First commit

Signed-off-by: Mattias Andrée <m@maandree.se>

1 files changed, 16 insertions, 0 deletions

diff --git a/libtellurian_gaussian_radius_radians.c b/libtellurian_gaussian_radius_radians.c
new file mode 100644
index 0000000..d61319a
--- /dev/null
+++ b/libtellurian_gaussian_radius_radians.c
@@ -0,0 +1,16 @@
+/* See LICENSE file for copyright and license details. */
+#include "common.h"
+
+
+double
+libtellurian_gaussian_radius_radians(double latitude)
+{
+	double a = LIBTELLURIAN_EQUATORIAL_RADIUS;
+	double b = LIBTELLURIAN_POLAR_RADIUS;
+	double f = 1.0 - b / a;
+	double neg_e2 = (f - 2.0) * f;
+	double neg_e2_plus_1 = fma(f - 2.0, f, 1.0);
+	double s = sin(latitude);
+	double denom = fma(neg_e2, s * s, 1.0);
+	return a * sqrt(neg_e2_plus_1) / denom;
+}