Marcin Rajner

Ocean Tidal Loading from the Gravity Measurements at Jozefoslaw Observatory

Ocean Tidal Loading from the Gravity Measurements at Jozefoslaw Observatory Ocean tidal loading is important source of disturbances in precise gravity measurements. Nowadays gravimeters reached unprecedented relative accuracy and loading signal can be observed also at large distances from the oceans. In this paper theoretical calculations are compared with analysis made on the basis of observations collected in Jóozefoslaw Observatory during last three years with use of LCR-ET spring gravimeter. Long series of consisted data allowed for investigation in small subtle gravity signals. Subtracting body tides from tidal analysis results yields discrepancies of a few nm /s2 for main tidal constituents which are in good agreement with computed ocean loading using most recent ocean models.

Free core nutation period inferred from the gravity measurements at Józefosław

The Free Core Nutation (FCN) is an important eigenmode which affects both Earth rotation and body tide. The FCN parameters, the resonance period and the quality factor are important for understanding the dynamics of the Earth at nearly diurnal periods. Those parameters are usually estimated either from the Very Long Baseline Interferometry (VLBI) observations of nutation, or from the tidal gravity measurements. In this paper we investigate the determination of the FCN parameters from gravity records covering a period of more than three years, collected with the use of a LaCoste&Romberg Earth Tide no. 26 gravimeter, located at Józefosław observatory near Warsaw. From the resonant enhancements of gravimetric factors and phases of diurnal tidal gravity waves, we could infer the FCN period to be equal to 430 sidereal days. This result is in very good agreement with previous gravimetric and VLBI nutation results, confirming the discrepancy in the dynamic flattening of the outer liquid core from its theoretical value based on the hydrostatic equilibrium assumption. The estimated FCN quality factor (Q ≈ 1300) is considerably smaller than the VLBI nutation result, which confirms that the local gravity measurements are more sensitive than VLBI global analyses to site-dependent phenomena (such as atmospheric and indirect ocean tidal effects). We also investigated the importance of gravimetric corrections in the FCN analysis, including numerical tests and simulations. This allowed us to estimate the uncertainty of FCN parameters due to improper or incomplete set of environmental corrections. We took also into account the impact of gravimetric factor errors and tidal wave selection on estimated FCN parameters. We demonstrated that despite relatively noisy measurements due to unfavorable gravimeter location, we were able to obtain very good results in case when proper correction and tidal wave selection were applied.

Large-scale map and 3D modelling of the Henryk Arctowski Polish Antarctic Station

This paper presents survey measurements carried out during the 39th Polish Antarctic Expedition to the Henryk Arctowski Polish Antarctic Station in March 2015. The measurements were used to create a map on a 1:500 scale and for 3D modelling of the station buildings and vicinity. The paper also presents the geodetic control network established around the station. We discuss the issue of creating a digital elevation model for the station and its surroundings. The elevation models were generated using terrestrial laser scanning data integrated with Global Navigation Satellite System real time kinematic and tacheometric surveying. The accuracy of these models was estimated using height differences in relation to survey data. The mean height difference was 0.03 m and root mean square error was 0.05 m. Furthermore, an analysis of changes to the coastline was conducted using archival cartographic materials to assess the threat of Admiralty Bay to the station buildings. The results are important for continued scientific activity and safety at Arctowski Station, and may be useful for future research on King George Island.

Participation of employees and students of the Faculty of Geodesy and Cartography in polar research

Abstract This year the Faculty of Geodesy and Cartography, Warsaw University of Technology celebrates its 95th jubilee, which provides an opportunity to present the Faculty’s rich traditions in polar research. Employees and students of the faculty for almost 60 years have taken part in research expeditions to the polar circle. The article presents various studies typical of geodesy and cartography, as well as miscellany of possible measurement applications and geodetic techniques used to support interdisciplinary research. Wide range of geodetic techniques used in polar studies includes classic angular and linear surveys, photogrammetric techniques, gravimetric measurements, GNSS satellite techniques and satellite imaging. Those measurements were applied in glaciological, geological, geodynamic, botanical researches as well as in cartographic studies. Often they were used in activities aiming to ensure continuous functioning of Polish research stations on both hemispheres. This study is a short overview of thematic scope and selected research results conducted by our employees and students.

Geodetic and Geodynamic Studies at Department of Geodesy and Geodetic Astronomy Wut

Abstract The article presents current issues and research work conducted in the Department of Geodesy and Geodetic Astronomy at the Faculty of Geodesy and Cartography at Warsaw University of Technology. It contains the most important directions of research in the fields of physical geodesy, satellite measurement techniques, GNSS meteorology, geodynamic studies, electronic measurement techniques and terrain information systems.

Assessment of continental hydrosphere loading using GNSS measurements

Abstract Presented paper is dedicated to problems of deformation of the Earths crust as a response to the surface loading caused by continental waters. The aim of this study was to specify areas particularly vulnerable to studied deformation and to compare calculated and observed displacements. Information of the continental water volume was taken from the WaterGAP Global Hydrological Model. Calculated values of the deformations were verified with the results obtained with programs SPOTL and grat. Vertical deformations were almost 10 times higher than the deformation in the horizontal plane, for which reason later part of the paper focuses on the former. In order to check agreement of the calculated and observed deformation 23 stations of International GNSS Service (IGS) were selected and divided into three groups (inland, near the shoreline and islands). Before comparison outliers and discontinuities were removed from GNSS observations. Modelled and observed signals were centred. The analysed time series of the vertical displacements showed that only for the inland stations it is possible to effectively remove displacements caused by mass transfer in the hydrosphere. For stations located in the coastal regions or islands, it is necessary to consider additional movement effects resulting from indirect ocean tidal loading or atmosphere loading.