This standard provides guidance on the installation, commissioning, maintenance, validation, and calibration of hydrostatic tank gauging systems for the direct measurement of static mass in petroleum storage tanks. This standard is applicable to hydrostatic tank gauging systems that use pressure sensors with one port open to the atmosphere. This standard is applicable to the use of hydrostatic tank gauging on vertical cylindrical atmospheric storage tanks with either fixed or floating roofs. This standard is not applicable to the use of hydrostatic tank gauging on pressurized tanks. Safety and material compatibility precautions should be taken when using HTG equipment. Manufacturer's recommendations on the use and installation of the equipment should be followed. Users should comply with all applicable codes and regulations, API standards, and the National Electric Code.