leonmvd

-- function that calculates the CBS Vierkantstatistieken grid cell for point coordinates in RD new.

create or replace function get_cbsvierkantid(fn_geom geometry, i_dist int) returns text as $$
select 
	'E' || 
	((st_x(fn_geom)::numeric - (st_x(fn_geom)::numeric % i_dist)) / 100)::int ||
	'N' || 
	((st_y(fn_geom)::numeric - (st_y(fn_geom)::numeric % i_dist)) / 100)::int
	as cbs_vierkant_id
;

leonmvd

-- blades part adapted from "https://gis.stackexchange.com/questions/104439/how-to-extend-a-straight-line-in-postgis"
with medialaxis_multi as(
    select
    	polygons.id,
        st_union(ST_ApproximateMedialAxis(geom)) as geom
    from
        polygons
    group by 
    	polygons.id
),