**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.

Starlink User Note 67

P. T. Wallace

12 October 1999

E-mail:ptw@star.rl.ac.uk