1. A method for the automatic location of particular zones on a surface, especially of points to be machined on the surface of a workpiece by an automatic machine which operates point by point, wherein said method consists: in giving said particular zones a distinctive appearance with respect to the region surrounding said zones on said surface, especially an appearance which is transparent at the center of an opaque pastille, in automatically scanning the surface in a system of two coordinates, especially perpendicular rectilinear coordinates, by means of a reader comprising at least one detecting element which is responsive to said distinctive appearance, in establishing by means of electrical signals delivered by the reader a primary image coded in binary notation in which two different states represent respectively the presence and absence of said distinctive appearance at each point of the surface which is scanned by the detector, in processing said primary image in coded form in order to erase in successive points from the edges thereof in accordance with said system of coordinates all the states which are representative of the presence of the distinctive appearance encountered before a zone of absence of said distinctive appearance in order to obtain a clear image in coded form only of those points which have said distinctive appearance and are separated from the edges of the image by one point or a plurality of successive points which do not have said distinctive appearance, in determining the coordinates of at least a certain number of the points having a distinctive appearance which remain on said clear image.