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[formulas] Flip sign of cos_lam12

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This fixes the inaccuracy caused during the
calculation of Newton's starting point.
This commit is contained in:
Adeel Ahmad
2018-06-12 15:44:07 +05:00
parent 71fbc86f44
commit 5bb581c932
1 changed files with 10 additions and 4 deletions
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14
include/boost/geometry/formulas/karney_inverse.hpp
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@@ -91,6 +91,7 @@ public:
CT tiny = std::sqrt(std::numeric_limits<CT>::min());
CT const n = f / two_minus_f;
CT const e2 = f * two_minus_f;
CT const ep2 = e2 / math::sqr(one_minus_f);
@@ -110,8 +111,15 @@ public:
CT sin_lam12;
CT cos_lam12;
lon12 > c90 ? math::sin_cos_degrees(lon12_error, sin_lam12, cos_lam12)
: math::sin_cos_degrees(lon12, sin_lam12, cos_lam12);
if (lon12 > c90)
{
math::sin_cos_degrees(lon12_error, sin_lam12, cos_lam12);
cos_lam12 *= -c1;
}
else
{
math::sin_cos_degrees(lon12, sin_lam12, cos_lam12);
}
// Make points close to the equator to lie on it.
lat1 = std::abs(lat1) > 90 ? math::NaN<CT>() : lat1;
@@ -421,8 +429,6 @@ public:
}
sin_alpha1 = cos_beta2 * sin_omega12;
// TODO: adl1995 - Resolve inaccuracy with
// cos_alpha1 calculation.
cos_alpha1 = cos_omega12 >= c0 ?
sin_beta12 + cos_beta2 * sin_beta1 * math::sqr(sin_omega12) / (c1 + cos_omega12) :
sin_beta12a - cos_beta2 * sin_beta1 * math::sqr(sin_omega12) / (c1 - cos_omega12);