 Monitoring rock displacements is important to understanding the behavior of a rock mass and to assessing its stability. The Global Positioning System (GPS) is a satellite-based positioning system developed in the USA; it was established as a navigation system and then as a method for long baseline surveys (e.g., Hoffman-Wellenhof et al. 2001; The Survey Advisory Board and the Public Land Survey Office for State of Washington Department of Natural Resources 2004; Misra and Enge 2006). GPS has the potential to monitor three-dimensional displacements over an extensive area with high accuracy. It began to be used for displacement monitoring in the mid-1980s in the fields of civil and mining engineering, and other related fields (e.g., Chrzanowski and Wells 1988; Burkholder 1988, 1989). Since then, practical applications have been performed by many researchers (e.g., Hudnut and Behr 1998; Gili et al. 2000; Malet et al. 2002; Kim et al. 2003; Taşçi 2008), and some guidelines have been published for displacement (deformation) monitoring (e.g., US Army Corps of Engineers 2002; Vermeer 2002; Bond 2004).