lwgeom_project_spheroid()

LWPOINT* lwgeom_project_spheroid	(	const LWPOINT *	r,
		const SPHEROID *	spheroid,
		double	distance,
		double	azimuth
	)

Calculate a projected point given a source point, a distance and a bearing.

Calculate the location of a point on a spheroid, give a start point, bearing and distance.

Parameters

r	- location of first point.
spheroid	- spheroid definition.
distance	- distance, in units of the spheroid def'n.
azimuth	- azimuth in radians.

Returns

s - location of projected point.

Definition at line 2095 of file lwgeodetic.c.

References distance(), geographic_point_init(), GEOGRAPHIC_POINT::lat, latitude_radians_normalize(), GEOGRAPHIC_POINT::lon, longitude_radians_normalize(), LW_FAILURE, LW_TRUE, LWDEBUGF, lwerror(), lwgeom_set_geodetic(), lwpoint_as_lwgeom(), lwpoint_construct(), lwpoint_get_x(), lwpoint_get_y(), POINT4D::m, ptarray_construct(), ptarray_set_point4d(), rad2deg, SPHEROID::radius, spheroid_project(), LWPOINT::srid, pixval::x, POINT4D::x, pixval::y, POINT4D::y, and POINT4D::z.

Referenced by geography_project().

{
        GEOGRAPHIC_POINT geo_source, geo_dest;
        POINT4D pt_dest;
        double x, y;
        POINTARRAY *pa;
        LWPOINT *lwp;

        /* Normalize distance to be positive*/
        if ( distance < 0.0 ) {
                distance = -distance;
                azimuth += M_PI;
        }

        /* Normalize azimuth */
        azimuth -= 2.0 * M_PI * floor(azimuth / (2.0 * M_PI));

        /* Check the distance validity */
        if ( distance > (M_PI * spheroid->radius) )
        {
                lwerror("Distance must not be greater than %g", M_PI * spheroid->radius);
                return NULL;
        }

        /* Convert to ta geodetic point */
        x = lwpoint_get_x(r);
        y = lwpoint_get_y(r);
        geographic_point_init(x, y, &geo_source);

        /* Try the projection */
        if( spheroid_project(&geo_source, spheroid, distance, azimuth, &geo_dest) == LW_FAILURE )
        {
                LWDEBUGF(3, "Unable to project from (%g %g) with azimuth %g and distance %g", x, y, azimuth, distance);
                lwerror("Unable to project from (%g %g) with azimuth %g and distance %g", x, y, azimuth, distance);
                return NULL;
        }

        /* Build the output LWPOINT */
        pa = ptarray_construct(0, 0, 1);
        pt_dest.x = rad2deg(longitude_radians_normalize(geo_dest.lon));
        pt_dest.y = rad2deg(latitude_radians_normalize(geo_dest.lat));
        pt_dest.z = pt_dest.m = 0.0;
        ptarray_set_point4d(pa, 0, &pt_dest);
        lwp = lwpoint_construct(r->srid, NULL, pa);
        lwgeom_set_geodetic(lwpoint_as_lwgeom(lwp), LW_TRUE);
        return lwp;
}

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