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set search_path to "sandbox","public";
DROP VIEW IF EXISTS grid_test_001;
CREATE VIEW grid_test_001 as (
SELECT g.gid, g.the_geom, count(*) FROM hex_grid_001 g
JOIN n1000_turisthytte p
ON g.the_geom && st_transform(p.wkb_geometry,4326)
GROUP BY g.gid, g.the_geom
);
CREATE TABLE sandbox.t_grid_n1000_byggpkt_0125 AS
SELECT g.gid,
g.the_geom,
count(*) AS count
FROM sandbox.hex_grid_0125 g
JOIN sandbox.n1000_bygningspunkt p ON g.the_geom && st_transform(p.wkb_geometry, 4326)
GROUP BY g.gid, g.the_geom;
--bug: overshooting y-max a lot. Need adjustments on the nrow calculations
--Thanks to: http://rexdouglass.com/spatial-hexagon-binning-in-postgis/
SET search_path TO "sandbox","public";
DROP TABLE IF EXISTS hex_grid;
CREATE TABLE hex_grid (gid serial not null primary key);
SELECT addgeometrycolumn('hex_grid','the_geom', 0, 'POLYGON', 2);
CREATE OR REPLACE FUNCTION genhexagons(width float, xmin float,ymin float,xmax float,ymax float )
RETURNS float AS $total$
declare
b float :=width/2;
a float :=b/2; --sin(30)=.5
c float :=2*a;
height float := 2*a+c; --1.1547*width;
ncol float :=ceil(abs(xmax-xmin)/width);
nrow float :=ceil(abs(ymax-ymin)/height);
polygon_string varchar := 'POLYGON((' ||
0 || ' ' || 0 || ' , ' ||
b || ' ' || a || ' , ' ||
b || ' ' || a+c || ' , ' ||
0 || ' ' || a+c+a || ' , ' ||
-1*b || ' ' || a+c || ' , ' ||
-1*b || ' ' || a || ' , ' ||
0 || ' ' || 0 ||
'))';
BEGIN
INSERT INTO hex_grid (the_geom)
SELECT st_translate(the_geom, x_series*(2*a+c)+xmin, y_series*(2*(c+a))+ymin)
FROM
generate_series(0, ncol::int,1) AS x_series,
generate_series(0, nrow::int,1) AS y_series,
(SELECT polygon_string::geometry AS the_geom
UNION
SELECT ST_Translate(polygon_string::geometry, b , a+c) AS the_geom
) AS two_hex;
ALTER TABLE hex_grid
ALTER COLUMN the_geom TYPE geometry(Polygon, 4326)
USING ST_SetSRID(the_geom,4326);
RETURN NULL;
END;
$total$ LANGUAGE plpgsql;
--width in the units of the projection, xmin,ymin,xmax,ymax
SELECT genhexagons(0.005,-5.0,50.0,35.0,90.0);
CREATE INDEX
ON hex_grid
USING gist
(the_geom);
DROP TABLE IF EXISTS hex_grid_005;
ALTER TABLE hex_grid RENAME TO hex_grid_005;
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