diff options
Diffstat (limited to 'ast/erfa/apco.c')
| -rw-r--r-- | ast/erfa/apco.c | 264 |
1 files changed, 264 insertions, 0 deletions
diff --git a/ast/erfa/apco.c b/ast/erfa/apco.c new file mode 100644 index 0000000..6681412 --- /dev/null +++ b/ast/erfa/apco.c @@ -0,0 +1,264 @@ +#include "erfa.h" + +void eraApco(double date1, double date2, + double ebpv[2][3], double ehp[3], + double x, double y, double s, double theta, + double elong, double phi, double hm, + double xp, double yp, double sp, + double refa, double refb, + eraASTROM *astrom) +/* +** - - - - - - - - +** e r a A p c o +** - - - - - - - - +** +** For a terrestrial observer, prepare star-independent astrometry +** parameters for transformations between ICRS and observed +** coordinates. The caller supplies the Earth ephemeris, the Earth +** rotation information and the refraction constants as well as the +** site coordinates. +** +** Given: +** date1 double TDB as a 2-part... +** date2 double ...Julian Date (Note 1) +** ebpv double[2][3] Earth barycentric PV (au, au/day, Note 2) +** ehp double[3] Earth heliocentric P (au, Note 2) +** x,y double CIP X,Y (components of unit vector) +** s double the CIO locator s (radians) +** theta double Earth rotation angle (radians) +** elong double longitude (radians, east +ve, Note 3) +** phi double latitude (geodetic, radians, Note 3) +** hm double height above ellipsoid (m, geodetic, Note 3) +** xp,yp double polar motion coordinates (radians, Note 4) +** sp double the TIO locator s' (radians, Note 4) +** refa double refraction constant A (radians, Note 5) +** refb double refraction constant B (radians, Note 5) +** +** Returned: +** 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) +** +** Notes: +** +** 1) The TDB date date1+date2 is a Julian Date, apportioned in any +** convenient way between the two arguments. For example, +** JD(TDB)=2450123.7 could be expressed in any of these ways, among +** others: +** +** date1 date2 +** +** 2450123.7 0.0 (JD method) +** 2451545.0 -1421.3 (J2000 method) +** 2400000.5 50123.2 (MJD method) +** 2450123.5 0.2 (date & time method) +** +** The JD method is the most natural and convenient to use in cases +** where the loss of several decimal digits of resolution is +** acceptable. The J2000 method is best matched to the way the +** argument is handled internally and will deliver the optimum +** resolution. The MJD method and the date & time methods are both +** good compromises between resolution and convenience. For most +** applications of this function the choice will not be at all +** critical. +** +** TT can be used instead of TDB without any significant impact on +** accuracy. +** +** 2) The vectors eb, eh, and all the astrom vectors, are with respect +** to BCRS axes. +** +** 3) The geographical coordinates are with respect to the ERFA_WGS84 +** reference ellipsoid. TAKE CARE WITH THE LONGITUDE SIGN +** CONVENTION: the longitude required by the present function is +** right-handed, i.e. east-positive, in accordance with geographical +** convention. +** +** 4) xp and yp are the coordinates (in radians) of the Celestial +** Intermediate Pole with respect to the International Terrestrial +** Reference System (see IERS Conventions), measured along the +** meridians 0 and 90 deg west respectively. sp is the TIO locator +** s', in radians, which positions the Terrestrial Intermediate +** Origin on the equator. For many applications, xp, yp and +** (especially) sp can be set to zero. +** +** Internally, the polar motion is stored in a form rotated onto the +** local meridian. +** +** 5) The refraction constants refa and refb are for use in a +** dZ = A*tan(Z)+B*tan^3(Z) model, where Z is the observed +** (i.e. refracted) zenith distance and dZ is the amount of +** refraction. +** +** 6) 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. +** +** 7) In cases where the caller does not wish to provide the Earth +** Ephemeris, the Earth rotation information and refraction +** constants, the function eraApco13 can be used instead of the +** present function. This starts from UTC and weather readings etc. +** and computes suitable values using other ERFA functions. +** +** 8) This is one of several functions that inserts into the astrom +** structure star-independent parameters needed for the chain of +** astrometric transformations ICRS <-> GCRS <-> CIRS <-> observed. +** +** The various functions support different classes of observer and +** portions of the transformation chain: +** +** functions observer transformation +** +** eraApcg eraApcg13 geocentric ICRS <-> GCRS +** eraApci eraApci13 terrestrial ICRS <-> CIRS +** eraApco eraApco13 terrestrial ICRS <-> observed +** eraApcs eraApcs13 space ICRS <-> GCRS +** eraAper eraAper13 terrestrial update Earth rotation +** eraApio eraApio13 terrestrial CIRS <-> observed +** +** Those with names ending in "13" use contemporary ERFA models to +** compute the various ephemerides. The others accept ephemerides +** supplied by the caller. +** +** The transformation from ICRS to GCRS covers space motion, +** parallax, light deflection, and aberration. From GCRS to CIRS +** comprises frame bias and precession-nutation. From CIRS to +** observed takes account of Earth rotation, polar motion, diurnal +** aberration and parallax (unless subsumed into the ICRS <-> GCRS +** transformation), and atmospheric refraction. +** +** 9) The context structure astrom produced by this function is used by +** eraAtioq, eraAtoiq, eraAtciq* and eraAticq*. +** +** Called: +** eraAper astrometry parameters: update ERA +** eraC2ixys celestial-to-intermediate matrix, given X,Y and s +** eraPvtob position/velocity of terrestrial station +** eraTrxpv product of transpose of r-matrix and pv-vector +** eraApcs astrometry parameters, ICRS-GCRS, space observer +** eraCr copy r-matrix +** +** Copyright (C) 2013-2014, NumFOCUS Foundation. +** Derived, with permission, from the SOFA library. See notes at end of file. +*/ +{ + double sl, cl, r[3][3], pvc[2][3], pv[2][3]; + + +/* Longitude with adjustment for TIO locator s'. */ + astrom->along = elong + sp; + +/* Polar motion, rotated onto the local meridian. */ + sl = sin(astrom->along); + cl = cos(astrom->along); + astrom->xpl = xp*cl - yp*sl; + astrom->ypl = xp*sl + yp*cl; + +/* Functions of latitude. */ + astrom->sphi = sin(phi); + astrom->cphi = cos(phi); + +/* Refraction constants. */ + astrom->refa = refa; + astrom->refb = refb; + +/* Local Earth rotation angle. */ + eraAper(theta, astrom); + +/* Disable the (redundant) diurnal aberration step. */ + astrom->diurab = 0.0; + +/* CIO based BPN matrix. */ + eraC2ixys(x, y, s, r); + +/* Observer's geocentric position and velocity (m, m/s, CIRS). */ + eraPvtob(elong, phi, hm, xp, yp, sp, theta, pvc); + +/* Rotate into GCRS. */ + eraTrxpv(r, pvc, pv); + +/* ICRS <-> GCRS parameters. */ + eraApcs(date1, date2, pv, ebpv, ehp, astrom); + +/* Store the CIO based BPN matrix. */ + eraCr(r, astrom->bpn ); + +/* Finished. */ + +} +/*---------------------------------------------------------------------- +** +** +** Copyright (C) 2013-2014, 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. +** +*/ |