what unit of measurement does quaternion ::getangle() returns the angle in?

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Hi

I am trying to write a UI to reflect the current orientation of the robot using the tf information published. While printing the angle value using the getangle() function provided by tf::quaternion i noticed that the value is not in degree. I also noticed from the API that the angle() function returns half angles.

Do anyone knows what unit of measurmen does the getangle() function returns the angle value in?

Thanks