The number of rows and columns making up the grid and the relative distances are fixed in relation to the purposes of the control and the state of the surface (where the grid may have a smaller pitch). Given the geometric characteristics of a tank, the shell (planking) and the two bottoms are distinguished by it, regardless of the horizontal or vertical type. Assuming a horizontal orientation for it, the lattice ideally constructed on the entire surface appears as shown in fig. 4. Italsabi operates throughout the Italian territory with ISO9712 level II technicians qualified to carry out ultrasonic thickness measurement. At the end of the control activity, our ISO 9712 level II technician will issue a test report containing all the results of the surveys performed.