edge_contains_coplanar_point()

int edge_contains_coplanar_point	(	const GEOGRAPHIC_EDGE *	e,
		const GEOGRAPHIC_POINT *	p
	)

True if the longitude of p is within the range of the longitude of the ends of e.

Definition at line 783 of file lwgeodetic.c.

{
        GEOGRAPHIC_EDGE g;
        GEOGRAPHIC_POINT q;
        double slon = fabs((e->start).lon) + fabs((e->end).lon);
        double dlon = fabs(fabs((e->start).lon) - fabs((e->end).lon));
        double slat = (e->start).lat + (e->end).lat;
 
        LWDEBUGF(4, "e.start == GPOINT(%.6g %.6g) ", (e->start).lat, (e->start).lon);
        LWDEBUGF(4, "e.end == GPOINT(%.6g %.6g) ", (e->end).lat, (e->end).lon);
        LWDEBUGF(4, "p == GPOINT(%.6g %.6g) ", p->lat, p->lon);
 
        /* Copy values into working registers */
        g = *e;
        q = *p;
 
        /* Vertical plane, we need to do this calculation in latitude */
        if ( FP_EQUALS( g.start.lon, g.end.lon ) )
        {
                LWDEBUG(4, "vertical plane, we need to do this calculation in latitude");
                /* Supposed to be co-planar... */
                if ( ! FP_EQUALS( q.lon, g.start.lon ) )
                        return LW_FALSE;
 
                if ( ( g.start.lat <= q.lat && q.lat <= g.end.lat ) ||
                     ( g.end.lat <= q.lat && q.lat <= g.start.lat ) )
                {
                        return LW_TRUE;
                }
                else
                {
                        return LW_FALSE;
                }
        }
 
        /* Over the pole, we need normalize latitude and do this calculation in latitude */
        if ( FP_EQUALS( slon, M_PI ) && ( SIGNUM(g.start.lon) != SIGNUM(g.end.lon) || FP_EQUALS(dlon, M_PI) ) )
        {
                LWDEBUG(4, "over the pole...");
                /* Antipodal, everything (or nothing?) is inside */
                if ( FP_EQUALS( slat, 0.0 ) )
                        return LW_TRUE;
 
                /* Point *is* the north pole */
                if ( slat > 0.0 && FP_EQUALS(q.lat, M_PI_2 ) )
                        return LW_TRUE;
 
                /* Point *is* the south pole */
                if ( slat < 0.0 && FP_EQUALS(q.lat, -1.0 * M_PI_2) )
                        return LW_TRUE;
 
                LWDEBUG(4, "coplanar?...");
 
                /* Supposed to be co-planar... */
                if ( ! FP_EQUALS( q.lon, g.start.lon ) )
                        return LW_FALSE;
 
                LWDEBUG(4, "north or south?...");
 
                /* Over north pole, test based on south pole */
                if ( slat > 0.0 )
                {
                        LWDEBUG(4, "over the north pole...");
                        if ( q.lat > FP_MIN(g.start.lat, g.end.lat) )
                                return LW_TRUE;
                        else
                                return LW_FALSE;
                }
                else
                        /* Over south pole, test based on north pole */
                {
                        LWDEBUG(4, "over the south pole...");
                        if ( q.lat < FP_MAX(g.start.lat, g.end.lat) )
                                return LW_TRUE;
                        else
                                return LW_FALSE;
                }
        }
 
        /* Dateline crossing, flip everything to the opposite hemisphere */
        else if ( slon > M_PI && ( SIGNUM(g.start.lon) != SIGNUM(g.end.lon) ) )
        {
                LWDEBUG(4, "crosses dateline, flip longitudes...");
                if ( g.start.lon > 0.0 )
                        g.start.lon -= M_PI;
                else
                        g.start.lon += M_PI;
                if ( g.end.lon > 0.0 )
                        g.end.lon -= M_PI;
                else
                        g.end.lon += M_PI;
 
                if ( q.lon > 0.0 )
                        q.lon -= M_PI;
                else
                        q.lon += M_PI;
        }
 
        if ( ( g.start.lon <= q.lon && q.lon <= g.end.lon ) ||
             ( g.end.lon <= q.lon && q.lon <= g.start.lon ) )
        {
                LWDEBUG(4, "true, this edge contains point");
                return LW_TRUE;
        }
 
        LWDEBUG(4, "false, this edge does not contain point");
        return LW_FALSE;
}

References GEOGRAPHIC_EDGE::end, FP_EQUALS, FP_MAX, FP_MIN, GEOGRAPHIC_POINT::lat, GEOGRAPHIC_POINT::lon, LW_FALSE, LW_TRUE, LWDEBUG, LWDEBUGF, SIGNUM, and GEOGRAPHIC_EDGE::start.