repositionable imaging system and method for creating a 3d image of a closed cavity of a patient &# 39 ; 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 &# 39 ; s motion and the structure of the cavity . the system &# 39 ; 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 .