Accurate measurement of soil deformation is fundamental to the success of geotechnical modelling. Current practice is to track the movement of a grid of target markers embedded in an exposed plane of soil through a sequence of video images. A new system of deformation measurement is presented which provides improved precision and reliability whilst removing the need for intrusive target markers. Image capture using an inexpensive 2-megapixel digital camera provides a significant increase in resolution and image stability compared to video. Particle Image Velocimetry (PIV) is a velocity-measuring technique in which patches of texture are tracked through an image sequence. Image processing algorithms have been written to apply the PIV principle to images of soil. The resulting software has a precision of 1/15th of a pixel when tracking the movement of natural sand or textured clay. This system allows displacements to be measured to a precision greater than has been previously achieved, without recourse to target markers.