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1

Expanding seismic surface waves measurements towards low periods with gravity measurements

Wilde-Piórko M., Dykowski P., Polkowski M., Olszak T., Grad M., Kryński J., Sękowski M., Krankowski A., Rajner M.

Geoinformation Issues

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2017

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Vol. 9, no. 1(9)

5--13

EN

Seismic events in gravity measurements are considered as disturbances and are usually removed from the records. However, the physical properties of tidal gravimetric instruments allow researchers to record seismic surface waves of very long periods. In the case of a superconducting gravimeter, periods of even up to 400 s can be determined. Simultaneous seismic and gravity records at the same locations allow the study of a wider response for incoming seismic waves by using two quite different instruments. For test purposes 4 seismometer-gravimeter pairs were temporarily deployed in Poland at three locations: Borowa Gora Geodetic-Geophysical Observatory (BG), Jozefoslaw Astro-Geodetic Observatory (JO), and Lamkowko Satellite Observatory (LA). During the test period from December 2016 to May 2017 several large teleseismic events were observed with well-formed surface waves. Group velocity dispersion curves for long surface waves, as well as periods of free oscillations are presented for selected events. The correlation of a broadband seismometer signal with different types of gravimetric sensors signals gives the opportunity to analyse gravimeter noise components, in the instrumental and micro-seismic domains.

PL

Zjawiska sejsmiczne w pomiarach grawimetrycznych są traktowane jako zakłócenia i zwykle ich efekty są usuwane z zapisów grawimetrycznych. Jednakże, grawimetry dzięki swojej konstrukcji umożliwiają rejestrację sejsmicznych fal powierzchniowych o bardzo długich okresach. W przypadku grawimetru nadprzewodnikowego, możliwe jest zaobserwowanie fal powierzchniowych, generowanych przez trzęsienia ziemi, o okresach nawet do 400 s. Przeprowadzenie równoczesnych rejestracji sejsmicznych i grawimetrycznych instrumentami zlokalizowanymi w tym samym miejscu, powinno umożliwić przeanalizowanie szerszego zakresu częstości sygnału sejsmicznego niż w przypadku użycia tylko jednego typu instrumentu. W celu sprawdzenia prawdziwości powyższego stwierdzenia, 4 pary instrumentów: sejsmometrów i grawimetrów zostały zainstalowane w Polsce w trzech lokalizacjach, w Obserwatorium Geodezyjno-Geofizycznym Borowa Góra (BG), Obserwatorium Astronomiczno-Geodezyjnym Józefosław (JO) oraz Obserwatorium Satelitarnym Lamkówko (LA). W czasie projektu pilotażowego, trwającego od grudnia 2016 do maja 2017 roku, zarejestrowano kilka dużych trzęsień ziemi z dobrze wykształconymi falami powierzchniowymi. W pracy zaprezentowano krzywe dyspersji grupowych prędkości fal powierzchniowych, jak również okresy oscylacji swobodnych dla wybranych zjawisk. Korelacja szerokopasmowego sygnału sejsmicznego z sygnałem zarejestrowanym przez różnego typu grawimetry umożliwi analizę szumu grawimetrycznego w zakresie częstości pływowych instrumentów, jak i w zakresie mikrosejsmicznym.

2

Participation of Employees and Students of the Faculty of Geodesy and Cartography in Polar Research

Pasik M., Adamek A., Rajner M., Kurczyński Z., Pachuta A., Woźniak M., Bylina P., Próchniewicz D.

Reports on Geodesy and Geoinformatics

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2016

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Vol. 100

235--252

EN

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.

3

Geodetic and geodynamic studies at Department of Geodesy and Geodetic Astronomy WUT

Brzeziński A., Barlik M., Andrasik E., Izdebski W., Kruczyk M., Liwosz T., Olszak T., Pachuta A., Pieniak M., Próchniewicz D., Rajner M., Szpunar R., Tercjak M., Walo J.

Reports on Geodesy and Geoinformatics

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2016

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Vol. 100

165--200

EN

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.

4

Assessment of continental hydrosphere loading using GNSS measurements

Zygmunt M., Rajner M., Liwosz T.

Reports on Geodesy and Geoinformatics

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2016

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Vol. 101

36--53

EN

Presented paper is dedicated to problems of deformation of the Earth's 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.

5

Earth crust deformation in Poland: modelling and its implication for positioning with satellite based geodetic techniques

Rajner M.

Reports on Geodesy

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2012

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z. 1/92

37—46

EN

This paper gives the general overview of the effects which continuously deform our planet. The main aim is to give the picture of the temporal and spatial range of this phenomena and to indicate their importance in high precision positioning with space geodetic techniques. We present here the ranges of magnitude and pattern of earth tides, ocean tidal loading, atmospheric radiation tides loading, polar motion and its oceanic indirect effect, as well as the non-tidal ocean loading. We pay the special attention to loading effects due to atmosphere and continental water storage, which can cause significant changes in point position time series. Our study concentrate mainly on the territory of Poland. The Jozefosław site was chosen as a representative example for the whole country. We present also here the impact of selected phenomena for relative geodetic measurements.

6

Earth free oscillation measurements with LCR-ET 26 Spring gravimeter

Rajner M., Rogowski J.B.

Reports on Geodesy

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2011

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z. 2/91

89-95

EN

After strong earthquakes the Earth oscillates with spheroidal and toroidal modes. The former cause gravity changes which can be detected with sensitive instruments. For this purpose we used continuous gravity measurements with LaCoste&Romberg Earth Tide spring gravimeter from Józefosław Observatory. Spectral analyses of records show significant peaks in normal mode frequencies. This peaks are above noise level and their eigenfrequencies are in good agreement with seismic theories. We show here some examples of free oscillations registration after particular earthquakes and stacking method as well. Some remarks concerning noise level in gravity measurements and data treatment are also given.

7

Studies of crustal deformation due to hydrological loading on GPS height estimates

Rajner M., Liwosz T.

Geodesy and Cartography

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2011

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Vol. 60, no 2

135-144

EN

The paper deals with large-scale crustal deformation due to hydrological surface loads and its influence on seasonal variation of GPS estimated heights. The research was concentrated on the area of Poland. The deformation caused by continental water storage has been computed on the basis of Water GAP Hydrological Model data by applying convolution of water masses with appropriate Green's function. Obtained site displacements were compared with height changes estimated from GPS observations using the Precise Point Positioning (PPP) method. Long time series of the solutions for 4 stations were used for evaluation of surface loading phenomena. Good agreement both in amplitude and phase was found, however some discrepancies remain which are assigned to single point positioning technique deficiencies. Annual repeatability of water cycle and demanding procedure for computing site displacements for each site, allowed to develop a simple model for Poland which could be applied to remove (or highly reduce) seasonal hydrological signal from time series of GPS solutions.

PL

Celem niniejszej pracy jest analiza wpływu zmian wielkoskalowych stosunków wodnych na deformacje skorupy ziemskiej. Przedstawiona jest również możliwość monitorowania tego efektu przy pomocy geodezyjnych technik satelitarnych. Na podstawie zmiennego rozkładu mas hydrosfery lądowej (do tego celu wykorzystano model hydrologiczny WGHM) oraz wykorzystując informacje dotyczące właściwości skorupy ziemskiej (tzw. funkcje Greena) zostały obliczone modelowe zmiany wysokości wybranych punktów na terenie Polski. Wyniki te zostały porównane ze zmianami wysokości wyznaczonymi dla czterech stacji permanentnych GNSS, które dysponują długimi ciągami obserwacyjnymi, tj. Borowa Góra, Borowiec, Józefosław oraz Lamkówko. Do opracowania obserwacji GPS wykorzystana została metoda Precise Point Positioning (PPP), czyli obserwacje dla każdej stacji były opracowywane niezależnie. Pozwoliło to na odseparowanie sygnałów właściwych dla danej stacji pomiarowej i prawidłowa interpretacje geodynamiczna. Wyniki te dobrze zgadzają się co do amplitudy i fazy z modelowym efektem. Przyczyny widocznych rozbieżności również zostały przedyskutowane. Wyraźna, roczna powtarzalność deformacji wynikających ze zmiennego rozkładu mas wodnych, pozwoliła na skonstruowanie prostego dwuparametrowego modelu dla terenu Polski, który pozwala znacznie zredukować wpływ tego efektu bez konieczności złożonych obliczeń.

8

Scientific expeditions to Antarctic and Spitsbergen with the participation of scientists from Faculty of Geodesy and Cartography, the Warsaw Universitety of Technology (WUT)

Pachuta A., Walo J., Adamek A., Rajner M., Węzka K., Próchniewicz D.

Reports on Geodesy

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2010

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z. 2/89

21-30

9

Investingation in tidal gravity results in Józefosław Observatory

Rajner M.

Reports on Geodesy

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2010

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z. 1/88

7-14

EN

In this paper we used 40 months (2007-2010) of continuous gravity measurements to study different tidal phenomena. The records are taken from the Observatory in Józefosław equipped with LaCoste&RombergEarth Tide Gravimeter. Tidal gravity parameters in diurnal and semi-diurnal bands are computed using international standard data processing techniques. Accuracy assessment, as well variation in time of those parameters are given. Long series of consistent data allow to investigate in small signals such as gravity changes due to ocean loading. Subtracting body tides from results yields a differences up 1 uGal which are in good agreement with computed indirect ocean effect using most recent models. It clearly explains main source of disagreement between results from measurements and tidal models, despite of long distance to mearest ocean. Paper deals also with barometric pressure influence on gravity measurements. Importance of reducing pressure variation in tidal analysis is discussed and admittance factor is computed.

10

Calibration of spring gravimeter using absolute gravity Measurements

Rajner M., Olszak T.

Reports on Geodesy

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2010

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z. 1/88

15-20

EN

Comparison of gravimeters relative to absolute measurements is frequently used method for determination of gravimeters scale factor. This technique as completely non-invasive is especially important in periodic control of continuously recording gravimetres. We used 30 repeated parallel observation of LaCoste&Romberg spring gravimeter with FG5 ballistic gravimeter in Józefosław Observatory carried out in last 40 months. Long series of repeated measurements allow us for comprehensive study on utility of calibration with this procedure. Different computational approaches was performed. Temporary variation of LCR scale factor with accuracy assessment aer comsidered. Discussion concerning reliability of calibration dependent on measurements length was also given.

11

Activities of Józefosław Astro-Geodetic Observatory in the last five decades

Rogowski J.B., Barlik M., Litwosz T., Kruczyk M., Kujawa L., Rajner M., Olszak T., Kurka W.

Reports on Geodesy

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2010

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z. 2/89

31-52

EN

Astro-Geodetic Observatory in Józefosław, witch belongs to the Departament of Geodesy and Geodetic Astronomy of the Warsaw University of Technology, started to permanent observations in 1958. First of them was time service started in February 1958, coordinated by BIH. From 1959 astrometrial latitude measurements have been done with aim to determine the parameters of the Earth rotation. In 1991 the Observatory was joned to the International GPS Service for Geodynamics (IGS) and started to operate as a permanent one in 1993. There have been performed many observations and scientific researches, such as: GPS in the frame of IGS/IGLOS/EUREF; tidal observations; absolute gravity measurements; changes of the vertical, based on the gravimetric measurements; astrometric observations and metrology. Moreover studies on RTK and DGPS measurements using mobile phone for data transmision are performed since 1998. WUT EUREF Lokal Analysis Centre, one of the 17 Lokal Analysis Centres acting in Europe, is a very important part of the Observatory. The Centre makes continuous service of one-week and daily aolution in the farme of EPN network, processes national and international GPS campaigns (CEGRN, EXTENDED SAGET etc.), models ionosphere and troposphere parameters, compute tidal components and changes of the vertical according to astrometric and gravimetric measurenents. This paper present history and current state of the art of the Observatory's activites.

12

Some remarks on determining short-period changes in glacier surface velocity using GPS technique - case study of Hans Glacier example

Rajner M.

Geodesy and Cartography

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2010

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Vol. 59, no 1

39-47

EN

Movement is one of the most spectacular phenomena involving glaciers. Determining glacier surface velocity is now a routine aspect of glaciological studies. These are geodetic methods, especially satellite positioning, that most frequently is applied in such work. Using the Hans Glacier (SW Spitsbergen) as an example, the presented paper is an attempt at defining the time resolution limit of changes in the velocity determined using GPS positioning technology. A test network was established in the area of the examined glacier in order to define the size and variability of the main satellite positioning biases as well as to define their impact on determining position and the calculated velocity. A discussion relating to achieved accuracy (differentiated from measurement precision) for baselines of a length of several kilometres in the high latitudes has also been presented.

PL

Jednym z najciekawszych i najbardziej spektakularnych zjawisk dotyczących lodowców jest ich ruch. Wyznaczanie powierzchniowej prędkości lodowców jest obecnie czynnością rutynową w pracach glacjologicznych. Do tych celów stosuje się najczęściej metody geodezyjne, głównie pozycjonowanie satelitarne. W niniejszej pracy przedstawiono próbę określenia granicznej rozdzielczości czasowej przy wyznaczaniu krótkookresowych zmian prędkości z obserwacji GPS na przykładzie lodowca Hansa na południowym Spitsbergenie. W tym celu została założona sieć pomiarowa, składająca się z jednego odbiornika na lodowcu oraz trzech odbiorników odniesienia w bezpośrednim sąsiedztwie lodowca. Na podstawie zebranych obserwacji zostały przedstawione rozważania dotyczące wpływu wybranych błędów pomiarowych technologii GPS oraz ich wpływu na określanie sub-dobowych zmian prędkości na dużych szerokościach geograficznych. Błędy pomiarowe, mimo krótkich wektorów, głównie związane ze zmienną konfiguracją satelitów GPS nie pozwoliły w tym przypadku na określanie zmian prędkości z rozdzielczością czasową większą niż doba.

13

Ocean tidal loading from the gravity measurements at Józefosław Observatory

Rajner M.

Artificial Satellites : Journal of Planetary Geodesy

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2010

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Vol. 45, No. 4

175--183

EN

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 Józefosław 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.

14

Scientific expeditions to Svalbard, organized by the Faculty of Geodesy and Cartography, the Warsaw University of Technology (WUT)

Pachuta A., Walo J., Adamek A., Woźniak M., Rajner M., Węzka K., Próchniewicz D

Reports on Geodesy

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2007

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z. 1/82

243-250

15

Monitoring of Hans Glacier movement dynamics (Hornsund Sw Spitsbergen, Svalbard)

Walo J., Puczko D., Adamek A., Węzka K., Malinowski Z., Rajner M.

Reports on Geodesy

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2006

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z. 1/76

173-179

EN

Fast and exact GPS measurements are independent from weather and season of the year. For achieving reliable results, survey should be conducted at least once a month and at least twice a month in summer season (June-September). GPS RTK is suggested for pole movement determination. In case of real-time corrections limited availability (i.e. screening by mountains) using Rapid Static is a good choice. To minimize multipath error antenna should be placed at least 0,5m eccentric to pole and at 1 m height. Ablation pole movement vectors of Hans glacier indicate few relations. Most important feature is speed being about 10 times greater in foremost zone of glacier than in lateral parties of glacier. Measurements of lateral profile indicate that, accordingly to expectations, surface speed of glacier is greater in middle axis comparing to the edges or glacier.