This part of ISO 25178 defnes Type S1 and Type S2 software measurement standards (etalons) for verifying the software of measuring instruments. It also defnes the fle format of Type S1 software measurement standards for the calibration of instruments for the measurement of surface texture by the areal method as defned in the areal surface texture chain of standards, chain link 6.NOTE Throughout this part of ISO 25178, the term “softgauge” is used as a substitute for “software measurement standard Type S1”.