Abstract
The availability of a GPS network of 10-20 km mean size, provides good topographical support for the measurement of ground displacements, even at a local scale such as a landslide. In particular, a series of multitemporal kinematic or rapid-static GPS acquisitions of a landslide allows a good characterization of its displacements if the measurements are referred to a GPS reference network. Nevertheless, a wider network formed by stations located at long distances, for example at several tens of kilometers, characterized by large spacing, can lead to results affected by high noise, degrading the accuracy of final point positions. In order to obtain an adequate GPS reference network, some virtual reference stations (VRSs) can be introduced, even if a network refinement based on VRS cannot reach the same accuracy of a real local network. Some experiments, including measurements on a real landslide, have been performed in order to evaluate the performance of this technique. The results point out that the standard deviation of the obtained solutions is about two or three times larger than those which can be reached using a real local network.
Highlights
The global positioning system (GPS), used in static and kinematic mode, provides highly accurate estimations of measured point coordinates and is widely applied for the Despite the fact that higher precision is achieved by static GPS applications, GPS kinematic surveying (Rizos and Han, 1998) can al-A
The Assogeo reference network consists of several permanent stations homogeneously distributed in the Emilia-Romagna and surrounding regions, allowing the generation of stable synthetic RINEX files at known and chosen coordinate points
A virtual station is created at a defined coordinate point using GPS data of surrounding permanent stations; the closer these stations are, the lower the noise of virtual station data obtained from interpolation/extrapolation procedures is
Summary
Despite the fact that higher precision is achieved by static GPS applications, GPS kinematic surveying (Rizos and Han, 1998) can al-. Casula so provide highly accurate trajectories, produced by a rover station which moves throughout measurement sessions This technique can be useful either to define the correct position of photogrammetric camera installed on aircraft platforms (Beutler et al, 1995; Achilli et al, 1997; Baldi et al, 2000), or to acquire a large number of points distributed on a physical surface when fast and accurate monitoring is required. The. VRS for GPS surveying: experiments and applications work is based on three key points to validate VRS methodology for monitoring proposal: i) investigation of possible systematic effects in the estimation of point coordinates; ii) test of the solution reliability and internal accuracy; iii) definition of a methodology useful in providing solution correctness during kinematic continuous surveying for topographic surface acquisition and modeling
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