Пример #1
0
    inline return_type apply(Point const& p,
                PointOfSegment const& sp1, PointOfSegment const& sp2) const
    {
        // http://williams.best.vwh.net/avform.htm#XTE
        return_type d1 = m_strategy.apply(sp1, p);

        // Actually, calculation of d2 not necessary if we know that the projected point is on the great circle...
        return_type d2 = m_strategy.apply(sp2, p);

        return_type crs_AD = course(sp1, p);
        return_type crs_AB = course(sp1, sp2);
        return_type XTD = m_radius * geometry::math::abs(asin(sin(d1 / m_radius) * sin(crs_AD - crs_AB)));

#ifdef BOOST_GEOMETRY_DEBUG_CROSS_TRACK
std::cout << "Course " << dsv(sp1) << " to " << dsv(p) << " " << crs_AD * geometry::math::r2d << std::endl;
std::cout << "Course " << dsv(sp1) << " to " << dsv(sp2) << " " << crs_AB * geometry::math::r2d << std::endl;
std::cout << "XTD: " << XTD << " d1: " <<  d1  << " d2: " <<  d2  << std::endl;
#endif


        // Return shortest distance, either to projected point on segment sp1-sp2, or to sp1, or to sp2
        return return_type((std::min)((std::min)(d1, d2), XTD));
    }
Пример #2
0
    inline return_type apply(Point const& p,
                PointOfSegment const& sp1, PointOfSegment const& sp2) const
    {
        // http://williams.best.vwh.net/avform.htm#XTE
        return_type d1 = m_strategy.apply(sp1, p);
        return_type d3 = m_strategy.apply(sp1, sp2);

        if (geometry::math::equals(d3, 0.0))
        {
            // "Degenerate" segment, return either d1 or d2
            return d1;
        }

        return_type d2 = m_strategy.apply(sp2, p);

        return_type crs_AD = course(sp1, p);
        return_type crs_AB = course(sp1, sp2);
        return_type crs_BA = crs_AB - geometry::math::pi<return_type>();
        return_type crs_BD = course(sp2, p);
        return_type d_crs1 = crs_AD - crs_AB;
        return_type d_crs2 = crs_BD - crs_BA;

        // d1, d2, d3 are in principle not needed, only the sign matters
        return_type projection1 = cos( d_crs1 ) * d1 / d3;
        return_type projection2 = cos( d_crs2 ) * d2 / d3;

#ifdef BOOST_GEOMETRY_DEBUG_CROSS_TRACK
        std::cout << "Course " << dsv(sp1) << " to " << dsv(p) << " " << crs_AD * geometry::math::r2d << std::endl;
        std::cout << "Course " << dsv(sp1) << " to " << dsv(sp2) << " " << crs_AB * geometry::math::r2d << std::endl;
        std::cout << "Course " << dsv(sp2) << " to " << dsv(p) << " " << crs_BD * geometry::math::r2d << std::endl;
        std::cout << "Projection AD-AB " << projection1 << " : " << d_crs1 * geometry::math::r2d << std::endl;
        std::cout << "Projection BD-BA " << projection2 << " : " << d_crs2 * geometry::math::r2d << std::endl;
#endif

        if(projection1 > 0.0 && projection2 > 0.0)
        {
            return_type XTD = m_radius * geometry::math::abs( asin( sin( d1 / m_radius ) * sin( d_crs1 ) ));

 #ifdef BOOST_GEOMETRY_DEBUG_CROSS_TRACK
            std::cout << "Projection ON the segment" << std::endl;
            std::cout << "XTD: " << XTD << " d1: " <<  d1  << " d2: " <<  d2  << std::endl;
#endif

            // Return shortest distance, projected point on segment sp1-sp2
            return return_type(XTD);
        }
        else
        {
#ifdef BOOST_GEOMETRY_DEBUG_CROSS_TRACK
            std::cout << "Projection OUTSIDE the segment" << std::endl;
#endif

            // Return shortest distance, project either on point sp1 or sp2
            return return_type( (std::min)( d1 , d2 ) );
        }
    }
Пример #3
0
    static inline void consider(iterator_type begin,
                iterator_type end,
                return_type const& max_dist, int& n,
                distance_strategy_type const& ps_distance_strategy)
    {
        std::size_t size = end - begin;

        // size must be at least 3
        // because we want to consider a candidate point in between
        if (size <= 2)
        {
#ifdef GL_DEBUG_DOUGLAS_PEUCKER
            if (begin != end)
            {
                std::cout << "ignore between " << dsv(begin->p)
                    << " and " << dsv((end - 1)->p)
                    << " size=" << size << std::endl;
            }
            std::cout << "return because size=" << size << std::endl;
#endif
            return;
        }

        iterator_type last = end - 1;

#ifdef GL_DEBUG_DOUGLAS_PEUCKER
        std::cout << "find between " << dsv(begin->p)
            << " and " << dsv(last->p)
            << " size=" << size << std::endl;
#endif


        // Find most far point, compare to the current segment
        //geometry::segment<Point const> s(begin->p, last->p);
        return_type md(-1.0); // any value < 0
        iterator_type candidate;
        for(iterator_type it = begin + 1; it != last; ++it)
        {
            return_type dist = ps_distance_strategy.apply(it->p, begin->p, last->p);

#ifdef GL_DEBUG_DOUGLAS_PEUCKER
            std::cout << "consider " << dsv(it->p)
                << " at " << double(dist)
                << ((dist > max_dist) ? " maybe" : " no") 
                << std::endl;

#endif
            if (dist > md)
            {
                md = dist;
                candidate = it;
            }
        }

        // If a point is found, set the include flag
        // and handle segments in between recursively
        if (md > max_dist)
        {
#ifdef GL_DEBUG_DOUGLAS_PEUCKER
            std::cout << "use " << dsv(candidate->p) << std::endl;
#endif

            candidate->included = true;
            n++;

            consider(begin, candidate + 1, max_dist, n, ps_distance_strategy);
            consider(candidate, end, max_dist, n, ps_distance_strategy);
        }
    }