The completion of this thesis was possible thanks to the contributions of four organizations and many persons. The ITC Faculty of the University of Twente, Fomicruz S.E., Cerro Vanguardia S.A., and Cerro Cazador S.A. provided the infrastructure, equipment, data, and financial and logistical support necessary for this research. I sincerely thank my promoter, Prof. dr. Freek van der Meer, for his always helpful advice, his knowledgeable scientific contributions, and his confidence that I would complete my PhD. I am particularly grateful to my co-promoter, Dr. Frank van Ruitenbeek, for his guidance and continuous contributions, suggestions and meetings either in person or remote, but also for his friendship and patience. I also thank Professor Martin Hale for his help and advice during the early stages of my PhD research.