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| author | William Joye <wjoye@cfa.harvard.edu> | 2018-09-21 17:04:03 (GMT) |
|---|---|---|
| committer | William Joye <wjoye@cfa.harvard.edu> | 2018-09-21 17:04:03 (GMT) |
| commit | 28518ab5eb4726fe91ee0c916b2322f8c47eb3ad (patch) | |
| tree | 2653f0ce7e9c70973f27fe6c0c38ec31e21ce5cf /ast/pal/palPrec.c | |
| parent | bd7d67f66c53df36bb50e3423bfc91eae8618201 (diff) | |
| download | blt-28518ab5eb4726fe91ee0c916b2322f8c47eb3ad.zip blt-28518ab5eb4726fe91ee0c916b2322f8c47eb3ad.tar.gz blt-28518ab5eb4726fe91ee0c916b2322f8c47eb3ad.tar.bz2 | |
update ast 8.6.3
Diffstat (limited to 'ast/pal/palPrec.c')
| -rw-r--r-- | ast/pal/palPrec.c | 107 |
1 files changed, 107 insertions, 0 deletions
diff --git a/ast/pal/palPrec.c b/ast/pal/palPrec.c new file mode 100644 index 0000000..678770d --- /dev/null +++ b/ast/pal/palPrec.c @@ -0,0 +1,107 @@ +/* +*+ +* Name: +* palPrec + +* Purpose: +* Form the matrix of precession between two epochs (IAU 2006) + +* Language: +* Starlink ANSI C + +* Type of Module: +* Library routine + +* Invocation: +* palPrec( double ep0, double ep1, double rmatp[3][3] ) + +* Arguments: +* ep0 = double (Given) +* Beginning epoch +* ep1 = double (Given) +* Ending epoch +* rmatp = double[3][3] (Returned) +* Precession matrix + +* Description: +* The IAU 2006 precession matrix from ep0 to ep1 is found and +* returned. The matrix is in the sense V(EP1) = RMATP * V(EP0). +* The epochs are TDB (loosely TT) Julian epochs. +* +* Though the matrix method itself is rigorous, the precession +* angles are expressed through canonical polynomials which are +* valid only for a limited time span of a few hundred years around +* the current epoch. + +* Authors: +* PTW: Pat Wallace (STFC) +* DSB: David Berry (JAC, Hawaii) +* {enter_new_authors_here} + +* History: +* 2012-02-10 (DSB): +* Initial version with documentation taken from Fortran SLA +* Adapted with permission from the Fortran SLALIB library. +* {enter_further_changes_here} + +* Copyright: +* Copyright (C) 1996 Rutherford Appleton Laboratory +* Copyright (C) 2012 Science and Technology Facilities Council. +* All Rights Reserved. + +* Licence: +* This program is free software: you can redistribute it and/or +* modify it under the terms of the GNU Lesser General Public +* License as published by the Free Software Foundation, either +* version 3 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 Lesser General Public License for more details. +* +* You should have received a copy of the GNU Lesser General +* License along with this program. If not, see +* <http://www.gnu.org/licenses/>. + +* Bugs: +* {note_any_bugs_here} +*- +*/ + +#include "pal.h" +#include "pal1sofa.h" + +void palPrec( double ep0, double ep1, double rmatp[3][3] ){ + +/* Local Variables: */ + double rmatq[3][3]; + double ep0_days; + double ep1_days; + +/* Convert supplied dates to days since J2000 */ + ep0_days = ( ep0 - 2000.0 )*ERFA_DJY; + ep1_days = ( ep1 - 2000.0 )*ERFA_DJY; + +/* If beginning epoch is J2000, just return the rotation matrix from + J2000 to EP1. */ + if( ep0 == 2000.0 ) { + eraPmat06( ERFA_DJ00, ep1_days, rmatp ); + +/* If end epoch is J2000, get the rotation matrix from J2000 to EP0 and + then transpose it to get the rotation matrix from EP0 to J2000. */ + } else if( ep1 == 2000.0 ) { + eraPmat06( ERFA_DJ00, ep0_days, rmatp ); + eraTr( rmatp, rmatp ); + +/* Otherwise. get the two matrices used above and multiply them + together. */ + } else { + eraPmat06( ERFA_DJ00, ep0_days, rmatp ); + eraTr( rmatp, rmatp ); + eraPmat06( ERFA_DJ00, ep1_days, rmatq ); + eraRxr( rmatp, rmatq, rmatp ); + } + +} |