A robotic surgical system is provided. An illustrative robotic surgical system includes a base having a known position relative to an operating table; an end effector configured to hold and align a surgical tool for performing a procedure on a subject on said operating table; at least one robotic arm connecting said base with said end effector; and a target attached to the end effector, wherein an image of the target attached to the end effector is used to determine a pose of the end effector.