diff options
Diffstat (limited to 'boost/geometry/strategies/geographic/area.hpp')
| -rw-r--r-- | boost/geometry/strategies/geographic/area.hpp | 23 |
1 files changed, 19 insertions, 4 deletions
diff --git a/boost/geometry/strategies/geographic/area.hpp b/boost/geometry/strategies/geographic/area.hpp index e1d3b09b5a..44dc2e6945 100644 --- a/boost/geometry/strategies/geographic/area.hpp +++ b/boost/geometry/strategies/geographic/area.hpp @@ -83,7 +83,7 @@ protected : CT const m_e2; // squared eccentricity CT const m_ep2; // squared second eccentricity CT const m_ep; // second eccentricity - CT const m_c2; // authalic radius + CT const m_c2; // squared authalic radius inline spheroid_constants(Spheroid const& spheroid) : m_spheroid(spheroid) @@ -92,12 +92,27 @@ protected : * (CT(2.0) - CT(formula::flattening<CT>(spheroid)))) , m_ep2(m_e2 / (CT(1.0) - m_e2)) , m_ep(math::sqrt(m_ep2)) - , m_c2((m_a2 / CT(2.0)) + - ((math::sqr(get_radius<2>(spheroid)) * boost::math::atanh(math::sqrt(m_e2))) - / (CT(2.0) * math::sqrt(m_e2)))) + , m_c2(authalic_radius(spheroid, m_a2, m_e2)) {} }; + static inline CT authalic_radius(Spheroid const& sph, CT const& a2, CT const& e2) + { + CT const c0 = 0; + + if (math::equals(e2, c0)) + { + return a2; + } + + CT const sqrt_e2 = math::sqrt(e2); + CT const c2 = 2; + + return (a2 / c2) + + ((math::sqr(get_radius<2>(sph)) * boost::math::atanh(sqrt_e2)) + / (c2 * sqrt_e2)); + } + struct area_sums { CT m_excess_sum; |