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/* prectest.cpp: demonstrates/shows results from precession funcs
Copyright (C) 2010, 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 <string.h>
#include <assert.h>
#include <math.h>
#include "watdefs.h"
#include "afuncs.h"
#include "date.h"
#include "lunar.h" /* for obliquity( ) prototype */
#define PI 3.1415926535897932384626433832795028841971693993751058209749445923
static const double arcsec_to_radians = PI / (180. * 3600.);
static const double marcsec_to_radians = PI / (180. * 3600.e+3);
/* Verify the final results of the 'eop_prec.cpp' functions for computing
precise Earth orientation against matrices generated by the USNO's on-line
earth orientation matrix calculator at
http://maia.usno.navy.mil/
(look down the page for "earth orientation matrix calculator"). Agreement
is within about a centimeter. I don't know why it isn't exact. I rather
with it were; I have no practical need for accuracy better than a few
meters, but an "exact" match to the USNO EOP calculator would be a
reassuring unit test. */
int main( const int argc, const char **argv)
{
const double utc = get_time_from_string( 0., argv[1], FULL_CTIME_YMD,
NULL);
const double tdt = utc + td_minus_utc( utc) / seconds_per_day;
int i, pass;
const double J2000 = 2451545.; /* JD 2451545 = 2000 Jan 1.5 */
double year = 2000. + (tdt - J2000) / 365.25;
int eop_rval = load_earth_orientation_params( "../eop/finals.all");
earth_orientation_params eo_params;
char tbuff[80];
if( eop_rval <= 0)
printf( "Problem loading EOPs: rval %d\n", eop_rval);
else
{
full_ctime( tbuff, 2400000.5 + (double)eop_rval,
FULL_CTIME_DATE_ONLY | FULL_CTIME_YMD);
printf( "EOPs run to MJD %d = %s (including predictions)\n",
eop_rval, tbuff);
}
full_ctime( tbuff, utc, FULL_CTIME_YMD);
printf( "For JD %f = %s UTC\n", utc, tbuff);
eop_rval = get_earth_orientation_params( tdt, &eo_params);
printf( "Polar motion: %f x, %f y (arcseconds)\n",
eo_params.dX / arcsec_to_radians,
eo_params.dY / arcsec_to_radians);
printf( "TDT - UT1 = %f seconds\n", eo_params.tdt_minus_ut1);
printf( "TDT - UT1 = %f seconds (from 'standard' function)\n",
td_minus_ut( tdt));
printf( "dPsi %f; dEps %f (milliarcseconds)\n",
eo_params.dPsi / marcsec_to_radians,
eo_params.dEps / marcsec_to_radians);
printf( "UT1 - UTC = %f\n", td_minus_utc( tdt) - eo_params.tdt_minus_ut1);
if( eop_rval)
printf( "Couldn't get some/all EOPs for that date : %d\n", eop_rval);
for( pass = 0; pass < 3; pass++)
{
double matrix[9];
const char *labels[3] = { "IAU1976 precession, no nutation:", "With IAU1980 nutation:",
"Including EOPs and rotation:" };
printf( "%s\n", labels[pass]);
switch( pass)
{
case 0:
setup_precession( matrix, 2000., year);
break;
case 1:
setup_precession_with_nutation( matrix, year);
break;
case 2:
setup_precession_with_nutation_eops( matrix, year);
break;
}
for( i = 0; i < 9; i++) /* print out the precession matrix */
printf( "%15.11f%s", matrix[i], (i % 3 == 2) ? "\n" : " ");
}
load_earth_orientation_params( NULL); /* free up memory */
return( 0);
}
/*
phred@phred:~/lunar$ ./prectest "2016 aug 1.25"
Polar motion: 0.213185 x, 0.449021 y (arcseconds)
TDT - UT1 = 68.409532 seconds
TDT - UT1 = 68.339919 seEEnds (from 'standard' function)
dPsi -103.968297; dEps -13.531305 (milliarcseconds)
TDT - UT1 = 68.409532
UT1 - UTC = -0.225532
IAU1976 precession, no nutation:
0.99999182608 -0.00370830410 -0.00161128711
0.00370830409 0.99999312421 -0.00000299239
0.00161128713 -0.00000298278 0.99999870187
With IAU1980 nutation:
0.99999183661 -0.00370830411 -0.00160474335
0.00370837498 0.99999312311 0.00004119141
0.00160457957 -0.00004714206 0.99999871155
Including EOPs and rotation:
0.76529242939 0.64368164969 -0.00119640076
-0.64368076755 0.76529336318 0.00106665942
0.00160218666 -0.00004620622 0.99999871543
computed using 2016 October 2 'finals.all'; EOPs may shift a little
as more data are included. Note that a unit change in the last
digit corresponds to about 0.06 millimeters on the earth's surface
(10^-11 earth radii, with the earth's radius being about 6378140 m.)
*/
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