A passive identification system for shipping containers. After the supply of the chemical agent is stopped, the substrate is rotated at a rotating speed higher than said low speed so as to centrifugally remove the chemical agent attached to the substrate. In other embodiments, transmitted services are scheduled such that services will rotate or \u201cmove\u201d between frames, thereby ensuring that a first slot for a service is not always transmitted in the same frequency. Criteria for process completion are applied to determine whether the adjusted 3D image is adequate.