European Space Agency

European Space Agency

Royal Belgian Institute for Aeronomy

Royal Belgian Institute for Aeronomy

../_images/whiteSpace.png

ut552 - Initialize a quaternion rotation matrix

subroutine  ut552(quat, ktrl, trans)
Parameters:

  • quat (4) [real8,in] :: Quaternion

  • ktrl [integer4,in] :: Control parameter

  • trans (3,3) [real8,in/out] :: Matrix transformation

Description

The subroutine ut552() initializes or modifies the coordinate transformation with the help of a normalized quaternion. A quaternion is a four-element vector that generalizes the complex number and which can be used to represent a rotation in a three dimensional space. Note that, for normalized quaternion, q12 + q22 + q32 + q42 has to be equal to one. The normalized quaternion rewritten as (u sin(theta), v sin(theta), w sin(theta), cos(theta)) represents a rotation by an angle theta around the axis (u, v, w).

The argument ktrl controls the way the rotation matrix trans is produced. When ktrl is equal to zero the Euler rotation matrix is copied into the argument trans; otherwise, the Euler rotation matrix is combined with the rotation matrix already stored in argument trans. When the value of argument ktrl is negative, the Euler rotation is applied before the rotation stored in argument trans. When the value is positive, the Euler rotation is applied after the stored rotation. The argument ktrl allows thus to easily combine the functionalities of subroutines ut550(), ut551() and ut552().

History

  • The subroutine UT552 does not exist in version 1.07 and earlier.

Diagnostics

None

Common Blocks

None

Dependencies

Called by

None

Calls

None

See also

Reported Bugs

None

Examples

None

UNILIB/tags/v3.02