Abstract. The main purpose of this research was to acquire information about consistency of ZTD (zenith total delay) linear trends and seasonal components between two consecutive GPS reprocessing campaigns. The analysis concerned two sets of the ZTD time series which were estimated during EUREF (Reference Frame Sub-Commission for Europe) EPN (Permanent Network) reprocessing campaigns according to 2008 and 2015 MUT AC (Military University of Technology Analysis Centre) scenarios. Firstly, Lomb-Scargle periodograms were generated for 57 EPN stations to obtain a characterisation of oscillations occurring in the ZTD time series. Then, the values of seasonal components and linear trends were estimated using the LSE (least squares estimation) approach. The Mann-Kendall trend test was also carried out to verify the presence of linear long-term ZTD changes. Finally, differences in seasonal signals and linear trends between these two data sets were investigated. All these analyses were conducted for the ZTD time series of two lengths: a shortened 16-year series and a full 18-year one. In the case of spectral analysis, amplitudes of the annual and semi-annual periods were almost exactly the same for both reprocessing campaigns. Exceptions were found for only a few stations and they did not exceed 1 mm. The estimated trends were also similar. However, for the reprocessing performed in 2008, the trends values were usually higher. In general, shortening of the analysed time period by 2 years resulted in a decrease of the linear trends values of about 0.07 mm yr −1 . This was confirmed by analyses based on two data sets.
The GPS system can play an important role in activities related to the monitoring of climate. Long time series, coherent strategy, and very high quality of tropospheric parameter Zenith Tropospheric Delay (ZTD) estimated on the basis of GPS data analysis allows to investigate its usefulness for climate research as a direct GPS product. This paper presents results of analysis of 16-year time series derived from EUREF Permanent Network (EPN) reprocessing performed by the Military University of Technology. For 58 stations Lomb-Scargle periodograms were performed in order to obtain information about the oscillations in ZTD time series. Seasonal components and linear trend were estimated using Least Square Estimation (LSE) and Mann-Kendall trend test was used to confirm the presence of a linear trend designated by LSE method. In order to verify the impact of the length of time series on trend value, comparison between 16 and 18 years were performed.
The aim of this paper is to present the strategy of determination of the reference solution for the ASG-EUPOS (Active Geodetic Network -European Position Determination System) coordinate monitoring system. ASG-EUPOS is a network of permanent GNSS (Global Navigation Satellite System) stations controlled by the Polish Head Office of Geodesy and Cartography (HOGC), which main role is to realize the ETRS89 (European Terrestrial Reference System) in the territory of Poland. The Centre of Applied Geomatics (CAG) of the Military University of Technology (MUT) performs a control processing of the network and it is the leader of the ASG+ (the supporting modules for ASG-EUPOS system real-time services) project within which the coordinate monitoring system was developed. The coordinate monitoring is aimed to assess the actual performance of the GNSS stations and the reliability of the system and its services. The Polish realization of the ETRS89 is also controlled, where the deviation of the actual coordinates from the reference values are monitored. Furthermore, the monitoring enables the analysis of factors that degrade the individual GNSS stations and assess the solution stability which has impact on the quality of the determined geodynamic parameters. The reference solutions (coordinates and their changes over time) were determined according to the recommendations of the IAG sub-commission for the European Reference Frame concerning densification of EUREF. The paper presents the determination of the reference cumulative solution and the results of the processing of a few years long series of GNSS observations. The analysis are performed by the Bernese 5.0 and CATREF software. The results consists of daily and subdaily ASG-EUPOS reference solutions. They are also considered as input data for geodynamic studies to determine the horizontal and vertical velocity fields. Estimation of the individual station velocities is of crucial importance for the ETRF (European Terrestrial Reference Frame) reference frame maintenance to assess the compatibility of the current station position with its catalogue (reference) value and apply coordinate correction if necessary.
The paper presents the method of GNSS (Global Navigation satellite System) permanent stations control by the monitoring of local ties between GNSS and SLR (Satellite Laser Ranging) stations. Co-locations are defined as two or more instruments occupying very close locations, which are very precisely surveyed by ground measurements in all three dimensions. The vector determined by classical or satellite methods is called a local tie. Every change of stations position obviously results in change of local tie value. The comparison of two independent stations' coordinates enable to distinguish the real movement of one of the stations, potential processing errors and equipment malfunction. The analysis were based on the data from several globally distributed GNSS-SLR sites. The data gathered between 1996-2012 by these two techniques were processed using coherent strategies (the same models and parameters were used). Monthly orbital arcs for laser observations were created basing on solutions from several SLR stations with the best solutions quality and the highest amount of observations. For GNSS stations coordinates determination about 130 sites belonging to the IGS (International GNSS Service) were selected: 30 with local ties to SLR sites and others basing on their geolocalization and solutions time series analysis. The GNSS and SLR station coordinates were expressed in ITRF2008 for the epoch of 2005. The GNSS solutions were reduced to the SLR markers positions using local ties values and then expressed in topocentric frame NEU for better interpretation. The analysis of differences between SLR and GNSS NEU coordinates proved that mutual control of two techniques can be helpful in detection of problems at specific GNSS stations like e.g. equipment failure or improper GNSS antenna's calibration. Comparisons of different techniques results enable to distinguish stations specific causes of coordinates discontinuities and phenomena with wider range like earthquakes. In case of temporal disturbances the proper actions can be taken, but the permanent change of the coordinates force the necessary of another local tie determination, because of the importance of inter technique connection for global reference frame construction.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.