This Standard specifies six methods for the determination of thickness of material based on the use of ultrasonic pulse-echo principles where scanning and reflecting surfaces are substantially parallel. The methods are as follows:(a) Single spot-single measurement (SS).(b) Single spot-double measurement (SD).(c) Multiple spot measurements (MS).(d) Close grid survey method (CG).(e) Open grid method (OG).(f) Scanning runs (SR).(g) Complete coverage method (CC).NOTES: 1 Appendix A provides guidelines on information to be provided to the manufacturer at the time of enquiry.2 Factors affecting the results and order of accuracy achieved are given in Appendix D.