I have included fixes to declare some floating point constants as double

instead of int, change the calculation method to use the haversine
formula
which is more accurrate for short distances, added a grant to public for
geo_distance and added a regression test.

I will resubmit the earth distance stuff based on cube after 7.3 is
released.

Bruno Wolff III

contrib/earthdistance/Makefile

@@ -1,4 +1,4 @@
-# $Header: /cvsroot/pgsql/contrib/earthdistance/Makefile,v 1.11 2001/09/06 10:49:29 petere Exp $
+# $Header: /cvsroot/pgsql/contrib/earthdistance/Makefile,v 1.12 2002/09/20 03:47:22 momjian Exp $
 
 subdir = contrib/earthdistance
 top_builddir = ../..
@@ -7,5 +7,6 @@ include $(top_builddir)/src/Makefile.global
 MODULES = earthdistance
 DATA_built = earthdistance.sql
 DOCS = README.earthdistance
+REGRESS = earthdistance
 
 include $(top_srcdir)/contrib/contrib-global.mk

contrib/earthdistance/README.earthdistance

@@ -1,3 +1,13 @@
+---------------------------------------------------------------------
+I corrected a bug in the geo_distance code where two double constants
+were declared as int. I changed the distance function to use the
+haversine formula which is more accurate for small distances.
+I added a regression test to the package. I added a grant statement
+to give execute access for geo_distance to public.
+
+Bruno Wolff III
+September 2002
+---------------------------------------------------------------------
 Date: Wed, 1 Apr 1998 15:19:32 -0600 (CST)
 From: Hal Snyder <hal@vailsys.com>
 To: vmehr@ctp.com

contrib/earthdistance/earthdistance.c

@@ -6,8 +6,8 @@
 
 
 /* Earth's radius is in statute miles. */
-const int	EARTH_RADIUS = 3958.747716;
-const int	TWO_PI = 2.0 * M_PI;
+const double	EARTH_RADIUS = 3958.747716;
+const double	TWO_PI = 2.0 * M_PI;
 
 double	   *geo_distance(Point *pt1, Point *pt2);
 
@@ -50,6 +50,7 @@ geo_distance(Point *pt1, Point *pt2)
 				long2,
 				lat2;
 	double		longdiff;
+        double		sino;
 	double	   *resultp = palloc(sizeof(double));
 
 	/* convert degrees to radians */
@@ -65,8 +66,10 @@ geo_distance(Point *pt1, Point *pt2)
 	if (longdiff > M_PI)
 		longdiff = TWO_PI - longdiff;
 
-	*resultp = EARTH_RADIUS * acos
-		(sin(lat1) * sin(lat2) + cos(lat1) * cos(lat2) * cos(longdiff));
+        sino = sqrt(sin(fabs(lat1-lat2)/2.)*sin(fabs(lat1-lat2)/2.) +
+                cos(lat1) * cos(lat2) * sin(longdiff/2.)*sin(longdiff/2.));
+        if (sino > 1.) sino = 1.;
+        *resultp = 2. * EARTH_RADIUS * asin(sino);
 
 	return resultp;
 }

contrib/earthdistance/earthdistance.sql.in

@@ -1,16 +1,12 @@
+begin;
 
 --------------- geo_distance
 
-DROP FUNCTION geo_distance (point, point);
-CREATE FUNCTION geo_distance (point, point) RETURNS float8
-  AS 'MODULE_PATHNAME' LANGUAGE 'c'
-  WITH (isstrict);
-
-SELECT geo_distance ('(1,2)'::point, '(3,4)'::point);
+CREATE OR REPLACE FUNCTION geo_distance (point, point) RETURNS float8
+  LANGUAGE 'c' IMMUTABLE STRICT AS 'MODULE_PATHNAME';
 
 --------------- geo_distance as operator <@>
 
-DROP OPERATOR <@> (point, point);
 CREATE OPERATOR <@> (
   leftarg = point,
   rightarg = point,
@@ -18,7 +14,11 @@ CREATE OPERATOR <@> (
   commutator = <@>
 );
 
--- ( 87.6, 41.8) is in Chicago
--- (106.7, 35.1) is in Albuquerque
--- The cities are about 1100 miles apart
-SELECT '(87.6,41.8)'::point <@> '(106.7,35.1)'::point;
+--
+-- By default this function is made executable by anyone. To restrict
+-- access by default, comment out the following grant command.
+--
+
+grant execute on function geo_distance(point, point) to public;
+
+commit;