9.8 m/s^2 need not be assumed. As long as you have a calibration standard, any scale can be calibrated correctly in any gravitational field. If you care about

9.8 m/s^2 need not be assumed. As long as you have a calibration standard, any scale can be calibrated correctly in any gravitational field. If you care about absolute masses at the ~percent scale or better, calibration is requisite.