From 24bebf0b725e965ed2b725dcb31a46f787e98dbf Mon Sep 17 00:00:00 2001
From: Bruce Momjian <bruce@momjian.us>
Date: Fri, 20 Sep 2002 03:47:22 +0000
Subject: [PATCH] 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             |  3 ++-
 contrib/earthdistance/README.earthdistance | 10 ++++++++++
 contrib/earthdistance/earthdistance.c      | 11 +++++++----
 contrib/earthdistance/earthdistance.sql.in | 22 +++++++++++-----------
 4 files changed, 30 insertions(+), 16 deletions(-)

diff --git a/contrib/earthdistance/Makefile b/contrib/earthdistance/Makefile
index 94ad370d59..49d1505f04 100644
--- a/contrib/earthdistance/Makefile
+++ b/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
diff --git a/contrib/earthdistance/README.earthdistance b/contrib/earthdistance/README.earthdistance
index f4ecef80fe..2ed5c28165 100644
--- a/contrib/earthdistance/README.earthdistance
+++ b/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
diff --git a/contrib/earthdistance/earthdistance.c b/contrib/earthdistance/earthdistance.c
index c1962272f4..f069edf131 100644
--- a/contrib/earthdistance/earthdistance.c
+++ b/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;
 }
diff --git a/contrib/earthdistance/earthdistance.sql.in b/contrib/earthdistance/earthdistance.sql.in
index 087484da51..04485589c7 100644
--- a/contrib/earthdistance/earthdistance.sql.in
+++ b/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;