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#include "erfa.h" |
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#include "erfadatextra.h" |
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int eraDat(int iy, int im, int id, double fd, double *deltat) |
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/* |
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** - - - - - - - |
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** e r a D a t |
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** - - - - - - - |
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** |
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** For a given UTC date, calculate Delta(AT) = TAI-UTC. |
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** |
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** :------------------------------------------: |
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** : : |
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** : IMPORTANT : |
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** : : |
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** : A new version of this function must be : |
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** : produced whenever a new leap second is : |
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** : announced. There are four items to : |
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** : change on each such occasion: : |
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** : : |
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** : 1) A new line must be added to the set : |
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** : of statements that initialize the : |
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** : array "changes". : |
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** : : |
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** : 2) The constant IYV must be set to the : |
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** : current year. : |
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** : : |
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** : 3) The "Latest leap second" comment : |
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** : below must be set to the new leap : |
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** : second date. : |
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** : : |
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** : 4) The "This revision" comment, later, : |
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** : must be set to the current date. : |
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** : : |
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** : Change (2) must also be carried out : |
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** : whenever the function is re-issued, : |
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** : even if no leap seconds have been : |
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** : added. : |
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** : : |
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** : Latest leap second: 2016 December 31 : |
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** : : |
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** :__________________________________________: |
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** |
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** Given: |
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** iy int UTC: year (Notes 1 and 2) |
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** im int month (Note 2) |
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** id int day (Notes 2 and 3) |
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** fd double fraction of day (Note 4) |
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** |
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** Returned: |
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** deltat double TAI minus UTC, seconds |
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** |
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** Returned (function value): |
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** int status (Note 5): |
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** 1 = dubious year (Note 1) |
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** 0 = OK |
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** -1 = bad year |
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** -2 = bad month |
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** -3 = bad day (Note 3) |
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** -4 = bad fraction (Note 4) |
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** -5 = internal error (Note 5) |
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** |
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** Notes: |
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** |
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** 1) UTC began at 1960 January 1.0 (JD 2436934.5) and it is improper |
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** to call the function with an earlier date. If this is attempted, |
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** zero is returned together with a warning status. |
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** |
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** Because leap seconds cannot, in principle, be predicted in |
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** advance, a reliable check for dates beyond the valid range is |
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** impossible. To guard against gross errors, a year five or more |
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** after the release year of the present function (see the constant |
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** IYV) is considered dubious. In this case a warning status is |
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** returned but the result is computed in the normal way. |
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** |
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** For both too-early and too-late years, the warning status is +1. |
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** This is distinct from the error status -1, which signifies a year |
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** so early that JD could not be computed. |
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** |
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** 2) If the specified date is for a day which ends with a leap second, |
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** the TAI-UTC value returned is for the period leading up to the |
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** leap second. If the date is for a day which begins as a leap |
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** second ends, the TAI-UTC returned is for the period following the |
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** leap second. |
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** |
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** 3) The day number must be in the normal calendar range, for example |
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** 1 through 30 for April. The "almanac" convention of allowing |
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** such dates as January 0 and December 32 is not supported in this |
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** function, in order to avoid confusion near leap seconds. |
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** |
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** 4) The fraction of day is used only for dates before the |
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** introduction of leap seconds, the first of which occurred at the |
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** end of 1971. It is tested for validity (0 to 1 is the valid |
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** range) even if not used; if invalid, zero is used and status -4 |
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** is returned. For many applications, setting fd to zero is |
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** acceptable; the resulting error is always less than 3 ms (and |
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** occurs only pre-1972). |
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** |
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** 5) The status value returned in the case where there are multiple |
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** errors refers to the first error detected. For example, if the |
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** month and day are 13 and 32 respectively, status -2 (bad month) |
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** will be returned. The "internal error" status refers to a |
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** case that is impossible but causes some compilers to issue a |
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** warning. |
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** |
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** 6) In cases where a valid result is not available, zero is returned. |
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** |
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** References: |
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** |
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** 1) For dates from 1961 January 1 onwards, the expressions from the |
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** file ftp://maia.usno.navy.mil/ser7/tai-utc.dat are used. |
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** |
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** 2) The 5ms timestep at 1961 January 1 is taken from 2.58.1 (p87) of |
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** the 1992 Explanatory Supplement. |
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** |
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** Called: |
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** eraCal2jd Gregorian calendar to JD |
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** |
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** Copyright (C) 2013-2020, NumFOCUS Foundation. |
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** Derived, with permission, from the SOFA library. See notes at end of file. |
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*/ |
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{ |
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/* Release year for this version of eraDat */ |
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enum { IYV = 2020}; |
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/* Reference dates (MJD) and drift rates (s/day), pre leap seconds */ |
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static const double drift[][2] = { |
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{ 37300.0, 0.0012960 }, |
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{ 37300.0, 0.0012960 }, |
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{ 37300.0, 0.0012960 }, |
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{ 37665.0, 0.0011232 }, |
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{ 37665.0, 0.0011232 }, |
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{ 38761.0, 0.0012960 }, |
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{ 38761.0, 0.0012960 }, |
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{ 38761.0, 0.0012960 }, |
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{ 38761.0, 0.0012960 }, |
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{ 38761.0, 0.0012960 }, |
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{ 38761.0, 0.0012960 }, |
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{ 38761.0, 0.0012960 }, |
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{ 39126.0, 0.0025920 }, |
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{ 39126.0, 0.0025920 } |
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}; |
143
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/* Number of Delta(AT) expressions before leap seconds were introduced */ |
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enum { NERA1 = (int) (sizeof drift / sizeof (double) / 2) }; |
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147
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/* Dates and Delta(AT)s */ |
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static const eraLEAPSECOND _changes[] = { |
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{ 1960, 1, 1.4178180 }, |
150
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{ 1961, 1, 1.4228180 }, |
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{ 1961, 8, 1.3728180 }, |
152
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{ 1962, 1, 1.8458580 }, |
153
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{ 1963, 11, 1.9458580 }, |
154
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{ 1964, 1, 3.2401300 }, |
155
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{ 1964, 4, 3.3401300 }, |
156
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{ 1964, 9, 3.4401300 }, |
157
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{ 1965, 1, 3.5401300 }, |
158
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{ 1965, 3, 3.6401300 }, |
159
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{ 1965, 7, 3.7401300 }, |
160
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{ 1965, 9, 3.8401300 }, |
161
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{ 1966, 1, 4.3131700 }, |
162
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{ 1968, 2, 4.2131700 }, |
163
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{ 1972, 1, 10.0 }, |
164
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{ 1972, 7, 11.0 }, |
165
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{ 1973, 1, 12.0 }, |
166
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{ 1974, 1, 13.0 }, |
167
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{ 1975, 1, 14.0 }, |
168
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{ 1976, 1, 15.0 }, |
169
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{ 1977, 1, 16.0 }, |
170
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{ 1978, 1, 17.0 }, |
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{ 1979, 1, 18.0 }, |
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{ 1980, 1, 19.0 }, |
173
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{ 1981, 7, 20.0 }, |
174
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{ 1982, 7, 21.0 }, |
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{ 1983, 7, 22.0 }, |
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{ 1985, 7, 23.0 }, |
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{ 1988, 1, 24.0 }, |
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{ 1990, 1, 25.0 }, |
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{ 1991, 1, 26.0 }, |
180
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{ 1992, 7, 27.0 }, |
181
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{ 1993, 7, 28.0 }, |
182
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{ 1994, 7, 29.0 }, |
183
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{ 1996, 1, 30.0 }, |
184
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{ 1997, 7, 31.0 }, |
185
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{ 1999, 1, 32.0 }, |
186
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{ 2006, 1, 33.0 }, |
187
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{ 2009, 1, 34.0 }, |
188
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{ 2012, 7, 35.0 }, |
189
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{ 2015, 7, 36.0 }, |
190
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{ 2017, 1, 37.0 } |
191
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}; |
192
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193
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/* Number of Delta(AT) changes */ |
194
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enum { _NDAT = (int) (sizeof _changes / sizeof _changes[0]) }; |
195
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196
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/* Get/initialise leap-second if needed */ |
197
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int NDAT; |
198
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eraLEAPSECOND *changes; |
199
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200
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4
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NDAT = eraDatini(_changes, _NDAT, &changes); |
201
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202
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/* Miscellaneous local variables */ |
203
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int j, i, m; |
204
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double da, djm0, djm; |
205
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206
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207
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/* Initialize the result to zero. */ |
208
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4
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*deltat = da = 0.0; |
209
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210
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/* If invalid fraction of a day, set error status and give up. */ |
211
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4
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50
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if (fd < 0.0 || fd > 1.0) return -4; |
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50
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212
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213
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/* Convert the date into an MJD. */ |
214
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4
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j = eraCal2jd(iy, im, id, &djm0, &djm); |
215
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216
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/* If invalid year, month, or day, give up. */ |
217
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4
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50
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if (j < 0) return j; |
218
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219
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/* If pre-UTC year, set warning status and give up. */ |
220
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4
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50
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if (iy < changes[0].iyear) return 1; |
221
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222
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/* If suspiciously late year, set warning status but proceed. */ |
223
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4
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50
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if (iy > IYV + 5) j = 1; |
224
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225
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/* Combine year and month to form a date-ordered integer... */ |
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m = 12*iy + im; |
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/* ...and use it to find the preceding table entry. */ |
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for (i = NDAT-1; i >=0; i--) { |
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if (m >= (12 * changes[i].iyear + changes[i].month)) break; |
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} |
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/* Prevent underflow warnings. */ |
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if (i < 0) return -5; |
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/* Get the Delta(AT). */ |
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da = changes[i].delat; |
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/* If pre-1972, adjust for drift. */ |
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if (i < NERA1) da += (djm + fd - drift[i][0]) * drift[i][1]; |
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/* Return the Delta(AT) value. */ |
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*deltat = da; |
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/* Return the status. */ |
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return j; |
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} |
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/*---------------------------------------------------------------------- |
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** |
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** |
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** Copyright (C) 2013-2020, NumFOCUS Foundation. |
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** All rights reserved. |
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** |
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** This library is derived, with permission, from the International |
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** Astronomical Union's "Standards of Fundamental Astronomy" library, |
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** available from http://www.iausofa.org. |
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** |
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** The ERFA version is intended to retain identical functionality to |
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** the SOFA library, but made distinct through different function and |
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** file names, as set out in the SOFA license conditions. The SOFA |
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** original has a role as a reference standard for the IAU and IERS, |
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** and consequently redistribution is permitted only in its unaltered |
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** state. The ERFA version is not subject to this restriction and |
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** therefore can be included in distributions which do not support the |
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** concept of "read only" software. |
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** |
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** Although the intent is to replicate the SOFA API (other than |
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** replacement of prefix names) and results (with the exception of |
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** bugs; any that are discovered will be fixed), SOFA is not |
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** responsible for any errors found in this version of the library. |
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** |
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** If you wish to acknowledge the SOFA heritage, please acknowledge |
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** that you are using a library derived from SOFA, rather than SOFA |
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** itself. |
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** |
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** |
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** TERMS AND CONDITIONS |
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** |
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** Redistribution and use in source and binary forms, with or without |
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** modification, are permitted provided that the following conditions |
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** are met: |
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** |
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** 1 Redistributions of source code must retain the above copyright |
285
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** notice, this list of conditions and the following disclaimer. |
286
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** |
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** 2 Redistributions in binary form must reproduce the above copyright |
288
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** notice, this list of conditions and the following disclaimer in |
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** the documentation and/or other materials provided with the |
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** distribution. |
291
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** |
292
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** 3 Neither the name of the Standards Of Fundamental Astronomy Board, |
293
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** the International Astronomical Union nor the names of its |
294
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** contributors may be used to endorse or promote products derived |
295
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** from this software without specific prior written permission. |
296
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** |
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** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
298
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** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
299
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** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS |
300
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** FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE |
301
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** COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, |
302
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** INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, |
303
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** BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; |
304
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** LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER |
305
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** CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
306
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|
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|
|
** LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN |
307
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|
|
** ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE |
308
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|
|
** POSSIBILITY OF SUCH DAMAGE. |
309
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|
** |
310
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*/ |