A system for directing performance of a hair graft harvesting or implanting procedure, comprising: an interface adapted to receive an image data containing images of a body surface; and a processor comprising a set of instructions for executing operations, wherein the set of instructions includes instructions for: recording first locations of a plurality of fiducials (320, 405, 605) appearing in one or more images of the body surface; updating and recording updated locations of at least some of the plurality of the fiducials (320, 405, 605) in one or more updated images of the body surface; determining an offset of the updated locations of the at least some of the plurality of the fiducials (320, 405, 605) relative to their first locations; characterised in that the set of instructions includes instructions for: selecting a new follicular unit harvesting or implanting site at which to perform the hair graft harvesting or implanting procedure based at least in part on the determined offset and a location of a previous procedure site; and instructing a tool to move to the selected new follicular unit harvesting or implanting site to perform the hair graft harvesting or implanting procedure. an interface adapted to receive an image data containing images of a body surface; and a processor comprising a set of instructions for executing operations, wherein the set of instructions includes instructions for: recording first locations of a plurality of fiducials (320, 405, 605) appearing in one or more images of the body surface; updating and recording updated locations of at least some of the plurality of the fiducials (320, 405, 605) in one or more updated images of the body surface; determining an offset of the updated locations of the at least some of the plurality of the fiducials (320, 405, 605) relative to their first locations; characterised in that the set of instructions includes instructions for: selecting a new follicular unit harvesting or implanting site at which to perform the hair graft harvesting or implanting procedure based at least in part on the determined offset and a location of a previous procedure site; and instructing a tool to move to the selected new follicular unit harvesting or implanting site to perform the hair graft harvesting or implanting procedure. recording first locations of a plurality of fiducials (320, 405, 605) appearing in one or more images of the body surface; updating and recording updated locations of at least some of the plurality of the fiducials (320, 405, 605) in one or more updated images of the body surface; determining an offset of the updated locations of the at least some of the plurality of the fiducials (320, 405, 605) relative to their first locations; characterised in that the set of instructions includes instructions for: selecting a new follicular unit harvesting or implanting site at which to perform the hair graft harvesting or implanting procedure based at least in part on the determined offset and a location of a previous procedure site; and instructing a tool to move to the selected new follicular unit harvesting or implanting site to perform the hair graft harvesting or implanting procedure. selecting a new follicular unit harvesting or implanting site at which to perform the hair graft harvesting or implanting procedure based at least in part on the determined offset and a location of a previous procedure site; and instructing a tool to move to the selected new follicular unit harvesting or implanting site to perform the hair graft harvesting or implanting procedure.