Engineering, Technology & Applied Science Research
This paper presents the application of the Parallel Small Baseline Subset (P-SBAS) algorithm, pro... more This paper presents the application of the Parallel Small Baseline Subset (P-SBAS) algorithm, provided by the Geohazards Exploitation Platform for the precise monitoring of an earth dam's ground deformation using C-band Sentinel-1 data. The test site object of this study was the Kramis dam, located in the Mostaganem State, Western Algeria. Among the multiple advanced DInSAR techniques, SBAS is very adequate for long-term displacement monitoring in areas with changing terrain and vegetation. Ten corner reflectors were installed as a backscattered radar signal amplification tool to reduce the effect of temporal decorrelation and delineate the dam area. Four Sentinel-1 A and B satellite tracks were available (T30, T37, T103, and T110) to measure displacements, in the Line of Site (LoS) direction, for two years since the installation of the CRs in July 2019. The results showed a subsiding area on the left bank of the dam dike, with a velocity of 4mm/yr, and an uplifting rate of 3-4m...
Advances in Remote Sensing and Geo Informatics Applications, 2018
The purpose of this work was to characterize the signals and noises of Geocenter variations time ... more The purpose of this work was to characterize the signals and noises of Geocenter variations time series obtained from different space geodesy techniques as Global Positioning System (GPS), Doppler Orbitography and Radiopositioning Integrated on Satellite (DORIS), and Satellite Laser Ranging (SLR). The methodology proposed is based on the estimation of periodic signals by performing the frequency analysis using FAMOUS software (Frequency Analysis Mapping On Unusual Sampling) and evaluation of noises level and type by Allan variance technique. The available data covers 13 years (from 1993 to 2006) of weekly series of Geocenter residuals components, according to ITRF2000. The results obtained are more accurate according to GPS and SLR of about 2–8 mm than DORIS of about 8–42 mm. The estimated seasonal signals amplitudes are of about of few mm per technique with centimetre level for Z Geocenter coordinate of DORIS. The Geocenter motion derived from the SLR technique is more accurate and close to the geodynamic models. The noise analysis shows a dominant white noise in the SLR and DORIS solutions at level of 0.6–1 mm and 10–40 mm, respectively. However, the GPS solution is characterized by a flicker noise at the millimetre level, relating to mismodelling systematic errors.
The paper describes a simplified transformation between geographical coordinates of two ellipsoid... more The paper describes a simplified transformation between geographical coordinates of two ellipsoidal surfaces (i.e. WGS84 and Clarke 1880), applied in the North of Algeria to express the new GPS coordinates into local coordinates, useful only in small regions and suited for large scale applications such as cadastre. This transformation approach (A. Leick, 90) is based on the mixed adjustment model to estimate the four parameters transformation (2 translations, 1 rotation and scale factor) and on the geodetic lines concept, respectively the called « Inverse » and « Forward » problem of geodesy. In this context, the program developed was based on methods described above. The necessary data, the steps of processing and the results obtained were discussed.
Synthetic Aperture Radar (SAR) satellite imagery is a source of data widely employed in the quant... more Synthetic Aperture Radar (SAR) satellite imagery is a source of data widely employed in the quantification and analysis of an earthquake coseismic displacement. However, due to the signal path along the atmosphere and to other sources, the interferometric phase becomes compromised. In this work, a methodology for the correction of tropospheric and orbital errors in the differential interferogram is presented. This methodology was applied to a couple of Sentinel-1A data. The phenomenon studied was the 11th November 2018 Zeribet el Oued earthquake, Mw. 5.2 (The state of Biskra, South East of Algeria). It was possible to correct both tropospheric and orbital errors, where the dominant one was the tropospheric delay, a displacement error of 4 cm was added to the differential interferogram by this noise source. The correction of orbital error led to a better interpretation of the coseismic displacement.
On Significant Applications of Geophysical Methods, 2019
This paper deals with generation of post-seismic velocity and deformation fields of the GNSS netw... more This paper deals with generation of post-seismic velocity and deformation fields of the GNSS network of New Zealand, due to the Kaikoura earthquake (Mw7.8), on November 13th, 2016. The PPP model was performed to estimate daily coordinates, during one year (November 2016–November 2017), of 138 stations of GeoNet with RTKLIB 2.4.2 software (University of Marine Sciences and Technology of Tokyo). The Deformation analysis software (Research Institute of Geodesy, Topography and Cartography, Czech Republic) was used for obtaining results in terms of displacements and deformations (strain tensors, total dilatation, and shears). This software, as a web application, uses Web Map Services (WMS) as its graphic representation of estimated results in GIS format. The results show clearly the post-seismic activity of New Zealand, particularly, near the epicenter and at frontier zone between South and North islands.
Recent Advances in Environmental Science from the Euro-Mediterranean and Surrounding Regions, 2018
The main purpose of the paper is to examine the potential of the Artificial Neural Networks (ANN)... more The main purpose of the paper is to examine the potential of the Artificial Neural Networks (ANN), the Singular Spectrum Analysis (SSA) and their combination for concrete Dam displacements according to the Hydrostatic, seasonal, time displacement (HST) model. The ANNs are powerful tools for approximation and prediction of dam deformation and the SSA method is well suitable method for characterisation of seasonal signals and trend in time series of dam displacements. The novelty here is the combination of SSA with ANN under HST model for dam displacements prediction.
Le reservoir en sol gele du terminal methanier du complexe SONATRACH GL4/Z d'Arzew, construit... more Le reservoir en sol gele du terminal methanier du complexe SONATRACH GL4/Z d'Arzew, construit en 1965 et d'une capacite d'environ 38000m3, est le seul stockage souterrain toujours en exploitation dans le monde. Il represente pour le complexe plus de 50% de ses capacites de stockage. L'auscultation geometrique par les techniques topographiques classiques a permis de constater les deformations importantes du bac et de son voisinage immediat qui demeurent en phase d'evolution continue. A ces methodes traditionnelles de positionnement se sont substituees de nouvelles techniques plus evoluees et plus precises, basees sur l'utilisation de satellites artificiels. En effet, les imperatifs de precision de positionnement pour un ouvrage de ce type (etendue, temps, en cout et en precision), comme le GPS, rendent necessaire la mise en oeuvre de ces nouvelles techniques et leur application aux travaux de detection des deformations. La surveillance du site industriel repre...
L'etude menee a travers cet article porte sur l'etablissement des reseaux geodesiques bid... more L'etude menee a travers cet article porte sur l'etablissement des reseaux geodesiques bidimensionnels base sur les methodes d'ajustements avec contraintes internes. La notion des contraintes internes ou des reseaux libres reste tres utilisee en geodesie grâce a leur propriete d'independance du choix de configuration du Datum. Cette independance permet l'obtention d'une solution optimale du reseau estime sans aucune influence des effets externes dus au systeme de reference. Cette methode offre certains avantages (...)
L'objectif de cet article est d'etudier l'impact des mesures laser (SLR) du satellite... more L'objectif de cet article est d'etudier l'impact des mesures laser (SLR) du satellite bas starlette dans la determination precise des produits geodesiques (EOP et Geocentre ) , sur une periode de 14 ans ( 1993-2007) .Les resultats ont montre que la precision sur les trois composantes de la translation ( Mouvement du Geocentre ) , est de l'ordre de 4 et 5 mm pour les solutions LAGEOS1/2 et starlette , respectivement .Concernant les EOP , les ecarts-types des solutions LAGEOS1/2 et starlette sont (...)
Dans l'analyse des déformations des réseaux géodésiques, on distingue deux méthodes classiques d'... more Dans l'analyse des déformations des réseaux géodésiques, on distingue deux méthodes classiques d'estimation des mouvements d'une zone d'étude: les vecteurs-déplacement et les tenseurs de déformations. Cependant, l'évaluation et la représentation de la déformation dépendent du système de référence à priori et de la configuration des figures choisies qui constituent l'ensemble du réseau. Ces contraintes rendent difficile l'interprétation des résultats obtenus. A travers ce présent article, une solution basée sur la méthode des éléments finis (MEF) est proposée pour affiner l'estimation et la représentation de la déformation des réseaux géodésiques. Dans ce cadre, une étude de la déformation est effectuée pour analyser les mouvements horizontaux du réseau géodésique de Cheliff, observé par triangulation classique en 1976 (par l'INCT) et en 1981 (par le CRAAG), en se basant sur un modèle bidimensionnel d'éléments finis élastiques. Les différents résultats sont illustrés en termes de vecteurs-déplacement, de tenseurs de déformations et de tenseurs de contraintes. La déformation de la région ainsi déterminée est interprétée suivant des études géophysiques antérieures. En outre, les différents résultats ont mis en évidence les phénomènes suivants :-Un phénomène compressif de la région de Cheliff, d'orientation NNO-SSE, dû au rapprochement des deux plaques tectoniques africaine et eurasienne qui a causé la faille inverse du fameux séisme du 10 octobre 1980.
Generally, to analyse and control the quality of these GPS networks, the statistical and reliabil... more Generally, to analyse and control the quality of these GPS networks, the statistical and reliability aspects are studied. These analyses have been augmented with geometrical strength analysis using strain technique, resulting in the concept of the robustness analysis. This later is a combination of reliability and deformation of the network. The network robustness is quantified according to threshold values which are computed from errors confidence of adjusted points. The displacements of GPS points are compared to these threshold values, this permit to identify the weakness regions of the network in order to remedy them by changing the configuration or improvement of observations until acceptable robustness. The deformation of the network, due to measurements errors, can be expressed in terms of robustness in scale, in configuration and in twist. Throw this work, a methodology of processing, reliability and robustness analyses of GPS networks has been established. The validation of...
2020 Mediterranean and Middle-East Geoscience and Remote Sensing Symposium (M2GARSS), 2020
In this work, we present a methodology for correcting the major dominating errors in SAR interfer... more In this work, we present a methodology for correcting the major dominating errors in SAR interferograms. Ionospheric effect, orbital and tropospheric errors can lead to a serious damage the interferometric phase, and case a limitation for the retrieval of land displacement information carried by the SAR phase. To reduce the effect of these errors on an interferogram, a combined correction is applied, the Split-Spectrum Algorithm (SSA) is used for the correction of Ionospheric effect, in addition, the GACOS data is employed for tropospheric error, and finally, to quantify orbital contribution, a nonlinear model is used. This methodology is applied to a set of Sentinel-1 data; the preliminary results show an improvement of the information after the application of this joint correction.
The present paper deals with the use of neural networks in the displacement and deformation field... more The present paper deals with the use of neural networks in the displacement and deformation fields modelling and analysis. The Generalized Regression Neural Network (GRNN) has proved its efficiency and reliability than the classical methods in the approximation of the displacement function. Based on the strain tensors, the deformation of GPS network is evaluated and represented according to a regular grid. In order to analyse this deformation, the concepts of deformability and deformation reliability are introduced, where the Monte Carlo method is employed to compute the significance degrees of the resulting tensors. At each stage of deformation field process, the GRNN neural network is used to perform an optimum interpolation of displacement field. The application concerns the GPS auscultation network of the Liquefied Natural Gas (LNG) underground tank of GL4/Z industrial complex (Arzew, Algeria). Composed of 119 points surrounding the LNG tank, the GPS network was observed between...
The paper deals with the presentation of the French Transportable Laser Ranging Station (FTLRS) a... more The paper deals with the presentation of the French Transportable Laser Ranging Station (FTLRS) and its experiences of geographic positioning at Corsica (France). The geodetic site ofAjaccioinCorsicais the main calibration site, in the Mediterranean area, of radars on board altimetric satellite. It has been developed for altimetric and oceanographic missions such as TOPEX/Poseidon (T/P, 1992), Jason-1 (2001), Envisat (2002) and Jason-2 (2008). The FTLRS was deployed there during laser campaigns, on 2002 and 2005, and recently on 2008. Here, we present the analysis results of the SLR data acquired by the FTLRS during 2002 and 2005 campaigns mainly on the low Earth geodetic satellites: Starlette and Stella (altitude of 800 km). The paper describes the different steps of the laser data processing. The average arcs RMS obtained are about 1-2 cm for Lageos-1&-2, Starlette and Stella satellites; it is showed that best results of satellite orbits determination and geocentric positioning ar...
In this paper we try to process time series of posi tion coordinates using Kalman filter and Kalm... more In this paper we try to process time series of posi tion coordinates using Kalman filter and Kalman smoother and to predict the position coordin ates in intervals that contain erroneous data. Coordinates are originally obtained by relati ve GPS in kinematic way. The Kalman filter which can be implemented in real time, utilizes for computing the current estimate the precedent measurements and current measurement toge ther with their variances. In turn, the Kalman smoother, also known as the RTS (Rauch-TungStriebel) smoother gives better estimates than Kalman filter since it exploits all data, i.e., after the total measurements have been done, then, it can be used only in post-proces sing.
The objective of this work is to characterize the signals and noises of Geocenter variations time... more The objective of this work is to characterize the signals and noises of Geocenter variations time series obtained from different space geodesy techniques as Global Positioning System (GPS), Doppler Orbitography and Radiopositioning Integrated on Satellite (DORIS), and Satellite Laser Ranging (SLR). The proposed methodology is based on the estimation of periodic signals by performing frequency analysis using FAMOUS software (Frequency Analysis Mapping On Unusual Sampling) and evaluation of level and type of noises by Allan variance technique and Three Corned Hat (TCH) method. The available data concern 13 years (from 1993 to 2006) of weekly series of Geocenter residuals components and scale factor variations, according to ITRF2000. The results estimated are more accurate according to GPS and SLR of about 2-8 mm than DORIS of about 8-42 mm, for Geocenter. Better RMS of scale factor was obtained of about 0.1ppb (0.6mm) for GPS technique than SLR and DORIS with 0.6 and 0.9 ppb (3.6 and ...
Engineering, Technology & Applied Science Research
This paper presents the application of the Parallel Small Baseline Subset (P-SBAS) algorithm, pro... more This paper presents the application of the Parallel Small Baseline Subset (P-SBAS) algorithm, provided by the Geohazards Exploitation Platform for the precise monitoring of an earth dam's ground deformation using C-band Sentinel-1 data. The test site object of this study was the Kramis dam, located in the Mostaganem State, Western Algeria. Among the multiple advanced DInSAR techniques, SBAS is very adequate for long-term displacement monitoring in areas with changing terrain and vegetation. Ten corner reflectors were installed as a backscattered radar signal amplification tool to reduce the effect of temporal decorrelation and delineate the dam area. Four Sentinel-1 A and B satellite tracks were available (T30, T37, T103, and T110) to measure displacements, in the Line of Site (LoS) direction, for two years since the installation of the CRs in July 2019. The results showed a subsiding area on the left bank of the dam dike, with a velocity of 4mm/yr, and an uplifting rate of 3-4m...
Advances in Remote Sensing and Geo Informatics Applications, 2018
The purpose of this work was to characterize the signals and noises of Geocenter variations time ... more The purpose of this work was to characterize the signals and noises of Geocenter variations time series obtained from different space geodesy techniques as Global Positioning System (GPS), Doppler Orbitography and Radiopositioning Integrated on Satellite (DORIS), and Satellite Laser Ranging (SLR). The methodology proposed is based on the estimation of periodic signals by performing the frequency analysis using FAMOUS software (Frequency Analysis Mapping On Unusual Sampling) and evaluation of noises level and type by Allan variance technique. The available data covers 13 years (from 1993 to 2006) of weekly series of Geocenter residuals components, according to ITRF2000. The results obtained are more accurate according to GPS and SLR of about 2–8 mm than DORIS of about 8–42 mm. The estimated seasonal signals amplitudes are of about of few mm per technique with centimetre level for Z Geocenter coordinate of DORIS. The Geocenter motion derived from the SLR technique is more accurate and close to the geodynamic models. The noise analysis shows a dominant white noise in the SLR and DORIS solutions at level of 0.6–1 mm and 10–40 mm, respectively. However, the GPS solution is characterized by a flicker noise at the millimetre level, relating to mismodelling systematic errors.
The paper describes a simplified transformation between geographical coordinates of two ellipsoid... more The paper describes a simplified transformation between geographical coordinates of two ellipsoidal surfaces (i.e. WGS84 and Clarke 1880), applied in the North of Algeria to express the new GPS coordinates into local coordinates, useful only in small regions and suited for large scale applications such as cadastre. This transformation approach (A. Leick, 90) is based on the mixed adjustment model to estimate the four parameters transformation (2 translations, 1 rotation and scale factor) and on the geodetic lines concept, respectively the called « Inverse » and « Forward » problem of geodesy. In this context, the program developed was based on methods described above. The necessary data, the steps of processing and the results obtained were discussed.
Synthetic Aperture Radar (SAR) satellite imagery is a source of data widely employed in the quant... more Synthetic Aperture Radar (SAR) satellite imagery is a source of data widely employed in the quantification and analysis of an earthquake coseismic displacement. However, due to the signal path along the atmosphere and to other sources, the interferometric phase becomes compromised. In this work, a methodology for the correction of tropospheric and orbital errors in the differential interferogram is presented. This methodology was applied to a couple of Sentinel-1A data. The phenomenon studied was the 11th November 2018 Zeribet el Oued earthquake, Mw. 5.2 (The state of Biskra, South East of Algeria). It was possible to correct both tropospheric and orbital errors, where the dominant one was the tropospheric delay, a displacement error of 4 cm was added to the differential interferogram by this noise source. The correction of orbital error led to a better interpretation of the coseismic displacement.
On Significant Applications of Geophysical Methods, 2019
This paper deals with generation of post-seismic velocity and deformation fields of the GNSS netw... more This paper deals with generation of post-seismic velocity and deformation fields of the GNSS network of New Zealand, due to the Kaikoura earthquake (Mw7.8), on November 13th, 2016. The PPP model was performed to estimate daily coordinates, during one year (November 2016–November 2017), of 138 stations of GeoNet with RTKLIB 2.4.2 software (University of Marine Sciences and Technology of Tokyo). The Deformation analysis software (Research Institute of Geodesy, Topography and Cartography, Czech Republic) was used for obtaining results in terms of displacements and deformations (strain tensors, total dilatation, and shears). This software, as a web application, uses Web Map Services (WMS) as its graphic representation of estimated results in GIS format. The results show clearly the post-seismic activity of New Zealand, particularly, near the epicenter and at frontier zone between South and North islands.
Recent Advances in Environmental Science from the Euro-Mediterranean and Surrounding Regions, 2018
The main purpose of the paper is to examine the potential of the Artificial Neural Networks (ANN)... more The main purpose of the paper is to examine the potential of the Artificial Neural Networks (ANN), the Singular Spectrum Analysis (SSA) and their combination for concrete Dam displacements according to the Hydrostatic, seasonal, time displacement (HST) model. The ANNs are powerful tools for approximation and prediction of dam deformation and the SSA method is well suitable method for characterisation of seasonal signals and trend in time series of dam displacements. The novelty here is the combination of SSA with ANN under HST model for dam displacements prediction.
Le reservoir en sol gele du terminal methanier du complexe SONATRACH GL4/Z d'Arzew, construit... more Le reservoir en sol gele du terminal methanier du complexe SONATRACH GL4/Z d'Arzew, construit en 1965 et d'une capacite d'environ 38000m3, est le seul stockage souterrain toujours en exploitation dans le monde. Il represente pour le complexe plus de 50% de ses capacites de stockage. L'auscultation geometrique par les techniques topographiques classiques a permis de constater les deformations importantes du bac et de son voisinage immediat qui demeurent en phase d'evolution continue. A ces methodes traditionnelles de positionnement se sont substituees de nouvelles techniques plus evoluees et plus precises, basees sur l'utilisation de satellites artificiels. En effet, les imperatifs de precision de positionnement pour un ouvrage de ce type (etendue, temps, en cout et en precision), comme le GPS, rendent necessaire la mise en oeuvre de ces nouvelles techniques et leur application aux travaux de detection des deformations. La surveillance du site industriel repre...
L'etude menee a travers cet article porte sur l'etablissement des reseaux geodesiques bid... more L'etude menee a travers cet article porte sur l'etablissement des reseaux geodesiques bidimensionnels base sur les methodes d'ajustements avec contraintes internes. La notion des contraintes internes ou des reseaux libres reste tres utilisee en geodesie grâce a leur propriete d'independance du choix de configuration du Datum. Cette independance permet l'obtention d'une solution optimale du reseau estime sans aucune influence des effets externes dus au systeme de reference. Cette methode offre certains avantages (...)
L'objectif de cet article est d'etudier l'impact des mesures laser (SLR) du satellite... more L'objectif de cet article est d'etudier l'impact des mesures laser (SLR) du satellite bas starlette dans la determination precise des produits geodesiques (EOP et Geocentre ) , sur une periode de 14 ans ( 1993-2007) .Les resultats ont montre que la precision sur les trois composantes de la translation ( Mouvement du Geocentre ) , est de l'ordre de 4 et 5 mm pour les solutions LAGEOS1/2 et starlette , respectivement .Concernant les EOP , les ecarts-types des solutions LAGEOS1/2 et starlette sont (...)
Dans l'analyse des déformations des réseaux géodésiques, on distingue deux méthodes classiques d'... more Dans l'analyse des déformations des réseaux géodésiques, on distingue deux méthodes classiques d'estimation des mouvements d'une zone d'étude: les vecteurs-déplacement et les tenseurs de déformations. Cependant, l'évaluation et la représentation de la déformation dépendent du système de référence à priori et de la configuration des figures choisies qui constituent l'ensemble du réseau. Ces contraintes rendent difficile l'interprétation des résultats obtenus. A travers ce présent article, une solution basée sur la méthode des éléments finis (MEF) est proposée pour affiner l'estimation et la représentation de la déformation des réseaux géodésiques. Dans ce cadre, une étude de la déformation est effectuée pour analyser les mouvements horizontaux du réseau géodésique de Cheliff, observé par triangulation classique en 1976 (par l'INCT) et en 1981 (par le CRAAG), en se basant sur un modèle bidimensionnel d'éléments finis élastiques. Les différents résultats sont illustrés en termes de vecteurs-déplacement, de tenseurs de déformations et de tenseurs de contraintes. La déformation de la région ainsi déterminée est interprétée suivant des études géophysiques antérieures. En outre, les différents résultats ont mis en évidence les phénomènes suivants :-Un phénomène compressif de la région de Cheliff, d'orientation NNO-SSE, dû au rapprochement des deux plaques tectoniques africaine et eurasienne qui a causé la faille inverse du fameux séisme du 10 octobre 1980.
Generally, to analyse and control the quality of these GPS networks, the statistical and reliabil... more Generally, to analyse and control the quality of these GPS networks, the statistical and reliability aspects are studied. These analyses have been augmented with geometrical strength analysis using strain technique, resulting in the concept of the robustness analysis. This later is a combination of reliability and deformation of the network. The network robustness is quantified according to threshold values which are computed from errors confidence of adjusted points. The displacements of GPS points are compared to these threshold values, this permit to identify the weakness regions of the network in order to remedy them by changing the configuration or improvement of observations until acceptable robustness. The deformation of the network, due to measurements errors, can be expressed in terms of robustness in scale, in configuration and in twist. Throw this work, a methodology of processing, reliability and robustness analyses of GPS networks has been established. The validation of...
2020 Mediterranean and Middle-East Geoscience and Remote Sensing Symposium (M2GARSS), 2020
In this work, we present a methodology for correcting the major dominating errors in SAR interfer... more In this work, we present a methodology for correcting the major dominating errors in SAR interferograms. Ionospheric effect, orbital and tropospheric errors can lead to a serious damage the interferometric phase, and case a limitation for the retrieval of land displacement information carried by the SAR phase. To reduce the effect of these errors on an interferogram, a combined correction is applied, the Split-Spectrum Algorithm (SSA) is used for the correction of Ionospheric effect, in addition, the GACOS data is employed for tropospheric error, and finally, to quantify orbital contribution, a nonlinear model is used. This methodology is applied to a set of Sentinel-1 data; the preliminary results show an improvement of the information after the application of this joint correction.
The present paper deals with the use of neural networks in the displacement and deformation field... more The present paper deals with the use of neural networks in the displacement and deformation fields modelling and analysis. The Generalized Regression Neural Network (GRNN) has proved its efficiency and reliability than the classical methods in the approximation of the displacement function. Based on the strain tensors, the deformation of GPS network is evaluated and represented according to a regular grid. In order to analyse this deformation, the concepts of deformability and deformation reliability are introduced, where the Monte Carlo method is employed to compute the significance degrees of the resulting tensors. At each stage of deformation field process, the GRNN neural network is used to perform an optimum interpolation of displacement field. The application concerns the GPS auscultation network of the Liquefied Natural Gas (LNG) underground tank of GL4/Z industrial complex (Arzew, Algeria). Composed of 119 points surrounding the LNG tank, the GPS network was observed between...
The paper deals with the presentation of the French Transportable Laser Ranging Station (FTLRS) a... more The paper deals with the presentation of the French Transportable Laser Ranging Station (FTLRS) and its experiences of geographic positioning at Corsica (France). The geodetic site ofAjaccioinCorsicais the main calibration site, in the Mediterranean area, of radars on board altimetric satellite. It has been developed for altimetric and oceanographic missions such as TOPEX/Poseidon (T/P, 1992), Jason-1 (2001), Envisat (2002) and Jason-2 (2008). The FTLRS was deployed there during laser campaigns, on 2002 and 2005, and recently on 2008. Here, we present the analysis results of the SLR data acquired by the FTLRS during 2002 and 2005 campaigns mainly on the low Earth geodetic satellites: Starlette and Stella (altitude of 800 km). The paper describes the different steps of the laser data processing. The average arcs RMS obtained are about 1-2 cm for Lageos-1&-2, Starlette and Stella satellites; it is showed that best results of satellite orbits determination and geocentric positioning ar...
In this paper we try to process time series of posi tion coordinates using Kalman filter and Kalm... more In this paper we try to process time series of posi tion coordinates using Kalman filter and Kalman smoother and to predict the position coordin ates in intervals that contain erroneous data. Coordinates are originally obtained by relati ve GPS in kinematic way. The Kalman filter which can be implemented in real time, utilizes for computing the current estimate the precedent measurements and current measurement toge ther with their variances. In turn, the Kalman smoother, also known as the RTS (Rauch-TungStriebel) smoother gives better estimates than Kalman filter since it exploits all data, i.e., after the total measurements have been done, then, it can be used only in post-proces sing.
The objective of this work is to characterize the signals and noises of Geocenter variations time... more The objective of this work is to characterize the signals and noises of Geocenter variations time series obtained from different space geodesy techniques as Global Positioning System (GPS), Doppler Orbitography and Radiopositioning Integrated on Satellite (DORIS), and Satellite Laser Ranging (SLR). The proposed methodology is based on the estimation of periodic signals by performing frequency analysis using FAMOUS software (Frequency Analysis Mapping On Unusual Sampling) and evaluation of level and type of noises by Allan variance technique and Three Corned Hat (TCH) method. The available data concern 13 years (from 1993 to 2006) of weekly series of Geocenter residuals components and scale factor variations, according to ITRF2000. The results estimated are more accurate according to GPS and SLR of about 2-8 mm than DORIS of about 8-42 mm, for Geocenter. Better RMS of scale factor was obtained of about 0.1ppb (0.6mm) for GPS technique than SLR and DORIS with 0.6 and 0.9 ppb (3.6 and ...
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Papers by bachir gourine