Some embodiments are directed to a target surface including one or more three-dimensional projections, each projection including a multiplicity of planar side surfaces, a stereoscopic camera operable to obtain images of the target surface, and a processing module operable to process images obtained by the stereoscopic camera of the target surface together with data identifying the position and orientation of the stereoscopic camera relative to a defined point in space to determine the positions relative to the defined point in space of the planar side surfaces defined by the at least one or more three-dimensional projections.
