The Integration of Collocated GPS, VLBI and SLR Results

In recent years space geodetic techniques such as the Global Positioning System (GPS), Very Long Baseline Interferometry (VLBI), and Satellite Laser Ranging (SLR) have been collocated to address many applications in geoscience. While results from all these techniques are contaminated by various biases and errors, a commonmode signal has been found among the collocated results of GPS, VLBI and SLR. An adaptive filter based on the Least-Mean-Square algorithm is proposed to integrate these techniques, i.e. to extract this common-mode signal by inputting to the filter the GPS result as the primary sequence and VLBI and/or SLR results as the reference sequences. Numerical simulation indicates that the filter is a powerful signal decomposer, which can separate the primary input into coherentand incoherent-components relative to the reference input. Data from the Matera Station in Italy and the Wettzell Station in Germany have been used to test the algorithm. The derived commonmode signal has better repeatability than the individual results of GPS, VLBI and SLR.