geography_project_geography()

Datum geography_project_geography

(

PG_FUNCTION_ARGS

)

Definition at line 1035 of file geography_measurement.c.

{
        LWGEOM *lwgeom1, *lwgeom2;
        LWPOINT *lwp1, *lwp2, *lwp3;
        GSERIALIZED *g1, *g2, *g3;
        double distance;
        SPHEROID s;
 
        /* Get our geometry object loaded into memory. */
        g1 = PG_GETARG_GSERIALIZED_P(0);
        g2 = PG_GETARG_GSERIALIZED_P(1);
 
        if ( gserialized_get_type(g1) != POINTTYPE ||
                 gserialized_get_type(g2) != POINTTYPE )
        {
                elog(ERROR, "ST_Project(geography) is only valid for point inputs");
                PG_RETURN_NULL();
        }
 
        distance = PG_GETARG_FLOAT8(2); /* Distance in meters */
 
        /* Handle the zero distance case */
        if ( FP_EQUALS(distance, 0.0) )
        {
                PG_RETURN_POINTER(g2);
        }
 
        lwgeom1 = lwgeom_from_gserialized(g1);
        lwgeom2 = lwgeom_from_gserialized(g2);
 
        /* EMPTY things cannot be projected from */
        if ( lwgeom_is_empty(lwgeom1) || lwgeom_is_empty(lwgeom2) )
        {
                lwgeom_free(lwgeom1);
                lwgeom_free(lwgeom2);
                elog(ERROR, "ST_Project(geography) cannot project from an empty point");
                PG_RETURN_NULL();
        }
 
        /* Initialize spheroid */
        spheroid_init_from_srid(lwgeom_get_srid(lwgeom1), &s);
 
        /* Calculate the length */
        lwp1 = lwgeom_as_lwpoint(lwgeom1);
        lwp2 = lwgeom_as_lwpoint(lwgeom2);
        lwp3 = lwgeom_project_spheroid_lwpoint(lwp1, lwp2, &s, distance);
 
        /* Something went wrong... */
        if ( lwp3 == NULL )
        {
                elog(ERROR, "lwgeom_project_spheroid_lwpoint returned null");
                PG_RETURN_NULL();
        }
 
        /* Clean up, but not all the way to the point arrays */
        lwgeom_free(lwgeom1);
        lwgeom_free(lwgeom2);
        g3 = geography_serialize(lwpoint_as_lwgeom(lwp3));
        lwpoint_free(lwp3);
 
        PG_FREE_IF_COPY(g1, 0);
        PG_FREE_IF_COPY(g2, 1);
        PG_RETURN_POINTER(g3);
}

References distance(), FP_EQUALS, gserialized_get_type(), lwgeom_as_lwpoint(), lwgeom_free(), lwgeom_from_gserialized(), lwgeom_get_srid(), lwgeom_is_empty(), lwgeom_project_spheroid_lwpoint(), lwpoint_as_lwgeom(), lwpoint_free(), POINTTYPE, and s.

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