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));
}
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 ) );
}
}
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);
}
}