SLA_DM2AV - Rotation Matrix to Axial Vector   

ACTION:

From a rotation matrix, determine the corresponding axial vector (double precision).

CALL:

CALL sla_DM2AV (RMAT, AXVEC)

GIVEN:

RMAT rotation matrix

RETURNED:

AXVEC 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.