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Diffstat (limited to 'ast/erfa/atoiq.c')
| -rw-r--r-- | ast/erfa/atoiq.c | 260 |
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diff --git a/ast/erfa/atoiq.c b/ast/erfa/atoiq.c new file mode 100644 index 0000000..d5501a7 --- /dev/null +++ b/ast/erfa/atoiq.c @@ -0,0 +1,260 @@ +#include "erfa.h" + +void eraAtoiq(const char *type, + double ob1, double ob2, eraASTROM *astrom, + double *ri, double *di) +/* +** - - - - - - - - - +** e r a A t o i q +** - - - - - - - - - +** +** Quick observed place to CIRS, given the star-independent astrometry +** parameters. +** +** 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 eraApio[13] or eraApco[13]. +** +** Given: +** type char[] type of coordinates: "R", "H" or "A" (Note 1) +** ob1 double observed Az, HA or RA (radians; Az is N=0,E=90) +** ob2 double observed ZD or Dec (radians) +** astrom eraASTROM* 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: +** ri double* CIRS right ascension (CIO-based, radians) +** di double* CIRS declination (radians) +** +** Notes: +** +** 1) "Observed" Az,El means the position that would be seen by a +** perfect geodetically aligned theodolite. This is related to +** the observed HA,Dec via the standard rotation, using the geodetic +** latitude (corrected for polar motion), while the observed HA and +** RA are related simply through the Earth rotation angle and the +** site longitude. "Observed" RA,Dec or HA,Dec thus means the +** position that would be seen by a perfect equatorial with its +** polar axis aligned to the Earth's axis of rotation. By removing +** from the observed place the effects of atmospheric refraction and +** diurnal aberration, the CIRS RA,Dec is obtained. +** +** 2) Only the first character of the type argument is significant. +** "R" or "r" indicates that ob1 and ob2 are the observed right +** ascension and declination; "H" or "h" indicates that they are +** hour angle (west +ve) and declination; anything else ("A" or +** "a" is recommended) indicates that ob1 and ob2 are azimuth (north +** zero, east 90 deg) and zenith distance. (Zenith distance is used +** rather than altitude in order to reflect the fact that no +** allowance is made for depression of the horizon.) +** +** 3) 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 eraAtioq and +** eraAtoiq 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. +** +** 4) 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. +** +** Called: +** eraS2c spherical coordinates to unit vector +** eraC2s p-vector to spherical +** eraAnp normalize angle into range 0 to 2pi +** +** Copyright (C) 2013-2016, NumFOCUS Foundation. +** Derived, with permission, from the SOFA library. See notes at end of file. +*/ +{ + int c; + double c1, c2, sphi, cphi, ce, xaeo, yaeo, zaeo, v[3], + xmhdo, ymhdo, zmhdo, az, sz, zdo, refa, refb, tz, dref, + zdt, xaet, yaet, zaet, xmhda, ymhda, zmhda, + f, xhd, yhd, zhd, xpl, ypl, w, hma; + + +/* Coordinate type. */ + c = (int) type[0]; + +/* Coordinates. */ + c1 = ob1; + c2 = ob2; + +/* Sin, cos of latitude. */ + sphi = astrom->sphi; + cphi = astrom->cphi; + +/* Standardize coordinate type. */ + if ( c == 'r' || c == 'R' ) { + c = 'R'; + } else if ( c == 'h' || c == 'H' ) { + c = 'H'; + } else { + c = 'A'; + } + +/* If Az,ZD, convert to Cartesian (S=0,E=90). */ + if ( c == 'A' ) { + ce = sin(c2); + xaeo = - cos(c1) * ce; + yaeo = sin(c1) * ce; + zaeo = cos(c2); + + } else { + + /* If RA,Dec, convert to HA,Dec. */ + if ( c == 'R' ) c1 = astrom->eral - c1; + + /* To Cartesian -HA,Dec. */ + eraS2c ( -c1, c2, v ); + xmhdo = v[0]; + ymhdo = v[1]; + zmhdo = v[2]; + + /* To Cartesian Az,El (S=0,E=90). */ + xaeo = sphi*xmhdo - cphi*zmhdo; + yaeo = ymhdo; + zaeo = cphi*xmhdo + sphi*zmhdo; + } + +/* Azimuth (S=0,E=90). */ + az = ( xaeo != 0.0 || yaeo != 0.0 ) ? atan2(yaeo,xaeo) : 0.0; + +/* Sine of observed ZD, and observed ZD. */ + sz = sqrt ( xaeo*xaeo + yaeo*yaeo ); + zdo = atan2 ( sz, zaeo ); + +/* +** Refraction +** ---------- +*/ + +/* Fast algorithm using two constant model. */ + refa = astrom->refa; + refb = astrom->refb; + tz = sz / zaeo; + dref = ( refa + refb*tz*tz ) * tz; + zdt = zdo + dref; + +/* To Cartesian Az,ZD. */ + ce = sin(zdt); + xaet = cos(az) * ce; + yaet = sin(az) * ce; + zaet = cos(zdt); + +/* Cartesian Az,ZD to Cartesian -HA,Dec. */ + xmhda = sphi*xaet + cphi*zaet; + ymhda = yaet; + zmhda = - cphi*xaet + sphi*zaet; + +/* Diurnal aberration. */ + f = ( 1.0 + astrom->diurab*ymhda ); + xhd = f * xmhda; + yhd = f * ( ymhda - astrom->diurab ); + zhd = f * zmhda; + +/* Polar motion. */ + xpl = astrom->xpl; + ypl = astrom->ypl; + w = xpl*xhd - ypl*yhd + zhd; + v[0] = xhd - xpl*w; + v[1] = yhd + ypl*w; + v[2] = w - ( xpl*xpl + ypl*ypl ) * zhd; + +/* To spherical -HA,Dec. */ + eraC2s(v, &hma, di); + +/* Right ascension. */ + *ri = eraAnp(astrom->eral + hma); + +/* Finished. */ + +} +/*---------------------------------------------------------------------- +** +** +** Copyright (C) 2013-2016, 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. +** +*/ |