Changes between Initial Version and Version 1 of UsersWikiCardinalDirection

Timestamp:

10/26/11 19:17:04 (13 years ago)

Author:

Mike Taves

Comment:

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UsersWikiCardinalDirection

@@ +1 @@
+= Determine Cardinal Direction =
+
+See [http://en.wikipedia.org/wiki/Cardinal_direction Wikipedia] for a description for cardinal direction.
+
+{{{
+-- Function: ST_Cardinal_Direction(azimuth float8)
+-- Returns N, NW, W, SW, S, SE, E, or NE from an azimuth direction
+-- By: Mike Toews
+--
+-- Usage:
+-- postgis=# SELECT ST_Cardinal_Direction(
+-- postgis(#          ST_Azimuth('POINT(3 5)', 'POINT(5 5)'));
+--  st_cardinal_direction
+-- -----------------------
+--  E
+-- (1 row)
+--
+-- DROP FUNCTION ST_Cardinal_Direction(float8);
+
+CREATE OR REPLACE FUNCTION ST_Cardinal_Direction(azimuth float8)
+  RETURNS character varying AS
+$BODY$SELECT CASE
+WHEN $1 < 0.0 THEN 'less than 0'
+WHEN $1*180/pi() < 22.5 THEN 'N'
+WHEN $1*180/pi() < 67.5 THEN 'NE'
+WHEN $1*180/pi() < 112.5 THEN 'E'
+WHEN $1*180/pi() < 157.5 THEN 'SE'
+WHEN $1*180/pi() < 202.5 THEN 'S'
+WHEN $1*180/pi() < 247.5 THEN 'SW'
+WHEN $1*180/pi() < 292.5 THEN 'W'
+WHEN $1*180/pi() < 337.5 THEN 'NW'
+WHEN $1*180/pi() <= 360.0 THEN 'N'
+END;$BODY$ LANGUAGE sql IMMUTABLE COST 100;
+COMMENT ON FUNCTION ST_Cardinal_Direction(float8) IS 'input azimuth in radians; returns N, NW, W, SW, S, SE, E, or NE';
+}}}