Created
December 15, 2010 15:06
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A function to create a PostGIS geometry out of a Google Tile X/Y/Z definition
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-- Function: v_get_tile(integer, integer, integer) | |
-- DROP FUNCTION v_get_tile(integer, integer, integer); | |
CREATE OR REPLACE FUNCTION v_get_tile(x integer, y integer, z integer) | |
RETURNS geometry AS | |
$BODY$ | |
DECLARE | |
origin_shift CONSTANT FLOAT := 20037508.342789244; | |
initial_resolution CONSTANT FLOAT := 156543.03392804062; | |
res float; | |
minx float; | |
miny float; | |
maxx float; | |
maxy float; | |
BEGIN | |
res := initial_resolution / (power(2,z)); | |
minx := (x*256)*res - origin_shift; | |
miny := -((y*256)*res - origin_shift); | |
maxx := ((x+1)*256)*res - origin_shift; | |
maxy := -(((y+1)*256)*res - origin_shift); | |
RETURN (ST_GeomFromText('POLYGON(('||minx||' '||maxy||','||maxx||' '||maxy||','||maxx||' '||miny||','||minx||' '||miny||','||minx||' '||maxy||'))',900913));END; | |
$BODY$ | |
LANGUAGE 'plpgsql' IMMUTABLE STRICT | |
COST 100; | |
ALTER FUNCTION v_get_tile(integer, integer, integer) OWNER TO postgres; |
True. Didnt realize you where doing all the coding for this. We should include this functions in all CartoDB
we are doing it on the client side and asking for the geometry inside the bbox
By the way, here is a method to generate all tiles for a specific zoom
SELECT ST_Transform(v_get_tile(x,y,2),3857) as the_geom_webmercator from(
select distinct * from generate_series(0,3) as x, generate_series(0,3) as y) as l
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this will be very useful for our vector tile server!