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[formulas] Use midpoint of bracket when value lies outside of range

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Adeel Ahmad
2018-06-20 21:31:18 +05:00
parent ead0b188f9
commit 02577bda55
1 changed files with 20 additions and 0 deletions
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20
include/boost/geometry/formulas/karney_inverse.hpp
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@@ -93,6 +93,10 @@ public:
CT const tol0 = std::numeric_limits<CT>::epsilon();
CT const tol1 = c200 * tol0;
CT const tol2 = sqrt(tol0);
// Check on bisection interval.
CT const tol_bisection = tol0 * tol2;
CT const etol2 = c0_1 * tol2 /
sqrt(std::max(c0_001, std::abs(f)) * std::min(c1, c1 - f / c2) / c2);
@@ -373,6 +377,22 @@ public:
continue;
}
}
// Either dv was not positive or updated value was outside legal
// range. Use the midpoint of the bracket as the next estimate.
// This mechanism is not needed for the WGS84 ellipsoid, but it does
// catch problems with more eeccentric ellipsoids. Its efficacy is
// such for the WGS84 test set with the starting guess set to alp1 =
// 90deg:
// the WGS84 test set: mean = 5.21, sd = 3.93, max = 24
// WGS84 and random input: mean = 4.74, sd = 0.99
sin_alpha1 = (sin_alpha1a + sin_alpha1b) / c2;
cos_alpha1 = (cos_alpha1a + cos_alpha1b) / c2;
math::normalize_values<CT>(sin_alpha1, cos_alpha1);
tripn = false;
tripb = (std::abs(sin_alpha1a - sin_alpha1) + (cos_alpha1a - cos_alpha1) < tol_bisection ||
std::abs(sin_alpha1 - sin_alpha1b) + (cos_alpha1 - cos_alpha1b) < tol_bisection);
}
}
}