184 lines
4.6 KiB
C++
184 lines
4.6 KiB
C++
// Boost.Geometry (aka GGL, Generic Geometry Library)
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// Copyright (c) 2016-2017 Oracle and/or its affiliates.
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// Contributed and/or modified by Vissarion Fisikopoulos, on behalf of Oracle
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// Contributed and/or modified by Adam Wulkiewicz, on behalf of Oracle
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// Use, modification and distribution is subject to the Boost Software License,
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// Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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#ifndef BOOST_GEOMETRY_STRATEGIES_SPHERICAL_AREA_HPP
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#define BOOST_GEOMETRY_STRATEGIES_SPHERICAL_AREA_HPP
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#include <boost/geometry/formulas/area_formulas.hpp>
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#include <boost/geometry/core/radius.hpp>
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#include <boost/geometry/core/srs.hpp>
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#include <boost/geometry/strategies/area.hpp>
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namespace boost { namespace geometry
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{
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namespace strategy { namespace area
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{
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/*!
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\brief Spherical area calculation
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\ingroup strategies
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\details Calculates area on the surface of a sphere using the trapezoidal rule
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\tparam PointOfSegment \tparam_segment_point
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\tparam CalculationType \tparam_calculation
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\qbk{
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[heading See also]
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[link geometry.reference.algorithms.area.area_2_with_strategy area (with strategy)]
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}
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*/
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template
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<
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typename PointOfSegment,
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typename CalculationType = void
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>
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class spherical
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{
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// Enables special handling of long segments
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static const bool LongSegment = false;
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typedef typename boost::mpl::if_c
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<
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boost::is_void<CalculationType>::type::value,
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typename select_most_precise
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<
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typename coordinate_type<PointOfSegment>::type,
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double
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>::type,
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CalculationType
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>::type CT;
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protected :
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struct excess_sum
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{
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CT m_sum;
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// Keep track if encircles some pole
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size_t m_crosses_prime_meridian;
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inline excess_sum()
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: m_sum(0)
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, m_crosses_prime_meridian(0)
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{}
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template <typename SphereType>
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inline CT area(SphereType sphere) const
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{
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CT result;
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CT radius = geometry::get_radius<0>(sphere);
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// Encircles pole
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if(m_crosses_prime_meridian % 2 == 1)
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{
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size_t times_crosses_prime_meridian
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= 1 + (m_crosses_prime_meridian / 2);
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result = CT(2)
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* geometry::math::pi<CT>()
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* times_crosses_prime_meridian
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- geometry::math::abs(m_sum);
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if(geometry::math::sign<CT>(m_sum) == 1)
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{
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result = - result;
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}
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} else {
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result = m_sum;
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}
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result *= radius * radius;
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return result;
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}
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};
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public :
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typedef CT return_type;
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typedef PointOfSegment segment_point_type;
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typedef excess_sum state_type;
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typedef geometry::srs::sphere<CT> sphere_type;
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// For backward compatibility reasons the radius is set to 1
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inline spherical()
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: m_sphere(1.0)
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{}
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template <typename T>
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explicit inline spherical(geometry::srs::sphere<T> const& sphere)
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: m_sphere(geometry::get_radius<0>(sphere))
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{}
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explicit inline spherical(CT const& radius)
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: m_sphere(radius)
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{}
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inline void apply(PointOfSegment const& p1,
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PointOfSegment const& p2,
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excess_sum& state) const
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{
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if (! geometry::math::equals(get<0>(p1), get<0>(p2)))
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{
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typedef geometry::formula::area_formulas<CT> area_formulas;
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state.m_sum += area_formulas::template spherical<LongSegment>(p1, p2);
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// Keep track whenever a segment crosses the prime meridian
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if (area_formulas::crosses_prime_meridian(p1, p2))
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{
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state.m_crosses_prime_meridian++;
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}
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}
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}
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inline return_type result(excess_sum const& state) const
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{
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return state.area(m_sphere);
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}
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private :
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/// srs Sphere
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sphere_type m_sphere;
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};
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#ifndef DOXYGEN_NO_STRATEGY_SPECIALIZATIONS
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namespace services
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{
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template <typename Point>
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struct default_strategy<spherical_equatorial_tag, Point>
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{
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typedef strategy::area::spherical<Point> type;
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};
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// Note: spherical polar coordinate system requires "get_as_radian_equatorial"
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template <typename Point>
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struct default_strategy<spherical_polar_tag, Point>
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{
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typedef strategy::area::spherical<Point> type;
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};
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} // namespace services
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#endif // DOXYGEN_NO_STRATEGY_SPECIALIZATIONS
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}} // namespace strategy::area
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}} // namespace boost::geometry
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#endif // BOOST_GEOMETRY_STRATEGIES_SPHERICAL_AREA_HPP
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