lwgeodetic_measures.c

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/*****************************************************************************
 *
 * This MobilityDB code is provided under The PostgreSQL License.
 * Copyright (c) 2016-2023, Université libre de Bruxelles and MobilityDB
 * contributors
 *
 * MobilityDB includes portions of PostGIS version 3 source code released
 * under the GNU General Public License (GPLv2 or later).
 * Copyright (c) 2001-2023, PostGIS contributors
 *
 * Permission to use, copy, modify, and distribute this software and its
 * documentation for any purpose, without fee, and without a written
 * agreement is hereby granted, provided that the above copyright notice and
 * this paragraph and the following two paragraphs appear in all copies.
 *
 * IN NO EVENT SHALL UNIVERSITE LIBRE DE BRUXELLES BE LIABLE TO ANY PARTY FOR
 * DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING
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 *****************************************************************************/
 
// #include "point/geography_funcs.h"
 
/* C */
#include <float.h>
/* PostGIS */
#include <liblwgeom_internal.h>
#include <lwgeodetic_tree.h>
 
/*****************************************************************************/
 
 
/***********************************************************************
 * ST_LineSubstring for geographies
 ***********************************************************************/
 
static void
interpolate_point4d_spheroid(
        const POINT4D *p1, const POINT4D *p2, POINT4D *p,
        const SPHEROID *s, double f)
 
{
        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));
        }
}
 
 
LWGEOM *
geography_substring(
        const LWLINE *lwline,
        const SPHEROID *s,
        double from, double to,
        double tolerance)
{
        POINTARRAY *dpa;
        POINTARRAY *ipa = lwline->points;
        LWGEOM *lwresult;
        POINT4D pt;
        POINT4D p1, p2;
        GEOGRAPHIC_POINT g1, g2;
        int nsegs, i;
        double length, slength, tlength;
        int state = 0; /* 0 = before, 1 = inside */
        uint32_t srid = lwline->srid;
 
        /*
        * Create a dynamic pointarray with an initial capacity
        * equal to full copy of input points
        */
        dpa = ptarray_construct_empty(
                (char) FLAGS_GET_Z(ipa->flags),
                (char) FLAGS_GET_M(ipa->flags),
                ipa->npoints);
 
        /* Compute total line length */
        length = ptarray_length_spheroid(ipa, s);
 
        /* Get 'from' and 'to' lengths */
        from = length * from;
        to = length * to;
        tlength = 0;
        getPoint4d_p(ipa, 0, &p1);
        geographic_point_init(p1.x, p1.y, &g1);
        nsegs = ipa->npoints - 1;
        for (i = 0; i < nsegs; i++)
        {
                double dseg;
                getPoint4d_p(ipa, (uint32_t) i+1, &p2);
                geographic_point_init(p2.x, p2.y, &g2);
 
                /* Find the length of this segment */
                /* Special sphere case */
                if ( s->a == s->b )
                        slength = s->radius * sphere_distance(&g1, &g2);
                /* Spheroid case */
                else
                        slength = spheroid_distance(&g1, &g2, s);
 
                /*  We are before requested start. */
                if (state == 0) /* before */
                {
                        if (fabs ( from - ( tlength + slength ) ) <= tolerance)
                        {
                                /* Second point is our start */
                                ptarray_append_point(dpa, &p2, LW_FALSE);
                                state = 1; /* we're inside now */
                                goto END;
                        }
                        else if (fabs(from - tlength) <= tolerance)
                        {
                                /*  First point is our start */
                                ptarray_append_point(dpa, &p1, LW_FALSE);
                                /*
                                 * We're inside now, but will check
                                 * 'to' point as well
                                 */
                                state = 1;
                        }
                        /*
                        * Didn't reach the 'from' point,
                        * nothing to do
                        */
                        else if (from > tlength + slength)
                        {
                                goto END;
                        }
                        else  /* tlength < from < tlength+slength */
                        {
                                /* Our start is between first and second point */
                                dseg = (from - tlength) / slength;
                                interpolate_point4d_spheroid(&p1, &p2, &pt, s, dseg);
                                ptarray_append_point(dpa, &pt, LW_FALSE);
                                /* We're inside now, but will check 'to' point as well */
                                state = 1;
                        }
            }
 
            if (state == 1) /* inside */
            {
                        /*  'to' point is our second point. */
                        if (fabs(to - ( tlength + slength ) ) <= tolerance )
                        {
                                ptarray_append_point(dpa, &p2, LW_FALSE);
                                break; /* substring complete */
                        }
                        /*
                        * 'to' point is our first point.
                        * (should only happen if 'to' is 0)
                        */
                        else if (fabs(to - tlength) <= tolerance)
                        {
                                ptarray_append_point(dpa, &p1, LW_FALSE);
                                break; /* substring complete */
                        }
                        /*
                        * Didn't reach the 'end' point,
                        * just copy second point
                        */
                        else if (to > tlength + slength)
                        {
                                ptarray_append_point(dpa, &p2, LW_FALSE);
                                goto END;
                        }
                        /*
                        * 'to' point falls on this segment
                        * Interpolate and break.
                        */
                        else if (to < tlength + slength )
                        {
                                dseg = (to - tlength) / slength;
                                interpolate_point4d_spheroid(&p1, &p2, &pt, s, dseg);
                                ptarray_append_point(dpa, &pt, LW_FALSE);
                                break;
                        }
            }
 
        END:
                tlength += slength;
                memcpy(&p1, &p2, sizeof(POINT4D));
        }
 
        if (dpa->npoints <= 1) {
                lwresult = lwpoint_as_lwgeom(lwpoint_construct(srid, NULL, dpa));
        }
        else {
                lwresult = lwline_as_lwgeom(lwline_construct(srid, NULL, dpa));
        }
 
        return lwresult;
}
 
 
/***********************************************************************
 * Interpolate a point along a geographic line.
 ***********************************************************************/
 
LWGEOM *
geography_interpolate_points(
        const LWLINE *line, double length_fraction,
        const SPHEROID *s, char repeat)
{
        POINT4D pt;
        uint32_t i;
        uint32_t points_to_interpolate;
        uint32_t points_found = 0;
        double length;
        double length_fraction_increment = length_fraction;
        double length_fraction_consumed = 0;
        char has_z = (char) lwgeom_has_z(lwline_as_lwgeom(line));
        char has_m = (char) lwgeom_has_m(lwline_as_lwgeom(line));
        const POINTARRAY* ipa = line->points;
        POINTARRAY *opa;
        POINT4D p1, p2;
        POINT3D q1, q2;
        LWGEOM *lwresult;
        GEOGRAPHIC_POINT g1, g2;
        uint32_t srid = line->srid;
 
        /* Empty.InterpolatePoint == Point Empty */
        if ( lwline_is_empty(line) )
        {
                return lwgeom_clone_deep(lwline_as_lwgeom(line));
        }
 
        /*
        * If distance is one of the two extremes, return the point on that
        * end rather than doing any computations
        */
        if ( length_fraction == 0.0 || length_fraction == 1.0 )
        {
                if ( length_fraction == 0.0 )
                        getPoint4d_p(ipa, 0, &pt);
                else
                        getPoint4d_p(ipa, ipa->npoints-1, &pt);
 
                opa = ptarray_construct(has_z, has_m, 1);
                ptarray_set_point4d(opa, 0, &pt);
                return lwpoint_as_lwgeom(lwpoint_construct(srid, NULL, opa));
        }
 
        /* Interpolate points along the line */
        length = ptarray_length_spheroid(ipa, s);
        points_to_interpolate = repeat ? (uint32_t) floor(1 / length_fraction) : 1;
        opa = ptarray_construct(has_z, has_m, points_to_interpolate);
 
        getPoint4d_p(ipa, 0, &p1);
        geographic_point_init(p1.x, p1.y, &g1);
        for ( i = 0; i < ipa->npoints - 1 && points_found < points_to_interpolate; i++ )
        {
                double segment_length_frac;
                getPoint4d_p(ipa, i+1, &p2);
                geographic_point_init(p2.x, p2.y, &g2);
 
                /* Special sphere case */
                if ( s->a == s->b )
                        segment_length_frac = s->radius * sphere_distance(&g1, &g2) / length;
                /* Spheroid case */
                else
                        segment_length_frac = spheroid_distance(&g1, &g2, s) / length;
 
                /* If our target distance is before the total length we've seen
                * so far. create a new point some distance down the current
                * segment.
                */
                while ( length_fraction < length_fraction_consumed + segment_length_frac && points_found < points_to_interpolate )
                {
                        geog2cart(&g1, &q1);
                        geog2cart(&g2, &q2);
                        double segment_fraction = (length_fraction - length_fraction_consumed) / segment_length_frac;
                        interpolate_point4d_spheroid(&p1, &p2, &pt, s, segment_fraction);
                        ptarray_set_point4d(opa, points_found++, &pt);
                        length_fraction += length_fraction_increment;
                }
 
                length_fraction_consumed += segment_length_frac;
 
                p1 = p2;
                g1 = g2;
        }
 
        /* Return the last point on the line. This shouldn't happen, but
        * could if there's some floating point rounding errors. */
        if (points_found < points_to_interpolate)
        {
                getPoint4d_p(ipa, ipa->npoints - 1, &pt);
                ptarray_set_point4d(opa, points_found, &pt);
        }
 
        if (opa->npoints <= 1)
        {
                lwresult = lwpoint_as_lwgeom(lwpoint_construct(srid, NULL, opa));
        } else {
                lwresult = lwmpoint_as_lwgeom(lwmpoint_construct(srid, opa));
        }
 
        return lwresult;
}
 
double
ptarray_locate_point_spheroid(
        const POINTARRAY *pa,
        const POINT4D *p4d,
        const SPHEROID *s,
        double tolerance,
        double *mindistout,
        POINT4D *proj4d)
{
        GEOGRAPHIC_EDGE e;
        GEOGRAPHIC_POINT a, b, nearest = {0}; /* make compiler quiet */
        POINT4D p1, p2;
        const POINT2D *p;
        POINT2D proj;
        uint32_t i, seg = 0;
        int use_sphere = (s->a == s->b ? 1 : 0);
        int hasz;
        double za = 0.0, zb = 0.0;
        double distance,
                length,   /* Used for computing lengths */
                seglength = 0.0,  /* length of the segment where the closest point is located */
                partlength = 0.0, /* length from the beginning of the point array to the closest point */
                totlength = 0.0;  /* length of the point array */
 
        /* Initialize our point */
        geographic_point_init(p4d->x, p4d->y, &a);
 
        /* Handle point/point case here */
        if ( pa->npoints <= 1)
        {
                double mindist = 0.0;
                if ( pa->npoints == 1 )
                {
                        p = getPoint2d_cp(pa, 0);
                        geographic_point_init(p->x, p->y, &b);
                        /* Sphere special case, axes equal */
                        mindist = s->radius * sphere_distance(&a, &b);
                        /* If close or greater than tolerance, get the real answer to be sure */
                        if ( ! use_sphere || mindist > 0.95 * tolerance )
                        {
                                mindist = spheroid_distance(&a, &b, s);
                        }
                }
                if ( mindistout ) *mindistout = mindist;
                return 0.0;
        }
 
        /* Make result really big, so that everything will be smaller than it */
        distance = FLT_MAX;
 
        /* Initialize start of line */
        p = getPoint2d_cp(pa, 0);
        geographic_point_init(p->x, p->y, &(e.start));
 
        /* Iterate through the edges in our line */
        for ( i = 1; i < pa->npoints; i++ )
        {
                double d;
                p = getPoint2d_cp(pa, i);
                geographic_point_init(p->x, p->y, &(e.end));
                /* Get the spherical distance between point and edge */
                d = s->radius * edge_distance_to_point(&e, &a, &b);
                /* New shortest distance! Record this distance / location / segment */
                if ( d < distance )
                {
                        distance = d;
                        nearest = b;
                        seg = i - 1;
                }
            /* We've gotten closer than the tolerance... */
                if ( d < tolerance )
                {
                        /* Working on a sphere? The answer is correct, return */
                        if ( use_sphere )
                        {
                                break;
                        }
                        /* Far enough past the tolerance that the spheroid calculation won't change things */
                        else if ( d < tolerance * 0.95 )
                        {
                                break;
                        }
                        /* On a spheroid and near the tolerance? Confirm that we are *actually* closer than tolerance */
                        else
                        {
                                d = spheroid_distance(&a, &nearest, s);
                                /* Yes, closer than tolerance, return! */
                                if ( d < tolerance )
                                        break;
                        }
                }
                e.start = e.end;
        }
 
        if ( mindistout ) *mindistout = distance;
 
        /* See if we have a third dimension */
        hasz = (bool) FLAGS_GET_Z(pa->flags);
 
        /* Initialize first point of array */
        getPoint4d_p(pa, 0, &p1);
        geographic_point_init(p1.x, p1.y, &a);
        if ( hasz )
                za = p1.z;
 
        /* Loop and sum the length for each segment */
        for ( i = 1; i < pa->npoints; i++ )
        {
                getPoint4d_p(pa, i, &p1);
                geographic_point_init(p1.x, p1.y, &b);
                if ( hasz )
                        zb = p1.z;
 
                /* Special sphere case */
                if ( s->a == s->b )
                        length = s->radius * sphere_distance(&a, &b);
                /* Spheroid case */
                else
                        length = spheroid_distance(&a, &b, s);
 
                /* Add in the vertical displacement if we're in 3D */
                if ( hasz )
                        length = sqrt( (zb-za)*(zb-za) + length*length );
 
                /* Add this segment length to the total length */
                totlength += length;
 
                /* Add this segment length to the partial length */
                if (i - 1 < seg)
                        partlength += length;
                else if (i - 1 == seg)
                        /* Save segment length for computing the final value of partlength */
                        seglength = length;
 
                /* B gets incremented in the next loop, so we save the value here */
                a = b;
                za = zb;
        }
 
        /* Copy nearest into 2D/4D holder */
        proj4d->x = proj.x = rad2deg(nearest.lon);
        proj4d->y = proj.y = rad2deg(nearest.lat);
 
        /* Compute distance from beginning of the segment to closest point */
 
        /* Start of the segment */
        getPoint4d_p(pa, seg, &p1);
        geographic_point_init(p1.x, p1.y, &a);
 
        /* Closest point */
        geographic_point_init(proj4d->x, proj4d->y, &b);
 
        /* Special sphere case */
        if ( s->a == s->b )
                length = s->radius * sphere_distance(&a, &b);
        /* Spheroid case */
        else
                length = spheroid_distance(&a, &b, s);
 
        if ( hasz )
        {
                /* Compute Z and M values for closest point */
                double f = length / seglength;
                getPoint4d_p(pa, seg + 1, &p2);
                proj4d->z = p1.z + ((p2.z - p1.z) * f);
                proj4d->m = p1.m + ((p2.m - p1.m) * f);
                /* Add in the vertical displacement if we're in 3D */
                za = p1.z;
                zb = proj4d->z;
                length = sqrt( (zb-za)*(zb-za) + length*length );
        }
 
        /* Add this segment length to the total */
        partlength += length;
 
        /* Location of any point on a zero-length line is 0 */
        /* See http://trac.osgeo.org/postgis/ticket/1772#comment:2 */
        if ( partlength == 0 || totlength == 0 )
                return 0.0;
 
        /* For robustness, force 0 when closest point == startpoint */
        p = getPoint2d_cp(pa, 0);
        if ( seg == 0 && p2d_same(&proj, p) )
                return 0.0;
 
        /* For robustness, force 1 when closest point == endpoint */
        p = getPoint2d_cp(pa, pa->npoints - 1);
        if ( (seg >= (pa->npoints-2)) && p2d_same(&proj, p) )
                return 1.0;
 
        return partlength / totlength;
}
 
/*****************************************************************************/