A computer program for the extraction of information about one or more spatial objects by a person, which program is designed for analyzing the sequence of images in real time, using image analysis techniques, and extracting information about said one or more objects, and communicating at least part of said information to the person in real time via the output means; wherein the information about said one or more objects comprises at least: the spatial position of said one or more objects; the spatial distance between two objects; the spatial relative angle between two essentially linear objects; and/or an indication regarding the realized accuracy of the extracted information.