source: trunk/FACT++/sofa/src/atio13.c@ 18375

Last change on this file since 18375 was 18346, checked in by tbretz, 11 years ago
File size: 11.2 KB
Line 
1#include "sofa.h"
2
3int iauAtio13(double ri, double di,
4 double utc1, double utc2, double dut1,
5 double elong, double phi, double hm, double xp, double yp,
6 double phpa, double tc, double rh, double wl,
7 double *aob, double *zob, double *hob,
8 double *dob, double *rob)
9/*
10** - - - - - - - - - -
11** i a u A t i o 1 3
12** - - - - - - - - - -
13**
14** CIRS RA,Dec to observed place. The caller supplies UTC, site
15** coordinates, ambient air conditions and observing wavelength.
16**
17** This function is part of the International Astronomical Union's
18** SOFA (Standards of Fundamental Astronomy) software collection.
19**
20** Status: support function.
21**
22** Given:
23** ri double CIRS right ascension (CIO-based, radians)
24** di double CIRS declination (radians)
25** utc1 double UTC as a 2-part...
26** utc2 double ...quasi Julian Date (Notes 1,2)
27** dut1 double UT1-UTC (seconds, Note 3)
28** elong double longitude (radians, east +ve, Note 4)
29** phi double geodetic latitude (radians, Note 4)
30** hm double height above ellipsoid (m, geodetic Notes 4,6)
31** xp,yp double polar motion coordinates (radians, Note 5)
32** phpa double pressure at the observer (hPa = mB, Note 6)
33** tc double ambient temperature at the observer (deg C)
34** rh double relative humidity at the observer (range 0-1)
35** wl double wavelength (micrometers, Note 7)
36**
37** Returned:
38** aob double* observed azimuth (radians: N=0,E=90)
39** zob double* observed zenith distance (radians)
40** hob double* observed hour angle (radians)
41** dob double* observed declination (radians)
42** rob double* observed right ascension (CIO-based, radians)
43**
44** Returned (function value):
45** int status: +1 = dubious year (Note 2)
46** 0 = OK
47** -1 = unacceptable date
48**
49** Notes:
50**
51** 1) utc1+utc2 is quasi Julian Date (see Note 2), apportioned in any
52** convenient way between the two arguments, for example where utc1
53** is the Julian Day Number and utc2 is the fraction of a day.
54**
55** However, JD cannot unambiguously represent UTC during a leap
56** second unless special measures are taken. The convention in the
57** present function is that the JD day represents UTC days whether
58** the length is 86399, 86400 or 86401 SI seconds.
59**
60** Applications should use the function iauDtf2d to convert from
61** calendar date and time of day into 2-part quasi Julian Date, as
62** it implements the leap-second-ambiguity convention just
63** described.
64**
65** 2) The warning status "dubious year" flags UTCs that predate the
66** introduction of the time scale or that are too far in the
67** future to be trusted. See iauDat for further details.
68**
69** 3) UT1-UTC is tabulated in IERS bulletins. It increases by exactly
70** one second at the end of each positive UTC leap second,
71** introduced in order to keep UT1-UTC within +/- 0.9s. n.b. This
72** practice is under review, and in the future UT1-UTC may grow
73** essentially without limit.
74**
75** 4) The geographical coordinates are with respect to the WGS84
76** reference ellipsoid. TAKE CARE WITH THE LONGITUDE SIGN: the
77** longitude required by the present function is east-positive
78** (i.e. right-handed), in accordance with geographical convention.
79**
80** 5) The polar motion xp,yp can be obtained from IERS bulletins. The
81** values are the coordinates (in radians) of the Celestial
82** Intermediate Pole with respect to the International Terrestrial
83** Reference System (see IERS Conventions 2003), measured along the
84** meridians 0 and 90 deg west respectively. For many
85** applications, xp and yp can be set to zero.
86**
87** 6) If hm, the height above the ellipsoid of the observing station
88** in meters, is not known but phpa, the pressure in hPa (=mB), is
89** available, an adequate estimate of hm can be obtained from the
90** expression
91**
92** hm = -29.3 * tsl * log ( phpa / 1013.25 );
93**
94** where tsl is the approximate sea-level air temperature in K
95** (See Astrophysical Quantities, C.W.Allen, 3rd edition, section
96** 52). Similarly, if the pressure phpa is not known, it can be
97** estimated from the height of the observing station, hm, as
98** follows:
99**
100** phpa = 1013.25 * exp ( -hm / ( 29.3 * tsl ) );
101**
102** Note, however, that the refraction is nearly proportional to
103** the pressure and that an accurate phpa value is important for
104** precise work.
105**
106** 7) The argument wl specifies the observing wavelength in
107** micrometers. The transition from optical to radio is assumed to
108** occur at 100 micrometers (about 3000 GHz).
109**
110** 8) "Observed" Az,ZD means the position that would be seen by a
111** perfect geodetically aligned theodolite. (Zenith distance is
112** used rather than altitude in order to reflect the fact that no
113** allowance is made for depression of the horizon.) This is
114** related to the observed HA,Dec via the standard rotation, using
115** the geodetic latitude (corrected for polar motion), while the
116** observed HA and RA are related simply through the Earth rotation
117** angle and the site longitude. "Observed" RA,Dec or HA,Dec thus
118** means the position that would be seen by a perfect equatorial
119** with its polar axis aligned to the Earth's axis of rotation.
120**
121** 9) The accuracy of the result is limited by the corrections for
122** refraction, which use a simple A*tan(z) + B*tan^3(z) model.
123** Providing the meteorological parameters are known accurately and
124** there are no gross local effects, the predicted astrometric
125** coordinates should be within 0.05 arcsec (optical) or 1 arcsec
126** (radio) for a zenith distance of less than 70 degrees, better
127** than 30 arcsec (optical or radio) at 85 degrees and better
128** than 20 arcmin (optical) or 30 arcmin (radio) at the horizon.
129**
130** 10) The complementary functions iauAtio13 and iauAtoi13 are self-
131** consistent to better than 1 microarcsecond all over the
132** celestial sphere.
133**
134** 11) It is advisable to take great care with units, as even unlikely
135** values of the input parameters are accepted and processed in
136** accordance with the models used.
137**
138** Called:
139** iauApio13 astrometry parameters, CIRS-observed, 2013
140** iauAtioq quick ICRS to observed
141**
142** This revision: 2013 October 9
143**
144** SOFA release 2015-02-09
145**
146** Copyright (C) 2015 IAU SOFA Board. See notes at end.
147*/
148{
149 int j;
150 iauASTROM astrom;
151
152/* Star-independent astrometry parameters for CIRS->observed. */
153 j = iauApio13(utc1, utc2, dut1, elong, phi, hm, xp, yp,
154 phpa, tc, rh, wl, &astrom);
155
156/* Abort if bad UTC. */
157 if ( j < 0 ) return j;
158
159/* Transform CIRS to observed. */
160 iauAtioq(ri, di, &astrom, aob, zob, hob, dob, rob);
161
162/* Return OK/warning status. */
163 return j;
164
165/* Finished. */
166
167/*----------------------------------------------------------------------
168**
169** Copyright (C) 2015
170** Standards Of Fundamental Astronomy Board
171** of the International Astronomical Union.
172**
173** =====================
174** SOFA Software License
175** =====================
176**
177** NOTICE TO USER:
178**
179** BY USING THIS SOFTWARE YOU ACCEPT THE FOLLOWING SIX TERMS AND
180** CONDITIONS WHICH APPLY TO ITS USE.
181**
182** 1. The Software is owned by the IAU SOFA Board ("SOFA").
183**
184** 2. Permission is granted to anyone to use the SOFA software for any
185** purpose, including commercial applications, free of charge and
186** without payment of royalties, subject to the conditions and
187** restrictions listed below.
188**
189** 3. You (the user) may copy and distribute SOFA source code to others,
190** and use and adapt its code and algorithms in your own software,
191** on a world-wide, royalty-free basis. That portion of your
192** distribution that does not consist of intact and unchanged copies
193** of SOFA source code files is a "derived work" that must comply
194** with the following requirements:
195**
196** a) Your work shall be marked or carry a statement that it
197** (i) uses routines and computations derived by you from
198** software provided by SOFA under license to you; and
199** (ii) does not itself constitute software provided by and/or
200** endorsed by SOFA.
201**
202** b) The source code of your derived work must contain descriptions
203** of how the derived work is based upon, contains and/or differs
204** from the original SOFA software.
205**
206** c) The names of all routines in your derived work shall not
207** include the prefix "iau" or "sofa" or trivial modifications
208** thereof such as changes of case.
209**
210** d) The origin of the SOFA components of your derived work must
211** not be misrepresented; you must not claim that you wrote the
212** original software, nor file a patent application for SOFA
213** software or algorithms embedded in the SOFA software.
214**
215** e) These requirements must be reproduced intact in any source
216** distribution and shall apply to anyone to whom you have
217** granted a further right to modify the source code of your
218** derived work.
219**
220** Note that, as originally distributed, the SOFA software is
221** intended to be a definitive implementation of the IAU standards,
222** and consequently third-party modifications are discouraged. All
223** variations, no matter how minor, must be explicitly marked as
224** such, as explained above.
225**
226** 4. You shall not cause the SOFA software to be brought into
227** disrepute, either by misuse, or use for inappropriate tasks, or
228** by inappropriate modification.
229**
230** 5. The SOFA software is provided "as is" and SOFA makes no warranty
231** as to its use or performance. SOFA does not and cannot warrant
232** the performance or results which the user may obtain by using the
233** SOFA software. SOFA makes no warranties, express or implied, as
234** to non-infringement of third party rights, merchantability, or
235** fitness for any particular purpose. In no event will SOFA be
236** liable to the user for any consequential, incidental, or special
237** damages, including any lost profits or lost savings, even if a
238** SOFA representative has been advised of such damages, or for any
239** claim by any third party.
240**
241** 6. The provision of any version of the SOFA software under the terms
242** and conditions specified herein does not imply that future
243** versions will also be made available under the same terms and
244** conditions.
245*
246** In any published work or commercial product which uses the SOFA
247** software directly, acknowledgement (see www.iausofa.org) is
248** appreciated.
249**
250** Correspondence concerning SOFA software should be addressed as
251** follows:
252**
253** By email: sofa@ukho.gov.uk
254** By post: IAU SOFA Center
255** HM Nautical Almanac Office
256** UK Hydrographic Office
257** Admiralty Way, Taunton
258** Somerset, TA1 2DN
259** United Kingdom
260**
261**--------------------------------------------------------------------*/
262
263}
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