Repositionable imaging system and method for creating a 3D image of a closed cavity of a patient's anatomy containing the imaging system, estimating characteristics of motion of the system within the cavity, and determining a metric dimension characterizing the cavity without the use of mechanical measurement. The system may include tracking device located externally with respect to the cavity to determine a scale measurement of the system's motion and the structure of the cavity. The system's computer processor is configured to determine triangulated features of the cavity and recover motion scale data with the use of data received from the tracking device. A specific imaging system includes an endoscope (equipped with an electrical coil and complemented with an external electromagnetic tracker).