Sorry I put in a 1 where their should have been a zero *blush*

We use accurate values of local G as we are calibrating pressure controllers using dead weight testers (AKA piston guages). We work to an accuracy of 0.0015% when we use the piston guage to calibrate a device of 0.01%. We use mass to correct a pressure measuring device that has an electrical output, therefore the mass has to be corrected.

If you use hydrostatic level sensors then you must also correct when calibrating as the pressure is generated by the column of liquid acting on the electrical sensor and that column unlike gas has a mass.

Makes a difference when measuring the level of oil or gasolene when measuring tank levels in terms of total tank contents.

Local G in China varies by as much as 2% north to south.