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author | William Joye <wjoye@cfa.harvard.edu> | 2016-10-17 15:22:52 (GMT) |
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committer | William Joye <wjoye@cfa.harvard.edu> | 2016-10-17 15:22:52 (GMT) |
commit | 7dd9b970cec6832b8f6118dc2dd91a08d2836648 (patch) | |
tree | 4b3c86596ab87f35a3c6213397da07afe1e24d3e /ast/erfa/pas.c | |
parent | d7bf7c61e8507e3cf51f195392c0f41f27ae18d8 (diff) | |
parent | 7fde2daeed593684120d75de07598154f3ddaf2c (diff) | |
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Merge commit '7fde2daeed593684120d75de07598154f3ddaf2c' as 'ast'
Diffstat (limited to 'ast/erfa/pas.c')
-rw-r--r-- | ast/erfa/pas.c | 105 |
1 files changed, 105 insertions, 0 deletions
diff --git a/ast/erfa/pas.c b/ast/erfa/pas.c new file mode 100644 index 0000000..a71da1b --- /dev/null +++ b/ast/erfa/pas.c @@ -0,0 +1,105 @@ +#include "erfa.h" + +double eraPas(double al, double ap, double bl, double bp) +/* +** - - - - - - - +** e r a P a s +** - - - - - - - +** +** Position-angle from spherical coordinates. +** +** Given: +** al double longitude of point A (e.g. RA) in radians +** ap double latitude of point A (e.g. Dec) in radians +** bl double longitude of point B +** bp double latitude of point B +** +** Returned (function value): +** double position angle of B with respect to A +** +** Notes: +** +** 1) The result is the bearing (position angle), in radians, of point +** B with respect to point A. It is in the range -pi to +pi. The +** sense is such that if B is a small distance "east" of point A, +** the bearing is approximately +pi/2. +** +** 2) Zero is returned if the two points are coincident. +** +** Copyright (C) 2013-2014, NumFOCUS Foundation. +** Derived, with permission, from the SOFA library. See notes at end of file. +*/ +{ + double dl, x, y, pa; + + + dl = bl - al; + y = sin(dl) * cos(bp); + x = sin(bp) * cos(ap) - cos(bp) * sin(ap) * cos(dl); + pa = ((x != 0.0) || (y != 0.0)) ? atan2(y, x) : 0.0; + + return pa; + +} +/*---------------------------------------------------------------------- +** +** +** 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. +** +*/ |