97 lines
2.6 KiB
C++
97 lines
2.6 KiB
C++
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// Boost.Geometry
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// Copyright (c) 2017 Oracle and/or its affiliates.
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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_FORMULAS_AUTHALIC_RADIUS_SQR_HPP
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#define BOOST_GEOMETRY_FORMULAS_AUTHALIC_RADIUS_SQR_HPP
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#include <boost/geometry/core/radius.hpp>
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#include <boost/geometry/core/tag.hpp>
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#include <boost/geometry/core/tags.hpp>
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#include <boost/geometry/formulas/eccentricity_sqr.hpp>
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#include <boost/geometry/util/math.hpp>
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#include <boost/geometry/algorithms/not_implemented.hpp>
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#include <boost/math/special_functions/atanh.hpp>
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namespace boost { namespace geometry
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{
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#ifndef DOXYGEN_NO_DISPATCH
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namespace formula_dispatch
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{
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template <typename ResultType, typename Geometry, typename Tag = typename tag<Geometry>::type>
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struct authalic_radius_sqr
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: not_implemented<Tag>
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{};
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template <typename ResultType, typename Geometry>
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struct authalic_radius_sqr<ResultType, Geometry, srs_sphere_tag>
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{
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static inline ResultType apply(Geometry const& geometry)
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{
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return math::sqr<ResultType>(get_radius<0>(geometry));
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}
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};
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template <typename ResultType, typename Geometry>
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struct authalic_radius_sqr<ResultType, Geometry, srs_spheroid_tag>
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{
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static inline ResultType apply(Geometry const& geometry)
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{
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ResultType const a2 = math::sqr<ResultType>(get_radius<0>(geometry));
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ResultType const e2 = formula::eccentricity_sqr<ResultType>(geometry);
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return apply(a2, e2);
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}
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static inline ResultType apply(ResultType const& a2, ResultType const& e2)
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{
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ResultType const c0 = 0;
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if (math::equals(e2, c0))
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{
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return a2;
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}
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ResultType const e = math::sqrt(e2);
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ResultType const c2 = 2;
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//ResultType const b2 = math::sqr(get_radius<2>(geometry));
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//return a2 / c2 + b2 * boost::math::atanh(e) / (c2 * e);
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ResultType const c1 = 1;
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return (a2 / c2) * ( c1 + (c1 - e2) * boost::math::atanh(e) / e );
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}
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};
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} // namespace formula_dispatch
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#endif // DOXYGEN_NO_DISPATCH
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#ifndef DOXYGEN_NO_DETAIL
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namespace formula
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{
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template <typename ResultType, typename Geometry>
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inline ResultType authalic_radius_sqr(Geometry const& geometry)
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{
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return formula_dispatch::authalic_radius_sqr<ResultType, Geometry>::apply(geometry);
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}
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} // namespace formula
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#endif // DOXYGEN_NO_DETAIL
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}} // namespace boost::geometry
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#endif // BOOST_GEOMETRY_FORMULAS_AUTHALIC_RADIUS_SQR_HPP
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