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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-16 19:46:48 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-16 19:46:48 +0000 |
commit | 311bcfc6b3acdd6fd152798c7f287ddf74fa2a98 (patch) | |
tree | 0ec307299b1dada3701e42f4ca6eda57d708261e /contrib/earthdistance/earthdistance.c | |
parent | Initial commit. (diff) | |
download | postgresql-15-upstream.tar.xz postgresql-15-upstream.zip |
Adding upstream version 15.4.upstream/15.4upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'contrib/earthdistance/earthdistance.c')
-rw-r--r-- | contrib/earthdistance/earthdistance.c | 104 |
1 files changed, 104 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); +} |