interpolate_point4d_spheroid()

static void interpolate_point4d_spheroid ( const POINT4D *  p1, const POINT4D *  p2, POINT4D *  p, const SPHEROID *  s, double  f  )

static

Find interpolation point p between geography points p1 and p2 so that the len(p1,p) == len(p1,p2) f and p falls on p1,p2 segment.

Definition at line 60 of file lwgeodetic_measures.c.

{
        GEOGRAPHIC_POINT g, g1, g2;
        geographic_point_init(p1->x, p1->y, &g1);
        geographic_point_init(p2->x, p2->y, &g2);
        int success;
        double dist, dir;
 
        /* Special sphere case */
        if ( s == NULL || s->a == s->b )
        {
                /* Calculate distance and direction between g1 and g2 */
                dist = sphere_distance(&g1, &g2);
                dir = sphere_direction(&g1, &g2, dist);
                /* Compute interpolation point */
                success = sphere_project(&g1, dist*f, dir, &g);
        }
        /* Spheroid case */
        else
        {
                /* Calculate distance and direction between g1 and g2 */
                dist = spheroid_distance(&g1, &g2, s);
                dir = spheroid_direction(&g1, &g2, s);
                /* Compute interpolation point */
                success = spheroid_project(&g1, s, dist*f, dir, &g);
        }
 
        /* If success, use newly computed lat and lon,
        * otherwise return precomputed cartesian result */
        if (success == LW_SUCCESS)
        {
                p->x = rad2deg(longitude_radians_normalize(g.lon));
                p->y = rad2deg(latitude_radians_normalize(g.lat));
        }
}

References geographic_point_init(), GEOGRAPHIC_POINT::lat, latitude_radians_normalize(), GEOGRAPHIC_POINT::lon, longitude_radians_normalize(), LW_SUCCESS, rad2deg, s, sphere_direction(), sphere_distance(), sphere_project(), spheroid_direction(), spheroid_distance(), spheroid_project(), POINT4D::x, and POINT4D::y.

Referenced by geography_interpolate_points(), and geography_substring().

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