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Diffstat (limited to 'ast/erfa/pv2s.c')
-rw-r--r-- | ast/erfa/pv2s.c | 153 |
1 files changed, 153 insertions, 0 deletions
diff --git a/ast/erfa/pv2s.c b/ast/erfa/pv2s.c new file mode 100644 index 0000000..7ed8db2 --- /dev/null +++ b/ast/erfa/pv2s.c @@ -0,0 +1,153 @@ +#include "erfa.h" + +void eraPv2s(double pv[2][3], + double *theta, double *phi, double *r, + double *td, double *pd, double *rd) +/* +** - - - - - - - - +** e r a P v 2 s +** - - - - - - - - +** +** Convert position/velocity from Cartesian to spherical coordinates. +** +** Given: +** pv double[2][3] pv-vector +** +** Returned: +** theta double longitude angle (radians) +** phi double latitude angle (radians) +** r double radial distance +** td double rate of change of theta +** pd double rate of change of phi +** rd double rate of change of r +** +** Notes: +** +** 1) If the position part of pv is null, theta, phi, td and pd +** are indeterminate. This is handled by extrapolating the +** position through unit time by using the velocity part of +** pv. This moves the origin without changing the direction +** of the velocity component. If the position and velocity +** components of pv are both null, zeroes are returned for all +** six results. +** +** 2) If the position is a pole, theta, td and pd are indeterminate. +** In such cases zeroes are returned for all three. +** +** Copyright (C) 2013-2014, NumFOCUS Foundation. +** Derived, with permission, from the SOFA library. See notes at end of file. +*/ +{ + double x, y, z, xd, yd, zd, rxy2, rxy, r2, rtrue, rw, xyp; + + +/* Components of position/velocity vector. */ + x = pv[0][0]; + y = pv[0][1]; + z = pv[0][2]; + xd = pv[1][0]; + yd = pv[1][1]; + zd = pv[1][2]; + +/* Component of r in XY plane squared. */ + rxy2 = x*x + y*y; + +/* Modulus squared. */ + r2 = rxy2 + z*z; + +/* Modulus. */ + rtrue = sqrt(r2); + +/* If null vector, move the origin along the direction of movement. */ + rw = rtrue; + if (rtrue == 0.0) { + x = xd; + y = yd; + z = zd; + rxy2 = x*x + y*y; + r2 = rxy2 + z*z; + rw = sqrt(r2); + } + +/* Position and velocity in spherical coordinates. */ + rxy = sqrt(rxy2); + xyp = x*xd + y*yd; + if (rxy2 != 0.0) { + *theta = atan2(y, x); + *phi = atan2(z, rxy); + *td = (x*yd - y*xd) / rxy2; + *pd = (zd*rxy2 - z*xyp) / (r2*rxy); + } else { + *theta = 0.0; + *phi = (z != 0.0) ? atan2(z, rxy) : 0.0; + *td = 0.0; + *pd = 0.0; + } + *r = rtrue; + *rd = (rw != 0.0) ? (xyp + z*zd) / rw : 0.0; + + return; + +} +/*---------------------------------------------------------------------- +** +** +** 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. +** +*/ |