This part of ISO 4266 gives guidance on the accuracy, installation, calibration and verification of automatic level gauges (ALGs), both intrusive and non-intrusive, for measuring the level of petroleum and liquid petroleum products having a Reid vapour pressure less than 100 kPa, transported aboard marine vessels (i.e. tankers and barges). This part of ISO 4266 gives guidance for buyers and sellers who mutually agree to use marine ALGs for either fiscal and/or custody transfer applications. This part of ISO 4266 is not applicable to the measurement of level in refrigerated cargo tanks.