PostGIS  2.5.7dev-r@@SVN_REVISION@@

## ◆ robust_cross_product()

 void robust_cross_product ( const GEOGRAPHIC_POINT * p, const GEOGRAPHIC_POINT * q, POINT3D * a )

Computes the cross product of two vectors using their lat, lng representations.

Good even for small distances between p and q.

Definition at line 634 of file lwgeodetic.c.

635 {
636  double lon_qpp = (q->lon + p->lon) / -2.0;
637  double lon_qmp = (q->lon - p->lon) / 2.0;
638  double sin_p_lat_minus_q_lat = sin(p->lat-q->lat);
639  double sin_p_lat_plus_q_lat = sin(p->lat+q->lat);
640  double sin_lon_qpp = sin(lon_qpp);
641  double sin_lon_qmp = sin(lon_qmp);
642  double cos_lon_qpp = cos(lon_qpp);
643  double cos_lon_qmp = cos(lon_qmp);
644  a->x = sin_p_lat_minus_q_lat * sin_lon_qpp * cos_lon_qmp -
645  sin_p_lat_plus_q_lat * cos_lon_qpp * sin_lon_qmp;
646  a->y = sin_p_lat_minus_q_lat * cos_lon_qpp * cos_lon_qmp +
647  sin_p_lat_plus_q_lat * sin_lon_qpp * sin_lon_qmp;
648  a->z = cos(p->lat) * cos(q->lat) * sin(q->lon-p->lon);
649 }
double z
Definition: liblwgeom.h:343
double x
Definition: liblwgeom.h:343
double y
Definition: liblwgeom.h:343

References GEOGRAPHIC_POINT::lat, GEOGRAPHIC_POINT::lon, POINT3D::x, POINT3D::y, and POINT3D::z.

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