geography_area()

Datum geography_area

(

PG_FUNCTION_ARGS

)

Definition at line 492 of file geography_measurement.c.

{
        LWGEOM *lwgeom = NULL;
        GSERIALIZED *g = NULL;
        GBOX gbox;
        double area;
        bool use_spheroid = LW_TRUE;
        SPHEROID s;
 
        /* Get our geometry object loaded into memory. */
        g = PG_GETARG_GSERIALIZED_P(0);
 
        /* Read our calculation type */
        use_spheroid = PG_GETARG_BOOL(1);
 
        /* Initialize spheroid */
        spheroid_init_from_srid(gserialized_get_srid(g), &s);
 
        lwgeom = lwgeom_from_gserialized(g);
 
        /* EMPTY things have no area */
        if ( lwgeom_is_empty(lwgeom) )
        {
                lwgeom_free(lwgeom);
                PG_RETURN_FLOAT8(0.0);
        }
 
        if ( lwgeom->bbox )
                gbox = *(lwgeom->bbox);
        else
                lwgeom_calculate_gbox_geodetic(lwgeom, &gbox);
 
#ifndef PROJ_GEODESIC
        /* Test for cases that are currently not handled by spheroid code */
        if ( use_spheroid )
        {
                /* We can't circle the poles right now */
                if ( FP_GTEQ(gbox.zmax,1.0) || FP_LTEQ(gbox.zmin,-1.0) )
                        use_spheroid = LW_FALSE;
                /* We can't cross the equator right now */
                if ( gbox.zmax > 0.0 && gbox.zmin < 0.0 )
                        use_spheroid = LW_FALSE;
        }
#endif /* ifndef PROJ_GEODESIC */
 
        /* User requests spherical calculation, turn our spheroid into a sphere */
        if ( ! use_spheroid )
                s.a = s.b = s.radius;
 
        /* Calculate the area */
        area = lwgeom_area_spheroid(lwgeom, &s);
 
        /* Clean up */
        lwgeom_free(lwgeom);
        PG_FREE_IF_COPY(g, 0);
 
        /* Something went wrong... */
        if ( area < 0.0 )
        {
                elog(ERROR, "lwgeom_area_spher(oid) returned area < 0.0");
                PG_RETURN_NULL();
        }
 
        PG_RETURN_FLOAT8(area);
}

References LWGEOM::bbox, FP_GTEQ, FP_LTEQ, gserialized_get_srid(), LW_FALSE, LW_TRUE, lwgeom_area_spheroid(), lwgeom_calculate_gbox_geodetic(), lwgeom_free(), lwgeom_from_gserialized(), lwgeom_is_empty(), s, GBOX::zmax, and GBOX::zmin.

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