Strains of the ground are of increasing importance in civil engineering for as projects get larger the strains they induce often exceed the natural strains. For the engineer to ensure the safety and stability of a structure and its surroundings he must be able to predict and, if need be, control the strains. Our approach is to measure the deformations in specific cases and to use the information to gain a better understanding of ground behaviour, to determine parameters of the ground to use in prediction and to check the safety and design of the project. It demands simple and sensitive instruments that can be used reliably under rigorous field conditions. Examples of recent studies are given.