From: Paul Ramsey <pramsey@cleverelephant.ca>
Date: Fri, 2 Oct 2009 01:38:02 +0000 (+0000)
Subject: Make the units of st_distance(geography, geography) meters
X-Git-Tag: 1.5.0b1~433
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=51e0a35518e387791ec65af8be089294cebf69a2;p=postgis

Make the units of st_distance(geography, geography) meters


git-svn-id: http://svn.osgeo.org/postgis/trunk@4577 b70326c6-7e19-0410-871a-916f4a2858ee
---

diff --git a/postgis/geography.h b/postgis/geography.h
index 8e1f3de39..4aae1c6eb 100644
--- a/postgis/geography.h
+++ b/postgis/geography.h
@@ -9,6 +9,13 @@
  *
  **********************************************************************/
 
+/*
+** Spherical radius.
+** Moritz, H. (1980). Geodetic Reference System 1980, by resolution of the XVII General Assembly of the IUGG in Canberra.
+** http://en.wikipedia.org/wiki/Earth_radius
+*/
+
+#define WGS84_RADIUS 6371009.0
 
 /**********************************************************************
 **  GIDX structure. 
diff --git a/postgis/geography_distance.c b/postgis/geography_distance.c
index 81713818b..7a6e4b538 100644
--- a/postgis/geography_distance.c
+++ b/postgis/geography_distance.c
@@ -60,6 +60,7 @@ Datum geography_distance_sphere(PG_FUNCTION_ARGS)
 	
 	/* Read our tolerance value. */
 	tolerance = PG_GETARG_FLOAT8(2);
+	tolerance = tolerance / WGS84_RADIUS;
 
 	/* Calculate the distance */
 	distance = lwgeom_distance_sphere(lwgeom1, lwgeom2, &gbox1, &gbox2, tolerance);
@@ -70,6 +71,8 @@ Datum geography_distance_sphere(PG_FUNCTION_ARGS)
 		elog(ERROR, "Error in geography_distance_sphere calculation.");
 		PG_RETURN_NULL();
 	}
+	
+	distance = distance * WGS84_RADIUS;
 
 	/* Clean up, but not all the way to the point arrays */
 	lwgeom_release(lwgeom1);