pxform_c |

## Procedurevoid pxform_c ( ConstSpiceChar * from, ConstSpiceChar * to, SpiceDouble et, SpiceDouble rotate[3][3] ) ## AbstractReturn the matrix that transforms position vectors from one specified frame to another at a specified epoch. ## Required_ReadingFRAMES ## KeywordsFRAMES ## Brief_I/OVARIABLE I/O DESCRIPTION -------- --- -------------------------------------------------- from I Name of the frame to transform from. to I Name of the frame to transform to. et I Epoch of the rotation matrix. rotate O A rotation matrix. ## Detailed_Inputfrom is the name of a reference frame in which a position vector is known. to is the name of a reference frame in which it is desired to represent a position vector. et is the epoch in ephemeris seconds past the epoch of J2000 (TDB) at which the position transformation matrix `rotate' should be evaluated. ## Detailed_Outputrotate is the matrix that transforms position vectors from the reference frame `from' to the frame `to' at epoch `et'. If (x, y, z) is a position relative to the frame `from' then the vector ( x', y', z') is the same position relative to the frame `to' at epoch `et'. Here the vector ( x', y', z' ) is defined by the equation: - - - - - - | x' | | | | x | | y' | = | rotate | | y | | z' | | | | z | - - - - - - ## ParametersNone. ## Exceptions1) If sufficient information has not been supplied via loaded SPICE kernels to compute the transformation between the two frames, the error will be diagnosed by a routine in the call tree of this routine. 2) If either frame `from' or `to' is not recognized the error SPICE(UNKNOWNFRAME) will be signaled. ## FilesNone. ## ParticularsThis routine provides the user level interface to computing position transformations from one reference frame to another. Note that the reference frames may be inertial or non-inertial. However, the user must take care that sufficient SPICE kernel information is loaded to provide a complete position transformation path from the from frame to the to frame. ## ExamplesSuppose that you have geodetic coordinates of a station on the surface of the earth and that you need the inertial (J2000) position of this station. The following code fragment illustrates how to transform the position of the station to a J2000 position. #include "SpiceUsr.h" . . . bodvcd_c ( 399, radii, 3, &n, abc ); equatr = abc[0]; polar = abc[2]; f = ( equatr - polar ) / equatr; georec_c ( long, lat, 0.0, equatr, f, epos ); ## RestrictionsNone. ## Literature_ReferencesNone. ## Author_and_InstitutionC.H. Acton (JPL) N.J. Bachman (JPL) B.V. Semenov (JPL) W.L. Taber (JPL) ## Version-CSPICE Version 1.0.4, 27-FEB-2008 (BVS) Added FRAMES to the Required_Reading section of the header. -CSPICE Version 1.0.3, 24-OCT-2005 (NJB) Header updates: example had invalid flattening factor computation; this was corrected. Reference to bodvar_c was replaced with reference to bodvcd_c. -CSPICE Version 1.0.2, 07-JAN-2004 (EDW) Trivial typo correction to example section. -CSPICE Version 1.0.1, 29-JUL-2003 (NJB) (CHA) Various header corrections were made. -CSPICE Version 1.0.0, 20-JUN-1999 (NJB) (WLT) ## Index_EntriesFind a position transformation matrix |

Wed Apr 5 17:54:41 2017