path: root/libtellurian_sea_level_radians.c

/* See LICENSE file for copyright and license details. */
#include "common.h"
#ifndef TEST


double
libtellurian_sea_level_radians(double latitude)
{
	double a = LIBTELLURIAN_EQUATORIAL_RADIUS;
	double b = LIBTELLURIAN_POLAR_RADIUS;
	double c = cos(latitude);
	double s = sin(latitude);
	double x = a * c * a;
	double y = b * s * b;
	double num = fma(x, x, y * y);
	double denom = fma(x, c, y * s);
	return sqrt(num / denom);
}


#else


int
main(void)
{
	double x = pow(LIBTELLURIAN_EQUATORIAL_RADIUS, 4.0) + pow(LIBTELLURIAN_POLAR_RADIUS, 4.0);
	x = sqrt(x / (pow(LIBTELLURIAN_EQUATORIAL_RADIUS, 2.0) + pow(LIBTELLURIAN_POLAR_RADIUS, 2.0)));
	ASSERT(libtellurian_sea_level_radians(0) == LIBTELLURIAN_EQUATORIAL_RADIUS);
	ASSERT(libtellurian_sea_level_radians(D90) == LIBTELLURIAN_POLAR_RADIUS);
	ASSERT(libtellurian_sea_level_radians(D180) == LIBTELLURIAN_EQUATORIAL_RADIUS);
	ASSERT(libtellurian_sea_level_radians(-D90) == LIBTELLURIAN_POLAR_RADIUS);
	ASSERT(libtellurian_sea_level_radians(D45) < LIBTELLURIAN_EQUATORIAL_RADIUS);
	ASSERT(libtellurian_sea_level_radians(D45) > LIBTELLURIAN_POLAR_RADIUS);
	ASSERT(libtellurian_sea_level_radians(-D45) == libtellurian_sea_level_radians(D45));
	ASSERT(fabs(libtellurian_sea_level_radians(D45) / x - 1.0) < 1.0e-12);
	return 0;
}


#endif