Abstract: Method for the correlation of three dimensional measurements obtained by at least one first (1) and one second (2) image capturing unit. The method comprises, for the calibration phase, the steps of: producing a calibrating ball (4) movably and rotatably mounted about an axis (7), successively and rotatingly shifting the calibrating ball (4) into the measuring positions which are visible to the acquisition units; measuring, for each of the measuring positions, the spherical cap seen by each of the image capturing units; determining, for each of the measuring positions, the center of the calibrating ball, to express the same reference frame in the first and second reference marks viewed by the first and second image capturing units respectively; calculating the matrix of the passage from the first reference mark to the second reference mark to correlate the measurements between the first and second optical image capturing units.