The observer should be the center, and questions should be centered on the characters in the picture.

To determine the observation point, that is, who sees who; To determine the relative orientation of the observed object at the observation point.

Extended data:

If the position of the object relative to the reference system is changing, it means that the object is moving relative to the reference system; If the position of the object relative to the frame of reference is unchanged, it indicates that the object is still relative to the frame of reference. Relative to different reference frames, the motion state of the same object can be different. In kinematics, the choice of reference system can be arbitrary. Studying and describing the motion of an object can only be carried out after selecting a frame of reference.

Baidu encyclopedia-frame of reference