/* sxform.f -- translated by f2c (version 19980913).
   You must link the resulting object file with the libraries:
	-lf2c -lm   (in that order)
*/

#include "f2c.h"

/* $Procedure      SXFORM ( State Transformation Matrix ) */
/* Subroutine */ int sxform_(char *from, char *to, doublereal *et, doublereal 
	*xform, ftnlen from_len, ftnlen to_len)
{
    integer fcode;
    extern /* Subroutine */ int chkin_(char *, ftnlen);
    integer tcode;
    extern /* Subroutine */ int errch_(char *, char *, ftnlen, ftnlen), 
	    frmchg_(integer *, integer *, doublereal *, doublereal *), 
	    namfrm_(char *, integer *, ftnlen), sigerr_(char *, ftnlen), 
	    chkout_(char *, ftnlen), setmsg_(char *, ftnlen);
    extern logical return_(void);

/* $ Abstract */

/*     Return the state transformation matrix from one frame to */
/*     another at a specified epoch. */

/* $ Disclaimer */

/*     THIS SOFTWARE AND ANY RELATED MATERIALS WERE CREATED BY THE */
/*     CALIFORNIA INSTITUTE OF TECHNOLOGY (CALTECH) UNDER A U.S. */
/*     GOVERNMENT CONTRACT WITH THE NATIONAL AERONAUTICS AND SPACE */
/*     ADMINISTRATION (NASA). THE SOFTWARE IS TECHNOLOGY AND SOFTWARE */
/*     PUBLICLY AVAILABLE UNDER U.S. EXPORT LAWS AND IS PROVIDED "AS-IS" */
/*     TO THE RECIPIENT WITHOUT WARRANTY OF ANY KIND, INCLUDING ANY */
/*     WARRANTIES OF PERFORMANCE OR MERCHANTABILITY OR FITNESS FOR A */
/*     PARTICULAR USE OR PURPOSE (AS SET FORTH IN UNITED STATES UCC */
/*     SECTIONS 2312-2313) OR FOR ANY PURPOSE WHATSOEVER, FOR THE */
/*     SOFTWARE AND RELATED MATERIALS, HOWEVER USED. */

/*     IN NO EVENT SHALL CALTECH, ITS JET PROPULSION LABORATORY, OR NASA */
/*     BE LIABLE FOR ANY DAMAGES AND/OR COSTS, INCLUDING, BUT NOT */
/*     LIMITED TO, INCIDENTAL OR CONSEQUENTIAL DAMAGES OF ANY KIND, */
/*     INCLUDING ECONOMIC DAMAGE OR INJURY TO PROPERTY AND LOST PROFITS, */
/*     REGARDLESS OF WHETHER CALTECH, JPL, OR NASA BE ADVISED, HAVE */
/*     REASON TO KNOW, OR, IN FACT, SHALL KNOW OF THE POSSIBILITY. */

/*     RECIPIENT BEARS ALL RISK RELATING TO QUALITY AND PERFORMANCE OF */
/*     THE SOFTWARE AND ANY RELATED MATERIALS, AND AGREES TO INDEMNIFY */
/*     CALTECH AND NASA FOR ALL THIRD-PARTY CLAIMS RESULTING FROM THE */
/*     ACTIONS OF RECIPIENT IN THE USE OF THE SOFTWARE. */

/* $ Required_Reading */

/*     FRAMES */

/* $ Keywords */

/*     FRAMES */

/* $ Declarations */
/* $ Brief_I/O */

/*     VARIABLE  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 state transformation matrix. */
/*     XFORM      O   A state transformation matrix. */

/* $ Detailed_Input */

/*     FROM        is the name of a reference frame in which a state is */
/*                 known. */

/*     TO          is the name of a reference frame in which it is */
/*                 desired to represent the state. */

/*     ET          is the epoch in ephemeris seconds past the epoch of */
/*                 J2000 (TDB) at which the state transformation matrix */
/*                 should be evaluated. */

/* $ Detailed_Output */

/*     XFORM       is the state transformation matrix that transforms */
/*                 states from the reference frame FROM to the frame TO */
/*                 at epoch ET.  If (x, y, z, dx, dy, dz) is a state */
/*                 relative to the frame FROM then the vector ( x', y', */
/*                 z', dx', dy', dz' ) is the same state relative to the */
/*                 frame TO at epoch ET.  Here the vector ( x', y', z', */
/*                 dx', dy', dz' ) is defined by the equation: */

/*                   -   -       -          -     -  - */
/*                  | x'  |     |            |   | x  | */
/*                  | y'  |     |            |   | y  | */
/*                  | z'  |  =  |   XFORM    |   | z  | */
/*                  | dx' |     |            |   | dx | */
/*                  | dy' |     |            |   | dy | */
/*                  | dz' |     |            |   | dz | */
/*                   -   -       -          -     -  - */

/* $ Parameters */

/*     None. */

/* $ Exceptions */

/*     1) 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 to this routine. */

/*     2) If either frame FROM or TO is not recognized the error */
/*        SPICE(UNKNOWNFRAME) will be signaled. */

/* $ Files */

/*     None. */

/* $ Particulars */

/*     This routine provides the user level interface to computing state */
/*     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 state transformation */
/*     path from the FROM frame to the TO frame. */

/* $ Examples */

/*     Suppose that you have geodetic coordinates of a station on */
/*     the surface of the earth and that you need the inertial */
/*     (J2000) state of this station.  The following code fragment */
/*     illustrates how to transform the position of the station to */
/*     a J2000 state. */

/*        CALL BODVRD ( 'EARTH', RADII, 3, N, ABC  ) */

/*        EQUATR   =  ABC(1) */
/*        POLAR    =  ABC(3) */
/*        F        = (EQUATR - POLAR) / EQUATR */

/*        CALL GEOREC ( LONG, LAT, 0.0D0,  EQUATR, F,  ESTATE ) */

/*        ESTATE(4) = 0.0D0 */
/*        ESTATE(5) = 0.0D0 */
/*        ESTATE(6) = 0.0D0 */

/*        CALL SXFORM ( 'IAU_EARTH', 'J2000',   ET, XFORM  ) */
/*        CALL MXVG   (  XFORM,       ESTATE, 6, 6, JSTATE ) */

/*     The state JSTATE is the desired J2000 state of the station. */

/* $ Restrictions */

/*     None. */

/* $ Literature_References */

/*     None. */

/* $ Author_and_Institution */

/*     C.H. Acton      (JPL) */
/*     N.J. Bachman    (JPL) */
/*     B.V. Semenov    (JPL) */
/*     W.L. Taber      (JPL) */

/* $ Version */

/* -    SPICELIB Version 1.0.3, 27-FEB-2008 (BVS) */

/*        Added FRAMES to the Required_Reading section. */

/* -    SPICELIB Version 1.0.2, 23-OCT-2005 (NJB) */

/*        Header example had invalid flattening factor computation; */
/*        this was corrected.  Reference to BODVAR in header was */
/*        replaced with reference to BODVRD. */

/* -    SPICELIB Version 1.0.1, 29-JUL-2003 (NJB) (CHA) */

/*        Minor header changes were made to improve clarity. */

/* -    SPICELIB Version 1.0.0, 19-SEP-1995 (WLT) */

/* -& */
/* $ Index_Entries */

/*     Find a state transformation matrix */

/* -& */

/*     Spicelib Functions */


/*     Local Variables. */


/*     Standard SPICE error handling. */

    if (return_()) {
	return 0;
    }
    chkin_("SXFORM", (ftnlen)6);
    namfrm_(from, &fcode, from_len);
    namfrm_(to, &tcode, to_len);

/*     Only non-zero id-codes are legitimate frame id-codes.  Zero */
/*     indicates that the frame wasn't recognized. */

    if (fcode != 0 && tcode != 0) {
	frmchg_(&fcode, &tcode, et, xform);
    } else if (fcode == 0 && tcode == 0) {
	setmsg_("Neither of the frames # or # was recognized as a known refe"
		"rence frame. ", (ftnlen)72);
	errch_("#", from, (ftnlen)1, from_len);
	errch_("#", to, (ftnlen)1, to_len);
	sigerr_("SPICE(UNKNOWNFRAME)", (ftnlen)19);
    } else if (fcode == 0) {
	setmsg_("The frame # was not recognized as a known reference frame. ",
		 (ftnlen)59);
	errch_("#", from, (ftnlen)1, from_len);
	sigerr_("SPICE(UNKNOWNFRAME)", (ftnlen)19);
    } else if (tcode == 0) {
	setmsg_("The frame # was not recognized as a known reference frame. ",
		 (ftnlen)59);
	errch_("#", to, (ftnlen)1, to_len);
	sigerr_("SPICE(UNKNOWNFRAME)", (ftnlen)19);
    }
    chkout_("SXFORM", (ftnlen)6);
    return 0;
} /* sxform_ */

