The Global Positioning System: A multipurpose tool

Abstract

The Global Positioning System (GPS) is arguably the most versatile navigation, surveying, and geodetic tool ever devised. Some of its diverse applications include: (1) terrestrial, marine, and air navigation; (2) land surveying, cadastral mapping, and GIS support; and (3) geodynamic research into such topics as plate motion, tectonism, and volcanism. Although a relative newcomer to volcanology, GPS has quickly carved a niche for itself among mainstream volcano-monitoring techniques. Unlike most other geodetic techniques, GPS measures not just a single parameter pertaining to the relative positions of two points (e.g., height difference, line-length, or bearing), but rather the full 3-D position of each point in an absolute reference frame.1 For the first time, a single technique can be used to monitor 3-D surface displacements remotely and continuously with millimeter accuracy.