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- ACTION:
- From a rotation matrix, determine the corresponding axial vector
(double precision).
- CALL:
- CALL sla_DM2AV (RMAT, AXVEC)
- GIVEN:
-
RMAT |
D(3,3) |
rotation matrix |
- RETURNED:
-
AXVEC |
D(3) |
axial vector (radians) |
- NOTES:
- 1.
- A rotation matrix describes a rotation about some arbitrary axis.
The axis is called the Euler axis, and the angle through
which the reference frame rotates is called the Euler angle.
The axial vector returned by this routine has the same
direction as the Euler axis, and its magnitude is the Euler angle
in radians.
- 2.
- The magnitude and direction of the axial vector can be separated
by means of the routine sla_DVN.
- 3.
- The reference frame rotates clockwise as seen looking along
the axial vector from the origin.
- 4.
- If RMAT is null, so is the result.
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SLALIB --- Positional Astronomy Library
Starlink User Note 67
P. T. Wallace
25 January 2000
E-mail:ptw@star.rl.ac.uk