1.1. This Recommendation deals with ships' tanks used either for the transport and measurement of liquid products in bulk, or for the storage and measurement of the fuel oil used by the ship herself, that are subject to the control of the National Service of Legal Metrology. Note: Ships used expressly for the transport of liquid products in bulk are normally known as "tankers". 1.2. The measurement of the quantities of liquids transported by a tanker is a complex operation and is generally less accurate than the measurement of liquid quantities in land-based tanks (see Annex 1). 1.3. This Recommendation lays down general requirements for tankers containing quantities subject to legal measurement. It applies to measurements made in wholesale transactions. When, in a particular country, barges and lighters are used for the reception and delivery of part loads and for their measurement, the additional errors that may then occur shall be taken into consideration. It is possible, in such cases, to specify a "minimum measurable height" (usually 500 mm) or a "minimum measurable volume", which shall then be mentioned in the calibration certificate.