Ground deformation monitoring at the open pit mine Kozmin has been conducted since 2008. The principles and results of the precise determination of the three dimensional displacements using GPS technology has been presented in this paper. In specific, establishment of the control network, patented technology of the field measurements, the strategy of GPS data post-processing, as well as the obtained displacements in the control network with their accuracy analysis have been presented. The research conducted with the developed technology indicates a high accuracy and reliability of the determined displacements of the controlled points.