This Standard applies to the measurement of displacements along a line by means of extensometers carried out for geotechnical monitoring. It is to be applied in conjunction with EN ISO 22474-1. Specifically, this Standard applies to investigating soils and rocks; checking geotechnical design values in connection with the Observational Design method; deriving geotechnical design values (e.g. pile load test; trial tunnelling); evaluating stability ahead of, during or after construction (e.g. natural slopes, slope cuts, embankments, excavation walls, foundations, dams, refuse dumps, tunnels).