The method involves receiving registration data comprising a set of two-dimensional coordinates, where the set of two-dimensional coordinates has pairs of two-dimensional coordinates corresponding to points on stereoscopic images, respectively. A three-dimensional geometric primitive defined by a portion of the registration data is determined using geometric calibration information. A value of geometric quantity intrinsic to an anatomical system is computed based on the primitive. A value of the computed geometric quantity is displayed on a screen. Independent claims are also included for the following: (1) a computer program comprising instructions for implementing a geometric quantity measuring method (2) a device for measuring a geometric quantity intrinsic to an anatomical system of a patient, from two geometrically calibrated, stereoscopic, two-dimensional images of the anatomical system.
