Thank you for the info. How should I explain it in more detail? I have a space of 3.50 m by 4.80 m. When I enter the room through the door, I have a base station on the right above the door in the corner of the room. Also diagonally opposite another. So in the top left corner, above my window. When I walk from the window towards the door, this currently corresponds to the X direction (right). If I walk to the left, that's the Z axis. Now I have a MoCap system (Perception Neuron from NOITOM), which uses the Z axis when running forward. And for the right, the X axis. Would like to put a tracker on the back of the hip and use it to correct the position. But somehow I have huge problems to use this correctly. Think I'm still too beginner. I hope I have understood that understandably. Also use the Google translator. Stephan