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/* oblitest.cpp: tests various obliquity formulae
Copyright (C) 2011, Project Pluto
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301, USA. */
#include <stdio.h>
#include <stdlib.h>
#include "watdefs.h"
#include "lunar.h"
#define PI 3.1415926535897932384626433832795028841971693993751058209749445923
/* By default, this program shows the obliquity from years 0 to 4000 at
200-year steps, using a variety of obliquity formulae. Command-line
arguments can change the range/step. */
double iau_obliquity( const double t_cen);
double file_obliquity( const double t_cen);
double spline_obliquity( const double t_cen);
int main( const int argc, const char **argv)
{
double t0 = (argc > 1 ? atof( argv[1]) : 0.);
const double dt = (argc > 2 ? atof( argv[2]) : 200.);
unsigned n_steps = (argc > 3 ? (unsigned)atoi( argv[3]) : 21);
const char *header_trailer =
" year : Laskar cubic file spline dSpline dCubic\n";
printf( "%s", header_trailer);
while( n_steps--)
{
const double t_cen = (t0 - 2000.) / 100.;
const double laskar_obliquity = mean_obliquity( t_cen);
const double iau_value = iau_obliquity( t_cen);
const double file_value = file_obliquity( t_cen);
const double spline_value = spline_obliquity( t_cen);
printf( "%10.2f: %.8f %.8f %.8f %.8f %.3f %.3f\n", t0,
laskar_obliquity * 180. / PI,
iau_value * 180. / PI,
file_value * 180. / PI,
spline_value * 180. / PI,
(laskar_obliquity - spline_value) * 3600. * 180. / PI,
(laskar_obliquity - iau_value) * 3600. * 180. / PI);
t0 += dt;
}
printf( "%s", header_trailer);
if( file_obliquity( 1.) == 0.)
{
printf( "'File' obliquity is interpolated from values found in files at\n\n");
printf( "http://cdsarc.u-strasbg.fr/viz-bin/Cat?VI/63\n\n");
printf( "Get those files, and the 'file' obliquities will be computed and shown.\n");
}
return( 0);
}
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