#include "sofa.h" void iauAtioq(double ri, double di, iauASTROM *astrom, double *aob, double *zob, double *hob, double *dob, double *rob) /* ** - - - - - - - - - ** i a u A t i o q ** - - - - - - - - - ** ** Quick CIRS to observed place transformation. ** ** Use of this function is appropriate when efficiency is important and ** where many star positions are all to be transformed for one date. ** The star-independent astrometry parameters can be obtained by ** calling iauApio[13] or iauApco[13]. ** ** This function is part of the International Astronomical Union's ** SOFA (Standards of Fundamental Astronomy) software collection. ** ** Status: support function. ** ** Given: ** ri double CIRS right ascension ** di double CIRS declination ** astrom iauASTROM* star-independent astrometry parameters: ** pmt double PM time interval (SSB, Julian years) ** eb double[3] SSB to observer (vector, au) ** eh double[3] Sun to observer (unit vector) ** em double distance from Sun to observer (au) ** v double[3] barycentric observer velocity (vector, c) ** bm1 double sqrt(1-|v|^2): reciprocal of Lorenz factor ** bpn double[3][3] bias-precession-nutation matrix ** along double longitude + s' (radians) ** xpl double polar motion xp wrt local meridian (radians) ** ypl double polar motion yp wrt local meridian (radians) ** sphi double sine of geodetic latitude ** cphi double cosine of geodetic latitude ** diurab double magnitude of diurnal aberration vector ** eral double "local" Earth rotation angle (radians) ** refa double refraction constant A (radians) ** refb double refraction constant B (radians) ** ** Returned: ** aob double* observed azimuth (radians: N=0,E=90) ** zob double* observed zenith distance (radians) ** hob double* observed hour angle (radians) ** dob double* observed declination (radians) ** rob double* observed right ascension (CIO-based, radians) ** ** Notes: ** ** 1) This function returns zenith distance rather than altitude in ** order to reflect the fact that no allowance is made for ** depression of the horizon. ** ** 2) The accuracy of the result is limited by the corrections for ** refraction, which use a simple A*tan(z) + B*tan^3(z) model. ** Providing the meteorological parameters are known accurately and ** there are no gross local effects, the predicted observed ** coordinates should be within 0.05 arcsec (optical) or 1 arcsec ** (radio) for a zenith distance of less than 70 degrees, better ** than 30 arcsec (optical or radio) at 85 degrees and better ** than 20 arcmin (optical) or 30 arcmin (radio) at the horizon. ** ** Without refraction, the complementary functions iauAtioq and ** iauAtoiq are self-consistent to better than 1 microarcsecond all ** over the celestial sphere. With refraction included, consistency ** falls off at high zenith distances, but is still better than ** 0.05 arcsec at 85 degrees. ** ** 3) It is advisable to take great care with units, as even unlikely ** values of the input parameters are accepted and processed in ** accordance with the models used. ** ** 4) The CIRS RA,Dec is obtained from a star catalog mean place by ** allowing for space motion, parallax, the Sun's gravitational lens ** effect, annual aberration and precession-nutation. For star ** positions in the ICRS, these effects can be applied by means of ** the iauAtci13 (etc.) functions. Starting from classical "mean ** place" systems, additional transformations will be needed first. ** ** 5) "Observed" Az,El means the position that would be seen by a ** perfect geodetically aligned theodolite. This is obtained from ** the CIRS RA,Dec by allowing for Earth orientation and diurnal ** aberration, rotating from equator to horizon coordinates, and ** then adjusting for refraction. The HA,Dec is obtained by ** rotating back into equatorial coordinates, and is the position ** that would be seen by a perfect equatorial with its polar axis ** aligned to the Earth's axis of rotation. Finally, the RA is ** obtained by subtracting the HA from the local ERA. ** ** 6) The star-independent CIRS-to-observed-place parameters in ASTROM ** may be computed with iauApio[13] or iauApco[13]. If nothing has ** changed significantly except the time, iauAper[13] may be used to ** perform the requisite adjustment to the astrom structure. ** ** Called: ** iauS2c spherical coordinates to unit vector ** iauC2s p-vector to spherical ** iauAnp normalize angle into range 0 to 2pi ** ** This revision: 2016 March 9 ** ** SOFA release 2018-01-30 ** ** Copyright (C) 2018 IAU SOFA Board. See notes at end. */ { /* Minimum cos(alt) and sin(alt) for refraction purposes */ const double CELMIN = 1e-6; const double SELMIN = 0.05; double v[3], x, y, z, xhd, yhd, zhd, f, xhdt, yhdt, zhdt, xaet, yaet, zaet, azobs, r, tz, w, del, cosdel, xaeo, yaeo, zaeo, zdobs, hmobs, dcobs, raobs; /* CIRS RA,Dec to Cartesian -HA,Dec. */ iauS2c(ri-astrom->eral, di, v); x = v[0]; y = v[1]; z = v[2]; /* Polar motion. */ xhd = x + astrom->xpl*z; yhd = y - astrom->ypl*z; zhd = z - astrom->xpl*x + astrom->ypl*y; /* Diurnal aberration. */ f = ( 1.0 - astrom->diurab*yhd ); xhdt = f * xhd; yhdt = f * ( yhd + astrom->diurab ); zhdt = f * zhd; /* Cartesian -HA,Dec to Cartesian Az,El (S=0,E=90). */ xaet = astrom->sphi*xhdt - astrom->cphi*zhdt; yaet = yhdt; zaet = astrom->cphi*xhdt + astrom->sphi*zhdt; /* Azimuth (N=0,E=90). */ azobs = ( xaet != 0.0 || yaet != 0.0 ) ? atan2(yaet,-xaet) : 0.0; /* ---------- */ /* Refraction */ /* ---------- */ /* Cosine and sine of altitude, with precautions. */ r = sqrt(xaet*xaet + yaet*yaet); r = r > CELMIN ? r : CELMIN; z = zaet > SELMIN ? zaet : SELMIN; /* A*tan(z)+B*tan^3(z) model, with Newton-Raphson correction. */ tz = r/z; w = astrom->refb*tz*tz; del = ( astrom->refa + w ) * tz / ( 1.0 + ( astrom->refa + 3.0*w ) / ( z*z ) ); /* Apply the change, giving observed vector. */ cosdel = 1.0 - del*del/2.0; f = cosdel - del*z/r; xaeo = xaet*f; yaeo = yaet*f; zaeo = cosdel*zaet + del*r; /* Observed ZD. */ zdobs = atan2(sqrt(xaeo*xaeo+yaeo*yaeo), zaeo); /* Az/El vector to HA,Dec vector (both right-handed). */ v[0] = astrom->sphi*xaeo + astrom->cphi*zaeo; v[1] = yaeo; v[2] = - astrom->cphi*xaeo + astrom->sphi*zaeo; /* To spherical -HA,Dec. */ iauC2s ( v, &hmobs, &dcobs ); /* Right ascension (with respect to CIO). */ raobs = astrom->eral + hmobs; /* Return the results. */ *aob = iauAnp(azobs); *zob = zdobs; *hob = -hmobs; *dob = dcobs; *rob = iauAnp(raobs); /* Finished. */ /*---------------------------------------------------------------------- ** ** Copyright (C) 2018 ** Standards Of Fundamental Astronomy Board ** of the International Astronomical Union. ** ** ===================== ** SOFA Software License ** ===================== ** ** NOTICE TO USER: ** ** BY USING THIS SOFTWARE YOU ACCEPT THE FOLLOWING SIX TERMS AND ** CONDITIONS WHICH APPLY TO ITS USE. ** ** 1. The Software is owned by the IAU SOFA Board ("SOFA"). ** ** 2. Permission is granted to anyone to use the SOFA software for any ** purpose, including commercial applications, free of charge and ** without payment of royalties, subject to the conditions and ** restrictions listed below. ** ** 3. You (the user) may copy and distribute SOFA source code to others, ** and use and adapt its code and algorithms in your own software, ** on a world-wide, royalty-free basis. That portion of your ** distribution that does not consist of intact and unchanged copies ** of SOFA source code files is a "derived work" that must comply ** with the following requirements: ** ** a) Your work shall be marked or carry a statement that it ** (i) uses routines and computations derived by you from ** software provided by SOFA under license to you; and ** (ii) does not itself constitute software provided by and/or ** endorsed by SOFA. ** ** b) The source code of your derived work must contain descriptions ** of how the derived work is based upon, contains and/or differs ** from the original SOFA software. ** ** c) The names of all routines in your derived work shall not ** include the prefix "iau" or "sofa" or trivial modifications ** thereof such as changes of case. ** ** d) The origin of the SOFA components of your derived work must ** not be misrepresented; you must not claim that you wrote the ** original software, nor file a patent application for SOFA ** software or algorithms embedded in the SOFA software. ** ** e) These requirements must be reproduced intact in any source ** distribution and shall apply to anyone to whom you have ** granted a further right to modify the source code of your ** derived work. ** ** Note that, as originally distributed, the SOFA software is ** intended to be a definitive implementation of the IAU standards, ** and consequently third-party modifications are discouraged. All ** variations, no matter how minor, must be explicitly marked as ** such, as explained above. ** ** 4. You shall not cause the SOFA software to be brought into ** disrepute, either by misuse, or use for inappropriate tasks, or ** by inappropriate modification. ** ** 5. The SOFA software is provided "as is" and SOFA makes no warranty ** as to its use or performance. SOFA does not and cannot warrant ** the performance or results which the user may obtain by using the ** SOFA software. SOFA makes no warranties, express or implied, as ** to non-infringement of third party rights, merchantability, or ** fitness for any particular purpose. In no event will SOFA be ** liable to the user for any consequential, incidental, or special ** damages, including any lost profits or lost savings, even if a ** SOFA representative has been advised of such damages, or for any ** claim by any third party. ** ** 6. The provision of any version of the SOFA software under the terms ** and conditions specified herein does not imply that future ** versions will also be made available under the same terms and ** conditions. * ** In any published work or commercial product which uses the SOFA ** software directly, acknowledgement (see www.iausofa.org) is ** appreciated. ** ** Correspondence concerning SOFA software should be addressed as ** follows: ** ** By email: sofa@ukho.gov.uk ** By post: IAU SOFA Center ** HM Nautical Almanac Office ** UK Hydrographic Office ** Admiralty Way, Taunton ** Somerset, TA1 2DN ** United Kingdom ** **--------------------------------------------------------------------*/ }