[en] Rock reliefs are used for assessing joint rock coefficients that serve in geotechnical engineering for computing shear strength of rock joints. The three-dimensional reliefs of small rock joints amounting to several centimetres may be digitally reconstructed in laboratories but large joints whose sizes reach several meters have to be reconstructed in terrains and require a specially adapted technique for three-dimensional reconstruction. This contribution describes one of the devices capable of performing digital reconstructions in terrains. This device has been developed in our laboratory on the basis of affordable components. (paper)