contrib/earthdistance/earthdistance.sql.in

   1 /* $PostgreSQL$ */
   2
   3 -- Adjust this setting to control where the objects get created.
   4 SET search_path = public;
   5
   6 -- The earth functions rely on contrib/cube having been installed and loaded.
   7
   8 -- earth() returns the radius of the earth in meters. This is the only
   9 -- place you need to change things for the cube base distance functions
  10 -- in order to use different units (or a better value for the Earth's radius).
  11
  12 CREATE OR REPLACE FUNCTION earth() RETURNS float8
  13 LANGUAGE SQL IMMUTABLE
  14 AS 'SELECT ''6378168''::float8';
  15
  16 -- Astromers may want to change the earth function so that distances will be
  17 -- returned in degrees. To do this comment out the above definition and
  18 -- uncomment the one below. Note that doing this will break the regression
  19 -- tests.
  20 --
  21 -- CREATE OR REPLACE FUNCTION earth() RETURNS float8
  22 -- LANGUAGE SQL IMMUTABLE
  23 -- AS 'SELECT 180/pi()';
  24
  25 -- Define domain for locations on the surface of the earth using a cube
  26 -- datatype with constraints. cube provides 3D indexing.
  27 -- The cube is restricted to be a point, no more than 3 dimensions
  28 -- (for less than 3 dimensions 0 is assumed for the missing coordinates)
  29 -- and that the point must be very near the surface of the sphere
  30 -- centered about the origin with the radius of the earth.
  31
  32 CREATE DOMAIN earth AS cube
  33   CONSTRAINT not_point check(cube_is_point(value))
  34   CONSTRAINT not_3d check(cube_dim(value) <= 3)
  35   CONSTRAINT on_surface check(abs(cube_distance(value, '(0)'::cube) /
  36   earth() - 1) < '10e-7'::float8);
  37
  38 CREATE OR REPLACE FUNCTION sec_to_gc(float8)
  39 RETURNS float8
  40 LANGUAGE SQL
  41 IMMUTABLE STRICT
  42 AS 'SELECT CASE WHEN $1 < 0 THEN 0::float8 WHEN $1/(2*earth()) > 1 THEN pi()*earth() ELSE 2*earth()*asin($1/(2*earth())) END';
  43
  44 CREATE OR REPLACE FUNCTION gc_to_sec(float8)
  45 RETURNS float8
  46 LANGUAGE SQL
  47 IMMUTABLE STRICT
  48 AS 'SELECT CASE WHEN $1 < 0 THEN 0::float8 WHEN $1/earth() > pi() THEN 2*earth() ELSE 2*earth()*sin($1/(2*earth())) END';
  49
  50 CREATE OR REPLACE FUNCTION ll_to_earth(float8, float8)
  51 RETURNS earth
  52 LANGUAGE SQL
  53 IMMUTABLE STRICT
  54 AS 'SELECT cube(cube(cube(earth()*cos(radians($1))*cos(radians($2))),earth()*cos(radians($1))*sin(radians($2))),earth()*sin(radians($1)))::earth';
  55
  56 CREATE OR REPLACE FUNCTION latitude(earth)
  57 RETURNS float8
  58 LANGUAGE SQL
  59 IMMUTABLE STRICT
  60 AS 'SELECT CASE WHEN cube_ll_coord($1, 3)/earth() < -1 THEN -90::float8 WHEN cube_ll_coord($1, 3)/earth() > 1 THEN 90::float8 ELSE degrees(asin(cube_ll_coord($1, 3)/earth())) END';
  61
  62 CREATE OR REPLACE FUNCTION longitude(earth)
  63 RETURNS float8
  64 LANGUAGE SQL
  65 IMMUTABLE STRICT
  66 AS 'SELECT degrees(atan2(cube_ll_coord($1, 2), cube_ll_coord($1, 1)))';
  67
  68 CREATE OR REPLACE FUNCTION earth_distance(earth, earth)
  69 RETURNS float8
  70 LANGUAGE SQL
  71 IMMUTABLE STRICT
  72 AS 'SELECT sec_to_gc(cube_distance($1, $2))';
  73
  74 CREATE OR REPLACE FUNCTION earth_box(earth, float8)
  75 RETURNS cube
  76 LANGUAGE SQL
  77 IMMUTABLE STRICT
  78 AS 'SELECT cube_enlarge($1, gc_to_sec($2), 3)';
  79
  80 --------------- geo_distance
  81
  82 CREATE OR REPLACE FUNCTION geo_distance (point, point)
  83 RETURNS float8
  84 LANGUAGE C IMMUTABLE STRICT AS 'MODULE_PATHNAME';
  85
  86 --------------- geo_distance as operator <@>
  87
  88 CREATE OPERATOR <@> (
  89   LEFTARG = point,
  90   RIGHTARG = point,
  91   PROCEDURE = geo_distance,
  92   COMMUTATOR = <@>
  93 );