This part of ISO 9863-1 specifies a method for the determination of the thickness of geosynthetics at specified pressures and defines the pressure at which the nominal thickness is determined. The test results are intended for identification purposes and for use in technical data sheets and/or as part of other test methods, e.g. tests of hydraulic properties. The method is applicable to all geosynthetics. NOTE 1 Normally the thickness of geosynthetics is determined by measuring one layer of the product. When two or more layers are used on top of each other in a design, the test may be made in accordance with this standard with the agreed number of layers instead of one. NOTE 2 When testing structured geosynthetics, care should be taken to ensure that the results are meaningful for the particular product.