summaryrefslogtreecommitdiffstats
path: root/ast/erfa/taiutc.c
diff options
context:
space:
mode:
authorWilliam Joye <wjoye@cfa.harvard.edu>2018-01-09 19:28:07 (GMT)
committerWilliam Joye <wjoye@cfa.harvard.edu>2018-01-09 19:28:07 (GMT)
commit3bfbbb90d4d6ebd44cc5eac38af24d1f78318a58 (patch)
treef278119398ae5d67a6a338705a76db420f6b8f7e /ast/erfa/taiutc.c
parent1332d38f2805d986ea130e43218c0d2e870b4dc1 (diff)
downloadblt-3bfbbb90d4d6ebd44cc5eac38af24d1f78318a58.zip
blt-3bfbbb90d4d6ebd44cc5eac38af24d1f78318a58.tar.gz
blt-3bfbbb90d4d6ebd44cc5eac38af24d1f78318a58.tar.bz2
update ast 8.6.2
Diffstat (limited to 'ast/erfa/taiutc.c')
-rw-r--r--ast/erfa/taiutc.c168
1 files changed, 168 insertions, 0 deletions
diff --git a/ast/erfa/taiutc.c b/ast/erfa/taiutc.c
new file mode 100644
index 0000000..ce3a177
--- /dev/null
+++ b/ast/erfa/taiutc.c
@@ -0,0 +1,168 @@
+#include "erfa.h"
+
+int eraTaiutc(double tai1, double tai2, double *utc1, double *utc2)
+/*
+** - - - - - - - - - -
+** e r a T a i u t c
+** - - - - - - - - - -
+**
+** Time scale transformation: International Atomic Time, TAI, to
+** Coordinated Universal Time, UTC.
+**
+** Given:
+** tai1,tai2 double TAI as a 2-part Julian Date (Note 1)
+**
+** Returned:
+** utc1,utc2 double UTC as a 2-part quasi Julian Date (Notes 1-3)
+**
+** Returned (function value):
+** int status: +1 = dubious year (Note 4)
+** 0 = OK
+** -1 = unacceptable date
+**
+** Notes:
+**
+** 1) tai1+tai2 is Julian Date, apportioned in any convenient way
+** between the two arguments, for example where tai1 is the Julian
+** Day Number and tai2 is the fraction of a day. The returned utc1
+** and utc2 form an analogous pair, except that a special convention
+** is used, to deal with the problem of leap seconds - see the next
+** note.
+**
+** 2) JD cannot unambiguously represent UTC during a leap second unless
+** special measures are taken. The convention in the present
+** function is that the JD day represents UTC days whether the
+** length is 86399, 86400 or 86401 SI seconds. In the 1960-1972 era
+** there were smaller jumps (in either direction) each time the
+** linear UTC(TAI) expression was changed, and these "mini-leaps"
+** are also included in the ERFA convention.
+**
+** 3) The function eraD2dtf can be used to transform the UTC quasi-JD
+** into calendar date and clock time, including UTC leap second
+** handling.
+**
+** 4) The warning status "dubious year" flags UTCs that predate the
+** introduction of the time scale or that are too far in the future
+** to be trusted. See eraDat for further details.
+**
+** Called:
+** eraUtctai UTC to TAI
+**
+** References:
+**
+** McCarthy, D. D., Petit, G. (eds.), IERS Conventions (2003),
+** IERS Technical Note No. 32, BKG (2004)
+**
+** Explanatory Supplement to the Astronomical Almanac,
+** P. Kenneth Seidelmann (ed), University Science Books (1992)
+**
+** Copyright (C) 2013-2016, NumFOCUS Foundation.
+** Derived, with permission, from the SOFA library. See notes at end of file.
+*/
+{
+ int big1;
+ int i, j;
+ double a1, a2, u1, u2, g1, g2;
+
+
+/* Put the two parts of the TAI into big-first order. */
+ big1 = ( tai1 >= tai2 );
+ if ( big1 ) {
+ a1 = tai1;
+ a2 = tai2;
+ } else {
+ a1 = tai2;
+ a2 = tai1;
+ }
+
+/* Initial guess for UTC. */
+ u1 = a1;
+ u2 = a2;
+
+/* Iterate (though in most cases just once is enough). */
+ for ( i = 0; i < 3; i++ ) {
+
+ /* Guessed UTC to TAI. */
+ j = eraUtctai(u1, u2, &g1, &g2);
+ if ( j < 0 ) return j;
+
+ /* Adjust guessed UTC. */
+ u2 += a1 - g1;
+ u2 += a2 - g2;
+ }
+
+/* Return the UTC result, preserving the TAI order. */
+ if ( big1 ) {
+ *utc1 = u1;
+ *utc2 = u2;
+ } else {
+ *utc1 = u2;
+ *utc2 = u1;
+ }
+
+/* Status. */
+ return j;
+
+}
+/*----------------------------------------------------------------------
+**
+**
+** Copyright (C) 2013-2016, NumFOCUS Foundation.
+** All rights reserved.
+**
+** This library is derived, with permission, from the International
+** Astronomical Union's "Standards of Fundamental Astronomy" library,
+** available from http://www.iausofa.org.
+**
+** The ERFA version is intended to retain identical functionality to
+** the SOFA library, but made distinct through different function and
+** file names, as set out in the SOFA license conditions. The SOFA
+** original has a role as a reference standard for the IAU and IERS,
+** and consequently redistribution is permitted only in its unaltered
+** state. The ERFA version is not subject to this restriction and
+** therefore can be included in distributions which do not support the
+** concept of "read only" software.
+**
+** Although the intent is to replicate the SOFA API (other than
+** replacement of prefix names) and results (with the exception of
+** bugs; any that are discovered will be fixed), SOFA is not
+** responsible for any errors found in this version of the library.
+**
+** If you wish to acknowledge the SOFA heritage, please acknowledge
+** that you are using a library derived from SOFA, rather than SOFA
+** itself.
+**
+**
+** TERMS AND CONDITIONS
+**
+** Redistribution and use in source and binary forms, with or without
+** modification, are permitted provided that the following conditions
+** are met:
+**
+** 1 Redistributions of source code must retain the above copyright
+** notice, this list of conditions and the following disclaimer.
+**
+** 2 Redistributions in binary form must reproduce the above copyright
+** notice, this list of conditions and the following disclaimer in
+** the documentation and/or other materials provided with the
+** distribution.
+**
+** 3 Neither the name of the Standards Of Fundamental Astronomy Board,
+** the International Astronomical Union nor the names of its
+** contributors may be used to endorse or promote products derived
+** from this software without specific prior written permission.
+**
+** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+** ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+** POSSIBILITY OF SUCH DAMAGE.
+**
+*/