1. Department of Mining Exploitation and Prospecting, Area of Cartographic, Geodesic and Photogrammetric Engineering, University of Oviedo, Mieres, Asturias, Spain
2. Instituto de Productos Lácteos de Asturias (IPLA-CSIC), Villaviciosa, Asturias, Spain
3. Department of Mining Technology, Topography and Structures, Universidad de León, Ponferrada (León), Spain