earthdistance.c File Reference

#include "postgres.h"
#include <math.h>
#include "utils/geo_decls.h"

Include dependency graph for earthdistance.c:

Go to the source code of this file.

Macros
#define	M_PI   3.14159265358979323846

Functions
static double	degtorad (double degrees)
static double	geo_distance_internal (Point *pt1, Point *pt2)
	PG_FUNCTION_INFO_V1 (geo_distance)
Datum	geo_distance (PG_FUNCTION_ARGS)

Variables
	PG_MODULE_MAGIC
static const double	EARTH_RADIUS = 3958.747716
static const double	TWO_PI = 2.0 * M_PI

Macro Definition Documentation

M_PI

#define M_PI   3.14159265358979323846

Definition at line 11 of file earthdistance.c.

Function Documentation

degtorad()

static double degtorad ( double  degrees )

static

Definition at line 31 of file earthdistance.c.

{
    return (degrees / 360.0) * TWO_PI;
}

References degrees(), and TWO_PI.

Referenced by geo_distance_internal().

geo_distance()

Datum geo_distance

(

PG_FUNCTION_ARGS

)

Definition at line 97 of file earthdistance.c.

{
    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);
}

References geo_distance_internal(), PG_GETARG_POINT_P, and PG_RETURN_FLOAT8.

geo_distance_internal()

static double geo_distance_internal ( Point *  pt1, Point *  pt2  )

static

Definition at line 50 of file earthdistance.c.

{
    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);
}

References degtorad(), EARTH_RADIUS, M_PI, TWO_PI, Point::x, and Point::y.

Referenced by geo_distance().

PG_FUNCTION_INFO_V1()

PG_FUNCTION_INFO_V1

(

geo_distance

)

Variable Documentation

EARTH_RADIUS

const double EARTH_RADIUS = 3958.747716

static

Definition at line 17 of file earthdistance.c.

Referenced by geo_distance_internal().

PG_MODULE_MAGIC

PG_MODULE_MAGIC

Definition at line 14 of file earthdistance.c.

TWO_PI

const double TWO_PI = 2.0 * M_PI

static

Definition at line 18 of file earthdistance.c.

Referenced by degtorad(), and geo_distance_internal().