to_quaternion#

DCM.to_quaternion(method: str = 'chiaverini', **kw) → ndarray#

Quaternion from Direction Cosine Matrix.

There are five methods available to obtain a quaternion from a Direction Cosine Matrix:

  • 'chiaverini' as described in [Chiaverini].

  • 'hughes' as described in [Hughes].

  • 'itzhack' as described in [Bar-Itzhack] using version 3 by default. Possible options are integers 1, 2 or 3.

  • 'sarabandi' as described in [Sarabandi] with a threshold equal to 0.0 by default. Possible threshold values are floats between -3.0 and 3.0.

  • 'shepperd' as described in [Shepperd].

Parameters:

method (str, default: 'chiaverini') – Method to use. Options are: 'chiaverini', 'hughes', 'itzhack', 'sarabandi', and 'shepperd'.

Examples

>>> R = DCM(rpy=[10.0, -20.0, 30.0])
>>> R.view()
DCM([[ 0.92541658, -0.31879578, -0.20487413],
     [ 0.16317591,  0.82317294, -0.54383814],
     [ 0.34202014,  0.46984631,  0.81379768]])
>>> R.to_quaternion()   # Uses method 'chiaverini' by default
array([ 0.94371436,  0.26853582, -0.14487813,  0.12767944])
>>> R.to_quaternion('shepperd')
array([ 0.94371436, -0.26853582,  0.14487813, -0.12767944])
>>> R.to_quaternion('hughes')
array([ 0.94371436, -0.26853582,  0.14487813, -0.12767944])
>>> R.to_quaternion('itzhack', version=2)
array([ 0.94371436, -0.26853582,  0.14487813, -0.12767944])
>>> R.to_quaternion('sarabandi', threshold=0.5)
array([0.94371436, 0.26853582, 0.14487813, 0.12767944])