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# Skeletal tracker?

I was trying to use the skeletal tracker under openni_kinect and i noticed that it publishes translation and rotation values. But the rotation is represented by w,x,y,z; what do these represent? Also in case of translation, which variable represents depth, which one for height and which one for left-right?

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The rotation is represented as a quaternion which has values in a non-readable format. You can use tf to convert between quaternions and euler angles ( e.g. tf::Quaternion createQuaternionFromRPY(double roll,double pitch,double yaw) ).

What do you mean by height and left-right? What joint are you referring to?

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If camera is the origin, then what are the three axes directed along (for any joint) ?
You can get the three axes by converting to euler angles using tf ... The euler angles represen the rotations around x,y and z axis.
In Python you can e.g. use: euler_angles = euler_from_quaternion([x,y,z,w]) ... the angles are in rad. Check: http://www.ros.org/doc/api/tf/html/namespacetf_1_1transformations.html for the API
This helped... Thanks a lot !! You can find the answers to your questions in REP103 - Standard Units of Measure and Coordinate Conventions.

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