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Accuracy analysis of gravity field changes from GRACE RL06 and RL05 data compared to in situ gravimetric measurements in the context of choosing optimal filtering type

Szabó Viktor, Marjańska Dorota

Artificial Satellites : Journal of Planetary Geodesy

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2020

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Vol. 55, No. 3

100--117

EN

Global satellite gravity measurements provide unique information regarding gravity field distribution and its variability on the Earth. The main cause of gravity changes is the mass transportation within the Earth, appearing as, e.g. dynamic fluctuations in hydrology, glaciology, oceanology, meteorology and the lithosphere. This phenomenon has become more comprehensible thanks to the dedicated gravimetric missions such as Gravity Recovery and Climate Experiment (GRACE), Challenging Minisatellite Payload (CHAMP) and Gravity Field and Steady-State Ocean Circulation Explorer (GOCE). From among these missions, GRACE seems to be the most dominating source of gravity data, sharing a unique set of observations from over 15 years. The results of this experiment are often of interest to geodesists and geophysicists due to its high compatibility with the other methods of gravity measurements, especially absolute gravimetry. Direct validation of gravity field solutions is crucial as it can provide conclusions concerning forecasts of subsurface water changes. The aim of this work is to present the issue of selection of filtration parameters for monthly gravity field solutions in RL06 and RL05 releases and then to compare them to a time series of absolute gravimetric data conducted in quasi-monthly measurements in Astro-Geodetic Observatory in Józefosław (Poland). The other purpose of this study is to estimate the accuracy of GRACE temporal solutions in comparison with absolute terrestrial gravimetry data and making an attempt to indicate the significance of differences between solutions using various types of filtration (DDK, Gaussian) from selected research centres.

2

Metoda rozdzielania składowych nierówności powierzchni za pomocą dwuwymiarowej transformaty falkowej

Makieła W., Gogolewski D.

Mechanik

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2016

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R. 89, nr 11

1716--1717

PL

W pracy przedstawiono możliwości wykorzystania transformaty falkowej w celu rozdzielania składowych nierówności powierzchni zmierzonej. Przeprowadzono badania porównawcze sygnałów chropowatości powierzchni otrzymanych po analizie filtrem Gaussa oraz po przeprowadzeniu dekompozycji falkowej. Analizując otrzymane wyniki badań statystycznych, stwierdzono, iż transformata falkowa może być stosowana do rozdzielnia składowych nierówności powierzchni.

EN

The paper presents the possibilities of using wavelet transform to separate the components of surface irregularities. Authors conducted comparative tests of surface roughness obtained by the Gaussian filtering and wavelet decomposition. Analyzing the results statistical research, it was concluded that the wavelet transform can be used for separating components of surface irregularities.

3

Feature Based Affine Invariant Watermarking Robust to Geometric Distortions

Hung K,L., He Sh-W.

Fundamenta Informaticae

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2009

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Vol. 92, nr 1-2

131-143

EN

This work, proposes a robust digital watermarking scheme based on feature points as a defense against illegal user attacks, such as, rotating, scaling and translation. First of all, a Gaussian filter is first adopted to discover the invariant feature points. The local maximum and the local minimum values are then calculated from those feature points. The Affine Invariant Region (AIR) is then divided by combination the values: local maximum, local minimum values and the center of mass. The AIR region is then transformed using affine transform to a block image, called the normalized image, in which the size of the block image is predefined. The watermarks are then embedded into the normalized image. Experimental results indicate that the proposed method can still extract the correct watermark, even after a geometric attack. The proposed method has a lower false positive rate and higher accuracy than Lu's [12] that making it a robust blind watermarking scheme.

4

Eliminacja zakłóceń przy zachowaniu ostrości krawędzi obiektów w obrazach cyfrowych

Bieda R.

Zeszyty Naukowe. Automatyka / Politechnika Śląska

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2006

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z. 146

105-128

PL

W artykule przedstawiona została propozycja nowego filtra dolno-przepustowego, zachowującego wyrazistość brzegów obiektów w scenie obrazowej. Wyniki filtracji porównane zostały z efektami działania innych algorytmów filtracji zastosowanych do obrazów zakłóconych szumem typu gaussowskiego i impulsowego. Prezentowany algorytm filtracji może być używany jako etap wstępny w obróbce obrazów przed dalszym procesem detekcji krawędzi obiektów w obrazie.

EN

In this paper a novel low-pass edge preserving filter is presented. The new algorithm is based on modification of weighted function used in the Gauss filter. The efficiency of the new filter is compared under a variety of performance criteria with the commonly used filters, such as the vector median and the anisotropic diffusion schemes. It is shown that, compared to existing techniques, the new technique are better able to suppress impulsive, Gaussian as well as mixed type noise. The presented filtering scheme can be used as a preliminary stage of edge detection algorithms.

5

The analysis of Gaussian regression filtering of surface profiles

Pawlus P., Dobrzański P.

Zeszyty Naukowe Politechniki Rzeszowskiej. Mechanika

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2004

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z. 62 [209]

281--288

EN

The paper is concerned with the use of Gaussian regression filter in surface profile assessment. The performance of Gaussian ISO 11562 digital filter is compared wilh that of Gaussian regression filter. The simulated sinusoidal and random profiles are the objects of investigation. Difference between filtering using two methods is discussed.