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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
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
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

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;