With remote transmitters being so good, are local level gauges still necessary?

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Definition of local instrument: An instrument installed near the object being measured or controlled, usually outdoors, without a transmitter and without any remote transmission signal. Such as pressure gauges, glass plate level gauges, bimetallic thermometers, etc. With the development of remote transmitters, local level gauges are increasingly being overlooked and even considered unnecessary. Clause 5.3.1 of SH 3136 \"Code for Safe Design of Spherical Storage Tanks for Liquefied Hydrocarbons\" requires that spherical tanks for liquefied hydrocarbons be equipped with remote and local level gauges, and this is a mandatory requirement ； Article 6.3.1 of SH/T 3007-2014 \"Design Code for Tank Areas in Petrochemical Storage and Transportation Systems\" stipulates that pressure tanks shall be equipped with local level gauges. So what is the function of an in-situ level gauge? Imagine a scenario where there are two remote-level gauges installed on a pressure tank in a production facility, and the readings from these two gauges differ significantly; it is necessary to calibrate the instruments. Without a local magnetic float level gauge available as a reference, one would be at a loss. This is perhaps the most direct function of local instruments. Generally, remote measuring instruments are calibrated using two-point calibration; without an on-site level gauge, it is simply impossible to carry out calibration for pressure tanks. Whether it is a radar level gauge or a magnetostrictive level gauge, calibration is required before they can be used. It’s fine for storage tanks at atmospheric pressure, as their height can be measured; but what can be used as a reference for pressure tanks? Furthermore, in the event of a power outage, if there is no local level gauge, how can one know the liquid level in the tank? For companies with standardized management practices, it is required that inspection personnel carrying out outdoor inspections use walkie-talkies to verify the liquid level with the control room every two hours or so. By comparing the readings from the local level gauges with those displayed in the control room, not only is the accuracy of the liquid level ensured, but information regarding the safety of the inspection personnel is also transmitted to the control room. Such a crucial and fundamental aspect is not given enough attention in some places. Regarding the requirement in the \"Design Code for Automation Systems of Petrochemical Tank Farms\" SH/T 3184 that storage tanks with a volume greater than 100 cubic meters should be equipped with on-tank indicators, this is also a requirement of a mandatory nature; it is a standard of a recommended nature. Additionally, I am quite in agreement with the requirement in Article 5.5 of GB 17681 \"Requirements for Safety Monitoring and Early Warning Systems in Flammable and Explosive Tank Areas\", which stipulates that a storage tank should be equipped with level gauges based on different measurement principles. Technically, no one holds absolute authority; without carrying out instrument maintenance and staying on site throughout the year, it is impossible to experience the various indications errors in instruments and equipment caused by changes in processes, conditions, or equipment. Without being on site, all theoretical knowledge remains just theoretical talk. However, if an on-site level gauge is installed, it also differs from level gauges based on other measurement principles.