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Publisher: Springer-Verlag (Total: 2351 journals)

 Acta Geodaetica et GeophysicaJournal Prestige (SJR): 0.305 Citation Impact (citeScore): 1Number of Followers: 2      Hybrid journal (It can contain Open Access articles) ISSN (Print) 2213-5812 - ISSN (Online) 2213-5820 Published by Springer-Verlag  [2351 journals]
• An improved torque type gravity gradiometer with dynamic modulation
• Authors: Jie Luo; Jia-Hao Xu; Qi Liu; Cheng-Gang Shao; Lin Zhu; Hui-Hui Zhao; Wei-Huang Wu
Pages: 171 - 187
Abstract: Traditional torque type gravity gradiometer has an important pole in gravity gradient measurements, while it is relatively inefficient and with the precision of about 1 E mainly caused by the static operating mode. In this paper, we develop an improved torque type gravity gradiometer to improve the measuring efficiency, which is based on the dynamic modulation. The dynamic modulation keeps the gradiometer rotating on a turntable steadily, measures the deflection angle of the torsion pendulum continuously and then obtains the gravity gradients. The result shows that after using the improved gradiometer, the gradients W xz and W yz are obtained with precisions of 0.45 E and 0.32 E respectively in a cycle of 20 min.
PubDate: 2018-06-01
DOI: 10.1007/s40328-017-0202-z
Issue No: Vol. 53, No. 2 (2018)

• Polynomial approximation for fast generation of associated Legendre
functions
• Authors: M. R. Seif; M. A. Sharifi; M. Eshagh
Pages: 275 - 293
Abstract: Today high-speed computers have simplified many computational problems, but fast techniques and algorithms are still relevant. In this study, the Hermitian polynomial approximation is used for fast evaluation of the associated Legendre functions (ALFs). It has lots of applications in geodesy and geophysics. This method approximates the ALFs instead of computing them by recursive formulae and generate them several times faster. The approximated ALFs by the Newtonian polynomials are compared with Hermitian ones and their differences are discussed. Here, this approach is applied for computing a global geoid model point-wise from EGM08 to degree and order 2160 and in propagating the orbit of a low Earth orbiting satellite. Our numerical results show that the CPU-time decreases at least two times for orbit propagation, and five times for geoid computation comparing to the case where recursive formulae for generation of ALFs are used. The approximation error in the orbit computation is at a sub-millimeter level over two weeks and that the computed geoid 0.01 mm, with a maximum of 1 mm.
PubDate: 2018-06-01
DOI: 10.1007/s40328-018-0216-1
Issue No: Vol. 53, No. 2 (2018)

• Solution for GNSS height anomaly fitting of mining area based on robust
TLS
• Authors: Yeqing Tao; Guangxiong Mao; Xiaozhong Zhou
Pages: 295 - 307
Abstract: Global navigation satellite system (GNSS) height solutions of mining area are readily contaminated by outliers because of the special geological environment. Additionally, GNSS height anomaly fitting model is a type of errors-in-variables model, and the traditional solution for parameter estimation does not account for error in the coefficient matrix. To solve these two problems, this paper presents a solution of the robust total least squares estimation for GNSS height anomaly fitting of mining area. Different from the traditional solution for robust estimation, an algorithm is established employing median method to obtain stable parameter values under the condition that observation data are highly contaminated. Employing Lagrange function and weight function, an iterative algorithm for the parameter estimation of GNSS anomaly fitting model is proposed, and the algorithm is verified using real data of mining area. The numerical results show that the proposed solution obtains stable parameter values when observation data are highly contaminated by outliers and demonstrate that the proposed algorithm is more accurate than traditional solutions for robust estimation.
PubDate: 2018-06-01
DOI: 10.1007/s40328-018-0217-0
Issue No: Vol. 53, No. 2 (2018)

• Preliminary Moho depth determination from receiver function analysis using
AlpArray stations in Hungary
• Authors: Dániel Kalmár; the AlpArray Working Group; Bálint Süle; István Bondár
Pages: 309 - 321
Abstract: Receiver function analysis is applied to the western part of the Pannonian Basin, a rather complex region both geologically and geodynamically. Previous receiver function analyses in this region had to deal with much smaller station density and time span than those available to us. In the analysis we used the data of some 48 seismological stations. These include not only the permanent stations from Hungary and permanent stations from neighbouring countries (Slovakia and Slovenia), but also the temporary broadband stations that were installed within the framework of the AlpArray project. Having applied rather strict manual quality control on the calculated radial receiver functions we stacked the receiver functions. Using the H–K grid search method we determined the Moho depth and the Vp/Vs ratio beneath the seismological stations in the western part of the Pannonian Basin. The unprecedented density of the AlpArray network, combined with the permanent stations, allowed us to derive high resolution Moho and Vp/Vs maps for the West Pannonian Basin, together with uncertainty estimates. Our preliminary results agree well with previous studies and complement them with finer details on the Moho topography and crustal thickness.
PubDate: 2018-06-01
DOI: 10.1007/s40328-018-0218-z
Issue No: Vol. 53, No. 2 (2018)

• Seasonal variation analysis of Greenland ice mass time-series
• Authors: Roghayeh Shamshiri; Hossein Nahavandchi; Gholamreza Joodaki
Pages: 1 - 14
Abstract: We derive the mass balance of Greenland ice sheet from the Gravity Recovery and Climate Experiment (GRACE) for the period January 2003–October 2014. We have found an ice mass loss with peak amplitude of −15 cm/yr in the southeastern and northwestern parts, and an acceleration of −2.5 cm/yr2 in the southwestern region. Global warming is a well-known suspected triggering factor of ice melting. We use MODIS-derived Ice Surface Temperature (IST), and continuous and cross wavelet transforms have been determined to investigate the common power and relative phase between GRACE derived time-series of ice mass changes and IST time-series. Results indicate a high common power between the two time-series for the whole study period, but with different time patterns.
PubDate: 2018-03-01
DOI: 10.1007/s40328-017-0198-4
Issue No: Vol. 53, No. 1 (2018)

• The 2D time-dependent similarity transformation model as a tool for
deformation monitoring
• Authors: Dimitrios Ampatzidis; Christian Gruber; Vasileios Kampouris
Pages: 81 - 92
Abstract: Besides the methodology of triangulation and geodetic networks nowadays, the permanent stations of satellite receivers exist, giving extra asset to geodetic daily practice. Permanent stations perform observations incessantly for the visible satellites. However, the coordinates of these stations are often changing over time due to geophysical and tectonic processes. Consequently, these changes are perceived to modern observations. So, along with the coordinates of geodetic points in a given epoch, their changes over time (e.g. the velocities of their movements) are also considered. Furthermore, any change to the reference system definition or/and to the network’s geometry can significantly impact the estimated coordinates and velocities. This paper investigates the reference datum definition problem (or datum problem, or zero order design problem) in a such network over time, which is later generalized for the study of the deformation control-networks. Emphasis is given to techniques of time-dependent 2D transformation models, with numerical tests on a simulation network.
PubDate: 2018-03-01
DOI: 10.1007/s40328-017-0205-9
Issue No: Vol. 53, No. 1 (2018)

• Active tectonic deformation and associated earthquakes: a case
study—South West Carpathians Bend zone
• Abstract: Active tectonic deformation is continuously shaping the landscape in the Alpine Orogenic system. Earthquakes are clear proves of neotectonic deformation process. In the Romanian Carpathians the most active deformation is recorded in the South Eastern Carpathian Bend Zone. Nevertheless, seismicity associated to latest orogenic stage of active deformation is not limited to this area. Other seismic regions, like the South West Carpathians Bend Zone, were identified. Recently, several earthquake sequences were recorded in the Caransebes-Mehadia (CMB) and Hateg basins (HB). These sedimentary basins developed over the South Carpathians, Getic/Supra Getic and Danubian basement napes, their evolution being related with the N-ward tectonic transport of the Carpathian Orogen, in the current position, during the Paleogene-Quaternary times. The aim of the present study is to perform a thorough analysis of the earthquakes recorded in these two basins in correlation with the observed geological structure to better understand and constrain the neotectonic processes affecting the SW Carpathians Bend Zone. The focal mechanisms determined for HB show a predominant strike-slip faulting component with the principal axes oriented approximately NW–SE (compression) and NE–SW (extension), a reorientation from the N-S one described for the Pliocene–Pleistocene phase. The focal mechanisms in CMB imply N–S extension with normal or strike-slip faulting. We argue that the present day tectonic processes are not restricted to the SE Carpathians Bend zone, as previously inferred. Instead they affect a much larger area of the Carpathian Orogen, like the SW Carpathians Bend zone.
PubDate: 2018-07-18

• Salt dome boundary detection in seismic image via resolution enhancement
by the improved NFG method
• Authors: M. Soleimani; H. Aghajani; S. Heydari-Nejad
Abstract: Accurate geological modeling of subsurface structures with all available geophysical data is a challenging task in geo-exploration studies. Concern in precise modeling will increase by increasing geological complexity of subsurface structures such as salt dome. Integrating various sources of geophysical data will reduce uncertainty in geological modeling in complex media. In this study, we introduce an integrated strategy for more appropriate detection of salt boundary in seismic image, by applying the normalized full gradient (NFG) method, used in processing of potential field data. In the proposed strategy, we initially, analyzed sensitivity of the NFG parameters by derivation of a synthetic model. Parameter analysis and optimization showed dependency of geometrical properties of the geological target to the harmonic number in the NFG method. Afterwards, seismic traces were processed by the NFG method. Results showed increase in vertical resolution of seismic envelope compared to the result of the well-known Hilbert Transform. The proposed strategy was applied on a synthetic seismic data contains complex salt model. Results have shown that application of the proposed strategy produced higher resolution seismic image compared to the Hilbert Transform method. The method also was applied on a field seismic data with a complex salt dome from southwest of Kazakhstan. Seismic image obtained by the integration procedure could better exhibit body of the salt dome, as well as better interpretation of faults, layer boundary truncation, salt bottom and subsalt layers. Thus, it was concluded that the proposed strategy could be considered as an alternative to resolve some of ambiguities in geological interpretation of seismic data in complex geological settings.
PubDate: 2018-07-09
DOI: 10.1007/s40328-018-0222-3

• Deformation of static datum: Turkish CORS network (TUSAGA-Aktif) is
considered
• Authors: Sermet Öğütcü
Abstract: The geocentric datum of Turkish CORS Network (TUSAGA-Aktif) is a semi-kinematic datum realized with respect to the International Terrestrial Reference Frame (ITRF 96) at the reference epoch of 1 January 2005 (2005.00). This realization was maintained by ITRF no net rotation (NNR) velocities of CORS stations. Up-to-date ITRF NNR velocities were determined by General Command of Mapping in Turkey using 7 years of CORS stations data from 2008 to 2015. In accordance with Turkish surveying regulation, there are two types of coordinate computation of the control points performed with Global Navigation Satellite System relative positioning technique based on the datum. Coordinates of the first-order and the second-order control points are computed in semi-kinematic datum, whereas the third-order control points are computed in static datum. Generally, CORS stations of TUSAGA-Aktif are used as fiducial stations for coordinate computation of these control points. In this study, baseline deformation effect of static datum on the three-dimensional position of the points are investigated. 20 CORS stations within TUSAGA-Aktif were chosen to simulate the rover and the fiducial stations. The results show that relative displacement from the reference epoch (2005.00) between the rover-fiducial stations at the measurement time and the positioning error of the rover station are in a good agreement. The differences are in the order of mm to cm level. The results also show that when more than one fiducial station used in static datum processing, mean relative displacement between the rover-fiducial stations at the measurement time and the positioning error of the rover are also in a good agreement. The results emphasized that, velocities of the fiducial stations should be known by the users for conducting static datum processing with minimum baseline deformation as much as possible.
PubDate: 2018-06-27
DOI: 10.1007/s40328-018-0223-2

• A generalized V S –N correlation using various regression analysis
and genetic algorithm
• Authors: Amit Shiuly; Narayan Roy
Abstract: Shear wave velocity (VS) is an important parameter from geotechnical earthquake engineering perspective. In the absence of the direct measurement of VS, VS–N correlation serves an alternative for evaluating the shear wave velocity (VS) from standard penetration resistance value (SPT-N) at a particular region. In the present study, an attempt has been made to propose generalized VS–N correlation from the globally available correlations for all soil and specific soil type using various regression procedures and genetic algorithm (GA). Various regression procedures along with GA have been used to assess the sensitivity of generalized VS–N correlations in connection with regression methodology. 1D ground response analysis has been carried out at two bore-hole locations in Kolkata city using the VS obtained from generated correlations and site specific response spectra have been generated at those two locations. Finally, performance of some typical buildings have been studied by nonlinear static analysis procedure using those site specific response spectra developed for proposed VS–N relationships for all type of soil and specific type of soil. The performance of the considered typical buildings has been represented in terms of base shear and roof displacement. Chi square ( $$\chi^{2}$$ ) test has also been conducted to check the confidence level of base shear and roof displacement obtained by using various developed VS–N relationships varies with the results obtained using available site specific relationships proposed by Nath (2016), and it reveals that VS–N relationships developed by GA perform better than the VS–N relationships developed by other regression method.
PubDate: 2018-06-19
DOI: 10.1007/s40328-018-0220-5

• Latitudinal variation of F-region ionospheric response during three
strongest geomagnetic storms of 2015
• Authors: Bapan Paul; Barin Kumar De; Anirban Guha
Abstract: The latitudinal ionospheric response of the three strongest geomagnetic storms of 2015 of the current solar cycle 24 during 16–19 March 2015, 21–24 June 2015 and 19–22 December 2015 is investigated using the total electron content data derived from a latitudinal chain of Global Positioning System (GPS) receivers extending from 70°N to 70°S. The storm time perturbations of the ionosphere during main and recovery phase is presented by the GPS derived vertical total electron content (VTEC) data which is further supported by ionospheric F region critical frequency (foF2) and F region peak height (hmF2) data. We observed symmetrical hemispheric response of the ionosphere during the strongest 17th March (St. Patrick’s Day) storm whereas asymmetrical hemispheric response of the ionosphere during 22nd June and 20th December storm over the Asian-Australian sector. The observations are explained by the combined transport of background inter-hemispheric seasonal wind and storm time disturbed meridional wind and by the global thermospheric compositional variation [O/N2] data.
PubDate: 2018-06-11
DOI: 10.1007/s40328-018-0221-4

• Underground current impulses as a possible source of unipolar magnetic
pulses
• Authors: P. Nenovski
Abstract: Recently several cases of observations of unipolar magnetic field pulses associated with earthquakes at different points (California, Italy, Peru) have been recorded. The paper attempts to model unipolar magnetic field pulses based on one mechanism that should be omnipresent for all measurement points, namely, the magnetic field diffusion through a conductive medium. The structure of magnetic fields supported by electric current sources is thoroughly modelled. The source of electric current is considered as an elongated volume of finite cross-section being immersed in a conductive medium. To model the unipolarity feature of the observed pulses prior to and at the earthquake main shock, the electric current of the source is of impulse form. Special attention is paid to the differences in the pulse structure (as amplitude envelope and the pulse width) that are measured by various magnetometers (fluxgate or search-coil). An analysis and comparison with recorded magnetic field pulse characteristics reveal that the observed unipolar pulses may have a common genesis, an electric current source within a conductive medium such as the earth crust.
PubDate: 2018-05-31
DOI: 10.1007/s40328-018-0219-y

• Developing a global model for the conversion of zenith wet tropospheric
delays to integrated water vapour
• Authors: Juni Ildikó; Rózsa Szabolcs
Abstract: The tropospheric wet delay is a significant systematic error of GNSS positioning, nevertheless it carries important information to meteorologists. It is closely related to the integrated water vapour that is the upper limit of precipitable water. The zenith wet delay can be converted to the integrated water vapour using a simple conversion factor. This conversion factor can be determined with the empirical formulae derived from radiosonde observations. In the past decades, numerous models were derived for this purpose, but all of these models rely on radiosonde observations stemming from a limited area of the globe. Although these models are valid for the area, where the underlying radiosonde observations were measured, there are several examples that these empirical formulae are used to validate GNSS based integrated water vapour estimations all over the globe. Our aim is to create a global model for the conversion of the zenith tropospheric delay to the integrated water vapour for realtime and nearrealtime applications using globally available Numerical Weather Models (NWM). Thus our model takes into consideration the fact that the model parameters strongly depend on the geographical location. 10 years of monthly mean ECMWF (European Center for Medium-Range Weather Forecast) dataset were used for the derivation of the model parameters in a grid with the resolution of 1° × 1°. The empirical coefficients of the developed models depend on two input parameters, namely the geographical location and the surface temperature measured at the station. Thus, the new models can be used for both realtime and near-realtime GNSS meteorological applications. The developed models were validated using 6 years of independent global ECMWF monthly mean analysis datasets (2011–2016). The results showed, that the application of the original models outside the area of the underlying radiosonde data sets can result in a relative systematic error of 7–8% in the estimation of the conversion factor as well as the estimated IWV values.
PubDate: 2018-04-19
DOI: 10.1007/s40328-018-0215-2

• AlpArray in Hungary: temporary and permanent seismological networks in the
transition zone between the Eastern Alps and the Pannonian basin
• Authors: Zoltán Gráczer; AlpArray Working Group; Gyöngyvér Szanyi; István Bondár; Csenge Czanik; Tibor Czifra; Erzsébet Győri; György Hetényi; István Kovács; Irene Molinari; Bálint Süle; Eszter Szűcs; Viktor Wesztergom; Zoltán Wéber
Abstract: In the last few decades dense large-scale seismic networks showed their importance in studying the structure of the lithosphere and the upper mantle. The better understanding of the Apennines–Alps–Carpathian–Dinarides system is the main target of the AlpArray European international initiative in which more than 50 institutes are involved. The core of AlpArray is the AlpArray Seismic Network (AASN). With its $$\sim$$ 600 broadband seismic stations ( $$\sim$$ 280 of which are temporary) the AASN is, so far, the largest passive seismic experiment in Europe. The MTA CSFK Geodetic and Geophysical Institute, as a Core Member of the AlpArray project, contributes to the AlpArray Seismic Network with its entire permanent network as well as with 11 temporary broadband seismic stations deployed in Western Hungary. Three additional station equipment were provided by the Swiss-AlpArray SINERGIA program. The average station distance together with the permanent stations is around 40 km in the area of interest. The temporary network has been installed between December 2015 and July 2016 and the planned operation period is 3 years. In this paper we describe the characteristics of the 29 permanent and temporary stations, introducing not only the equipment, but the location, housing and geological setting, as well. We present median power spectral density curves in order to characterise the noise conditions at each station.
PubDate: 2018-03-20
DOI: 10.1007/s40328-018-0213-4

• The application of a combination of weighted least-squares and
autoregressive methods in predictions of polar motion parameters
• Authors: Fei Wu; Kazhong Deng; Guobin Chang; Qianxin Wang
Abstract: This study employs a combination of weighted least-squares extrapolation and an autoregressive model to produce medium-term predictions of polar motion (PM) parameters. The precisions of PM parameters extracted from earth orientation parameter (EOP) products are applied to determine the weight matrix. This study employs the EOP products released by the analysis center of the ‘International Global Navigation Satellite System Service and International Earth Rotation and Reference Systems Service’ needs to be modified to ‘International Global Navigation Satellite System Service (IGS) and International Earth Rotation and Reference Systems Service (IERS)’ as primary data. The polar motion parameters and their precisions are extracted from the EOP products to predict the changes in polar motion over spans of 1–360 days. Compared with the combination of least-squares and autoregressive model, this method shows considerable improvement in the prediction of PM parameters.
PubDate: 2018-03-19
DOI: 10.1007/s40328-018-0214-3

• On the noise characteristics of time series recorded with nearby located
GPS receivers and superconducting gravity meters
• Authors: Janusz Bogusz; Severine Rosat; Anna Klos; Artur Lenczuk
Abstract: The inter-comparison of ground gravity measurements and vertical surface displacements enables to better understand the structure, dynamics and evolution of the Earth’s system. Within this research we analyzed the Global Positioning System vertical position time series acquired in the vicinity of the superconducting gravimeters. We estimated of noise character of GPS and SG by comparison of the satellite and terrestrial measurements collected at 18 globally distributed neighboring sites. The comparable results were provided by applying the appropriate and corresponding models of geophysical phenomena to obtain residual time series, and by unifying the sampling rate since the noise characteristics may depend on it. The deterministic part of the series was assumed to follow the Polynomial Trend Model and was subtracted prior to noise analysis. Then, a combination of power-law and white noise was presumed and the Maximum Likelihood Estimation implemented in the Hector software to investigate the stochastic part was applied. Within the paper, we show that the spectral indices for all SG time series fall in the area of fractional Brownian motion (− 2 < κ < − 1), while GPS data are best characterized by fractional Gaussian noises (− 1 < κ < 0). The estimated ratio between spectral indices of GPS and SG is stable worldwide with a global median value of about 0.5. Concerning the power-law amplitudes, these are very consistent worldwide for the GPS position time series and fluctuate around 15 mm/year−κ/4, while in the case of SG records they spread between 60 and 300 nm/s2/year−κ/4. The fraction of power-law noise employed in the assumed combination is equal to 100% for almost all SG stations, while in case of GPS it varies between 26.1 and 99.9%. The main finding of this research is that the assumption of power-law noise is much more preferred for SG data than the assumption of a pure white noise being used until now.
PubDate: 2018-01-25
DOI: 10.1007/s40328-018-0212-5

• Possible mechanisms of co-seismic electromagnetic effect
• Authors: V. V. Surkov; V. A. Pilipenko; A. K. Sinha
Abstract: We analyze theoretically two possible sources of co-seismic electromagnetic response to the propagation of various types of seismic waves caused either by the electrokinetic phenomena or geomagnetic inductive effect. The differences between these two generation mechanisms have been examined for different types of seismic waves (P, S, and Rayleigh-Love). Theoretical relationships describing the dependence of the co-seismic signal amplitude, polarization and apparent impedance on the earthquake seismic moment and magnitude have been derived as a function of distance. We indicate an observational possibility to discriminate seismo-electrokinetic and seismo-magnetic effects and to estimate their contribution into a recorded co-seismic electromagnetic signal. Magnitudes and polarization of these signals are shown to depend strongly on the type of seismic wave and local crust parameters, such as streaming potential coupling coefficient, conductivity, inhomogeneity, etc. Co-seismic electromagnetic signals, though not directly applied for earthquake prediction, contain a useful information on local crustal phenomena, and can be used to identify “sensitive” zones perspective for the monitoring of precursory electromagnetic disturbances.
PubDate: 2018-01-18
DOI: 10.1007/s40328-018-0211-6

• Metropolis algorithm driven factor analysis for lithological
characterization of shallow marine sediments
• Authors: A. Abordán; N. P. Szabó
Abstract: Factor analysis of well logging data can be effectively applied to calculate shale volume in hydrocarbon formations. A global optimization approach is developed to improve the result of traditional factor analysis by reducing the misfit between the observed well logs and theoretical data calculated by the factor model. Formation shaliness is directly calculated from the factor scores by a nonlinear regression relation, which is consistent in the studied area in Alaska, USA. The added advantage of the implementation of the Simulated Annealing method is the estimation of the theoretical values of nuclear, sonic, electrical as well as caliper well-logging data. The results of globally optimized factor analysis are compared and verified by independent estimates of self-potential log-based deterministic modeling. The suggested method is tested in two different shaly-sand formations in the North Aleutian Basin of Alaska and the comparative study shows that the assumed nonlinear connection between the factor scores and shale volume is applicable with the same regression constants in different burial depths. The study shows that factor analysis solved by the random search technique provides an independent in situ estimate to shale content along arbitrary depth intervals of a borehole, which may improve the geological model of the hydrocarbon structure in the investigated area.
PubDate: 2018-01-06
DOI: 10.1007/s40328-017-0210-z

• On modelling GPS phase correlations: a parametric model
• Authors: Gael Kermarrec; Steffen Schön
Abstract: Least-squares estimates are unbiased with minimal variance if the correct stochastic model is used. However, due to computational burden, diagonal variance covariance matrices (VCM) are often preferred where only the elevation dependency of the variance of GPS observations is described. This simplification that neglects correlations between measurements leads to a less efficient least-squares solution. In this contribution, an improved stochastic model based on a simple parametric function to model correlations between GPS phase observations is presented. Built on an adapted and flexible Mátern function accounting for spatiotemporal variabilities, its parameters are fixed thanks to maximum likelihood estimation. Consecutively, fully populated VCM can be computed that both model the correlations of one satellite with itself as well as the correlations between one satellite and other ones. The whitening of the observations thanks to such matrices is particularly effective, allowing a more homogeneous Fourier amplitude spectrum with respect to the one obtained by using diagonal VCM. Wrong Mátern parameters—as for instance too long correlation or too low smoothness—are shown to skew the least-squares solution impacting principally results of test statistics such as the apriori cofactor matrix of the estimates or the aposteriori variance factor. The effects at the estimates level are minimal as long as the correlation structure is not strongly wrongly estimated. Thus, taking correlations into account in least-squares adjustment for positioning leads to a more realistic precision and better distributed test statistics such as the overall model test and should not be neglected. Our simple proposal shows an improvement in that direction with respect to often empirical used model.
PubDate: 2017-10-31
DOI: 10.1007/s40328-017-0209-5

• Application of the PCA/EOF method for the analysis and modelling of
temporal variations of geoid heights over Poland
• Authors: Walyeldeen Godah; Malgorzata Szelachowska; Jan Krynski
Abstract: Temporal variations of geoid heights are vitally important in geodesy and Earth science. They are essentially needed for dynamic and kinematic updates of the static geoid model. These temporal variations, which substantially differ for different geographic locations, can successfully be determined using the Gravity Recovery And Climate Experiment (GRACE) mission data. So far, statistical decomposition methods, e.g. the Principal Component Analysis/Empirical Orthogonal Function (PCA/EOF) method, have not been implemented for the analysis and modelling of temporal mass variations within the Earth’s system over the area of Poland. The aim of this contribution is to analyse and model temporal variations of geoid heights obtained from GRACE mission data over the area of Poland using the PCA/EOF method. Temporal variations of geoid heights were obtained from the latest release, i.e. release five, of monthly GRACE-based Global Geopotential Models. They can reach the level of 10 mm. The PCA modes and their corresponding EOF loading patterns were estimated using two different algorithms. The results obtained revealed that significant part of the signal of temporal variations of geoid heights over Poland can be obtained from the first three PCA modes and EOF loading patterns. They demonstrate the suitability of the PCA/EOF method for analysing and modelling temporal variations of geoid heights over the area investigated.
PubDate: 2017-09-25
DOI: 10.1007/s40328-017-0206-8

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