DuckDB function ST_TileEnvelope

The ST_TileEnvelope scalar function generates tile envelope rectangular polygons from specified zoom level and tile indices.

This is used in MVT generation to select the features corresponding to the tile extent. The envelope is in the Web Mercator coordinate reference system (EPSG:3857). The tile pyramid starts at zoom level 0, corresponding to a single tile for the world. Each zoom level doubles the number of tiles in each direction, such that zoom level 1 is 2 tiles wide by 2 tiles high, zoom level 2 is 4 tiles wide by 4 tiles high, and so on. Tile indices start at [x=0, y=0] at the top left, and increase down and right. For example, at zoom level 2, the top right tile is [x=3, y=0], the bottom left tile is [x=0, y=3], and the bottom right is [x=3, y=3].

SELECT ST_TileEnvelope(2, 3, 1);
```.


[x=0, y=0]: R:x=0,%20y=0
[x=3, y=0]: R:x=3,%20y=0
[x=0, y=3]: R:x=0,%20y=3
[x=3, y=3]: R:x=3,%20y=3

Usage

ST_TileEnvelope(tile_zoom, tile_x, tile_y)

Arguments

tile_zoom, tile_x, tile_y

INTEGER

Value

GEOMETRY

Provided by

The spatial extension (LOAD spatial;).

SQL examples

SELECT ST_TileEnvelope(2, 3, 1);
-- +-----------------------------------------------------------------------------------------------------------+
-- |                                         st_tileenvelope(2, 3, 1)                                          |
-- |                                                 geometry                                                  |
-- +-----------------------------------------------------------------------------------------------------------+
-- | POLYGON ((1.00188E+07 0, 1.00188E+07 1.00188E+07, 2.00375E+07 1.00188E+07, 2.00375E+07 0, 1.00188E+07 0)) |
-- +-----------------------------------------------------------------------------------------------------------+