This part of ISO 9863 specifies a method for the determination of the thickness of geosynthetics at specified pressures and specified load plate areas or under specified point loads. It defines the pressures or the load at which the 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.