Analysis and research results of GNSS data representativeness in estimation of modern horizontal motion of the earth’s surface (on the example of Europe’s territory)
Received: September 15, 2017
Lviv Polytechnic National University
Department of Geodesy and Cartography, National University of Water and Environmental Engineering
National University of Water and Environmental Engineering

Aim. This article analyses the modern usage of GNSS data for solving problems in geodynamics and examines the level of data suitability for estimation of regional motion and deformations of the Earth’s surface according to their accuracy and the overall time of observation during which the representative estimation results can be provided. Method. This research was prompted by the following factors: absence of clearly established motion parameters of lithospheric plates; different strategies in processing observations and related software; unregulated minimum duration of observations; the need to increase the density of the area coverage; the need to use numerous stations for specification of tectonic models, deformation analysis, area zoning, and identification of anomalous zones of potentially dangerous geological processes. As input data, we chose three public bases of time coordinate series of stations within the Eurasian plate in Europe that are in the SOPAC archive: SIO database, formed as a result of processed observations in GAMIT-GLOBK (177 stations), and two JPL databases (204 stations) where coordinate series are obtained by processing observations using GIPSY-OASIS and combined QOCA-solution. Subject to empirical investigation for each database were coordinate series during the period 1.01.2005-1.01.2015 with a one month sampling interval. The experiment aimed at determining such integrated motion parameters of the surface under study like the weighted arithmetic linear offsets, vector length and direction, and velocity. These parameters are computed for all stations after their culling according to two formal representativeness criteria: 1) absolute values of stations offsets are greater than their average squared errors; 2) absolute values of an offset are greater than their marginal errors. According to these criteria, we determined stations that were culled most often and, thus, needed to thoroughly and individually analyzed during their usage for the purposes of geodynamics. Results. The experiment results showed that the minimal duration of observations is not constant and must be determined for each set of empirical data. According to the most optimistic estimates, the millimeter accuracy of motion parameters computation can be achieved after more than 2.5 years observation and usage of coordinate time series of the JPL (QOCA) database. This period is achieved using both criteria for culling of the observation period of 2005-2008 that approximately fits the limits of the official ITRF version. The centimeter accuracy under the same conditions can be achieved after more than 0.8 of a year. For the entire 10 year research period, the specified periods are more than doubled. The only explanation for such considerable differences is that they are the consequence of the motion and unadjusted position of the origin of the ITRS. The scientific novelty and practical significance. The obtained results indicate that there is a need to introduce a modern ITRF and to adjust the position of the origin more frequently. If the specified minimal periods are adhered to, the culling according to the marginal criterion is inappropriate because as a result many stations are discarded. The experiment results proved the advantages of QOCA solutions in terms of usage of the obtained coordinate time series comparing to GIPSY-OASIS and GAMIT-GLOBK.

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