130 lines
3.0 KiB
C
130 lines
3.0 KiB
C
/* 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
|
|
*
|
|
* If float8 is passed-by-value, the oldstyle version-0 calling convention
|
|
* is unportable, so we use version-1. However, if it's passed-by-reference,
|
|
* continue to use oldstyle. This is just because we'd like earthdistance
|
|
* to serve as a canary for any unintentional breakage of version-0 functions
|
|
* with float8 results.
|
|
******************************************************/
|
|
|
|
#ifdef USE_FLOAT8_BYVAL
|
|
|
|
Datum geo_distance(PG_FUNCTION_ARGS);
|
|
|
|
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);
|
|
}
|
|
#else /* !USE_FLOAT8_BYVAL */
|
|
|
|
double *geo_distance(Point *pt1, Point *pt2);
|
|
|
|
double *
|
|
geo_distance(Point *pt1, Point *pt2)
|
|
{
|
|
double *resultp = palloc(sizeof(double));
|
|
|
|
*resultp = geo_distance_internal(pt1, pt2);
|
|
return resultp;
|
|
}
|
|
|
|
#endif /* USE_FLOAT8_BYVAL */
|