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-rw-r--r--contrib/earthdistance/earthdistance.c104
-rw-r--r--contrib/earthdistance/earthdistance.control6
2 files changed, 110 insertions, 0 deletions
diff --git a/contrib/earthdistance/earthdistance.c b/contrib/earthdistance/earthdistance.c
new file mode 100644
index 0000000..e6ebfd1
--- /dev/null
+++ b/contrib/earthdistance/earthdistance.c
@@ -0,0 +1,104 @@
+/* contrib/earthdistance/earthdistance.c */
+
+#include "postgres.h"
+
+#include <math.h>
+
+#include "utils/geo_decls.h" /* for Point */
+
+#ifndef M_PI
+#define M_PI 3.14159265358979323846
+#endif
+
+PG_MODULE_MAGIC;
+
+/* Earth's radius is in statute miles. */
+static const double EARTH_RADIUS = 3958.747716;
+static const double TWO_PI = 2.0 * M_PI;
+
+
+/******************************************************
+ *
+ * degtorad - convert degrees to radians
+ *
+ * arg: double, angle in degrees
+ *
+ * returns: double, same angle in radians
+ ******************************************************/
+
+static double
+degtorad(double degrees)
+{
+ return (degrees / 360.0) * TWO_PI;
+}
+
+/******************************************************
+ *
+ * geo_distance_internal - distance between points
+ *
+ * args:
+ * a pair of points - for each point,
+ * x-coordinate is longitude in degrees west of Greenwich
+ * y-coordinate is latitude in degrees above equator
+ *
+ * returns: double
+ * distance between the points in miles on earth's surface
+ ******************************************************/
+
+static double
+geo_distance_internal(Point *pt1, Point *pt2)
+{
+ double long1,
+ lat1,
+ long2,
+ lat2;
+ double longdiff;
+ double sino;
+
+ /* convert degrees to radians */
+
+ long1 = degtorad(pt1->x);
+ lat1 = degtorad(pt1->y);
+
+ long2 = degtorad(pt2->x);
+ lat2 = degtorad(pt2->y);
+
+ /* compute difference in longitudes - want < 180 degrees */
+ longdiff = fabs(long1 - long2);
+ if (longdiff > M_PI)
+ longdiff = TWO_PI - 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.;
+
+ return 2. * EARTH_RADIUS * asin(sino);
+}
+
+
+/******************************************************
+ *
+ * geo_distance - distance between points
+ *
+ * args:
+ * a pair of points - for each point,
+ * x-coordinate is longitude in degrees west of Greenwich
+ * y-coordinate is latitude in degrees above equator
+ *
+ * returns: float8
+ * distance between the points in miles on earth's surface
+ ******************************************************/
+
+PG_FUNCTION_INFO_V1(geo_distance);
+
+Datum
+geo_distance(PG_FUNCTION_ARGS)
+{
+ Point *pt1 = PG_GETARG_POINT_P(0);
+ Point *pt2 = PG_GETARG_POINT_P(1);
+ float8 result;
+
+ result = geo_distance_internal(pt1, pt2);
+ PG_RETURN_FLOAT8(result);
+}
diff --git a/contrib/earthdistance/earthdistance.control b/contrib/earthdistance/earthdistance.control
new file mode 100644
index 0000000..5816d22
--- /dev/null
+++ b/contrib/earthdistance/earthdistance.control
@@ -0,0 +1,6 @@
+# earthdistance extension
+comment = 'calculate great-circle distances on the surface of the Earth'
+default_version = '1.1'
+module_pathname = '$libdir/earthdistance'
+relocatable = true
+requires = 'cube'