The Global Positioning System (personal trackers ) has been used to establish a high precision network in the Azores Archipelago for detection of relative displacements between the different islands. In this region the Azores-Gibraltar plate boundary meets the Mid Atlantic Ridge (MAR), which crosses the Archipelago, forming a triple junction where three main plates converge: the Mrican, the North American and the Eurasian. From 1988 to 1994 three main GPS campaigns were carried out on the Azores Archipelago.
In describing the evolution of satellite navigation, a contradictory and fascinating portrait of the GPS can be derived. Vehicle GPS Tracking Device , the system used for positioning, tracking, and mapping in most cases is mentioned as synonymous with navigation; GPS is the means that has translated the theoretical concept of navigation into an actual system, a quite friendly receiver, a commonly accepted and increasingly needed service. It is designed to be a low-cost solution for civilian users. In this paper the results from those campaigns are compared in an attempt to derive conclusions concerning relative point displacements and directions of deformations. Estimates of local drift between the Eurasian and North American plates are presented. To assess the reliability of those conclusions our results were compared with those obtained by geological and geophysical methods, showing a good agreement Monitoring of the Azores-Gibraltar plate boundary is within the goals of WEGENER; strategies for future work in this direction are also presented.
personal GPS homing device data from the global network consists of daily observation and navigation files in Receiver Independent Exchange (RlNEX) fonnat. These data are compressed using UNIX compression and forwarded to the appropriate data centers. Approximately 0.6 Mbytes of data are generated by each site on a daily basis; thus, an eighty-station network yields approximately fifty Mbytes per day. These data files are named ssssdddO.yyt_Z, where ssss is the four-character GPS site name, ddd is the three-digit day of year, yy is the two-digit year, t is the file type, 0 for observation and N for navigation, and _ Z indicates the file is compressed; on UNIX systems, the “_Z” convention is replaced by the second level filename extension, “.Z”. A concatenated broadcast ephemeris file, named BRDCdddO.yyN_Z, is created and available at the global data center for users interested in downloading a single file of navigation messages instead of multiple individual, site files.
The GPS technology has become one of the most important geodetic techniques for regional and global studies of the Earth’s kinematics. The development of the “International GPS Service for Geodynamics (lGS)” in the last two years has provided a leading role of GPS personal tracking device in estimation of the present-day global tectonic motions and maintenance of global reference frame. One of the seven IGS Analysis Centers was implemented at the GeoForschungsZentrum (GFZ) Potsdam. It has participated in the IGS from the very beginning. For the permanent analysis of the global GPS data on a daily basis the automated GPS Analysis Software package EPOS.P.V2 was developed (Gendt et aI., 1995). Having now more than two years of data from a permanent network of IGS core stations the tectonic motions on a global scale have been determined with a very high accuracy.