Welcome to the Harris Geospatial product documentation center. Here you will find reference guides, help documents, and product libraries.


  >  Docs Center  >  Libraries  >  Markwardt  >  QTEULER

QTEULER

QTEULER

Name


  QTEULER

Author


  Craig B. Markwardt, NASA/GSFC Code 662, Greenbelt, MD 20770
  craigm@lheamail.gsfc.nasa.gov
  UPDATED VERSIONs can be found on my WEB PAGE:
      http://cow.physics.wisc.edu/~craigm/idl/idl.html

Purpose


  Compose a series of euler-type rotations into a single quaternion

Major Topics


  Geometry

Calling Sequence


  Q = QTEULER(AXES, ANG0, ANG1, ... )

Description



  The function QTEULER composes a series of Euler-type rotations into
  a single set of quaternion representations.
  The user specifies a set of axes, and the angles to rotation about
  those axes, and QTEULER constructs the corresponding quaternion.
  There must be a one-to-one correspondence between the elements of
  AXES and the number of rotations. AXES specifies the rotation axes
  as an string, which must be one of 'X', 'Y', or 'Z'. Other axes
  are invalid. For example, the following call:
    QTEULER(['X','Z'], THETA, PHI)
  will rotate first about the *Z* axis by the angle PHI, and then
  around the *resulting X* axis by angle THETA.
  Several things are worth noting here. First, rotations are applied
  first from the right, not the left. This conforms to the usual
  matrix notation for applying rotations to a vector on the right
  hand side. For example, in matrix notation,
      XNEW = A3 A2 A1 XOLD
  applies first A1, then A2 and finally A3 to the XOLD vector,
  resulting in the new vector XNEW. The same semantics apply here.
  A second thing to bear in mind is that the axes themselves change
  during the rotations. Thus, the coordinates specified in AXES
  should be considered attached to the "body" and not the inertial
  frame.

Inputs



  AXES - a string array, specifies the rotation axes. Rotations are
        applied last element first. Each element of AXES must be
        one of 'X', 'Y' or 'Z'.
  ANG0, ..., ANGi - the successive rotation angles. [radians]
        Angle ANGi corresponds to axis AXES(i).
        If ANGi is a scalar, then it will be promoted to a vector
        the same size as the other rotation angles being performed.
        Otherwise, if the angles ANGi are vectors, then they must
        all be of the same size.

Returns



  The resulting quaternion (or, if ANGi are vectors, array of
  quaternions), which represent the requested rotations.

Keyword Parameters



  NONE

Example



    ;; Precession Nutation
    qtot = qteuler(['z','y','z', 'x','z','x' ], $
                    -zeta, +theta, -z, +eps0, -dpsi, -eps)
  Applies a series of rotations to correct for earth nutation and
  precession. The order of rotations on a vector would be
  X-Z-X-Z-Y-Z (i.e., the reverse order printed).

See Also


  QTANG, QTAXIS, QTCOMPOSE, QTERP, QTEXP, QTFIND, QTINV, QTLOG,
  QTMAT, QTMULT, QTPOW, QTVROT

Modification History


  Written, 27 Jan 2002, CM
  More error checking, 03 Mar 2002, CM
  $Id: qteuler.pro,v 1.5 2012/09/27 23:53:08 cmarkwar Exp $



© 2018 Harris Geospatial Solutions, Inc. |  Privacy Policy
My Account    |    Store    |    Contact Us