geography_measurement.c

Go to the documentation of this file.

/**********************************************************************
 *
 * PostGIS - Spatial Types for PostgreSQL
 * http://postgis.net
 *
 * PostGIS is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 2 of the License, or
 * (at your option) any later version.
 *
 * PostGIS is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with PostGIS.  If not, see <http://www.gnu.org/licenses/>.
 *
 **********************************************************************
 *
 * Copyright (C) 2009 Paul Ramsey <pramsey@cleverelephant.ca>
 *
 **********************************************************************/
 
 
#include "postgres.h"
#include "catalog/pg_type.h" /* for CSTRINGOID */
 
#include "../postgis_config.h"
 
#include <math.h>
#include <float.h>
#include <string.h>
#include <stdio.h>
 
#include "liblwgeom.h"                  /* For standard geometry types. */
#include "liblwgeom_internal.h"         /* For FP comparators. */
#include "lwgeom_pg.h"                  /* For debugging macros. */
#include "geography.h"                  /* For utility functions. */
#include "geography_measurement_trees.h" /* For circ_tree caching */
#include "lwgeom_transform.h"            /* For SRID functions */
 
#ifdef PROJ_GEODESIC
/* round to 10 nm precision */
#define INVMINDIST 1.0e8
#else
/* round to 100 nm precision */
#define INVMINDIST 1.0e7
#endif
 
Datum geography_distance(PG_FUNCTION_ARGS);
Datum geography_distance_uncached(PG_FUNCTION_ARGS);
Datum geography_distance_knn(PG_FUNCTION_ARGS);
Datum geography_distance_tree(PG_FUNCTION_ARGS);
Datum geography_dwithin(PG_FUNCTION_ARGS);
Datum geography_dwithin_uncached(PG_FUNCTION_ARGS);
Datum geography_area(PG_FUNCTION_ARGS);
Datum geography_length(PG_FUNCTION_ARGS);
Datum geography_expand(PG_FUNCTION_ARGS);
Datum geography_point_outside(PG_FUNCTION_ARGS);
Datum geography_covers(PG_FUNCTION_ARGS);
Datum geography_coveredby(PG_FUNCTION_ARGS);
Datum geography_bestsrid(PG_FUNCTION_ARGS);
Datum geography_perimeter(PG_FUNCTION_ARGS);
Datum geography_project(PG_FUNCTION_ARGS);
Datum geography_azimuth(PG_FUNCTION_ARGS);
Datum geography_segmentize(PG_FUNCTION_ARGS);
 
 
PG_FUNCTION_INFO_V1(geography_distance_knn);
Datum geography_distance_knn(PG_FUNCTION_ARGS)
{
        LWGEOM *lwgeom1 = NULL;
        LWGEOM *lwgeom2 = NULL;
        GSERIALIZED *g1 = NULL;
        GSERIALIZED *g2 = NULL;
        double distance;
        double tolerance = FP_TOLERANCE;
        bool use_spheroid = false; /* must use sphere, can't get index to harmonize with spheroid */
        SPHEROID s;
 
        /* Get our geometry objects loaded into memory. */
        g1 = PG_GETARG_GSERIALIZED_P(0);
        g2 = PG_GETARG_GSERIALIZED_P(1);
 
        gserialized_error_if_srid_mismatch(g1, g2, __func__);
 
        /* Initialize spheroid */
        spheroid_init_from_srid(gserialized_get_srid(g1), &s);
 
        /* Set to sphere if requested */
        if ( ! use_spheroid )
                s.a = s.b = s.radius;
 
        lwgeom1 = lwgeom_from_gserialized(g1);
        lwgeom2 = lwgeom_from_gserialized(g2);
 
        /* Return NULL on empty arguments. */
        if ( lwgeom_is_empty(lwgeom1) || lwgeom_is_empty(lwgeom2) )
        {
                PG_FREE_IF_COPY(g1, 0);
                PG_FREE_IF_COPY(g2, 1);
                PG_RETURN_NULL();
        }
 
        /* Make sure we have boxes attached */
        lwgeom_add_bbox_deep(lwgeom1, NULL);
        lwgeom_add_bbox_deep(lwgeom2, NULL);
 
        distance = lwgeom_distance_spheroid(lwgeom1, lwgeom2, &s, tolerance);
 
        POSTGIS_DEBUGF(2, "[GIST] '%s' got distance %g", __func__, distance);
 
        /* Clean up */
        lwgeom_free(lwgeom1);
        lwgeom_free(lwgeom2);
        PG_FREE_IF_COPY(g1, 0);
        PG_FREE_IF_COPY(g2, 1);
 
        /* Something went wrong, negative return... should already be eloged, return NULL */
        if ( distance < 0.0 )
        {
                PG_RETURN_NULL();
        }
 
        PG_RETURN_FLOAT8(distance);
}
 
/*
** geography_distance_uncached(GSERIALIZED *g1, GSERIALIZED *g2, double tolerance, boolean use_spheroid)
** returns double distance in meters
*/
PG_FUNCTION_INFO_V1(geography_distance_uncached);
Datum geography_distance_uncached(PG_FUNCTION_ARGS)
{
        LWGEOM *lwgeom1 = NULL;
        LWGEOM *lwgeom2 = NULL;
        GSERIALIZED *g1 = NULL;
        GSERIALIZED *g2 = NULL;
        double distance;
        double tolerance = FP_TOLERANCE;
        bool use_spheroid = true;
        SPHEROID s;
 
        /* Get our geometry objects loaded into memory. */
        g1 = PG_GETARG_GSERIALIZED_P(0);
        g2 = PG_GETARG_GSERIALIZED_P(1);
 
        /* Read our tolerance value. */
        if ( PG_NARGS() > 2 && ! PG_ARGISNULL(2) )
                tolerance = PG_GETARG_FLOAT8(2);
 
        /* Read our calculation type. */
        if ( PG_NARGS() > 3 && ! PG_ARGISNULL(3) )
                use_spheroid = PG_GETARG_BOOL(3);
 
        gserialized_error_if_srid_mismatch(g1, g2, __func__);
 
        /* Initialize spheroid */
        spheroid_init_from_srid(gserialized_get_srid(g1), &s);
 
        /* Set to sphere if requested */
        if ( ! use_spheroid )
                s.a = s.b = s.radius;
 
        lwgeom1 = lwgeom_from_gserialized(g1);
        lwgeom2 = lwgeom_from_gserialized(g2);
 
        /* Return NULL on empty arguments. */
        if ( lwgeom_is_empty(lwgeom1) || lwgeom_is_empty(lwgeom2) )
        {
                PG_FREE_IF_COPY(g1, 0);
                PG_FREE_IF_COPY(g2, 1);
                PG_RETURN_NULL();
        }
 
        /* Make sure we have boxes attached */
        lwgeom_add_bbox_deep(lwgeom1, NULL);
        lwgeom_add_bbox_deep(lwgeom2, NULL);
 
        distance = lwgeom_distance_spheroid(lwgeom1, lwgeom2, &s, tolerance);
 
        POSTGIS_DEBUGF(2, "[GIST] '%s' got distance %g", __func__, distance);
 
        /* Clean up */
        lwgeom_free(lwgeom1);
        lwgeom_free(lwgeom2);
        PG_FREE_IF_COPY(g1, 0);
        PG_FREE_IF_COPY(g2, 1);
 
        /* Something went wrong, negative return... should already be eloged, return NULL */
        if ( distance < 0.0 )
        {
                PG_RETURN_NULL();
        }
 
        PG_RETURN_FLOAT8(distance);
}
 
 
/*
** geography_distance(GSERIALIZED *g1, GSERIALIZED *g2, double tolerance, boolean use_spheroid)
** returns double distance in meters
*/
PG_FUNCTION_INFO_V1(geography_distance);
Datum geography_distance(PG_FUNCTION_ARGS)
{
        SHARED_GSERIALIZED *shared_geom1 = ToastCacheGetGeometry(fcinfo, 0);
        SHARED_GSERIALIZED *shared_geom2 = ToastCacheGetGeometry(fcinfo, 1);
        const GSERIALIZED *g1 = shared_gserialized_get(shared_geom1);
        const GSERIALIZED *g2 = shared_gserialized_get(shared_geom2);
        double distance;
        bool use_spheroid = true;
        SPHEROID s;
 
 
        if (PG_NARGS() > 2)
                use_spheroid = PG_GETARG_BOOL(2);
 
        gserialized_error_if_srid_mismatch(g1, g2, __func__);
 
        /* Initialize spheroid */
        spheroid_init_from_srid(gserialized_get_srid(g1), &s);
 
        /* Set to sphere if requested */
        if ( ! use_spheroid )
                s.a = s.b = s.radius;
 
        /* Return NULL on empty arguments. */
        if ( gserialized_is_empty(g1) || gserialized_is_empty(g2) )
        {
                PG_RETURN_NULL();
        }
 
        /* Do the brute force calculation if the cached calculation doesn't tick over */
        if (LW_FAILURE == geography_distance_cache(fcinfo, shared_geom1, shared_geom2, &s, &distance))
        {
                /* default to using tree-based distance calculation at all times */
                /* in standard distance call. */
                geography_tree_distance(g1, g2, &s, FP_TOLERANCE, &distance);
                /*
                LWGEOM* lwgeom1 = lwgeom_from_gserialized(g1);
                LWGEOM* lwgeom2 = lwgeom_from_gserialized(g2);
                distance = lwgeom_distance_spheroid(lwgeom1, lwgeom2, &s, tolerance);
                lwgeom_free(lwgeom1);
                lwgeom_free(lwgeom2);
                */
        }
 
        /* Knock off any funny business at the nanometer level, ticket #2168 */
        distance = round(distance * INVMINDIST) / INVMINDIST;
 
        /* Something went wrong, negative return... should already be eloged, return NULL */
        if ( distance < 0.0 )
        {
                elog(ERROR, "distance returned negative!");
                PG_RETURN_NULL();
        }
 
        PG_RETURN_FLOAT8(distance);
}
 
/*
** geography_dwithin(GSERIALIZED *g1, GSERIALIZED *g2, double tolerance, boolean use_spheroid)
** returns double distance in meters
*/
PG_FUNCTION_INFO_V1(geography_dwithin);
Datum geography_dwithin(PG_FUNCTION_ARGS)
{
        SHARED_GSERIALIZED *shared_geom1 = ToastCacheGetGeometry(fcinfo, 0);
        SHARED_GSERIALIZED *shared_geom2 = ToastCacheGetGeometry(fcinfo, 1);
        const GSERIALIZED *g1 = shared_gserialized_get(shared_geom1);
        const GSERIALIZED *g2 = shared_gserialized_get(shared_geom2);
        SPHEROID s;
        double tolerance = FP_TOLERANCE;
        bool use_spheroid = true;
        double distance;
        int dwithin = LW_FALSE;
 
        gserialized_error_if_srid_mismatch(g1, g2, __func__);
 
        /* Read our tolerance value. */
        if ( PG_NARGS() > 2 && ! PG_ARGISNULL(2) )
                tolerance = PG_GETARG_FLOAT8(2);
 
        /* Read our calculation type. */
        if ( PG_NARGS() > 3 && ! PG_ARGISNULL(3) )
                use_spheroid = PG_GETARG_BOOL(3);
 
        /* Initialize spheroid */
        spheroid_init_from_srid(gserialized_get_srid(g1), &s);
 
        /* Set to sphere if requested */
        if ( ! use_spheroid )
                s.a = s.b = s.radius;
 
        /* Return FALSE on empty arguments. */
        if ( gserialized_is_empty(g1) || gserialized_is_empty(g2) )
                PG_RETURN_BOOL(false);
 
        /* Do the brute force calculation if the cached calculation doesn't tick over */
        if (LW_FAILURE == geography_dwithin_cache(fcinfo, shared_geom1, shared_geom2, &s, tolerance, &dwithin))
        {
                LWGEOM* lwgeom1 = lwgeom_from_gserialized(g1);
                LWGEOM* lwgeom2 = lwgeom_from_gserialized(g2);
                distance = lwgeom_distance_spheroid(lwgeom1, lwgeom2, &s, tolerance);
                /* Something went wrong... */
                if ( distance < 0.0 )
                        elog(ERROR, "lwgeom_distance_spheroid returned negative!");
                dwithin = (distance <= tolerance);
                lwgeom_free(lwgeom1);
                lwgeom_free(lwgeom2);
        }
 
        PG_RETURN_BOOL(dwithin);
}
 
PG_FUNCTION_INFO_V1(geography_intersects);
Datum geography_intersects(PG_FUNCTION_ARGS)
{
        PG_RETURN_BOOL(CallerFInfoFunctionCall2(
                geography_dwithin, fcinfo->flinfo, InvalidOid,
                PG_GETARG_DATUM(0), PG_GETARG_DATUM(1)));
}
 
/*
** geography_distance_tree(GSERIALIZED *g1, GSERIALIZED *g2, double tolerance, boolean use_spheroid)
** returns double distance in meters
*/
PG_FUNCTION_INFO_V1(geography_distance_tree);
Datum geography_distance_tree(PG_FUNCTION_ARGS)
{
        GSERIALIZED *g1 = NULL;
        GSERIALIZED *g2 = NULL;
        double tolerance = 0.0;
        double distance;
        bool use_spheroid = true;
        SPHEROID s;
 
        /* Get our geometry objects loaded into memory. */
        g1 = PG_GETARG_GSERIALIZED_P(0);
        g2 = PG_GETARG_GSERIALIZED_P(1);
 
        gserialized_error_if_srid_mismatch(g1, g2, __func__);
 
        /* Return zero on empty arguments. */
        if ( gserialized_is_empty(g1) || gserialized_is_empty(g2) )
        {
                PG_FREE_IF_COPY(g1, 0);
                PG_FREE_IF_COPY(g2, 1);
                PG_RETURN_FLOAT8(0.0);
        }
 
        /* Read our tolerance value. */
        if ( PG_NARGS() > 2 && ! PG_ARGISNULL(2) )
                tolerance = PG_GETARG_FLOAT8(2);
 
        /* Read our calculation type. */
        if ( PG_NARGS() > 3 && ! PG_ARGISNULL(3) )
                use_spheroid = PG_GETARG_BOOL(3);
 
        /* Initialize spheroid */
        spheroid_init_from_srid(gserialized_get_srid(g1), &s);
 
        /* Set to sphere if requested */
        if ( ! use_spheroid )
                s.a = s.b = s.radius;
 
        if  ( geography_tree_distance(g1, g2, &s, tolerance, &distance) == LW_FAILURE )
        {
                elog(ERROR, "geography_distance_tree failed!");
                PG_RETURN_NULL();
        }
        /* Knock off any funny business at the nanometer level, ticket #2168 */
        distance = round(distance * INVMINDIST) / INVMINDIST;
 
        PG_RETURN_FLOAT8(distance);
}
 
 
 
/*
** geography_dwithin_uncached(GSERIALIZED *g1, GSERIALIZED *g2, double tolerance, boolean use_spheroid)
** returns double distance in meters
*/
PG_FUNCTION_INFO_V1(geography_dwithin_uncached);
Datum geography_dwithin_uncached(PG_FUNCTION_ARGS)
{
        LWGEOM *lwgeom1 = NULL;
        LWGEOM *lwgeom2 = NULL;
        GSERIALIZED *g1 = NULL;
        GSERIALIZED *g2 = NULL;
        double tolerance = 0.0;
        double distance;
        bool use_spheroid = true;
        SPHEROID s;
 
        /* Get our geometry objects loaded into memory. */
        g1 = PG_GETARG_GSERIALIZED_P(0);
        g2 = PG_GETARG_GSERIALIZED_P(1);
        gserialized_error_if_srid_mismatch(g1, g2, __func__);
 
        /* Read our tolerance value. */
        if ( PG_NARGS() > 2 && ! PG_ARGISNULL(2) )
                tolerance = PG_GETARG_FLOAT8(2);
 
        /* Read our calculation type. */
        if ( PG_NARGS() > 3 && ! PG_ARGISNULL(3) )
                use_spheroid = PG_GETARG_BOOL(3);
 
        /* Initialize spheroid */
        spheroid_init_from_srid(gserialized_get_srid(g1), &s);
 
        /* Set to sphere if requested */
        if ( ! use_spheroid )
                s.a = s.b = s.radius;
 
        lwgeom1 = lwgeom_from_gserialized(g1);
        lwgeom2 = lwgeom_from_gserialized(g2);
 
        /* Return FALSE on empty arguments. */
        if ( lwgeom_is_empty(lwgeom1) || lwgeom_is_empty(lwgeom2) )
        {
                PG_RETURN_BOOL(false);
        }
 
        distance = lwgeom_distance_spheroid(lwgeom1, lwgeom2, &s, tolerance);
 
        /* Clean up */
        lwgeom_free(lwgeom1);
        lwgeom_free(lwgeom2);
        PG_FREE_IF_COPY(g1, 0);
        PG_FREE_IF_COPY(g2, 1);
 
        /* Something went wrong... should already be eloged, return FALSE */
        if ( distance < 0.0 )
        {
                elog(ERROR, "lwgeom_distance_spheroid returned negative!");
                PG_RETURN_BOOL(false);
        }
 
        PG_RETURN_BOOL(distance <= tolerance);
}
 
 
/*
** geography_expand(GSERIALIZED *g) returns *GSERIALIZED
**
** warning, this tricky little function does not expand the
** geometry at all, just re-writes bounding box value to be
** a bit bigger. only useful when passing the result along to
** an index operator (&&)
*/
PG_FUNCTION_INFO_V1(geography_expand);
Datum geography_expand(PG_FUNCTION_ARGS)
{
        GSERIALIZED *g = NULL;
        GSERIALIZED *g_out = NULL;
        double unit_distance, distance;
 
        /* Get a wholly-owned pointer to the geography */
        g = PG_GETARG_GSERIALIZED_P_COPY(0);
 
        /* Read our distance value and normalize to unit-sphere. */
        distance = PG_GETARG_FLOAT8(1);
        /* Magic 1% expansion is to bridge difference between potential */
        /* spheroidal input distance and fact that expanded box filter is */
        /* calculated on sphere */
        unit_distance = 1.01 * distance / WGS84_RADIUS;
 
        /* Try the expansion */
        g_out = gserialized_expand(g, unit_distance);
 
        /* If the expansion fails, the return our input */
        if ( g_out == NULL )
        {
                PG_RETURN_POINTER(g);
        }
 
        if ( g_out != g )
        {
                pfree(g);
        }
 
        PG_RETURN_POINTER(g_out);
}
 
/*
** geography_area(GSERIALIZED *g)
** returns double area in meters square
*/
PG_FUNCTION_INFO_V1(geography_area);
Datum geography_area(PG_FUNCTION_ARGS)
{
        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);
}
 
/*
** geography_perimeter(GSERIALIZED *g)
** returns double perimeter in meters for area features
*/
PG_FUNCTION_INFO_V1(geography_perimeter);
Datum geography_perimeter(PG_FUNCTION_ARGS)
{
        LWGEOM *lwgeom = NULL;
        GSERIALIZED *g = NULL;
        double length;
        bool use_spheroid = LW_TRUE;
        SPHEROID s;
        int type;
 
        /* Get our geometry object loaded into memory. */
        g = PG_GETARG_GSERIALIZED_P(0);
 
        /* Only return for area features. */
        type = gserialized_get_type(g);
        if ( ! (type == POLYGONTYPE || type == MULTIPOLYGONTYPE || type == COLLECTIONTYPE) )
        {
                PG_RETURN_FLOAT8(0.0);
        }
 
        lwgeom = lwgeom_from_gserialized(g);
 
        /* EMPTY things have no perimeter */
        if ( lwgeom_is_empty(lwgeom) )
        {
                lwgeom_free(lwgeom);
                PG_RETURN_FLOAT8(0.0);
        }
 
        /* Read our calculation type */
        use_spheroid = PG_GETARG_BOOL(1);
 
        /* Initialize spheroid */
        spheroid_init_from_srid(gserialized_get_srid(g), &s);
 
        /* User requests spherical calculation, turn our spheroid into a sphere */
        if ( ! use_spheroid )
                s.a = s.b = s.radius;
 
        /* Calculate the length */
        length = lwgeom_length_spheroid(lwgeom, &s);
 
        /* Something went wrong... */
        if ( length < 0.0 )
        {
                elog(ERROR, "lwgeom_length_spheroid returned length < 0.0");
                PG_RETURN_NULL();
        }
 
        /* Clean up, but not all the way to the point arrays */
        lwgeom_free(lwgeom);
 
        PG_FREE_IF_COPY(g, 0);
        PG_RETURN_FLOAT8(length);
}
 
/*
** geography_length(GSERIALIZED *g)
** returns double length in meters
*/
PG_FUNCTION_INFO_V1(geography_length);
Datum geography_length(PG_FUNCTION_ARGS)
{
        LWGEOM *lwgeom = NULL;
        GSERIALIZED *g = NULL;
        double length;
        bool use_spheroid = LW_TRUE;
        SPHEROID s;
 
        /* Get our geometry object loaded into memory. */
        g = PG_GETARG_GSERIALIZED_P(0);
        lwgeom = lwgeom_from_gserialized(g);
 
        /* EMPTY things have no length */
        if ( lwgeom_is_empty(lwgeom) || lwgeom->type == POLYGONTYPE || lwgeom->type == MULTIPOLYGONTYPE )
        {
                lwgeom_free(lwgeom);
                PG_RETURN_FLOAT8(0.0);
        }
 
        /* Read our calculation type */
        use_spheroid = PG_GETARG_BOOL(1);
 
        /* Initialize spheroid */
        spheroid_init_from_srid(gserialized_get_srid(g), &s);
 
        /* User requests spherical calculation, turn our spheroid into a sphere */
        if ( ! use_spheroid )
                s.a = s.b = s.radius;
 
        /* Calculate the length */
        length = lwgeom_length_spheroid(lwgeom, &s);
 
        /* Something went wrong... */
        if ( length < 0.0 )
        {
                elog(ERROR, "lwgeom_length_spheroid returned length < 0.0");
                PG_RETURN_NULL();
        }
 
        /* Clean up */
        lwgeom_free(lwgeom);
 
        PG_FREE_IF_COPY(g, 0);
        PG_RETURN_FLOAT8(length);
}
 
/*
** geography_point_outside(GSERIALIZED *g)
** returns point outside the object
*/
PG_FUNCTION_INFO_V1(geography_point_outside);
Datum geography_point_outside(PG_FUNCTION_ARGS)
{
        GBOX gbox;
        LWGEOM *lwpoint = NULL;
        POINT2D pt;
 
        /* We need the bounding box to get an outside point for area algorithm */
        if (gserialized_datum_get_gbox_p(PG_GETARG_DATUM(0), &gbox) == LW_FAILURE)
        {
                POSTGIS_DEBUG(4, "gserialized_datum_get_gbox_p returned LW_FAILURE");
                elog(ERROR, "Error in gserialized_datum_get_gbox_p calculation.");
                PG_RETURN_NULL();
        }
        POSTGIS_DEBUGF(4, "got gbox %s", gbox_to_string(&gbox));
 
        /* Get an exterior point, based on this gbox */
        gbox_pt_outside(&gbox, &pt);
 
        lwpoint = (LWGEOM*) lwpoint_make2d(4326, pt.x, pt.y);
 
        PG_RETURN_POINTER(geography_serialize(lwpoint));
}
 
/*
** geography_covers(GSERIALIZED *g, GSERIALIZED *g) returns boolean
** Only works for (multi)points and (multi)polygons currently.
** Attempts a simple point-in-polygon test on the polygon and point.
** Current algorithm does not distinguish between points on edge
** and points within.
*/
PG_FUNCTION_INFO_V1(geography_covers);
Datum geography_covers(PG_FUNCTION_ARGS)
{
        LWGEOM *lwgeom1 = NULL;
        LWGEOM *lwgeom2 = NULL;
        GSERIALIZED *g1 = NULL;
        GSERIALIZED *g2 = NULL;
        int result = LW_FALSE;
 
        /* Get our geometry objects loaded into memory. */
        g1 = PG_GETARG_GSERIALIZED_P(0);
        g2 = PG_GETARG_GSERIALIZED_P(1);
        gserialized_error_if_srid_mismatch(g1, g2, __func__);
 
        /* Construct our working geometries */
        lwgeom1 = lwgeom_from_gserialized(g1);
        lwgeom2 = lwgeom_from_gserialized(g2);
 
        /* EMPTY never intersects with another geometry */
        if ( lwgeom_is_empty(lwgeom1) || lwgeom_is_empty(lwgeom2) )
        {
                lwgeom_free(lwgeom1);
                lwgeom_free(lwgeom2);
                PG_FREE_IF_COPY(g1, 0);
                PG_FREE_IF_COPY(g2, 1);
                PG_RETURN_BOOL(false);
        }
 
        /* Calculate answer */
        result = lwgeom_covers_lwgeom_sphere(lwgeom1, lwgeom2);
 
        /* Clean up */
        lwgeom_free(lwgeom1);
        lwgeom_free(lwgeom2);
        PG_FREE_IF_COPY(g1, 0);
        PG_FREE_IF_COPY(g2, 1);
 
        PG_RETURN_BOOL(result);
}
 
PG_FUNCTION_INFO_V1(geography_coveredby);
Datum geography_coveredby(PG_FUNCTION_ARGS)
{
        LWGEOM *lwgeom1 = NULL;
        LWGEOM *lwgeom2 = NULL;
        GSERIALIZED *g1 = NULL;
        GSERIALIZED *g2 = NULL;
        int result = LW_FALSE;
 
        /* Get our geometry objects loaded into memory. */
        /* Pick them up in reverse order to covers */
        g1 = PG_GETARG_GSERIALIZED_P(1);
        g2 = PG_GETARG_GSERIALIZED_P(0);
        gserialized_error_if_srid_mismatch(g1, g2, __func__);
 
        /* Construct our working geometries */
        lwgeom1 = lwgeom_from_gserialized(g1);
        lwgeom2 = lwgeom_from_gserialized(g2);
 
        /* EMPTY never intersects with another geometry */
        if ( lwgeom_is_empty(lwgeom1) || lwgeom_is_empty(lwgeom2) )
        {
                lwgeom_free(lwgeom1);
                lwgeom_free(lwgeom2);
                PG_FREE_IF_COPY(g1, 1);
                PG_FREE_IF_COPY(g2, 0);
                PG_RETURN_BOOL(false);
        }
 
        /* Calculate answer */
        result = lwgeom_covers_lwgeom_sphere(lwgeom1, lwgeom2);
 
        /* Clean up */
        lwgeom_free(lwgeom1);
        lwgeom_free(lwgeom2);
        PG_FREE_IF_COPY(g1, 1);
        PG_FREE_IF_COPY(g2, 0);
 
        PG_RETURN_BOOL(result);
}
 
/*
** geography_bestsrid(GSERIALIZED *g, GSERIALIZED *g) returns int
** Utility function. Returns negative SRID numbers that match to the
** numbers handled in code by the transform(lwgeom, srid) function.
** UTM, polar stereographic and mercator as fallback. To be used
** in wrapping existing geometry functions in SQL to provide access
** to them in the geography module.
*/
PG_FUNCTION_INFO_V1(geography_bestsrid);
Datum geography_bestsrid(PG_FUNCTION_ARGS)
{
        GBOX gbox, gbox1, gbox2;
        GSERIALIZED *g1 = NULL;
        GSERIALIZED *g2 = NULL;
        int empty1 = LW_FALSE;
        int empty2 = LW_FALSE;
        double xwidth, ywidth;
        POINT2D center;
        LWGEOM *lwgeom;
 
        /* Get our geometry objects loaded into memory. */
        g1 = PG_GETARG_GSERIALIZED_P(0);
        /* Synchronize our box types */
        gbox1.flags = gserialized_get_lwflags(g1);
        /* Calculate if the geometry is empty. */
        empty1 = gserialized_is_empty(g1);
 
        /* Convert g1 to LWGEOM type */
        lwgeom = lwgeom_from_gserialized(g1);
 
        /* Calculate a geocentric bounds for the objects */
        if ( ! empty1 && gserialized_get_gbox_p(g1, &gbox1) == LW_FAILURE )
                elog(ERROR, "Error in geography_bestsrid calling gserialized_get_gbox_p(g1, &gbox1)");
 
        POSTGIS_DEBUGF(4, "calculated gbox = %s", gbox_to_string(&gbox1));
 
        if ( !lwgeom_isfinite(lwgeom) ) {
                elog(ERROR, "Error in geography_bestsrid calling with infinite coordinate geographies");
        }
        lwgeom_free(lwgeom);
 
        /* If we have a unique second argument, fill in all the necessary variables. */
        if (PG_NARGS() > 1)
        {
                g2 = PG_GETARG_GSERIALIZED_P(1);
                gbox2.flags = gserialized_get_lwflags(g2);
                empty2 = gserialized_is_empty(g2);
                if ( ! empty2 && gserialized_get_gbox_p(g2, &gbox2) == LW_FAILURE )
                        elog(ERROR, "Error in geography_bestsrid calling gserialized_get_gbox_p(g2, &gbox2)");
 
                /* Convert g2 to LWGEOM type */
                lwgeom = lwgeom_from_gserialized(g2);
 
                if ( !lwgeom_isfinite(lwgeom) ) {
                        elog(ERROR, "Error in geography_bestsrid calling with second arg infinite coordinate geographies");
                }
                lwgeom_free(lwgeom);
        }
        /*
        ** If no unique second argument, copying the box for the first
        ** argument will give us the right answer for all subsequent tests.
        */
        else
        {
                gbox = gbox2 = gbox1;
        }
 
        /* Both empty? We don't have an answer. */
        if ( empty1 && empty2 )
                PG_RETURN_NULL();
 
        /* One empty? We can use the other argument values as infill. Otherwise merge the boxen */
        if ( empty1 )
                gbox = gbox2;
        else if ( empty2 )
                gbox = gbox1;
        else
                gbox_union(&gbox1, &gbox2, &gbox);
 
        gbox_centroid(&gbox, &center);
 
        /* Width and height in degrees */
        xwidth = 180.0 * gbox_angular_width(&gbox)  / M_PI;
        ywidth = 180.0 * gbox_angular_height(&gbox) / M_PI;
 
        POSTGIS_DEBUGF(2, "xwidth %g", xwidth);
        POSTGIS_DEBUGF(2, "ywidth %g", ywidth);
        POSTGIS_DEBUGF(2, "center POINT(%g %g)", center.x, center.y);
 
        /* Are these data arctic? Lambert Azimuthal Equal Area North. */
        if ( center.y > 70.0 && ywidth < 45.0 )
        {
                PG_RETURN_INT32(SRID_NORTH_LAMBERT);
        }
 
        /* Are these data antarctic? Lambert Azimuthal Equal Area South. */
        if ( center.y < -70.0 && ywidth < 45.0 )
        {
                PG_RETURN_INT32(SRID_SOUTH_LAMBERT);
        }
 
        /*
        ** Can we fit these data into one UTM zone?
        ** We will assume we can push things as
        ** far as a half zone past a zone boundary.
        ** Note we have no handling for the date line in here.
        */
        if ( xwidth < 6.0 )
        {
                int zone = floor((center.x + 180.0) / 6.0);
 
                if ( zone > 59 ) zone = 59;
 
                /* Are these data below the equator? UTM South. */
                if ( center.y < 0.0 )
                {
                        PG_RETURN_INT32( SRID_SOUTH_UTM_START + zone );
                }
                /* Are these data above the equator? UTM North. */
                else
                {
                        PG_RETURN_INT32( SRID_NORTH_UTM_START + zone );
                }
        }
 
        /*
        ** Can we fit into a custom LAEA area? (30 degrees high, variable width)
        ** We will allow overlap into adjoining areas, but use a slightly narrower test (25) to try
        ** and minimize the worst case.
        ** Again, we are hoping the dateline doesn't trip us up much
        */
        if ( ywidth < 25.0 )
        {
                int xzone = -1;
                int yzone = 3 + floor(center.y / 30.0); /* (range of 0-5) */
 
                /* Equatorial band, 12 zones, 30 degrees wide */
                if ( (yzone == 2 || yzone == 3) && xwidth < 30.0 )
                {
                        xzone = 6 + floor(center.x / 30.0);
                }
                /* Temperate band, 8 zones, 45 degrees wide */
                else if ( (yzone == 1 || yzone == 4) && xwidth < 45.0 )
                {
                        xzone = 4 + floor(center.x / 45.0);
                }
                /* Arctic band, 4 zones, 90 degrees wide */
                else if ( (yzone == 0 || yzone == 5) && xwidth < 90.0 )
                {
                        xzone = 2 + floor(center.x / 90.0);
                }
 
                /* Did we fit into an appropriate xzone? */
                if ( xzone != -1 )
                {
                        PG_RETURN_INT32(SRID_LAEA_START + 20 * yzone + xzone);
                }
        }
 
        /*
        ** Running out of options... fall-back to Mercator
        ** and hope for the best.
        */
        PG_RETURN_INT32(SRID_WORLD_MERCATOR);
 
}
 
/*
** geography_project(GSERIALIZED *g, distance, azimuth)
** returns point of projection given start point,
** azimuth in radians (bearing) and distance in meters
*/
PG_FUNCTION_INFO_V1(geography_project);
Datum geography_project(PG_FUNCTION_ARGS)
{
        LWGEOM *lwgeom = NULL;
        LWPOINT *lwp_projected;
        GSERIALIZED *g = NULL;
        GSERIALIZED *g_out = NULL;
        double azimuth = 0.0;
        double distance;
        SPHEROID s;
        uint32_t type;
 
        /* Return NULL on NULL distance or geography */
        if ( PG_NARGS() < 2 || PG_ARGISNULL(0) || PG_ARGISNULL(1) )
                PG_RETURN_NULL();
 
        /* Get our geometry object loaded into memory. */
        g = PG_GETARG_GSERIALIZED_P(0);
 
        /* Only return for points. */
        type = gserialized_get_type(g);
        if ( type != POINTTYPE )
        {
                elog(ERROR, "ST_Project(geography) is only valid for point inputs");
                PG_RETURN_NULL();
        }
 
        distance = PG_GETARG_FLOAT8(1); /* Distance in Meters */
        lwgeom = lwgeom_from_gserialized(g);
 
        /* EMPTY things cannot be projected from */
        if ( lwgeom_is_empty(lwgeom) )
        {
                lwgeom_free(lwgeom);
                elog(ERROR, "ST_Project(geography) cannot project from an empty start point");
                PG_RETURN_NULL();
        }
 
        if ( PG_NARGS() > 2 && ! PG_ARGISNULL(2) )
                azimuth = PG_GETARG_FLOAT8(2); /* Azimuth in Radians */
 
        /* Initialize spheroid */
        spheroid_init_from_srid(gserialized_get_srid(g), &s);
 
        /* Handle the zero distance case */
        if( FP_EQUALS(distance, 0.0) )
        {
                PG_RETURN_POINTER(g);
        }
 
        /* Calculate the length */
        lwp_projected = lwgeom_project_spheroid(lwgeom_as_lwpoint(lwgeom), &s, distance, azimuth);
 
        /* Something went wrong... */
        if ( lwp_projected == NULL )
        {
                elog(ERROR, "lwgeom_project_spheroid returned null");
                PG_RETURN_NULL();
        }
 
        /* Clean up, but not all the way to the point arrays */
        lwgeom_free(lwgeom);
        g_out = geography_serialize(lwpoint_as_lwgeom(lwp_projected));
        lwpoint_free(lwp_projected);
 
        PG_FREE_IF_COPY(g, 0);
        PG_RETURN_POINTER(g_out);
}
 
 
/*
** geography_azimuth(GSERIALIZED *g1, GSERIALIZED *g2)
** returns direction between points (north = 0)
** azimuth (bearing) and distance
*/
PG_FUNCTION_INFO_V1(geography_azimuth);
Datum geography_azimuth(PG_FUNCTION_ARGS)
{
        LWGEOM *lwgeom1 = NULL;
        LWGEOM *lwgeom2 = NULL;
        GSERIALIZED *g1 = NULL;
        GSERIALIZED *g2 = NULL;
        double azimuth;
        SPHEROID s;
        uint32_t type1, type2;
 
        /* Get our geometry object loaded into memory. */
        g1 = PG_GETARG_GSERIALIZED_P(0);
        g2 = PG_GETARG_GSERIALIZED_P(1);
 
        /* Only return for points. */
        type1 = gserialized_get_type(g1);
        type2 = gserialized_get_type(g2);
        if ( type1 != POINTTYPE || type2 != POINTTYPE )
        {
                elog(ERROR, "ST_Azimuth(geography, geography) is only valid for point inputs");
                PG_RETURN_NULL();
        }
 
        lwgeom1 = lwgeom_from_gserialized(g1);
        lwgeom2 = lwgeom_from_gserialized(g2);
 
        /* EMPTY things cannot be used */
        if ( lwgeom_is_empty(lwgeom1) || lwgeom_is_empty(lwgeom2) )
        {
                lwgeom_free(lwgeom1);
                lwgeom_free(lwgeom2);
                elog(ERROR, "ST_Azimuth(geography, geography) cannot work with empty points");
                PG_RETURN_NULL();
        }
 
        /* Initialize spheroid */
        spheroid_init_from_srid(gserialized_get_srid(g1), &s);
 
        /* Calculate the direction */
        azimuth = lwgeom_azumith_spheroid(lwgeom_as_lwpoint(lwgeom1), lwgeom_as_lwpoint(lwgeom2), &s);
 
        /* Clean up */
        lwgeom_free(lwgeom1);
        lwgeom_free(lwgeom2);
 
        PG_FREE_IF_COPY(g1, 0);
        PG_FREE_IF_COPY(g2, 1);
 
        /* Return NULL for unknown (same point) azimuth */
        if( isnan(azimuth) )
        {
                PG_RETURN_NULL();
        }
 
        PG_RETURN_FLOAT8(azimuth);
}
 
 
 
/*
** geography_segmentize(GSERIALIZED *g1, double max_seg_length)
** returns densified geometry with no segment longer than max
*/
PG_FUNCTION_INFO_V1(geography_segmentize);
Datum geography_segmentize(PG_FUNCTION_ARGS)
{
        LWGEOM *lwgeom1 = NULL;
        LWGEOM *lwgeom2 = NULL;
        GSERIALIZED *g1 = NULL;
        GSERIALIZED *g2 = NULL;
        double max_seg_length;
        uint32_t type1;
 
        /* Get our geometry object loaded into memory. */
        g1 = PG_GETARG_GSERIALIZED_P(0);
        type1 = gserialized_get_type(g1);
 
        /* Convert max_seg_length from metric units to radians */
        max_seg_length = PG_GETARG_FLOAT8(1) / WGS84_RADIUS;
 
        /* We can't densify points or points, reflect them back */
        if ( type1 == POINTTYPE || type1 == MULTIPOINTTYPE || gserialized_is_empty(g1) )
                PG_RETURN_POINTER(g1);
 
        /* Deserialize */
        lwgeom1 = lwgeom_from_gserialized(g1);
 
        /* Calculate the densified geometry */
        lwgeom2 = lwgeom_segmentize_sphere(lwgeom1, max_seg_length);
 
        /*
        ** Set the geodetic flag so subsequent
        ** functions do the right thing.
        */
        lwgeom_set_geodetic(lwgeom2, true);
 
        /* Recalculate the boxes after re-setting the geodetic bit */
        lwgeom_drop_bbox(lwgeom2);
 
        /* We are trusting geography_serialize will add a box if needed */
        g2 = geography_serialize(lwgeom2);
 
        /* Clean up */
        lwgeom_free(lwgeom1);
        lwgeom_free(lwgeom2);
        PG_FREE_IF_COPY(g1, 0);
 
        PG_RETURN_POINTER(g2);
}