The Potsdam Open Source Radio Interferometry Tool (PORT) is the very long baseline interferometry (VLBI) analysis software developed and maintained at the GFZ German Research Centre for Geosciences. Chiefly, PORT is tasked with the timely processing of VLBI sessions and post-processing activities supporting the generation of celestial and terrestrial reference frames. In addition, it serves as a framework for research and development within the GFZ’s VLBI working group and is part of the tool set employed in educating young researchers. Starting out from VLBI group delays, PORT estimates station and radio sources positions, as well as Earth orientation parameters, tropospheric parameters, and station clock offsets and drifts. The estimation procedures take into account all the necessary data analysis models that were agreed on for contributing to the ITRF2020 processing activities. The PORT code base is implemented in the MATLAB ® and Python programming languages. It is licensed under the terms of the GNU General Public License and available for download at GFZ’s Git server https://git.gfz-potsdam.de/vlbi-data-analysis/port.

Geodetic Networks designed as Deformation Networks or Continuous Networks are observed in different epochs/ sessions and evaluated as a function of time. Those can be design as global GNSS networks for aim monitoring active tectonic movements or as regional densification geodetic and deformation networks for monitoring local earthquakes and surface movements. The areas covered geodetic networks are assumed as any surface on ellipsoid or sphere. Characteristics of surfaces are analyzed with Geometric Strain Models using deformation data on surface points. In this case, effect rates on geodetic network area are determined from local surface movements or regional active earthquakes and interpreted as experimental. On the other hand, undetermined outliers by model hypothesis test affect coordinateunknowns separately. Outliers cause deformations in certain magnitude on networks points. Therefore, network points strain in different rates and directions. Query of maximum affects caused by these strain rates is a referenced reliability method called "Robustness Analysis in Geodetic Networks". Mentioned strain rates are modelled by various estimation methods. Thus, deformation results could be interpreted together by the obtained strain components and deformation vector. In this paper, possible strain components belonging to network points are determined with methods of L1 Norm, Least Median Squares (LMS) and Least Squares Estimation (LSE). These estimation methods are tested on KOUSAGA (Kocaeli University Permanent GPS Network). Strain components are estimated by use polyhedrons covered by network points. Obtained results are compared and analyzed according to weakness and strengths of proposed estimation methods.

ÖzYerkabuğu hareketleri doğal gaz, ulaşım, iletişim enerji vb yasamsal alt yapı sistemlerini olumsuz yönde etkilerler. Bu nedenle ekonomik değeri yüksek olan, kamu hizmetleri kapsamındaki yaşamsal altyapı sistemleri jeodezik kontrol noktaları/ağları yardımıyla düzenli aralıklarla izlenmeleri gerekli ve zorunludur.Bu çalışmada, bilimsel amaçlı bir araştırma projesi kapsamında izlenmekte olan Kocaeli İZDOGAP Sıklaştırma GPS Ağı, gerçek bir yaşamsal altyapı izleme sistemi olarak seçilmiştir. Belli aralıklarla izlenmekte olan İZDOGAP GPS Ağı'ndan elde edilen konum ve hız bilgileri kullanılarak; bölgede olası yıllık yer kabuğu hareketlerini algılayabilme düzeyi ve bu ağı temsil eden bölgesel gerinim parametreleri irdelenmektedir. Elde edilen deneysel bulgular matematik/istatistik modellerle yorumlanmakta, sonuçlar karşılaştırmalı olarak sergilenmektedir.Anahtar Kelimeler: Algılayabilirlik, Hız Alanı, Gerinim, Jeodezik Ağlar. Monitoring of Lifeline Systems with Densification GPS Networks and Interpretation of deformations: Application of Kocaeli IZDOGAP GPS Network AbstractEarth crustal movements affect negatively Lifeline systems such as natural gas, electrical power, communication and transportation facilities. Therefore Lifeline systems with high economic value must be monitored temporal with geodetic networks.In this study, the Kocaeli İZDOGAP Densification GPS Network monitored within the scope of a scientific research project is selected as a real lifeline monitoring system. The sensitivity level of possible annual crustal movements in the region and regional strain parameters of the network are analysed by using position and velocity values of IZDOGAP GPS Network. The experimental findings obtained are interpreted with mathematical / statistical models and the results are presented comparatively.

Very Long Baseline Interferometry (VLBI) plays an indispensable role in the realization of global terrestrial and celestial reference frames and in the determination of the full set of the Earth Orientation Parameters (EOP). The main goal of this research is to assess the quality of the VLBI observations based on the sensitivity and robustness criteria. Sensitivity is defined as the minimum displacement value that can be detected in coordinate unknowns. Robustness describes the deformation strength induced by the maximum undetectable errors with the internal reliability analysis. The location of a VLBI station and the total weights of the observations at the station are most important for the sensitivity analysis. Furthermore, the total observation number of a radio source and the quality of the observations are important for the sensitivity levels of the radio sources. According to the robustness analysis of station coordinates, the worst robustness values are caused by atmospheric delay effects with high temporal and spatial variability. During CONT14, it is determined that FORTLEZA, WESTFORD, and TSUKUB32 have robustness values changing between 0.8 and 1.3 mm, which are significantly worse in comparison to the other stations. The radio sources 0506-612, NRAO150, and 3C345 have worse sensitivity levels compared to other radio sources. It can be concluded that the sensitivity and robustness analysis are reliable measures to obtain high accuracy VLBI solutions.