1. A method for determining, with a digital image processing system, the position of a rectangular data matrix within a substantially circular region, the data matrix being positioned within a predetermined portion of a circular crown region, the circular crown region being defined by an inner circle and by an outer circle having the center substantially coincident with the center of the substantially circular region, the predetermined portion of the circular crown region being identified by at least one visual mark, the method comprising: acquiring a digital representation of the substantially circular region; determining the center of the substantially circular region; building a detecting ring area including the inner and the outer circles; radially scanning the detecting ring area to identify the at least one visual mark indicative of the start position of the predetermined portion of the circular crown region; and starting from the start position, scanning the detecting ring area to determine the position of the border of the data matrix.