source: trunk/FACT++/sofa/src/dtf2d.c@ 18368

Last change on this file since 18368 was 18346, checked in by tbretz, 11 years ago
File size: 9.2 KB
Line 
1#include "sofa.h"
2#include <string.h>
3
4int iauDtf2d(const char *scale, int iy, int im, int id,
5 int ihr, int imn, double sec, double *d1, double *d2)
6/*
7** - - - - - - - - -
8** i a u D t f 2 d
9** - - - - - - - - -
10**
11** Encode date and time fields into 2-part Julian Date (or in the case
12** of UTC a quasi-JD form that includes special provision for leap
13** seconds).
14**
15** This function is part of the International Astronomical Union's
16** SOFA (Standards of Fundamental Astronomy) software collection.
17**
18** Status: support function.
19**
20** Given:
21** scale char[] time scale ID (Note 1)
22** iy,im,id int year, month, day in Gregorian calendar (Note 2)
23** ihr,imn int hour, minute
24** sec double seconds
25**
26** Returned:
27** d1,d2 double 2-part Julian Date (Notes 3,4)
28**
29** Returned (function value):
30** int status: +3 = both of next two
31** +2 = time is after end of day (Note 5)
32** +1 = dubious year (Note 6)
33** 0 = OK
34** -1 = bad year
35** -2 = bad month
36** -3 = bad day
37** -4 = bad hour
38** -5 = bad minute
39** -6 = bad second (<0)
40**
41** Notes:
42**
43** 1) scale identifies the time scale. Only the value "UTC" (in upper
44** case) is significant, and enables handling of leap seconds (see
45** Note 4).
46**
47** 2) For calendar conventions and limitations, see iauCal2jd.
48**
49** 3) The sum of the results, d1+d2, is Julian Date, where normally d1
50** is the Julian Day Number and d2 is the fraction of a day. In the
51** case of UTC, where the use of JD is problematical, special
52** conventions apply: see the next note.
53**
54** 4) JD cannot unambiguously represent UTC during a leap second unless
55** special measures are taken. The SOFA internal convention is that
56** the quasi-JD day represents UTC days whether the length is 86399,
57** 86400 or 86401 SI seconds. In the 1960-1972 era there were
58** smaller jumps (in either direction) each time the linear UTC(TAI)
59** expression was changed, and these "mini-leaps" are also included
60** in the SOFA convention.
61**
62** 5) The warning status "time is after end of day" usually means that
63** the sec argument is greater than 60.0. However, in a day ending
64** in a leap second the limit changes to 61.0 (or 59.0 in the case
65** of a negative leap second).
66**
67** 6) The warning status "dubious year" flags UTCs that predate the
68** introduction of the time scale or that are too far in the future
69** to be trusted. See iauDat for further details.
70**
71** 7) Only in the case of continuous and regular time scales (TAI, TT,
72** TCG, TCB and TDB) is the result d1+d2 a Julian Date, strictly
73** speaking. In the other cases (UT1 and UTC) the result must be
74** used with circumspection; in particular the difference between
75** two such results cannot be interpreted as a precise time
76** interval.
77**
78** Called:
79** iauCal2jd Gregorian calendar to JD
80** iauDat delta(AT) = TAI-UTC
81** iauJd2cal JD to Gregorian calendar
82**
83** This revision: 2013 July 26
84**
85** SOFA release 2015-02-09
86**
87** Copyright (C) 2015 IAU SOFA Board. See notes at end.
88*/
89{
90 int js, iy2, im2, id2;
91 double dj, w, day, seclim, dat0, dat12, dat24, dleap, time;
92
93/* Today's Julian Day Number. */
94 js = iauCal2jd(iy, im, id, &dj, &w);
95 if ( js ) return js;
96 dj += w;
97
98/* Day length and final minute length in seconds (provisional). */
99 day = DAYSEC;
100 seclim = 60.0;
101
102/* Deal with the UTC leap second case. */
103 if ( ! strcmp(scale,"UTC") ) {
104
105 /* TAI-UTC at 0h today. */
106 js = iauDat(iy, im, id, 0.0, &dat0);
107 if ( js < 0 ) return js;
108
109 /* TAI-UTC at 12h today (to detect drift). */
110 js = iauDat(iy, im, id, 0.5, &dat12);
111 if ( js < 0 ) return js;
112
113 /* TAI-UTC at 0h tomorrow (to detect jumps). */
114 js = iauJd2cal ( dj, 1.5, &iy2, &im2, &id2, &w);
115 if ( js ) return js;
116 js = iauDat(iy2, im2, id2, 0.0, &dat24);
117 if ( js < 0 ) return js;
118
119 /* Any sudden change in TAI-UTC between today and tomorrow. */
120 dleap = dat24 - (2.0*dat12 - dat0);
121
122 /* If leap second day, correct the day and final minute lengths. */
123 day += dleap;
124 if ( ihr == 23 && imn == 59 ) seclim += dleap;
125
126 /* End of UTC-specific actions. */
127 }
128
129/* Validate the time. */
130 if ( ihr >= 0 && ihr <= 23 ) {
131 if ( imn >= 0 && imn <= 59 ) {
132 if ( sec >= 0 ) {
133 if ( sec >= seclim ) {
134 js += 2;
135 }
136 } else {
137 js = -6;
138 }
139 } else {
140 js = -5;
141 }
142 } else {
143 js = -4;
144 }
145 if ( js < 0 ) return js;
146
147/* The time in days. */
148 time = ( 60.0 * ( (double) ( 60 * ihr + imn ) ) + sec ) / day;
149
150/* Return the date and time. */
151 *d1 = dj;
152 *d2 = time;
153
154/* Status. */
155 return js;
156
157/*----------------------------------------------------------------------
158**
159** Copyright (C) 2015
160** Standards Of Fundamental Astronomy Board
161** of the International Astronomical Union.
162**
163** =====================
164** SOFA Software License
165** =====================
166**
167** NOTICE TO USER:
168**
169** BY USING THIS SOFTWARE YOU ACCEPT THE FOLLOWING SIX TERMS AND
170** CONDITIONS WHICH APPLY TO ITS USE.
171**
172** 1. The Software is owned by the IAU SOFA Board ("SOFA").
173**
174** 2. Permission is granted to anyone to use the SOFA software for any
175** purpose, including commercial applications, free of charge and
176** without payment of royalties, subject to the conditions and
177** restrictions listed below.
178**
179** 3. You (the user) may copy and distribute SOFA source code to others,
180** and use and adapt its code and algorithms in your own software,
181** on a world-wide, royalty-free basis. That portion of your
182** distribution that does not consist of intact and unchanged copies
183** of SOFA source code files is a "derived work" that must comply
184** with the following requirements:
185**
186** a) Your work shall be marked or carry a statement that it
187** (i) uses routines and computations derived by you from
188** software provided by SOFA under license to you; and
189** (ii) does not itself constitute software provided by and/or
190** endorsed by SOFA.
191**
192** b) The source code of your derived work must contain descriptions
193** of how the derived work is based upon, contains and/or differs
194** from the original SOFA software.
195**
196** c) The names of all routines in your derived work shall not
197** include the prefix "iau" or "sofa" or trivial modifications
198** thereof such as changes of case.
199**
200** d) The origin of the SOFA components of your derived work must
201** not be misrepresented; you must not claim that you wrote the
202** original software, nor file a patent application for SOFA
203** software or algorithms embedded in the SOFA software.
204**
205** e) These requirements must be reproduced intact in any source
206** distribution and shall apply to anyone to whom you have
207** granted a further right to modify the source code of your
208** derived work.
209**
210** Note that, as originally distributed, the SOFA software is
211** intended to be a definitive implementation of the IAU standards,
212** and consequently third-party modifications are discouraged. All
213** variations, no matter how minor, must be explicitly marked as
214** such, as explained above.
215**
216** 4. You shall not cause the SOFA software to be brought into
217** disrepute, either by misuse, or use for inappropriate tasks, or
218** by inappropriate modification.
219**
220** 5. The SOFA software is provided "as is" and SOFA makes no warranty
221** as to its use or performance. SOFA does not and cannot warrant
222** the performance or results which the user may obtain by using the
223** SOFA software. SOFA makes no warranties, express or implied, as
224** to non-infringement of third party rights, merchantability, or
225** fitness for any particular purpose. In no event will SOFA be
226** liable to the user for any consequential, incidental, or special
227** damages, including any lost profits or lost savings, even if a
228** SOFA representative has been advised of such damages, or for any
229** claim by any third party.
230**
231** 6. The provision of any version of the SOFA software under the terms
232** and conditions specified herein does not imply that future
233** versions will also be made available under the same terms and
234** conditions.
235*
236** In any published work or commercial product which uses the SOFA
237** software directly, acknowledgement (see www.iausofa.org) is
238** appreciated.
239**
240** Correspondence concerning SOFA software should be addressed as
241** follows:
242**
243** By email: sofa@ukho.gov.uk
244** By post: IAU SOFA Center
245** HM Nautical Almanac Office
246** UK Hydrographic Office
247** Admiralty Way, Taunton
248** Somerset, TA1 2DN
249** United Kingdom
250**
251**--------------------------------------------------------------------*/
252}
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