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Abstract

The paper presents national report of Poland for IAG on positioning and applications. The selected research presented was carried out at leading Polish research institutions and concern precise multi-GNSS satellite positioning – relative and absolute – and also GNSS-based ionosphere and troposphere modelling and studies. The research resulted in noticeable advancements in these subjects confirmed by the development of new algorithms and methods. New and improved methods of precise GNSS positioning were developed, and also GNSS metrology was studied. New advanced troposphere models were presented and tested. In particular, these models allowed testing IPW variability on regional and global scales. Also, new regional ionosphere monitoring web-based services were developed and launched.
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Abstract

This review paper presents research results on geodetic positioning and applications carried out in Poland, and related to the activities of the International Association of Geodesy (IAG) Commission 4 “Positioning and Applications” and its working groups. It also constitutes the chapter 4 of the national report of Poland for the International Union of Geodesy and Geodynamics (IUGG) covering the period of 2015-2018. The paper presents selected research, reviewed and summarized here, that were carried out at leading Polish research institutions, and is concerned with the precise multi-GNSS (Global Navigation Satellite Systems) satellite positioning and also GNSS-based ionosphere and troposphere modelling and studies. The research, primarily carried out within working groups of the IAG Commission 4, resulted in important advancements that were published in leading scientific journals. During the review period, Polish research groups carried out studies on multi-GNSS functional positioning models for both relative and absolute solutions, stochastic positioning models, new carrier phase integer ambiguity resolution methods, inter system bias calibration, high-rate GNSS applications, monitoring terrestrial reference frames with GNSS, assessment of the real-time precise satellite orbits and clocks, advances in troposphere and ionosphere GNSS remote sensing methods and models, and also their applications to weather, space weather and climate studies.
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Abstract

The accuracy and reliability of Kalman filter are easily affected by the gross errors in observations. Although robust Kalman filter based on equivalent weight function models can reduce the impact of gross errors on filtering results, the conventional equivalent weight function models are more suitable for the observations with the same noise level. For Precise Point Positioning (PPP) with multiple types of observations that have different measuring accuracy and noise levels, the filtering results obtained with conventional robust equivalent weight function models are not the best ones. For this problem, a classification robust equivalent weight function model based on the t-inspection statistics is proposed, which has better performance than the conventional equivalent weight function models in the case of no more than one gross error in a certain type of observations. However, in the case of multiple gross errors in a certain type of observations, the performance of the conventional robust Kalman filter based on the two kinds of equivalent weight function models are barely satisfactory due to the interaction between gross errors. To address this problem, an improved classification robust Kalman filtering method is further proposed in this paper. To verify and evaluate the performance of the proposed method, simulation tests were carried out based on the GPS/BDS data and their results were compared with those obtained with the conventional robust Kalman filtering method. The results show that the improved classification robust Kalman filtering method can effectively reduce the impact of multiple gross errors on the positioning results and significantly improve the positioning accuracy and reliability of PPP.
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Abstract

Technical development, new applications and requests for increased accuracy in georeferencing are setting new demands for accuracy and reliability of reference frames. Due to crustal deformations and local movements of benchmarks, a static reference network deteriorates with time, thus eventually requiring update of the whole system. Technically, renewal of a reference frame is straightforward and should be done whenever enough new data or updated information exist to get an improvement in accuracy. An example is the International Terrestrial Reference Frame, ITRF, which is renewed regularly. The situation is more complicated with national reference frames which may have been given a legal status, and parameters defined by the national legislation. Even without that, renewal and implementation of such a frame is a multi-million euro project taking years to complete. Crustal deformations and movements deteriorate static reference frames (defined by fixed/static coordinates of benchmarks) with time. Eventually, distortions in a static reference frame will become bigger than the uncertainties of GNSS measurements, thus deteriorating the obtainable accuracy of the measurement technique. Instead of a static reference frame, one can use semi-kinematic or kinematic approach where either the transformation from global to the national reference frame or the coordinates of reference frame benchmarks are time-dependent. In this paper we give a short overview of the topic, and discuss on technical issues and future aspects of the reference frames in the viewpoint of National Mapping and Cadastre Authorities (NMA) with an example on the national strategy in Finland.
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