This part of ISO 7507 specifies a calibration procedure for application to tanks above 8 m in diameter with cylindrical courses that are substantially vertical. It provides a method for determining the volumetric quantity contained within a tank at gauged liquid levels. The measurements required to determine the radius are made either internally (Clause 10) or externally (Clause 11). The external method is applicable only to tanks that are free of insulation. This method is suitable for tanks tilted up to a 3 % deviation from the vertical provided that a correction is applied for the measured tilt as described in ISO 7507-1.