Due in large part to the advent of GPS, geodesy has become an important discipline within the Earth sciences. It is practiced and taught at a growing number of universities and research institutions worldwide, and provides the underpinnings for geographical information and locational awareness in modern life and commerce. The main advantage of GPS geodesy is the ability to directly measure very precise static, kinematic‚ and dynamic positions and displacements with respect to a global reference frame. GPS geodesy attracted the attention of geophysicists in the early 1980s when the potential for significant advances in the understanding of tectonic motion, crustal deformation‚ and geodynamics became apparent. Since then – something that was certainly not anticipated by the pioneers of the GPS in the 1970s – it has been applied to investigations of natural and anthropogenic processes and hazards, including earthquakes, tsunamis, volcanoes, the cryosphere, extreme weather, sea level rise, climate change‚ and hydrology. Contributing to its success have been advances in technology and the development of a global GPS infrastructure consisting of thousands of continuous stations spanning nearly all of the tectonic plate boundaries and hundreds of global stations to provide precise orbits and access to a global reference frame. GPS as a measuring tool is complementary to other terrestrial, ocean, atmospheric‚ and spaceborne instrumentation including seismometers, synthetic aperture radars, GPS/acoustic methods, gravimeters, radiometers, and UAV and LiDAR imaging. This chapter provides a historical perspective of GPS geodesy through to its current practice.
