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Diffstat (limited to 'ast/erfa/utcut1.c')
| -rw-r--r-- | ast/erfa/utcut1.c | 156 |
1 files changed, 156 insertions, 0 deletions
diff --git a/ast/erfa/utcut1.c b/ast/erfa/utcut1.c new file mode 100644 index 0000000..0ba94bc --- /dev/null +++ b/ast/erfa/utcut1.c @@ -0,0 +1,156 @@ +#include "erfa.h" + +int eraUtcut1(double utc1, double utc2, double dut1, + double *ut11, double *ut12) +/* +** - - - - - - - - - - +** e r a U t c u t 1 +** - - - - - - - - - - +** +** Time scale transformation: Coordinated Universal Time, UTC, to +** Universal Time, UT1. +** +** Given: +** utc1,utc2 double UTC as a 2-part quasi Julian Date (Notes 1-4) +** dut1 double Delta UT1 = UT1-UTC in seconds (Note 5) +** +** Returned: +** ut11,ut12 double UT1 as a 2-part Julian Date (Note 6) +** +** Returned (function value): +** int status: +1 = dubious year (Note 3) +** 0 = OK +** -1 = unacceptable date +** +** Notes: +** +** 1) utc1+utc2 is quasi Julian Date (see Note 2), apportioned in any +** convenient way between the two arguments, for example where utc1 +** is the Julian Day Number and utc2 is the fraction of a day. +** +** 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. +** +** 3) 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. +** +** 4) The function eraDtf2d converts from calendar date and time of +** day into 2-part Julian Date, and in the case of UTC implements +** the leap-second-ambiguity convention described above. +** +** 5) Delta UT1 can be obtained from tabulations provided by the +** International Earth Rotation and Reference Systems Service. +** It is the caller's responsibility to supply a dut1 argument +** containing the UT1-UTC value that matches the given UTC. +** +** 6) The returned ut11,ut12 are such that their sum is the UT1 Julian +** Date. +** +** 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) +** +** Called: +** eraJd2cal JD to Gregorian calendar +** eraDat delta(AT) = TAI-UTC +** eraUtctai UTC to TAI +** eraTaiut1 TAI to UT1 +** +** Copyright (C) 2013-2014, NumFOCUS Foundation. +** Derived, with permission, from the SOFA library. See notes at end of file. +*/ +{ + int iy, im, id, js, jw; + double w, dat, dta, tai1, tai2; + + +/* Look up TAI-UTC. */ + if ( eraJd2cal(utc1, utc2, &iy, &im, &id, &w) ) return -1; + js = eraDat ( iy, im, id, 0.0, &dat); + if ( js < 0 ) return -1; + +/* Form UT1-TAI. */ + dta = dut1 - dat; + +/* UTC to TAI to UT1. */ + jw = eraUtctai(utc1, utc2, &tai1, &tai2); + if ( jw < 0 ) { + return -1; + } else if ( jw > 0 ) { + js = jw; + } + if ( eraTaiut1(tai1, tai2, dta, ut11, ut12) ) return -1; + +/* Status. */ + return js; + +} +/*---------------------------------------------------------------------- +** +** +** Copyright (C) 2013-2014, 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. +** +*/ |