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

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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
This commit is contained in:
Bruce Momjian 2002-09-20 03:47:22 +00:00
parent a834cbe1e9
commit 24bebf0b72
4 changed files with 30 additions and 16 deletions
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3
contrib/earthdistance/Makefile
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@ -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

10
contrib/earthdistance/README.earthdistance
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@ -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

11
contrib/earthdistance/earthdistance.c
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@ -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;
}

22
contrib/earthdistance/earthdistance.sql.in
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@ -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;