Image processing is used to determine information about the position of a designated object, particularly where the object is difficult to view or locate. In particular, use in endoscopic surgery can determine positional information about an anatomical feature within a patient's body. The positional information is then used to position or reposition a surgical instrument in relation to the designated object. An instrument placed in relation to the designated object is capable of sending information about the object to a computer. Image processing generates images and determines positional information, which can be used as input to robotic devices or rendered to a human user.