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[geometry] applied patch of Karsten Ahnert to fix cross-track error

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[SVN r79207]
This commit is contained in:
Barend Gehrels
2012-07-01 15:44:11 +00:00
parent d35eb8f2df
commit ea99120ca1
1 changed files with 40 additions and 7 deletions
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47
include/boost/geometry/strategies/spherical/distance_cross_track.hpp
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@@ -101,23 +101,56 @@ public :
{
// 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;
}
// 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)));
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 << "XTD: " << XTD << " d1: " << d1 << " d2: " << d2 << std::endl;
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 ) ));
// 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));
#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 ) );
}
}
inline return_type radius() const { return m_radius; }