zres.sql

-- ZRES
-- Takes a web mercator zoom level and returns the pixel resolution for that
-- scale, assuming 256x256 pixel tiles. Non-integer zoom levels are accepted.
-- For databases with the PostGIS extension enabled.

create or replace function zres(z float)
    returns float
    language plpgsql immutable
as $func$
begin
    return (40075016.6855785/(256*2^z));
end;
$func$;