008040000000000000804000000000000080400000000000F073400000000000D882400000000000F07340
select st_asmvtgeom(st_h3fromlatlng(20.5, 128.2, 5), st_tileenvelope(0, 0, 0));
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0103000020110F00000100000006000000000000000064AB400000000000449C40000000000066AB400000000000489C40000000000066AB4000000000004C9C40000000000062AB4000000000004C9C40000000000062AB400000000000489C40000000000064AB400000000000449C40
select st_asmvtgeom(st_h3fromlatlng(20.5, 128.2, 5), 'SRID=4326;POLYGON((-180 -85,-180 85, 180 85, 180 -85, -180 -85))');
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0103000020E61000000100000007000000000000000064AB400000000000449840000000000066AB400000000000489840000000000066AB400000000000509840000000000064AB400000000000549840000000000062AB400000000000549840000000000062AB4000000000004C9840000000000064AB40000000000044984