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  • 1.
    Bagherbandi, Mohammad
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences. KTH.
    Jouybari, Arash
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    Nilfouroushan, Faramarz
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    Ågren, Jonas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences. Lantmäteriet.
    Deflection of Vertical Effect on Direct Georeferencing in Aerial Mobile Mapping Systems: A Case Study in Sweden2022In: Photogrammetric Record, ISSN 0031-868X, E-ISSN 1477-9730, Vol. 37, no 179, p. 285-305Article in journal (Refereed)
    Abstract [en]

    GNSS/INS applications are being developed, especially for direct georeferencing in airborne photogrammetry. Achieving accurately georeferenced products from the integration of GNSS and INS requires removing systematic errors in the mobile mapping systems. The INS sensor's uncertainty is decreasing; therefore, the influence of the deflection of verticals (DOV, the angle between the plumb line and normal to the ellipsoid) should be considered in the direct georeferencing. Otherwise, an error is imposed for calculating the exterior orientation parameters of the aerial images and aerial laser scanning. This study determines the DOV using the EGM2008 model and gravity data in Sweden. The impact of the DOVs on horizontal and vertical coordinates, considering different flight altitudes and camera field of view, is assessed. The results confirm that the calculated DOV components using the EGM2008 model are sufficiently accurate for aerial mapping system purposes except for mountainous areas because the topographic signal is not modelled correctly.

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  • 2.
    Bagherbandi, Mohammad
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences. KTH.
    Jouybari, Arash
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    Nilfouroushan, Faramarz
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences. Lantmäteriet.
    Ågren, Jonas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences. Lantmäteriet.
    Importance of precise gravity field modeling in direct georeferencing and aerial photogrammetry: a case study for Sweden2022In: The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XLIII-B2-2022XXIV ISPRS Congress (2022 edition), ISPRS , 2022Conference paper (Refereed)
    Abstract [en]

    Direct georeferencing of airborne mobile mapping systems is developing with unprecedented speed using GNSS/INSintegration. Removal of systematic errors is required for achieving a high accurate georeferenced product in mobile mappingplatforms with integrated GNSS/INS sensors. It is crucial to consider the deflection of verticals (DOV) in direct georeferencing dueto the recently improved INS sensor accuracy. This study determines the DOV using Sweden’s EGM2008 model and gravity data.The influence of the DOVs on horizontal and vertical coordinates and considering different flight heights is assessed. The resultsconfirm that the calculated DOV components using the EGM2008 model are sufficiently accurate for aerial photogrammetrypurposes except for the mountainous areas because the topographic signal is not modeled correctly.

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  • 3. Buiter, S.
    et al.
    Schreurs, G.
    Albertz, M.
    Beaumont, C.
    Burberry, C.
    Callot, Jean-Paul
    Cavozzi, C.
    Cerca, M.
    Chen, J. H.
    Cristallini, E.
    Cruden, A.
    Cruz, L.
    Cooke, M.
    Daniel, J. M.
    Egholm, D.
    Ellis, S.
    Gerya, T.
    Hodkinson, L.
    Hofmann, F.
    Garcia, V. H.
    Gomes, C.
    Grall, C.
    Guillou, H.
    Guzmán, C.
    Nur Hidayah, T.
    Hilley, G.
    Kaus, B.
    Klinkmüller, M.
    Koyi, H.
    Uppsala universitet, Berggrundsgeologi.
    Lazor, Peter
    Uppsala universitet, Berggrundsgeologi.
    Lu, C. Y.
    Macauley, J.
    Maillot, B.
    Meriaux, C.
    Mishin, Y.
    Nilfouroushan, Faramarz
    Uppsala universitet, Berggrundsgeologi.
    Pan, C. C.
    Pascal, C.
    Pillot, D.
    Portillo, R.
    Rosenau, R.
    Schellart, W. P.
    Schlische, R.
    Soulomiac, P.
    Take, A.
    Vendeville, B.
    Vettori, M.
    Vergnaud, M.
    Wang, S. H.
    Withjack, M.
    Yagupsky, D.
    Yamada, Y.
    Benchmarking the Sandbox: Quantitative Comparisons of Numerical and Analogue Models of Brittle Wedge Dynamics2010Conference paper (Refereed)
  • 4.
    Carrillo, Emilio
    et al.
    Departament de Geoquímica, Petrologia i Prospecció Geològica, Universitat de Barcelona, Barcelona, Spain; School of Geological Sciences and Engineering, Yachay Tech University, San Miguel de Urcuquí, Ecuador.
    Koyi, Hemin
    Hans Ramberg Tectonic Laboratory, Department of Earth Sciences, Uppsala University, Uppsala, Sweden.
    Nilfouroushan, Faramarz
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Land management, GIS. Lantmäteriet, Gävle, Sweden.
    Structural significance of an evaporite formation with lateral stratigraphic heterogeneities (Southeastern Pyrenean Basin, NE Spain)2017In: Marine and Petroleum Geology, ISSN 0264-8172, E-ISSN 1873-4073, Vol. 86, p. 1310-1326Article in journal (Refereed)
    Abstract [en]

    We run a series of analogue models to study the effect of stratigraphic heterogeneities of an evaporite formation on thin-skinned deformation of the Southeastern Pyrenean Basin (SPB; NE Spain). This basin is characterized by the existence of evaporites, deposited during the Early-Middle Eocene with lateral variations in thickness and lithological composition. These evaporites are distributed in three lithostratigraphic units, known as Serrat Evaporites, Vallfogona and Beuda Gypsum formations and acted as décollement levels, during compressional deformation in the Lutetian. In addition to analogue modeling, we have used field data, detailed geological mapping and key cross-sections supported by seismic and well data to build a new structural interpretation for the SPB. In this interpretation, it is recognized that the basal and upper parts of the Serrat Evaporites acted as the main décollement levels of the so-called Cadí thrust sheet and Serrat unit. A balanced restoration of the basin indicates that thrust faults nucleated at the stratigraphic transition of the Serrat Evaporites (zone with lateral variations of thickness and lithological composition), characterized by a wedge of anhydrite and shale. The analogue models were setup based on information extracted from cross-sections, built in two sectors with different lithology and stratigraphy of the evaporites, and the restored section of the SPB. In these models, deformation preferentially concentrated in areas where thickness change, defined by wedges of the ductile materials, was inbuilt. Based on the structural interpretation and model results, a kinematic evolution of the SPB is proposed. The kinematic model is characterized by the generation of out-of-sequence structures developed due to lateral stratigraphic variations of the Serrat Evaporites. The present work shows a good example of the role of stratigraphic heterogeneities of an evaporite formation which acts as décollement level on structural deformation in a fold-thrust belt. The results of this work have implications for hydrocarbon exploration and are relevant for studying structural geometry and mechanics in shortened evaporite basins.

  • 5.
    Darvishi, Mehdi
    et al.
    Institute for Earth Observation, EURAC Research, 18957 Bolzano, Trentino-Alto Adige Italy.
    Cuozzo, Giovanni
    Institute for Earth Observation, EURAC Research, 18957 Bolzano, Trentino-Alto Adige Italy.
    Bruzzone, Lorenzo
    Department of Information Engineering and Computer Science, Universita degli Studi di Trento, 19034 Trento, Trentino-Alto Adige Italy.
    Nilfouroushan, Faramarz
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    Performance evaluation of phase and weather-based models in atmospheric correction with Sentinel-1data: Corvara landslide in the Alps2020In: IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, ISSN 1939-1404, E-ISSN 2151-1535, Vol. 13, p. 1332-1346Article in journal (Refereed)
    Abstract [en]

    Phase delay caused by atmospheric effects due to spatial and temporal variations of pressure, temperature, and water vapor content is one of the major errors ources in estimation of ground deformation by interferometric synthetic aperture radar (InSAR). Therefore, accuracy of ground deformation measurement is highly contingent on the robustness of the atmospheric correction techniques. These techniques rely eitheron auxiliary data such as numerical weather models or on the analysis of the interferometric phase itself. The accuracyin phase delays estimation of mixing effectsof turbulent delay in atmosphere and stratified delay in lower troposphere is a key factor in determination of performanceof each technique. Hence, the performance evaluation of the techniques is required in order toassess their potentials, robustness and limitations. This paper analyzes and evaluates the performance of four numerical weather models (i.e., ERA-Interim, ERA5, MERRA2 and WRF) and two phase-based techniques (i.e., linear and power law) to estimate phase delay using Sentinel-1A/B data over the Corvara landslide located in the Alps. The GPS data and GACOS product were used to validate the results. We generally found that ERA5 outperformed among other weather models with a phase standard deviation reduction of 77.7%(with respect to the InSAR phase), a correlation coefficient of 0.86 (between InSAR phase and estimated tropospheric delay) and a less significant error in the velocity estimation of the landslide.

  • 6. Darvishi, Mehdi
    et al.
    Eriksson, Leif E. B.
    Edman, Tobias
    Toller, Erik
    Nilfouroushan, Faramarz
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    Elgered, Gunnar
    Dehls, John
    InSAR-based Ground Motion Service of Sweden: evaluation and benefit analysis of a nationwide InSAR service2022Conference paper (Refereed)
    Abstract [en]

    Space-geodetic techniques such as Global Navigation Satellite Systems (GNSS) and Syntenic Aperture Radar interferometry (InSAR) are powerful tools to measure and monitor ground surface motion. InSAR has widely been used for the detection and quantification of slow mass movements over the past three decades mainly at the local and regional scales. The high performance and millimeter-level measurement accuracy of radar satellite to provide a dense deformation map at different spatial and temporal resolutions are the key factors to think of using SAR data and InSAR technique as an efficient tool for geohazards motoring system at the nationwide scale.Sweden has recently joined to the countries having InSAR Ground Motion Service (GMS) at a nationwide scale. The InSAR service of Sweden, which will soon be freely available for users, provides the displacement time-series of measurement points for the entire country. The Swedish GMS project was started last year and is an ongoing collaboration between the Geological Survey of Norway (NGU) and several Swedish organizations (led by the Swedish National Space Agency (SNSA)). The InSAR-based GMS of Sweden has been generated by NGU using Sentinel-1 data (2015–2020) and the Persistent Scatterer Interferometry (PSI) technique. The web-based GMS of Sweden consists of ~1,5 billion time-series measurement points obtained from both descending and ascending satellite orbital modes.Currently, the Swedish GMS is under evaluation and validation phase and the given plan has been designed to assess the quality or validate the GMS products. We plan to conduct the data validation through two main phases: 1) a cross-comparison between InSAR measurement points and ancillary data such as GNSS, Corner Reflectors (CR), Electronic Corner Reflectors (ECR) and leveling data, and 2) assessment of tropospheric and ionospheric effects on InSAR measurement points. Specifically, we will evaluate different approaches and data for the InSAR tropospheric corrections, such as Very-Long-Baseline Interferometry (VLBI), Water Vapour Radiometry (WVR), and GNSS data at the Onsala Space Observatory (OSO).In the first phase of validation, leveling data collected in Gothenburg and Stockholm cities, mainly over the residential areas and public transport infrastructures compared to the corresponding InSAR measurements points (vertically converted) for a five-year period. The initial results present a high correlation between two sets of the vertical displacements. The same procedure will be performed for the Kiruna city where the mining activities resulted in adrastic urban land subsidence. Since the CRs and ECRs have recently been installed in different parts of Sweden, we do not have them as PS points in the current version of the GMS. Therefore, those CR-based measurement points will be used in future accuracy assessments. In the second phase, we investigated the effects of phase delay induced by troposphere on displacement time-series using two approaches, i.e., time-space filtering and using external data (e.g., atmospheric reanalysis data, GNSS, VLBI and Water Vapor Radiometer (WVR)). Recently, European GMS (EGMS) has been released and the Ortho displacement map is now available for users freely. We also evaluated and compared the EGMS-Ortho displacement map with our independent InSAR processing and GNSS data over the Kiruna.As the InSAR-based GMS can be used to monitor and identify the potential risk of geo-related hazards in Sweden, the society will directly benefit from the outcomes of this project. This open access product will help the stakeholders with decision support for prioritization of risk-reducing measures, and identification of the need for further investigations for areas in danger. The service could also assist municipalities and county administrative boards to have an update information regarding urban areas which are more prone to land subsidence and disruption urban infrastructure.

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  • 7.
    Darvishi, Mehdi
    et al.
    Chalmers University of Technology, Sweden.
    Eriksson, Leif E. B.
    Chalmers University of Technology, Sweden.
    Edman, Tobias
    Swedish National Space Agency, Sweden.
    Toller, Erik
    Swedish Transport Administration (Trafikverket), Sweden.
    Nilfouroushan, Faramarz
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences. Lantmäteriet.
    Elgered, Gunnar
    Chalmers University of Technology, Sweden.
    Dehls, John
    Geological Survey of Norwa.
    InSAR-based Ground Motion Service of Sweden: evaluation and benefit analysis of a nationwide InSAR service2022Conference paper (Refereed)
    Abstract [en]

    Space-geodetic techniques such as Global Navigation Satellite Systems (GNSS) and Syntenic Aperture Radar interferometry (InSAR) are powerful tools to measure and monitor ground surface motion. InSAR has widely been used for the detection and quantification of slow mass movements over the past three decades mainly at the local and regional scales. The high performance and millimeter-level measurement accuracy of radar satellite to provide a dense deformation map at different spatial and temporal resolutions are the key factors to think of using SAR data and InSAR technique as an efficient tool for geohazards motoring system at the nationwide scale.Sweden has recently joined to the countries having InSAR Ground Motion Service (GMS) at a nationwide scale. The InSAR service of Sweden, which will soon be freely available for users, provides the displacement time-series of measurement points for the entire country. The Swedish GMS project was started last year and is an ongoing collaboration between the Geological Survey of Norway (NGU) and several Swedish organizations (led by the Swedish National Space Agency (SNSA)). The InSAR-based GMS of Sweden has been generated by NGU using Sentinel-1 data (2015–2020) and the Persistent Scatterer Interferometry (PSI) technique. The web-based GMS of Sweden consists of ~1,5 billion time-series measurement points obtained from both descending and ascending satellite orbital modes.Currently, the Swedish GMS is under evaluation and validation phase and the given plan has been designed to assess the quality or validate the GMS products. We plan to conduct the data validation through two main phases: 1) a cross-comparison between InSAR measurement points and ancillary data such as GNSS, Corner Reflectors (CR), Electronic Corner Reflectors (ECR) and leveling data, and 2) assessment of tropospheric and ionospheric effects on InSAR measurement points. Specifically, we will evaluate different approaches and data for the InSAR tropospheric corrections, such as Very-Long-Baseline Interferometry (VLBI), Water Vapour Radiometry (WVR), and GNSS data at the Onsala Space Observatory (OSO).

    In the first phase of validation, leveling data collected in Gothenburg and Stockholm cities, mainly over the residential areas and public transport infrastructures compared to the corresponding InSAR measurements points (vertically converted) for a five-year period. The initial results present a high correlation between two sets of the vertical displacements. The same procedure will be performed for the Kiruna city where the mining activities resulted in a drastic urban land subsidence. Since the CRs and ECRs have recently been installed in different parts of Sweden, we do not have them as PS points in the current version of the GMS. Therefore, those CR-based measurement points will be used in future accuracy assessments.

    As the InSAR-based GMS can be used to monitor and identify the potential risk of geo-related hazards in Sweden, the society will directly benefit from the outcomes of this project. This open access product will help the stakeholders with decision support for prioritization of risk-reducing measures, and identification of the need for further investigations for areas in danger. The service could also assist municipalities and county administrative boards to have an update information regarding urban areas which are more prone to land subsidence and disruption urban infrastructure.

  • 8.
    Deng, Hongling
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Mineralogi, petrologi och tektonik.
    Koyi, Hemin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Mineralogi, petrologi och tektonik.
    Nilfouroushan, Faramarz
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Mineralogi, petrologi och tektonik.
    Superimposed folding and thrusting by two phases of mutually orthogonal or oblique shortening in analogue models2016In: Journal of Structural Geology, ISSN 0191-8141, E-ISSN 1873-1201, Vol. 83, p. 28-45Article in journal (Refereed)
    Abstract [en]

    Orogens may suffer more than one phase shortening resulting in superposition of structures of different generations. Superimposition of orthogonal or oblique shortening is studied using sandbox and centrifuge modelling. Results of sand models show that in orthogonal superimposition, the two resulting structural trends are approximately orthogonal to each other. In oblique superimposition, structures trend obliquely to each other in the relatively thin areas of the model (foreland), and mutually orthogonal in areas where the model is thickened during the first phase of shortening (i.e. the hinterland). Thrusts formed during the first shortening phase may be reactivated during the later shortening phase. Spacing of the later phase structures is not as wide as expected, considering they across the pre-existing thickened wedge. Superposition of structures results in formation of type 1 fold interference pattern. Bedding is curved outwards both in the dome and basin structures. Folded layers are dipping and plunging outwards in a dome, while they are dipping and plunging inwards in a basin. In the areas between two adjacent domes or basins (i.e. where an anticline is superimposed by a syncline or a syncline is superimposed by an anticline), bedding is curved inwards, and the anticlines plunge inwards and the synclines outwards. The latter feature could be helpful to determine the age relationship for type 2 fold interference pattern. In tectonic regions where multiple phases of shortening have occurred, the orogenic-scale dome-and-basin and arrowhead-shaped interference patterns are commonly formed, as in the models. However, in some areas, the fold interference pattern might be modified by a later phase of thrusting. Similar to models results, superimposition of two and/or even more deformation phases may not be recorded by structures all over the tectonic area.

  • 9.
    Edey, A.
    et al.
    University of Durham, UK.
    Allen, M. B
    University of Durham, UK.
    Nilfouroushan, Faramarz
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences. Lantmäteriet.
    Kinematic variation within the Fars Arc, eastern Zagros, and the development of fold‐and‐thrust belt curvature2020In: Tectonics, ISSN 0278-7407, E-ISSN 1944-9194, Vol. 39, no 8, article id e2019TC005941Article in journal (Refereed)
    Abstract [en]

    We analyze deformation of the Fars Arc in the eastern Zagros, Iran, including earthquake slip vectors, GPS velocities, paleomagnetism data, and fold orientations, to understand how this fold‐and‐thrust belt works, and so better understand the generic issue of fold‐and‐thrust belt curvature. The Fars Arc is curved, convex southwards. GPS‐derived rotation rates are ≤0.5° Myr‐1: rotation is clockwise west of 53° E, and counter‐clockwise to the east. These rotation senses are opposite to previous predictions of passive “bookshelf” models for strike‐slip faults during north‐south convergence. West of 53° E, average GPS vectors, thrust earthquake slip vectors, strain axes derived from GPS data and orthogonal directions to fold trends are all aligned, towards ~218°. East of this meridian, the average GPS vector is towards 208°, but the averages of the other datasets are distinctly different, all towards ~190°. We propose that fault blocks in eastern Fars, each ~20‐40 km long, rotate predominantly counter‐clockwise, whereas in western Fars the regional clockwise rotation takes place mainly on the array of active right‐lateral faults in this area. Thus localized block faulting and rotations accumulate to produce the overall strain and regional curvature. Active folds of different orientations in eastern Fars intersect to produce domal interference patterns, without involving separate deformation phases, indicating that fold interference patterns should not be interpreted in terms of changing stress orientations unless there is clear evidence. Fars Arc curvature is best explained by deformation being restricted at tectonic boundaries at its eastern and western margins, without significant gravitational spreading.

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  • 10.
    Farzipour-Saein, Ali
    et al.
    Department of Geology, University of Isfahan, Iran.
    Nilfouroushan, Faramarz
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Koyi, Hemin
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    The effect of basement step/topography on the geometry of the Zagros fold and thrust belt (SW Iran): an analogue modeling approach2013In: International journal of earth sciences, ISSN 1437-3254, E-ISSN 1437-3262, Vol. 102, no 8, p. 2117-2135Article in journal (Refereed)
    Abstract [en]

    Systematic analogue models are run to study the variation in deformation across basement steps in the Zagros Fold-Thrust Belt. Our model results demonstrate that basement configuration/topography influences the sedimentation thickness and, hence, the kinematics and geometric evolution of the fold and thrust belt. The greater the difference in thickness between the adjacent cover units across a basement step, the sharper and clearer will be the offset the deformation front. Based on model results, we conclude that in a fold-thrust belt, where basement step/topography is covered by a layer of ductile salt acting as a decollement, the effect of the salt decollement on the evolution of the belt is far greater than the effect of thickness variation of the cover units.

  • 11. Fryksten, Jonas
    et al.
    Nilfouroushan, Faramarz
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    Analysis of Clay-Induced Land Subsidence in Uppsala City Using Sentinel-1 SAR Data and Precise Leveling2019In: Remote Sensing, E-ISSN 2072-4292, Vol. 11, no 23, article id 2764Article in journal (Refereed)
    Abstract [en]

    Land subsidence and its subsequent hazardous effects on buildings and urban infrastructure are important issues in many cities around the world. The city of Uppsala in Sweden is undergoing significant subsidence in areas that are located on clay. Underlying clay units in parts of Uppsala act as mechanically weak layers, which for instance, cause sinking of the ground surface and tilting buildings. Interferometric Synthetic Aperture Radar (InSAR) has given rise to new methods of measuring movements on earth surface with a precision of a few mm. In this study, a Persistent Scatterer InSAR (PSI) analysis was performed to map the ongoing ground deformation in Uppsala. The subsidence rate measured with PSI was validated with precise leveling data at different locations. Two ascending and descending data sets were analyzed using SARPROZ software, with Sentinel-1 data from the period March 2015 to April 2019. After the PSI analyses, comparative permanent scatterer (PS) points and metal pegs (measured with precise leveling) were identified creating validation pairs. According to the PSI analyses, Uppsala was undergoing significant subsidence in some areas, with an annual rate of about 6 mm/year in the line-of-sight direction. Interestingly, the areas of great deformation were exclusively found on postglacial clay.

  • 12.
    Ganas, Athanassios
    et al.
    National Observatory of Athens, Greece.
    Kapetanidis, Vasilis
    University of Athens, Greece.
    Nilfouroushan, Faramarz
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Land management, GIS.
    Steffen, Holger
    Lidberg, Martin
    Deprez, Aline
    CNRS-UGA, France.
    Socquet, Anne
    CNRS-UGA, France.
    Walpersdorf, Andrea
    University of Grenoble, France.
    D'Agostino, Nicola
    INGV, France.
    Avallone, Antonio
    INGV, France.
    Legrand, Juliette
    ROB.
    Fernandes, Rui
    UBI-C4G.
    Nastase, Eduard Ilie
    National Institute for Earth Physics.
    Bos, Machiel
    UBI-C4G.
    Kenyeres, Ambrus
    BFKH Budapest, Bulgaria.
    Developments on the EPOS-IP pan-european strain rate product2018In: Book of Abstracts of the 36th General Assembly of the European Seismological Commission / [ed] D'Amico S., Galea P., Bozionelos G., Colica E., Farrugia D., Agius M.R., 2018, article id ESC2018-S2-749Conference paper (Refereed)
    Abstract [en]

    Strain rates are of great importance for Solid Earth Sciences. Within the EU Horizon 2020 project EPOS-IP WP10 (Global Navigation Satellite System - GNSS thematic core services) a series of products focused on strain rates derived from GNSS data is envisaged. In this contribution, we present preliminary results from 452 permanent European GNSS stations, operating until 2017 and processed at UGA-CNRS (Université Grenoble Alpes, Centre National de la Recherche Scientifique). We calculate the strain-rate field using two open-source algorithms recommended by EPOS-IP, namely the VISR (Velocity Interpolation for Strain Rate) algorithm (Shen et al., 2015) and STIB (Strain Tensor from Inversion of Baselines), developed by Masson et al., (2014) as well as the SSPX software suite (Cardozo and Allmendinger, 2009). The vertical velocity component is ignored in this stage and other sources of deformation (GIA, hydrological, anthropogenic et al.) are not considered in the interpretation. We compare the results derived from different methods and discuss the similarities and differences. Overall, our first results reproduce the gross features of tectonic deformation in both Italy and Greece, such as NE-SW extension across the Apennines and N-S extension in Central Greece. It is anticipated that the significant increase of GNSS data amount associated with the operational phase of EPOS project in the forthcoming years will be of great value to perform an unprecedented, reliable strain rate computation over the western Eurasian plate.

  • 13.
    Gido, Nureldin A. A.
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    Amin, Hadi
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    Bagherbandi, Mohammad
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    Nilfouroushan, Faramarz
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    Satellite monitoring of mass changes and ground subsidence in Sudan’s oil fields using GRACE and Sentinel-1 data2020Conference paper (Other (popular science, discussion, etc.))
    Abstract [en]

    Monitoring environmental hazards, due to natural and anthropogenic causes, is one of the important issues, which requires proper data, models, and cross-validation of the results. The geodetic satellite missions, e.g. the Gravity Recovery and Climate Experiment (GRACE) and Sentinel-1, are very useful in this aspect. GRACE missions are dedicated to model the temporal variations of the Earth’s gravity field and mass transportation in the Earth’s surface, whereas Sentinel-1 collects Synthetic Aperture Radar (SAR) data which enables us to measure the ground movements accurately. Extraction of large volumes of water and oil decreases the reservoir pressure, form compaction and consequently land subsidence occurs which can be analyzed by both GRACE and Sentinel-1 data. In this paper, large-scale groundwater storage (GWS) changes are studied using the GRACE monthly gravity field models together with different hydrological models over the major oil reservoirs in Sudan, i.e. Heglig, Bamboo, Neem, Diffra and Unity-area oil fields. Then we correlate the results with the available oil wells production data for the period of 2003-2012. In addition, using the only freely available Sentinel-1 data, collected between November 2015 and April 2019, the ground surface deformation associated with this oil and water depletion is studied. Due to the lack of terrestrial geodetic monitoring data in Sudan, the use of GRACE and Sentinel-1 satellite data is very valuable to monitor water and oil storage changes and their associated land subsidence over our region of interest. Our results show that there is a significant correlation between the GRACE-based GWS change and extracted oil and water volumes. The trend of GWS changes due to water and oil depletion ranged from -18.5 to -6.2mm/year using the CSR GRACE monthly solutions and the best tested hydrological model in this study. Moreover, our Sentinel-1 SAR data analysis using Persistent Scatterer Interferometry (PSI) method shows high rate of subsidence i.e. -24.5, -23.8, -14.2 and -6 mm/year over Heglig, Neem, Diffra and Unity-area oil fields respectively. The results of this study can help us to control the integrity and safety of operations and infrastructure in that region, as well as to study the groundwater/oil storage behavior.

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  • 14.
    Gido, Nureldin A. A.
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    Amin, Hadi
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    Bagherbandi, Mohammad
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    Nilfouroushan, Faramarz
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    Satellite Monitoring of Mass Changes and Ground Subsidence in Sudan’s Oil Fields Using GRACE and Sentinel-1 Data2020In: Remote Sensing, E-ISSN 2072-4292, Vol. 12, no 11, article id 1792Article in journal (Refereed)
    Abstract [en]

    Monitoring environmental hazards, owing to natural and anthropogenic causes, is an important issue, which requires proper data, models, and cross-validation of the results. The geodetic satellite missions, for example, the Gravity Recovery and Climate Experiment (GRACE) and Sentinel-1, are very useful in this respect. GRACE missions are dedicated to modeling the temporal variations of the Earth’s gravity field and mass transportation in the Earth’s surface, whereas Sentinel-1 collects synthetic aperture radar (SAR) data, which enables us to measure the ground movements accurately. Extraction of large volumes of water and oil decreases the reservoir pressure and form compaction and, consequently, land subsidence occurs, which can be analyzed by both GRACE and Sentinel-1 data. In this paper, large-scale groundwater storage (GWS) changes are studied using the GRACE monthly gravity field models together with different hydrological models over the major oil reservoirs in Sudan, that is, Heglig, Bamboo, Neem, Diffra, and Unity-area oil fields. Then, we correlate the results with the available oil wells production data for the period of 2003–2012. In addition, using the only freely available Sentinel-1 data, collected between November 2015 and April 2019, the ground surface deformation associated with this oil and water depletion is studied. Owing to the lack of terrestrial geodetic monitoring data in Sudan, the use of GRACE and Sentinel-1 satellite data is very valuable to monitor water and oil storage changes and their associated land subsidence over our region of interest. Our results show that there is a significant correlation between the GRACE-based GWS anomalies (ΔGWS) and extracted oil and water volumes. The trend of ΔGWS changes due to water and oil depletion ranged from –18.5 ± 6.3 to –6.2 ± 1.3 mm/year using the CSR GRACE monthly solutions and the best tested hydrological model in this study. Moreover, our Sentinel-1 SAR data analysis using the persistent scatterer interferometry (PSI) method shows a high rate of subsidence, that is, –24.5 ± 0.85, –23.8 ± 0.96, –14.2 ± 0.85, and –6 ± 0.88 mm/year over Heglig, Neem, Diffra, and Unity-area oil fields, respectively. The results of this study can help us to control the integrity and safety of operations and infrastructure in that region, as well as to study the groundwater/oil storage behavior.

  • 15.
    Gido, Nureldin A. A.
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences. KTH.
    Bagherbandi, Mohammad
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences. KTH.
    Nilfouroushan, Faramarz
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences. Lantmäteriet.
    Localized subsidence zones in Gävle city detected by Sentinel-1 PSI and leveling data2020In: Remote Sensing, E-ISSN 2072-4292, Vol. 12, no 16, article id 2629Article in journal (Refereed)
    Abstract [en]

    Among different sets of constraints and hazards that have to be considered in management of cities and land use, land surface subsidence is one of the important issues that can lead to many problems and its economic consequences cannot be ignored. In this study, the ground surface deformation of Gävle city in Sweden is investigated using Persistent Scatterer Interferometry (PSI) technique as well as analyzing the historical leveling data. The PSI technique is used to map the location of hazard zones and their ongoing subsidence rate. Two ascending and descending Sentinel-1 data sets, collected between Jan 2015 and May 2020, covering the Gävle city were processed and analyzed. In addition, a long record of leveling dataset, covering the period from 1974 to 2019, was used to detect the rate of subsidence in some locations which were not reported before. Our PSI analysis reveals that the center of Gävle is relatively stable with minor deformation ranged between -2±0.5 mm/yr to +2±0.5 mm/yr in vertical and East-West components. However, the land surface toward the northeast of the city is relatively subsiding with higher annual rate up to -6±0.46 mm/yr. The comparison at sparse locations shows a close agreement between the subsidence rates obtained from precise leveling and PSI results. The regional quaternary deposits map was overlaid with PSI results and it shows the subsidence areas are mostly located in zones where the subsurface layer is marked by artificial fill materials. The knowledge of the spatio-temporal extents of land surface subsidence for undergoing urban areas can help to develop and establish models to mitigate hazards associated with such land settlement.

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  • 16. Gruber, T
    et al.
    Ågren, Jonas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    Angermann, D.
    Ellmann, A.
    Engfeldt, A.
    Gisinger, C.
    Jaworski, L.
    Marila, M.
    Nastula, J.
    Nilfouroushan, Faramarz
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    Oikonomidou, X.
    Poutanen, M.
    Saari, T
    Schlaak, M
    Światek, A
    Sander, V
    Zdunek, R
    Geodetic SAR for Height System Unification and Sea Level Research - Observation Concept and Results in the Baltic Sea2021Conference paper (Refereed)
    Abstract [en]

    Traditionally, sea level is observed at tide gauge stations, which usually also serve as height reference stations for national leveling networks and therefore define a height system of a country. Thus, sea level research across countries is closely linked to height system unification and needs to be regarded jointly. One of the main deficiencies to use tide gauge data for geodetic sea level research and height systems unification is that only a few stations are connected to permanent GNSS receivers next to the tide gauge in order to systematically observe vertical land motion. As a new observation technique, absolute positioning by SAR using active transponders on ground can fill this gap by systematically observing time series of geometric heights at tide gauge stations. By additionally knowing the tide gauge geoid heights in a global height reference frame, one can finally obtain absolute sea level heights at each tide gauge. With this information the impact of climate change on the sea level can be quantified in an absolute manner and height systems can be connected across the oceans. First results from applying this technique at selected tide gauges at the Baltic coasts are promising but also exhibit some problems related to the new technique. The paper presents the concept of using the new observation type in an integrated sea level observing system and provides results for a test network in the Baltic sea area by combining geometric and physical heights with tide gauge readings.

  • 17.
    Gruber, Thomas
    et al.
    Technical University of Munich, Germany.
    Angermann, Detlef
    Technical University of Munich, Germany.
    Schlaak, Marius
    Technical University of Munich, Germany.
    Oikonomidou, Xanthi
    Technical University of Munich, Germany.
    Gisinger, Christoph
    Deutsches Zentrum für Luft- und Raumfahrt.
    Brcic, Ramon
    Deutsches Zentrum für Luft- und Raumfahrt.
    Poutanen, Markku
    Finnish Geospatial Research Institute.
    Marila, Simo
    Finnish Geospatial Research Institute.
    Koivula, Hannu
    Finnish Geospatial Research Institute.
    Nordman, Maaria
    Finnish Geospatial Research Institute.
    Saari, Timo
    Finnish Geospatial Research Institute.
    Nastula, Jolanta
    Centrum Badań Kosmicznych Polskiej Akademii Nauk.
    Zdunek, Ruszard
    Tallinn University of Technology.
    Ellmann, Art
    Tallinn University of Technology.
    Sander, Varbla
    Tallinn University of Technology.
    Ågren, Jonas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences. Lantmäteriet.
    Nilfouroushan, Faramarz
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences. Lantmäteriet.
    Geodetic SAR for Baltic Height System Unification and Baltic Sea Level Research2021Report (Refereed)
    Abstract [en]

    Traditionally, sea level is observed at tide gauge stations, which usually also serve as height reference stations for national levelling networks and therefore define a height system of a country. Thus, sea level research across countries is closely linked to height system unification and needs to be regarded jointly. The project aims to make use of a new observation technique, namely SAR positioning, which can help to connect the GNSS basic network of a country to tide gauge stations and as such to link the sea level records of tide gauge stations to the geometric network. By knowing the geoid heights at the tide gauge stations in a global height reference frame with high precision, one can finally obtain absolute sea level heights of the tide gauge stations in a common reference system and can link them together. By this method, on the one hand national height systems can be connected and on the other hand the absolute sea level at the tide gauge stations can be determined. By analysing time series of absolute sea level heights their changes can be determined in an absolute sense in a global reference frame and the impact of climate change on sea level can be quantified (e.g. by ice sheet and glacier melting, water inflow, global warming). The major scientific challenges to be addressed by this project then can be summarized as follows: (1) Connection of the tide gauge markers with the GNSS network geometrically in order to determine the relative vertical motion and to correct the tide gauge readings. For this the new technique of SAR positioning is applied. (2) Determination of a GOCE based high resolution geoid at tide gauge stations in order to deliver absolute heights of tide gauges with respect to a global equipotential surface as reference. (3) Joint analysis of geometrical and physical reference frames to make them compatible, and to determine corrections to be applied for combined analysis of geometric and physical heights.

  • 18.
    Gruber, Thomas
    et al.
    Technical University of Munich (TUM), Germany.
    Ågren, Jonas
    Lantmäteriet.
    Angermann, Detlef
    Technical University of Munich (TUM), Germany.
    Ellmann, Artu
    Tallinn University of Technology (TUT), Estonia.
    Engfeldt, Andreas
    Lantmäteriet.
    Gisinger, Christoph
    German Aerospace Center (DLR).
    Jaworski, Leszek
    Centrum Badań Kosmicznych, Polskiej Akademii Nauk (CBK-PAN), Poland.
    Kur, Tomasz
    Centrum Badań Kosmicznych, Polskiej Akademii Nauk (CBK-PAN), Poland.
    Marila, Simo
    Finnish Geospatial Research Institute (FGI).
    Nastula, Jolanta
    Centrum Badań Kosmicznych, Polskiej Akademii Nauk (CBK-PAN), Poland.
    Nilfouroushan, Faramarz
    Lantmäteriet.
    Nordman, Maria
    Finnish Geospatial Research Institute (FGI); Aalto University, Finland.
    Poutanen, Markku
    Finnish Geospatial Research Institute (FGI).
    Saari, Timo
    Finnish Geospatial Research Institute (FGI).
    Schlaak, Marius
    Technical University of Munich (TUM).
    Świątek, Anna
    Centrum Badań Kosmicznych, Polskiej Akademii Nauk (CBK-PAN), Poland.
    Varbla, Sander
    Tallinn University of Technology (TUT).
    Zdunek, Ryszard
    Centrum Badań Kosmicznych, Polskiej Akademii Nauk (CBK-PAN), Poland.
    Geodetic SAR for Height System Unification and Sea Level Research - Results in the Baltic Sea Test Network2022In: Remote Sensing, E-ISSN 2072-4292, Vol. 14, no 14, article id 3250Article in journal (Refereed)
    Abstract [en]

    Coastal sea level is observed at tide gauge stations, which usually also serve as height reference stations for national networks. One of the main issues with using tide gauge data for sea level research is that only a few stations are connected to permanent GNSS stations needed to correct for vertical land motion. As a new observation technique, absolute positioning by SAR using off the shelf active radar transponders can be installed instead. SAR data for the year 2020 are collected at 12 stations in the Baltic Sea area, which are co-located to tide gauges or permanent GNSS stations. From the SAR data, 3D coordinates are estimated and jointly analyzed with GNSS data, tide gauge records and regional geoid height estimates. The obtained results are promising but also exhibit some problems related to the electronic transponders and their performance. At co-located GNSS stations, the estimated ellipsoidal heights agree in a range between about 2 and 50 cm for both observation systems. From the results, it can be identified that, most likely, variable systematic electronic instrument delays are the main reason, and that each transponder instrument needs to be calibrated individually. Nevertheless, the project provides a valuable data set, which offers the possibility of enhancing methods and procedures in order to develop a geodetic SAR positioning technique towards operability. 

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  • 19.
    Gruber, Thomas
    et al.
    Technical University of Munich.
    Ågren, Jonas
    Lantmäteriet.
    Angermann, Detlef
    Technical University of Munich.
    Ellmann, Artu
    Tallinn University of Technology.
    Engfeldt, Andreas
    Lantmäteriet.
    Gisinger, Christoph
    German Aerospace Center.
    Jaworski, Leszek
    Polskiej Akademii Nauk.
    Marila, Simo
    Finnish Geospatial Research Institute.
    Nastula, Jolanta
    Polskiej Akademii Nauk.
    Nilfouroushan, Faramarz
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences. Lantmäteriet.
    Oikonomidou, Xanthi
    Technical University of Munich.
    Poutanen, Markku
    Saari, Timo
    Finnish Geospatial Research Institute.
    Schlaak, Marius
    Technical University of Munich .
    Światek, Anna
    Polskiej Akademii Nauk.
    Varbla, Sander
    Tallinn University of Technology.
    Zdunek, Ryszard
    Tallinn University of Technology.
    Geodetic SAR for Height System Unification and Sea Level Research - Observation Concept and Preliminary Results in the Baltic Sea2020In: Remote Sensing, E-ISSN 2072-4292, Vol. 12, no 22Article in journal (Refereed)
    Abstract [en]

    Traditionally, sea level is observed at tide gauge stations, which usually also serve as height reference stations for national leveling networks and therefore define a height system of a country. One of the main deficiencies to use tide gauge data for geodetic sea level research and height systems unification is that only a few stations are connected to the geometric network of a country by operating permanent GNSS receivers next to the tide gauge. As a new observation technique, absolute positioning by SAR using active transponders on ground can fill this gap by systematically observing time series of geometric heights at tide gauge stations. By additionally knowing the tide gauge geoid heights in a global height reference frame, one can finally obtain absolute sea level heights at each tide gauge. With this information the impact of climate change on the sea level can be quantified in an absolute manner and height systems can be connected across the oceans. First results from applying this technique at selected tide gauges at the Baltic coasts are promising but also exhibit some problems related to the new technique. The paper presents the concept of using the new observation type in an integrated sea level observing system and provides some early results for SAR positioning in the Baltic sea area.

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  • 20.
    Gruber, Thomas
    et al.
    Technical University of Munich, Institute of Astronomical and Physical Geodesy, Germany.
    Ågren, Jonas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences. Lantmäteriet.
    Angermann, Detlef
    Technical University of Munich, Deutsches Geodätisches Forschungsinstitut, Germany.
    Ellmann, Artu
    Tallinn University of Technology, School of Engineering, Estonia.
    Gisinger, Christoph
    German Aerospace Center, Remote Sensing Technology, Germany.
    Nastula, Jolanta
    Centrum Badań Kosmicznych, Polskiej Akademii Nauk, Poland.
    Poutanen, Markku
    Finnish Geospatial Research Institute, Finland.
    Schlaak, Marius
    Technical University of Munich, Germany.
    Nilfouroushan, Faramarz
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences. Lantmäteriet.
    Varbla, Sander
    Tallinn University of Technology, School of Engineering, Estonia.
    Zdunek, Ryszard
    Centrum Badań Kosmicznych, Polskiej Akademii Nauk, Poland.
    Marila, Simo
    Finnish Geospatial Research Institute, Finland.
    Engfeldt, Andreas
    Lantmäteriet, Swedish Mapping, Cadastral and Land Registration Authority, Sweden.
    Saari, Timo
    Finnish Geospatial Research Institute, Finland.
    Świątek, Anna
    Centrum Badań Kosmicznych, Polskiej Akademii Nauk, Poland.
    Geodetic SAR for Height System Unification and Sea Level Research - Observation Concept and Results in the Baltic Sea2022Conference paper (Refereed)
    Abstract [en]

    Traditionally, sea level is observed at tide gauge stations, which usually also serve as height reference stations for national leveling networks and therefore define a height system of a country. Thus, sea level research across countries is closely linked to height system unification and needs to be regarded jointly. One of the main deficiencies to use tide gauge data for geodetic sea level research and height systems unification is that only a few stations are connected to permanent GNSS receivers next to the tide gauge in order to systematically observe vertical land motion. As a new observation technique, absolute positioning by SAR using active transponders on ground can fill this gap by systematically observing time series of geometric heights at tide gauge stations. By additionally knowing the tide gauge geoid heights in a global height reference frame, one can finally obtain absolute sea level heights at each tide gauge. With this information the impact of climate change on the sea level can be quantified in an absolute manner and height systems can be connected across the oceans.The paper presents the results of a project, which was conducted in the years 2019 to 2021 in the frame of ESA´s Baltic+ initiative. Within this project a test network of electronic corner reflectors (ECR) as targets for Sentinel-1 was realized in the Baltic Sea area. The ECR locations were either co-located with tide gauges or with permanent GNSS stations in order to observe systematically the ellipsoidal heights of the tide gauges and possibly also any vertical land motion at the stations. Data for the year 2020 were collected at 10 stations in Estonia, Finland, Poland and Sweden and jointly analyzed with GNSS data, tide gauge records and regional geoid height estimates. The obtained results are promising, but also exhibit some problems related to the ECR´s and their performance. At co-located GNSS stations the estimated ellipsoidal heights agree in a range between about 2 and 50 cm between both observation systems. From the results it could be identified that most likely variable systematic electronic instrument delays of the ECR´s are the main reason for these differences and that each instrument needs to be calibrated individually. Nevertheless, the project provides a valuable data set, which offers the possibility to enhance methods and procedures in order to develop the geodetic SAR positioning technique towards operability. All data and reports are accessible at the following web site: https://www.asg.ed.tum.de/iapg/baltic/

  • 21.
    Jivall, Lotti
    et al.
    Lantmäteriet.
    Nilfouroushan, Faramarz
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Land management, GIS.
    Mast-based versus Pillar-based Networks for Coordinate Estimation of SWEREF points: – using the Bernese and GAMIT-GLOBK Software Packages2015Report (Other academic)
    Abstract [en]

    For about 20 years, the fundamental pillar stations in SWEPOS network (the Swedish Permanent GNSS network) have been used as the carrier of the Swedish national reference frame, SWEREF 99, and used as control points for several geodetic and geodynamic studies. Today, each pillar station has a close-by truss mast station, mostly in 10 meters distance. Switching from pillar-based network to mast-based network (with stations equipped with more modern receivers and calibrated antennas), as reference network,need careful analysis, for example, comparing solutions from these networks. In this study, we use both the Bernese GNSS Software (BSW) and GAMIT-GLOBK softwareand process the same data set with almost the same processing strategy and compare the results. Our solutions and their comparisons show that BSWhas slightly lower rate of resolved integer ambiguities for the mast-basednetwork compared to the pillar-basednetwork (3-4percentage pointsfor the selected 14 SWEREF points and 1-2percentage pointsfor all SWEREFpoints (50) processed in this study).For GAMIT-GLOBK, we don’tsee any significant difference in the rate of resolved integer ambiguities between the network types.Furthermore, the comparison of resulting coordinates between the two software, show avery good compliancefor the pillar-based network (on average at the 1 mm level for the horizontal components and 2 mm for the height component), but for the mast-based network there is 3-4 mm systematic difference in the height component.The good compliance between the GAMIT-GLOBK and BSW solutions for the pillar network,makes it possible to use results also from GAMIT-GLOBK for coordinate determination of SWEREF points. The systematic height difference between the two software solutions for the mast-based network,as well as slightly degraded quality measures mainlyfor BSW,indicate that there are some problems with the mast stations that need further investigation.

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  • 22.
    Jivall, Lotti
    et al.
    Lantmäteriet.
    Nilfouroushan, Faramarz
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    Al Munaizel, Naim
    Lantmäteriet.
    Analysis of 20 years of GPS data from SWEREF consolidation points – using BERNESE and GAMIT-GLOBK software2022Report (Other (popular science, discussion, etc.))
    Abstract [en]

    The SWEREF 99 national geodetic reference frame has been used in Sweden since 2007 and it was adopted by EUREF in 2000 as the national realisation of ETRS89 in Sweden [Jivall and Lidberg, 2000]. The SWEREF 99 reference frame is defined by an active approach through the 21 original (fundamental) SWEPOS GNSS stations, hence relying on positioning services such as the network real time kinematic (NRTK) and post processing services. The SWEREF 99 coordinates are assumed to be fixed in time and no temporal variations are expected. However, the stability of the stations and their coordinates can be altered due to equipment change or software as well as local movements at the reference stations.To be able to check all alterations mentioned above and having a backup national network of GNSS points, approximately 300 passive so-called consolidation points are used. The consolidation points are a subset (the main part) of the so-called SWEREF points established from 1996 and onwards. All 300 points are remeasured with static GNSS for 2x24 hours using choke ring antennas on a yearly basis with 50 points each year. The original data processing was done with the Bernese GNSS software in a regular basis and the reprocessing was carried out with both the Bernese and the GAMIT-GLOBK software packages during 2017-2018.The resulting coordinates in SWEREF 99 from GAMIT and Bernese processing are equal at 1–2 mm level for the horizontal and 4 mm for the vertical components (1 sigma) when using almost the same models and processing strategy. The result from the original processing, which partly is based on other models and parameters, differs slightly more for the north component compared to the reprocessing results (RMS of 2 mm compared to 1 mm).Our analysis both of Bernese and GAMIT results shows that the standard uncertainties for a single SWEREF 99 coordinate determination (with 2x24 hrs observation) is about 2 mm for the horizontal components and 6 mm in height. It is interesting to note that the coordinate repeatability is on the same level also for the original processing, where we have differences in models and parameters used during the years. This indicates that our concept for determining SWEREF 99 coordinates has worked well on the mentioned uncertainty level.We performed trend analysis and statistical tests for the points having minimum three observations to investigate the stability of the estimated SWEREF 99 coordinates. The low rate of redundancy (just one redundant observation in case of three observations) was a problem so a modified version of the F-test was developed which gave good agreement with visual interpretation of the time series. This strategy showed that about 10% of the points had trends (with notable movements), but we should be aware of the low redundancy. With more observations in the future, we can determine trends more reliably.We will continue to analyse the point coordinate repeatability and trends when we get more data. Further on, some reprocessing is needed to be compatible with the SWEREF 99 update 2021 at SWEPOS. We will also study the effect of using different satellite systems and finally prepare for the publication of updated coordinates in the Digital Geodetic Archive (DGA) provided by Lantmäteriet.

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  • 23.
    Jivall, Lotti
    et al.
    Geodata Division, Lantmäteriet, Gävle, Sweden.
    Nilfouroushan, Faramarz
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences. Geodata Division, Lantmäteriet, Gävle, Sweden.
    Al Munaizel, Naim
    Geodata Division, Lantmäteriet, Gävle, Sweden.
    Lilje, Christina
    Geodata Division, Lantmäteriet, Gävle, Sweden.
    Kempe, Christina
    Geodata Division, Lantmäteriet, Gävle, Sweden.
    Maintenance of the National Realization of ETRS89 in Sweden : re-analysis of 20 years’ GPS data for SWEREF stations2019In: EUREF 2019 Symposium: Abstracts, 2019Conference paper (Refereed)
    Abstract [en]

    The national geodetic reference frame of Sweden called SWEREF 99, was adopted in 2000 by EUREF as the realisation of ETRS89 in Sweden and was officially introduced in 2001 as a national reference frame, that eventually in 2007 replaced the former reference frame. The SWEREF 99 reference frame is defined by an active approach through the 21 fundamental SWEPOS permanent GNSS stations, hence relying on positioning services such as the network real time kinematic (NRTK) and post processing service. The SWEREF 99 coordinates are assumed to be fixed in time and no temporal variations are expected. However, the stability of the stations and their coordinates can be altered due to equipment change or software as well as local movements at the reference stations.

    To be able to check all alterations mentioned above and having a backup national network of GNSS stations, approximately 300 passive so-called consolidation stations are used. The consolidation stations are a subset (main part) of the so-called SWEREF stations established from 1996 and onwards. All 300 stations are remeasured with static GNSS for 2x24 hours using choke ring antennas on a yearly basis with 50 stations each year. The original processing was done with the Bernese GNSS software (here called Bernese original) and the reprocessing was carried out with both the Bernese and the GAMIT-GLOBK software packages during 2017-2018.

    The resulting coordinates in SWEREF 99 from GAMIT and Bernese processing are equal at 1.2 mm level for horizontal and 4 mm for vertical components (1 sigma) when using the same models and processing strategy. The original processing, which partly is based on other models and parameters, differs slightly more (rms 2.4mm) for the north component. Our analysis both from Bernese and GAMIT shows that the standard uncertainties for a single SWEREF 99 determination (2x24 hrs) is 2 mm for the horizontal components and 6-7 mm in height. However, since some stations are slowly moving they have slightly increased the estimated uncertainties. It is interesting to note that the repeatability is on the same level also for the original processing, where we have differences in models and parameters used during the years. This indicates that the SWEREF-concept of determining SWEREF 99 coordinates has worked well on the mentioned uncertainty level.

    We performed trend analysis and statistical tests to investigate the stability of the estimated SWEREF 99 coordinates. The analysed station time series (minimum three observations) showed that about 14% of the stations had significant trends at the 95%-level. The possible explanation for those trends can be either local deformation and/or residuals of uplift model and/or computational effects such as lack of good or enough close-by stations for Helmert transformations from ITRF to SWEREF 99.

    The outcomes of the new processing and analysis reported here, are used to analyse the stability of SWEREF99 after two decades. The results have also been used to define the SWEREF 99 component in the fit of theSWEN17_RH2000 new geoid model to SWEREF 99 and RH 2000 (Swedish realisation of EVRS).

  • 24.
    Joudaki, Masoud
    et al.
    Univ Isfahan, Dept Geol, Esfahan, Iran.
    Farzipour-Saein, Ali
    Univ Isfahan, Dept Geol, Esfahan, Iran.
    Nilfouroushan, Faramarz
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Kinematics and surface fracture pattern of the Anaran basement fault zone in NW of the Zagros Fold-Thrust Belt2016In: International journal of earth sciences, ISSN 1437-3254, E-ISSN 1437-3262, Vol. 105, no 3, p. 869-883Article in journal (Refereed)
    Abstract [en]

    The preexisting north-south trending basement faults and their reactivation played an important role during the evolution of the Zagros fold-thrust belt. The Anaran basement fault in the Lurestan region, NW of the Zagros, has been considered as a N-S trending basement lineament, although its surface structural expression is still debated. In this study, we use satellite images and field observations to identify and analyze the fractures in the sedimentary cover above the Anaran basement fault. Fracture analysis demonstrates that approaching the Anaran basement fault, the fracture pattern changes. The fractures association with reactivation of the deep-seated preexisting Anaran basement fault can be categorized in 4 sets based on their directions. The mean direction for maximum compressional stress is different between the fault- and fold-related fractures within and around the ABF shear zone. We estimated an orientation of N30±5° for the fault-related fractures and N45±5° for the fold-related fracture sets outside of the ABF shear zone. This difference suggests that the fold-related and fault-related fracture sets have been formed in different two stages of deformation throughout the area. The axial traces of some folds, especially the Anaran anticline, demonstrate a right-lateral offset along the ABF, such that, in central part of the Anaran anticline, the fold axis of this anticline is changed from its original NW–SE trend to approximately north-south trend of the ABF.

  • 25.
    Jouybari, Arash
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    Bagherbandi, Mohammad
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    Nilfouroushan, Faramarz
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    Assessment of Different GNSS and IMU Observation Weights on Photogrammetry Aerial Triangulation2020Conference paper (Refereed)
    Abstract [en]

    Nowadays, the Global Navigation Satellite System (GNSS) and Inertial Navigation System (INS) are playing a prominent character in high accuracy navigation applications. Beside camera calibration and tie points which are crucial, GNSS shift and drift errors, which caused by either unknown GNSS antenna-eccentricity, atmospheric effect, GNSS and INS observation qualities, unsolved datum correction between coordinate systems and far away GNSS reference stations from the project area, are important factors in bundle block adjustment ultimate accuracy. In this study, the influence of different a priori observation uncertainties of GNSS and Inertial Measurement Unit (IMU) using block- Aerial Triangulation (AT) method is examined. We investigate the effect of IMU and GNSS uncertainties on the final AT results using Trimble Inpho Match-AT software by evaluating the checkpoints RMS residual and employing a statistical t-test for determining the number of images with the gross error. In our study area, the most trustworthy observation uncertainties was 0.2, 0.2, 0.2 meter for East, North, and Height of the GNSS components respectively, and 0.007, 0.007, 0.009 for Omega, Phi, and Kappa for the IMU orientations, respectively.

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  • 26.
    Jouybari, Arash
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    Bagherbandi, Mohammad
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    Nilfouroushan, Faramarz
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    Comparison of the strip- and block-wise aerial triangulation using different exterior orientation parameters weights2022In: Journal of Spatial Science, ISSN 1449-8596, Vol. 67, no 3, p. 377-394Article in journal (Refereed)
    Abstract [en]

    In this study, three different procedures: checkpoint RMS of residuals, statistical evaluation of AT results using t-test, and comparison of a photogrammetric digital surface model (DSM) and LiDAR data are used to analyse the effect of IMU and GNSS uncertainties on the final adjusted results. The outcome suggests that the method of block-wise GNSS shift correction is the better method for aerial triangulation and one should use appropriate observable weights in AT. The comparison of checkpoint RMS residuals between the two methods shows that the block-wise solution is on average 6cm more accurate than the strip-wise solution.

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  • 27.
    Jouybari, Arash
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    Bagherbandi, Mohammad
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences. KTH.
    Nilfouroushan, Faramarz
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences. Lantmäteriet.
    Impact of GNSS Signal outage on EOPs using forward Kalman filter and smoothing algorithm2022In: The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XLIII-B2-2022XXIV ISPRS Congress (2022 edition), ISPRS , 2022, p. 59-64Conference paper (Refereed)
    Abstract [en]

    The global navigation satellite system (GNSS) has been playing the principal role in positioning applications in past decades. Position robustness degrades with a standalone receiver due to GNSS signal outage in mobile mapping systems. The GNSS and inertial measurement unit (IMU) integration is used to solve positioning degradation. This article studies the GNSS/IMU integration processing (i.e., forward Kalman filter (KF) and smoothing algorithm) using a single or a network of nearby GNSS reference stations. In addition, we analyze the impact of simulated GNSS signal outage on exterior orientation parameters (EOPs). The outcomes confirm that the smoothing algorithm works better than the forward KF and improves the accuracy for position and orientation in the case when there is no GNSS signal outage. Also, it improves the position and orientation accuracy by about 95% and 60% when there is a 180 second GNSS signal outage, respectively.

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  • 28.
    Jouybari, Arash
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    Bagherbandi, Mohammad
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences. KTH.
    Nilfouroushan, Faramarz
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences. Lantmäteriet.
    Numerical Analysis of GNSS Signal Outage Effect on EOPs Solutions Using Tightly Coupled GNSS/IMU Integration: A Simulated Case Study in Sweden2023In: Sensors, E-ISSN 1424-8220, Vol. 23, no 14, article id 6361Article in journal (Refereed)
    Abstract [en]

    The absence of a reliable Global Navigation Satellite System (GNSS) signal leads to degraded position robustness in standalone receivers. To address this issue, integrating GNSS with inertial measurement units (IMUs) can improve positioning accuracy. This article analyzes the performance of tightly coupled GNSS/IMU integration, specifically the forward Kalman filter and smoothing algorithm, using both single and network GNSS stations and the post-processed kinematic (PPK) method. Additionally, the impact of simulated GNSS signal outage on exterior orientation parameters (EOPs) solutions is investigated. Results demonstrate that the smoothing algorithm enhances positioning uncertainty (RMSE) for north, east, and heading by approximately 17–43% (e.g., it improves north RMSE from 51 mm to a range of 42 mm, representing a 17% improvement). Orientation uncertainty is reduced by about 60% for roll, pitch, and heading. Moreover, the algorithm mitigates the effects of GNSS signal outage, improving position uncertainty by up to 95% and orientation uncertainty by up to 60% using the smoothing algorithm instead of the forward Kalman filter for signal outages up to 180 s.

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  • 29. Kaviani, A.
    et al.
    Mahmoodabadi, M.
    Rümpker, G.
    Yamini-Fard, F.
    Tatar, M.
    Motavalli-Anbaran, J.
    Rahimzadeh, S.
    Moradi, A.
    Nilfouroushan, Faramarz
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    Complex pattern of seismic anisotropy beneath the Iranian plateau and Zagros2019Conference paper (Refereed)
    Abstract [en]

    We performed shear wave splitting analyses on core-refracted teleseismic shear waveforms from 150 broad-bandstations across the Iranian plateau and Zagros to investigate seismic anisotropy in the region. Seismic anisotropyis quantified by shear-wave splitting parameters, i.e. fast polarization direction and split delay time.Our measurements revealed a complex pattern of splitting parameters with variations in the trend and strength ofanisotropy across the tectonic boundaries. This complex pattern implies that a system of simple asthenosphericflow related to the absolute plate motion cannot alone explain our observations and that the lithosphere also hasa significant contribution in many parts. We compare our results to the surface deformation and velocity fieldsinferred from geodetic measurements to assess the role of the mantle in continental deformation. The rotationalpattern of the fast directions around the collision zone in Central Zagros may indicate the presence of a mantleflow around a continental keel beneath the Zagros. The agreement between the crustal and mantle deformationfield in Central Iran implies a vertically coherent deformation in this region, whereas the azimuthal variations insplitting parameters in the collision zone may suggest multi-layered anisotropy with different contributions fromthe crust and mantle.

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  • 30.
    Kaviani, Ayoub
    et al.
    Goethe University, Frankfurt.
    Mahmoodabadi, Meysam
    Goethe University, Frankfurt; International Institute of Earthquake Engineering and Seismology, Tehran, Iran.
    Rümpker, Georg
    Goethe University, Frankfurt.
    Pilia, Simone
    University of Cambridge.
    Tatar, Mohammad
    International Institute of Earthquake Engineering and Seismology, Tehran, Iran.
    Nilfouroushan, Faramarz
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences. Lantmäteriet.
    Yamini-Fard, Farzam
    International Institute of Earthquake Engineering and Seismology, Tehran, Iran.
    Moradi, Ali
    University of Tehran.
    Ali, Mohammed Y
    Khalifa University of Science and Technology, Abu Dhabi.
    Mantle-flow diversion beneath the Iranian plateau induced by Zagros’ lithospheric keel2021In: Scientific Reports, E-ISSN 2045-2322, Vol. 11, no 1, article id 2848Article in journal (Refereed)
    Abstract [en]

    Previous investigation of seismic anisotropy indicates the presence of a simple mantle flow regime beneath the Turkish-Anatolian Plateau and Arabian Plate. Numerical modeling suggests that this simple flow is a component of a large-scale global mantle flow associated with the African superplume, which plays a key role in the geodynamic framework of the Arabia-Eurasia continental collision zone. However, the extent and impact of the flow pattern farther east beneath the Iranian Plateau and Zagros remains unclear. While the relatively smoothly varying lithospheric thickness beneath the Anatolian Plateau and Arabian Plate allows progress of the simple mantle flow, the variable lithospheric thickness across the Iranian Plateau is expected to impose additional boundary conditions on the mantle flow field. In this study, for the first time, we use an unprecedented data set of seismic waveforms from a network of 245 seismic stations to examine the mantle flow pattern and lithospheric deformation over the entire region of the Iranian Plateau and Zagros by investigation of seismic anisotropy. We also examine the correlation between the pattern of seismic anisotropy, plate motion using GPS velocities and surface strain fields. Our study reveals a complex pattern of seismic anisotropy that implies a similarly complex mantle flow field. The pattern of seismic anisotropy suggests that the regional simple mantle flow beneath the Arabian Platform and eastern Turkey deflects as a circular flow around the thick Zagros lithosphere. This circular flow merges into a toroidal component beneath the NW Zagros that is likely an indicator of a lateral discontinuity in the lithosphere. Our examination also suggests that the main lithospheric deformation in the Zagros occurs as an axial shortening across the belt, whereas in the eastern Alborz and Kopeh-Dagh a belt-parallel horizontal lithospheric deformation plays a major role.

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  • 31.
    Kaviani, Ayoub
    et al.
    Johann Wolfgang Goethe University, Germany.
    Mahmoodabadi, Meysam
    Johann Wolfgang Goethe University, Germany; International Institute of Earthquake Engineering and Seismology, Tehran, Iran.
    Rümpker, Georg
    Johann Wolfgang Goethe University, Germany.
    Yamini-Fard, Farzam
    International Institute of Earthquake Engineering and Seismology, Tehran, Iran.
    Tatar, Mohammad
    International Institute of Earthquake Engineering and Seismology, Tehran, Iran.
    Moradi, Ali
    University of Tehran, Iran.
    Nilfouroushan, Faramarz
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences. Lantmäteriet.
    SKS splitting observations across the Iranian plateau and Zagros: the role of lithosphere deformation and mantle flow2020Conference paper (Refereed)
    Abstract [en]

    We used more than one decade of core-refracted teleseismic shear (SKS) waveforms recorded atmore than 160 broadband seismic stations across the Iranian plateau and Zagros to investigateseismic anisotropy beneath the region. Splitting analysis of SKS waveforms provides two mainparameters, i.e., fast polarization direction and split delay time, which serve as proxies for thetrend and strength of seismic anisotropy beneath the stations. Our observation revealed acomplex pattern of splitting parameters with variations in the trend and strength of anisotropyacross the tectonic boundaries. We also verified the presence of multiple layers of anisotropy inconjunction with the lithosphere deformation and mantle flow field. Our observation andmodeling imply that a combined system of lithosphere deformation and asthenospheric flow islikely responsible for the observed pattern of anisotropy across the Iranian Plateau and Zagros.The rotational pattern of the fast polarization directions observed locally in Central Zagros mayindicate the diversion of mantle flow around a continental keel beneath the Zagros. Thecorrelation between the variation in lithosphere thickness and the trend of anisotropy in the studyarea implies that the topography of the base of lithosphere is also a determining factor for thepattern of mantle flow inferred from the observations.

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  • 32.
    Khorrami, F.
    et al.
    National Cartographic Center, Geodesy and Land Surveying, Tehran, Iran (Islamic Republic of).
    Vernant, P.
    Géosciences Montpellier- CNRS, Geosciences, Montpeliier, France.
    Masson, F.
    IPGS/EOST CNRS/University Strasbourg, Earth Sciences, Strasbourg, France.
    Nilfouroushan, Faramarz
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences. Lantmäteriet, Gävle, Sweden.
    Mousavi, Z.
    Institute for Advanced Studies in Basic Sciences IASBS.
    Nankali, H.
    National Cartographic Center, Geodesy and Land Surveying, Tehran, Iran (Islamic Republic of).
    Saadat, S.A.
    National Cartographic Center, Geodesy and Land Surveying, Tehran, Iran (Islamic Republic of).
    Walpersdorf, A.
    University Grenoble Alpes- CNRS, ISTerre, Grenoble, France.
    Hosseini, S.
    National Cartographic Center, Geodesy and Land Surveying, Tehran, Iran (Islamic Republic of).
    Tavakoli, P.
    National Cartographic Center, Geodesy and Land Surveying, Tehran, Iran (Islamic Republic of).
    Aghamohammadi, A.
    National Cartographic Center, Geodesy and Land Surveying, Tehran, Iran (Islamic Republic of).
    Alijanzade, M.
    National Cartographic Center, Geodesy and Land Surveying, Tehran, Iran (Islamic Republic of).
    An up-to-date block model and strain rate map of Iran using integrated campaign-mode and permanent GPS velocities2019In: 27th IUGG General Assembly: G06 - Posters - Monitoring and Understanding the Dynamic Earth With Geodetic Observations, 2019Conference paper (Refereed)
    Abstract [en]

    Iran accommodates a large part of the ongoing Arabia-Eurasia collision deformation. Because of such active tectonics, the country suffers from intensive seismicity and frequent destructive earthquakes in different locations.To study further the crustal deformation in Iran, we processed the data collected during 10 years (2006-2015) from the Iranian Permanent GNSS Network and combined them with previously published velocity solutions from GPS survey measurements during 1997–2013. We analysed this velocity field using a continuum approach to compute a new strain rate map for this region and we designed a block model based on the main geological, morphological, and seismic structures. Comparison between both approaches suggests similar results and allow us to present the first comprehensive first order fault slip rate estimates for the whole of Iran. Our results confirm most of the results from previous geodetic studies. Moreover, we also show a trade-off between the coupling ratio of the Iranian Makran subduction interface and the kinematic of the faults north of the Makran in the Jazmurian depression. Although too scarce to accurately estimate a coupling ratio, we show that coupling higher than 0.4 on the plate interface down to a depth of 25 km will induce extension on the E-W faults in the Jazmurian region. However, the sites close to the shoreline suggest a low coupling ratio, hence the coupling on this plate interface is probably more complicated than previously described and the Iranian Makran subduction interface mechanical behaviour might be similar to that on the Hellenic subduction zone.

  • 33. Khorrami, Fateme
    et al.
    Masson, Frederic
    Nilfouroushan, Faramarz
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Land management, GIS.
    Vernant, Philippe
    Saadat, Seyed Abdoreza
    Nankali, Hamidreza
    Hosseini, Sedigheh
    Aghamohamadi, Azadeh
    An up-to-date GPS velocity field of Iran2017In: Geophysical Research Abstracts, 2017, Vol. 19, article id EGU2017-7268Conference paper (Refereed)
    Abstract [en]

    In this study we present an up-to-date velocity field of Iran, including the largest number of data ever presentedon this region. It includes both a synthesis of all previously published campaign data (Raeesi et al., 2016) andall data from the Iranian Permanent GNSS Network (IPGN). The IPGN data cover some parts of Iran whichwere previously scarcely documented. These stations have been measured for 7 years. In total, more than 400instrumented sites are presented. From this velocity field, we calculated the strain rate.In this paper, we will show the contribution of this very dense velocity field to the detailed understanding of theactive tectonics of the various regions of Iran (Makran, Zagros, Alborz, ...).

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  • 34.
    Khorrami, Fatemeh
    et al.
    National Cartographic Center, Tehran, Iran.
    Vernant, Philippe
    Géosciences Montpellier, CNRS/University Montpellier, Montpellier, France.
    Masson, Frederic
    IPGS/EOST CNRS/University Strasbourg, Strasbourg Cedex, France.
    Nilfouroushan, Faramarz
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences. Lantmäteriet, Gävle, Sweden.
    Mousavi, Zahra
    Department of Earth Sciences, Institute for Advanced Studies in Basic Sciences (IASBS), Zanjan, Iran.
    Nankali, Hamidreza
    National Cartographic Center, Tehran, Iran.
    Saadat, Seyed Abdolreza
    National Cartographic Center, Tehran, Iran.
    Walpersdorf, Andrea
    University Grenoble Alpes, CNRS, IRD, IFSTTAR, ISTerre, Grenoble, France.
    Hosseini, Sedighe
    National Cartographic Center, Tehran, Iran.
    Tavakoli, Parastoo
    National Cartographic Center, Tehran, Iran.
    Aghamohammadi, Azade
    National Cartographic Center, Tehran, Iran.
    Alijanzade, Mahnaz
    National Cartographic Center, Tehran, Iran.
    An up-to-date crustal deformation map of Iran using integrated campaign-mode and permanent GPS velocities2019In: Geophysical Journal International, ISSN 0956-540X, E-ISSN 1365-246X, Vol. 217, no 2, p. 832-843Article in journal (Refereed)
    Abstract [en]

    We present the most extensive and up-to-date unified GPS velocity field for Iran. We processed the data collected during 10 years (2006–2015) from the Iranian Permanent GNSS Network (IPGN) and combined them with previously published velocity solutions from GPS survey measurements during 1997–2013. We analysed this velocity field using a continuum approach to compute a new strain rate map for this region and we designed a block model based on the main geological, morphological, and seismic structures. Comparison between both approaches suggests similar results and allow us to present the first comprehensive first order fault slip rate estimates for the whole of Iran. Our results confirm most of the results from previous geodetic studies. But we also show a trade-off between the coupling ratio of the Iranian Makran subduction interface and the kinematic of the faults north of the Makran in the Jazmurian depression. Indeed, although too scarce to accurately estimate a coupling ratio, we show that coupling higher than 0.4 on the plate interface down to a depth of 25 km will induce extension on the E-W faults in the Jazmurian region. However, the sites close to the shoreline suggest a low coupling ratio, hence the coupling on this plate interface is probably more complicated than previously described and the Iranian Makran subduction interface mechanical behaviour might be similar to that on the Hellenic subduction zone.

  • 35.
    Khoshlahjeh Azar, Mahdi
    et al.
    K. N. Toosi University of Technology, Tehran, Iran.
    Shami, Siavash
    K. N. Toosi University of Technology, Tehran, Iran.
    Nilfouroushan, Faramarz
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences. Lantmäteriet.
    Salimi, Maryam
    Shahid Beheshti University, Tehran, Iran.
    Bolorfroshan, Mahdieh Ghayoor
    Ferdowsi University of Mashhad, Mashhad, Iran.
    Reshadi, Mir Amir Mohammad
    University of Waterloo, Waterloo, ON, Canada.
    Integrated analysis of Hashtgerd plain deformation, using Sentinel-1 SAR, geological and hydrological data2022In: Scientific Reports, E-ISSN 2045-2322, Vol. 12, article id 21522Article in journal (Refereed)
    Abstract [en]

    Due to its proximity to Tehran, the Hashtgerd catchment in Iran is an important region that has experienced alarming subsidence rates in recent years. This study estimated the ground surface deformation in the Hashtgerd plain between 2015 and 2020 using Sentinel-1 SAR data and InSAR technique. The average LOS displacement of the ascending and descending tracks was -23 cm/year and -22 cm/year, respectively. The central area of the plain experienced the greatest vertical subsidence, with a more than -100 cm cumulative displacement. The Karaj-Qazvin railway and highway that pass through this area have been damaged by subsidence, according to an analysis of profiles drawn along the transportation lines. The southern sections of Hashtgerd city have experienced a total displacement of -30 cm/year over the course of about six years. The relationship between changes in groundwater level and subsidence rate in this region was examined using piezometer and precipitation data. Geoelectric sections and piezometric well logs were also utilized to investigate the geological characteristics of the Hashtgerd aquifer. According to the findings, the leading causes of subsidence were uncontrolled groundwater abstraction. This research highlights the need to comprehend the spatial distribution of confined aquifers and their effect on subsidence, which can aid in the development of a suitable management strategy to restore these aquifers.

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  • 36.
    Koyi, Hemin
    et al.
    Hans Ramberg Tectonic Laboratory, Department of Earth Sciences, Uppsala University, Uppsala, Sweden.
    Nilfouroushan, Faramarz
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Land management, GIS. Hans Ramberg Tectonic Laboratory, Deptartment of Earth Sciences, Uppsala University, Uppsala, Sweden.
    Hessami, Khaled
    International Institute of Earthquake Engineering and Seismology (IIEES), Tehran, Iran.
    Modelling role of basement block rotation and strike-slip faulting on structural pattern in cover units of fold-and-thrust belts2016In: Geological Magazine, ISSN 0016-7568, E-ISSN 1469-5081, Vol. 153, no 5-6, p. 827-844Article in journal (Refereed)
    Abstract [en]

    A series of scaled analogue models are used to study (de)coupling between basement and cover deformation. Rigid basal blocks were rotated about a vertical axis in a 'bookshelf'€™ fashion, which caused strike-slip faulting along the blocks and in the overlying cover units of loose sand. Three different combinations of cover–basement deformations are modelled: (i) cover shortening before basement fault movement; (ii) basement fault movement before cover shortening; and (iii) simultaneous cover shortening with basement fault movement. Results show that the effect of the basement faults depends on the timing of their reactivation. Pre- and syn-orogenic basement fault movements have a significant impact on the structural pattern of the cover units, whereas post-orogenic basement fault movement has less influence on the thickened hinterland of the overlying belt. The interaction of basement faulting and cover shortening results in the formation of rhombic structures. In models with pre- and syn-orogenic basement strike-slip faults, rhombic blocks develop as a result of shortening of the overlying cover during basement faulting. These rhombic blocks are similar in appearance to flower structures, but are different in kinematics, genesis and structural extent. We compare these model results to both the Zagros fold-and-thrust belt in southwestern Iran and the Alborz Mountains in northern Iran. Based on the model results, we conclude that the traces of basement faults in cover units rotate and migrate towards the foreland during regional shortening. As such, these traces do not necessarily indicate the actual location or orientation of the basement faults which created them.

  • 37.
    Lacombe, Olivier
    et al.
    Institut des Sciences de la Terre de Paris (iSTeP), Sorbonne Universités, Paris, France.
    Ruh, Jonas
    Institut des Sciences de la Terre de Paris (iSTeP), Sorbonne Universités, Paris, France; Instituto de Ciencias de la Tierra “Jaume Almera”, CSIC, Barcelona, Spain.
    Brown, Dennis
    Instituto de Ciencias de la Tierra “Jaume Almera”, CSIC, Barcelona, Spain.
    Nilfouroushan, Faramarz
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Land management, GIS. Geodetic infrastructure Department, Lantmäteriet, Gävle, Sweden.
    Introduction: tectonic evolution and mechanics of basement-involved fold-and-thrust belts2016In: Geological Magazine, ISSN 0016-7568, E-ISSN 1469-5081, Vol. 153, no 5-6, p. 759-762Article in journal (Refereed)
    Abstract [en]

    Defining the structural style of fold-and-thrust belts is an important step for understanding the factors that control their long- and short-term dynamics, for comprehending seismic hazard associated with them, and for assessing their economic potential. While the thin-skinned model (no basement involvement) has long been the driving methodology for cross section construction and restoration of foreland fold-and-thrustbelts, a wealth of new geological and geophysical studies have shown that they are often thick-skinned, that is, basement-involved.

  • 38.
    Liu, Zhina
    et al.
    Uppsala universitet, Berggrundsgeologi.
    Koyi, Hemin
    Uppsala universitet, Berggrundsgeologi.
    Nilfouroushan, Faramarz
    Uppsala universitet, Berggrundsgeologi.
    Kinematics and internal deformation within 3-D granular slopes: insights from analogue models and natural slopes2013Conference paper (Refereed)
    Abstract [en]

    This study uses results of a series of analogue models, scanned data of natural landslides, and sections of natural failed slopes to investigate the kinematics and internal deformation during the failure of an unstable slope. The models simulate collapse of granular slopes by focusing on the spatial and temporal distribution of their internal structures. Model results show that the collapse of granular slopes resulted in different-generation extensional normal faults at the back of the slope, and contractional structures such as overturned folds, shealth folds and thrusts at the toe of the slope. The failure surfaces and the volume of the failure mass changed both spatially and temporally. Our model results show also that the nature of runout base has a significant influence on the kinematics and internal deformational structures. The runout distance increased with decreasing basal friction of a rigid runout base, and the topography at the slope toe was much gentler in the model with lower basal friction along the rigid runout base. The runout distance was shortest in the granular slope with deformable runout base. More extensional normal faults occurred in the model with low-friction runout base, whereas more shortening structures formed in the model with high-friction runout base. Similar tomodel results, our field observations indicate the presence of at least two generations of failure surfaces where the older ones are steeper.

  • 39.
    Liu, Zhina
    et al.
    Uppsala universitet, Institutionen för geovetenskaper.
    Koyi, Hemin
    Uppsala universitet, Institutionen för geovetenskaper.
    Nilfouroushan, Faramarz
    Uppsala universitet, Institutionen för geovetenskaper.
    Swantesson, Jan
    Karlstads universitet, Fakulteten för samhälls- och livsvetenskaper, Avdelningen för hälsa och miljö.
    Reshetyuk, Yuriy
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Urban and regional planning/GIS-institute.
    Internal deformation within an unstable granular slope: insights from physical modeling2012Conference paper (Other academic)
    Abstract [en]

    The collapses of granular materials frequently occur in nature in the form of, for example, rock avalanches, debrisavalanches and debris flow. In previous studies of collapses of a granular material, most of the focus has been onthe effect of initial geometry and mechanical properties of the granular materials, the run-out distance, and thetopography of final deposit. In this study, results of analogue models and scanned natural failed slopes are usedto outline the mode of failure of an unstable slope. Model results and field observations are used to argue that agranular mass moves downslope in a wavy pattern resulting in its intensive deformation.In the models, we mainly investigated the internal deformation of collapses of granular slopes in terms of theirinternal structures and the spatial and temporal distribution of the latter. Model results showed that a displacedmass of the granular slope has the following two features: (1) Initial collapse resulted in a series of normal faults,where hanging-wall blocks were slightly deformed, like the slump-shear structures in nature; (2) With furthercollapse, a set of secondary structures, such as deformed/folded fault surfaces, faulted folds, displaced inclinedfolds, and overturned folds formed near the slope surface. The occurrence of these structures reflects the failureprocess of the granular mass in space and time. In addition, our model results show that the nature of basal frictionhas a significant influence on the geometry and kinematics of these structures at the slope toe. Model results showalso that the mass does not glide downslope along only one surface, but includes several gliding surfaces each ofwhich take part of the sliding. These gliding surfaces become steeper deeper in the sliding mass. Some of thesefeatures observed in the models are also detected in the field. Scanned failed slope surfaces show a wavy patternsimilar to that in the models, reflecting the presence of normal faults at the head of the slope and folding at theslope toe.

  • 40.
    Liu, Zhina
    et al.
    Uppsala universitet, Berggrundsgeologi.
    Koyi, Hemin
    Uppsala universitet, Berggrundsgeologi.
    Swantesson, Jan
    Karlstad University.
    Nilfouroushan, Faramarz
    Uppsala universitet, Berggrundsgeologi.
    Reshetyuk, Yuriy
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Urban and regional planning/GIS-institute.
    Kinematics and 3-D internal deformation of granular slopes: analogue models and natural landslides2013In: Journal of Structural Geology, ISSN 0191-8141, E-ISSN 1873-1201, Vol. 53, p. 27-42Article in journal (Refereed)
    Abstract [en]

    This study uses results from a series of analogue models, and field observations, scanned data and sections of natural landslides to investigate the kinematics and internal deformation during the failure of an unstable slope. The models simulate collapse of granular slopes and focus on the spatial and temporal distribution of their internal structures. Using a series of systematically designed models, we have studied the effect of friction and deformability of the runout base on internal deformation within a granular slope. The results of these different models show that the collapse of granular slopes resulted in different-generation extensional faults at the back of the slope, and contractional structures (overturned folds, sheath folds and thrusts) at the toe of the slope. The failure surfaces and the volume of the failure mass changed both spatially and temporally. Younger failure surfaces formed in the back of the older ones by incorporating additional new material from the head of the slope. Our model results also show that the nature of the runout base has a significant influence on the runout distance, topography and internal deformation of a granular slope. Model results are compared with natural landslides where local profiles were dug in order to decipher the internal structures of the failure mass. The natural cases show similar structural distribution at the head and toe of the failure mass. As in model results, our field observations indicate the presence of at least two generations of failure surfaces where the older ones are steeper.

  • 41.
    Malehmir, Alireza
    et al.
    Uppsala universitet.
    Darvishi, Mehdi
    Stockholms universitet.
    Nilfouroushan, Faramarz
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences. Lantmäteriet.
    Integration of InSAR and ground-based geophysical measurements to study an area prone to quick-clay landslide in Sweden2021In: EGU General Assembly 2021, 2021Conference paper (Refereed)
    Abstract [en]

    Landslides and floods are the two most important geohazards in Sweden. Due to the climate change effects, it is believed that the risk of occurring these geohazards will increase in Sweden causing for example the land to become more prone to landslides. Additionally, due to the isostatic uplift caused by the retreating of the ice sheet, approximately 10,000 years ago, marine sediments involving marine clays have become exposed above sea level in Scandinavia. Infiltration of fresh water has (and is) leached the salt from the pores within the marine clays leading to the formation a special kind of clay known as the quick clay in the northern countries. These glacial clays and postglacial silts cause more ground surface instability and slopes become more prone to trigger landslides, which is the case for concentration of the most landslides in the southwest of Sweden. Hence, quick-clay landslides are common geohazards in Nordic countries, which potentially could cause a considerable economical and live cost. The most recent Gjerdurm landslide in Norway was of this kind quick-clay related. In recent years, an area close to the Göta River of southeast of Sweden has been the subject of numerous surface and airborne geophysical surveys for detailed subsurface mapping and delineation of the quick-clay and sediments hosting them including the very undulating the crystalline bedrock. These existing studies including access to bore hole observations and geotechnical studies motivated us to study also long-term surface deformation in order to study climate effects, erosion, precipitation and underlying quick-clay presence in this area and neighboring regions. We employed radar data with Syntenic Aperture Radar (SAR) interferometry techniques. To this end, Sentinel-1 data from 2015 to 2019 were processed with the Small BAslineSubset (SBAS) technique to estimate time-series displacements and to generate deformation map for that region. The initial results show that the heterogenous deformation observed in the study area with maximum subsidence rate of -22 mm/yr. The deforming areas appear to be located on regions with the thickest column of the clay near the river where we anticipate also thicker quickclay layers present. The quick-clays in this region overlie a thick (ca. 20 m) coarse-grained layer interpreted from the surface geophysical measurements to be associated with the formation and triggering of quick-clays in the area. With such a large surface deformation and the underling geology, we observe two phenomena in the study. A possible sudden risk of quick-clay landslide but also a long-term creeping of clays and destabilizing effect that may accelerate erosion at the river bank causing more landslides in the future. The cause of the large deformation is still unclear and will be investigated together with hydrogeological and geophysical data available in the study.This study however provides compelling evidence of major surface deformation that should be considered for long-term risk mitigation and planning.

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  • 42.
    Mehrabi, Ali
    et al.
    Department of Geography, Shahid Bahonar University of Kerman, Kerman, Iran.
    Derakhshani, Reza
    Department of Geology, Shahid Bahonar University of Kerman, Kerman, Iran;Department of Earth Sciences, Utrecht University, Utrecht, Netherlands.
    Nilfouroushan, Faramarz
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences. Lantmäteriet.
    Rahnamarad, Jafar
    Department of Geology, Islamic Azad University, Zahedan Branch, Zahedan, Iran.
    Azarafza, Mohammad
    Department of Civil Engineering, University of Tabriz, Tabriz, Iran.
    Spatiotemporal subsidence over Pabdana coal mine Kerman Province, central Iran using time-series of Sentinel-1 remote sensing imagery2023In: Episodes, ISSN 0705-3797, Vol. 46, no 1, p. 19-33Article in journal (Refereed)
    Abstract [en]

    Environmental monitoring of mining regions using satellite imagery is crucial for sustainable exploitation andnpreventing geohazards. Movements due to the failure of the roof in underground coal mining, by migrating upwards and outwards from the seam being mined, could eventually appear as ground deformation. To investigate the matter further, the surface deformation that occurred over the Pabdana mining area was monitored in three time periods, between October 2, 2014, and July 27, 2019. Persistent scatterer interferometry (PSI) was used based on 150 ascending and descending Sentinel-1A images. The maximum mining subsidence rate during the studied periods was about 30 to 35 mm/yr. The PSI analysis shows that the subsidence rate varied both temporally and spatially during the three studied periods. The time series and the displacement rate for various cross-sections highlight a clear quantitative relationship between coal extraction progress and subsidence, which proceeded southward throughout the three study periods. So, considering coal mining subsidence as a geohazard, land developments and structures over the mining area may be safeguarded. The approach used in this investigation can be implemented in other similar coal mining zones.

  • 43.
    Mousavi, Z.
    et al.
    ISTerre, Université Joseph Fourier, Grenoble, France; National Cartographic Center, Geodetic Department, Tehran, Iran.
    Walpersdorf, A.
    ISTerre, Université Joseph Fourier, Grenoble, France.
    Walker, R.T.
    Department of Earth Sciences, University of Oxford, Oxford, UK.
    Tavakoli, F.
    National Cartographic Center, Geodetic Department, Tehran, Iran.
    Pathier, E.
    ISTerre, Université Joseph Fourier, Grenoble, France.
    Nankali, H.
    National Cartographic Center, Geodetic Department, Tehran, Iran.
    Nilfouroushan, Faramarz
    Department of Earth Sciences, Uppsala University, Uppsala, Sweden.
    Djamour, Y.
    National Cartographic Center, Geodetic Department, Tehran, Iran.
    Global Positioning System constraints on the active tectonics of NE Iran and the South Caspian region2013In: Earth and Planetary Science Letters, ISSN 0012-821X, E-ISSN 1385-013X, Vol. 377-378, p. 287-298Article in journal (Refereed)
    Abstract [en]

    We present a velocity field compiled from a network of 27 permanent and 20 campaign GPS stations  across NE Iran. This new GPS velocity field helps to investigate how Arabia-Eurasia collision deformation is accommodated at the northern boundary of the deforming zone. The present-day northward motion decreases eastward from 11 mm/yr at Tehran (~52°E) to 1.5 mm/yr at Mashhad  (~60°E). N-S shortening across the Kopeh Dagh, Binalud and Kuh-e-Surkh ranges sums to 4.5±0.5 mm/yr at longitude 59°E. The available GPS velocities allow us to describe the rigid-body rotation of the South Caspian about an Euler pole that is located further away than previously thought. We suggest that two new stations (MAVT and MAR2), which are sited far from the block boundaries, are most  likely to indicate the full motion of the South Caspian basin. These stations suggest that NW motion is accommodated by right-lateral slip on the Ashkabad fault (at a rate of up to 7 mm/yr) and by up to 4-6 mm/yr of summed left-lateral slip across the Shahroud left-lateral strike-slip system. Our new GPS results are important for assessing seismic hazard in NE Iran, which contains numerous large population centers and possesses an abundant historical earthquake record. Our results suggest that the fault zones along the eastern Alborz and western Kopeh Dagh may accommodate slip at much faster rates than previously thought. Fully assessing the role of these faults, and the hazard that they represent, requires independent verification of their slip-rates through additional GPS measurements and geological fieldwork.

  • 44.
    Nilfouroushan, Faramarz
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    Komplettering av den Nationella Geodetiska infrastrukturen för InSAR-tillämpningar2022Conference paper (Refereed)
    Abstract [sv]

    Markrörelsetjänster baserade på InSAR-teknik finns redan tillgängliga för allmänheten via olika web-GIS. I dessa applikationer redovisas hur ett stort antal punkter på marken i Sverige (~1.5 miljarder) rör sig relativt varandra. Tekniken bygger på att såväl artificiella som naturliga objekt i terrängen reflekterar radarsignaler från satelliter och efter upprepade passager av satelliterna kan objektens relativa rörelser skattas. Lantmäteriet kompletterar nu den nationella geodetiska infrastrukturen med aktiva och passiva reflektorer för InSAR-mätning. Reflektorerna samlokaliseras med våra fasta referensstationer för GNSS i Swepos-nätet. Genom att korrelera markrörelse mätta med olika tekniker (GNSS och InSAR) får vi mer tillförlitliga resultat och markrörelserna skattade med InSAR kan transformeras från relativa rörelser inom en satellitscen till absoluta tal i ett geodetiskt referenssystem, t. ex. SWEREF 99.Vi kan dessutom komplettera den högupplösta informationen i satellitscenerna med mer långvågiga rörelser som t. ex. landhöjning.

  • 45.
    Nilfouroushan, Faramarz
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Land management, GIS. Geodetic infrastructure Department, Lantmäteriet, Gävle, Sweden.
    Bagherbandi, Mohammad
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Land management, GIS.
    Gido, Nureldin
    Ground Subsidence And Groundwater Depletion In Iran: Integrated approach Using InSAR and Satellite Gravimetry2017Conference paper (Other academic)
    Abstract [en]

    Long-term monitoring of temporal gravity field and ground water level changes in Iran and its associated ground subsidence seen by geodetic methods are important for water source and hazard management.The high-rate (cm to dm/year) ground subsidence in Iran has been widely investigated by using different geodetic techniques such as precise leveling, GPS and interferometric synthetic aperture radar (InSAR). The previous individual SAR sensors (e.g. ERS, ENVISAT and ALOS) or multi-sensors approach have successfully shown localized subsidence in different parts of Iran. Now, thanks to freely available new SAR sensor Sentinel-1A data, we aim at investigate further the subsidence problem in this region.

    In this ongoing research, firstly, we use a series of Sentinel-1A SAR Images, acquired between 2014 to 2017 to generate subsidence-rate maps in different parts of the country. Then, we correlate the InSAR results with the monthly observations of the Gravity Recovery and Climate Experiment (GRACE) satellite mission in this region. The monthly GRACE data computed at CNES from 2002 to 2017 are used to compute the time series for total water storage changes. The Global Land Data Assimilation System( GLDAS) hydrological model (i.e. soil moisture, snow water equivalent and surface water) is used to estimate Groundwater changes from total water storage changes obtiaend from GRACE data.

    So far, we have generated a few interferograms, using Sentinel-1A data and SNAP software, which shows a few cm subsidence in western Tehran in last 2 years. We will try more Sentinel images for this area to better constrain the rate and extent of deformation and will continue InSAR processing for the rest of the country to localize the deformation zones and their rates. We will finally comapre the rates of subsidence obtained from InSAR and the rate of groundwater changes estimated from GRACE data.

  • 46.
    Nilfouroushan, Faramarz
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences. Lantmäteriet.
    Fryksten, Jonas
    Lantmäteriet; The Geological Survey of Sweden, Uppsala.
    Analysis of Clay-Induced Land Subsidence in Uppsala City Using Sentinel-1 SAR Data and Precise Leveling2020Conference paper (Refereed)
    Abstract [en]

    Land subsidence and its subsequent hazardous effects on buildings and urban infrastructure areimportant issues in many cities around the world. The city of Uppsala in Sweden is undergoing significant subsidence in areas that are located on clay. Underlying clay units in parts of Uppsalaact as mechanically weak layers, which for instance, cause sinking of the ground surface and tilting buildings. In this study, a Persistent Scatterer InSAR (PSI) analysis was performed to map theongoing ground deformation in Uppsala. The subsidence rate measured with PSI was validatedwith precise leveling data at different locations. Two ascending and descending data sets wereanalyzed using SARPROZ software, with Sentinel-1 data from the period March 2015 to April 2019.After the PSI analyses, comparative permanent scatterer (PS) points and metal pegs (measuredwith precise leveling) were identified creating validation pairs. According to the PSI analyses,Uppsala was undergoing significant subsidence in some areas, with an annual rate of about 6mm/year in the line-of-sight direction. Interestingly, the areas of great deformation wereexclusively found on postglacial clay.

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  • 47.
    Nilfouroushan, Faramarz
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    Gido, Nureldin A. A.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    Olsson, Per-Anders
    Establishment of a new geodetic infrastructure in Sweden using SAR Corner Reflectors: Progress report2022Conference paper (Refereed)
    Abstract [en]

    Interferometric Synthetic Aperture Radar (InSAR) is a remote sensing and geodetic technique for ground deformation measurements using radar images of the Earth's surface that are collected regularly by orbiting satellites equipped with SAR sensors. Natural reflectors on the ground which backscatter the radar signal to the satellite are monitored in different time and changes of the line of sight (LOS) distances can detect ground surface movements. Natural reflectors are abundant in many places specially in urban areas. However, areas that are densely vegetated or covered by snow have limitations for InSAR technique and therefore artificial corner reflectors, passive or active ones, can be used instead. These corner reflectors are devices which provide precise measurement points and can be installed at desired locations. These devices can measure temporal LOS changes of the measurement point precisely using InSAR technique.

    Since 2020, Lantmäteriet has installed three active electronic corner reflectors (ECR) and several types of passive reflectors (CR) in different locations of Sweden. The plan is to continue and complement the national geodetic infrastructure with at least 20 passive reflectors which are collocated with permanent GNSS stations and/or tide gauges. Among others, these colocated permanent GNSS stations and corner reflectors can potentially contribute to the development and validation of the national and European ground motion services. Moreover, the colocation helps to map the relative ground motions estimated with InSAR to an absolute geodetic refercne frame. 

     

  • 48.
    Nilfouroushan, Faramarz
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    Gido, Nureldin A. A.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    Olsson, Per-Anders
    Puwakpitiya Gedara, Chrishan
    Status report on the installations of geodetic SAR corner reflectors in Sweden2022Conference paper (Refereed)
    Abstract [en]

    Interferometric Synthetic Aperture Radar (InSAR) is a remote sensing and geodetic technique for ground deformation measurements using radar images of the Earth's surface that are collected regularly by orbiting satellites equipped with SAR sensors. Natural reflectors on the ground which backscatter the radar signal to the satellite are monitored at different time and changes of the line of sight (LOS) distances can detect ground surface movements. Natural reflectors are abundant in many places, especially in urban areas. However, areas that are densely vegetated or covered by snow have limitations for InSAR technique and therefore artificial corner reflectors, passive, or active ones, can be used instead. These corner reflectors are devices which provide precise measurement points and can be installed at selected locations. These devices can measure temporal LOS changes of the measurement point precisely using the InSAR technique.

    Since 2020, Lantmäteriet has installed three active electronic corner reflectors (ECR) and several types of artificial passive reflectors (CR) in different locations of Sweden. The corner reflectors are anchored to the bedrock like GNSS stations using metal masts. The installation is in progress and the plan is to continue and complement the national geodetic infrastructure with at least 20 passive corner reflectors which are collocated with permanent GNSS stations and/or tide gauges and/or absolute gravity points. Among other applications, these collocated points link different geodetic measurement techniques, including InSAR and GNSS, and contribute to the development and validation of the national and European ground motion services. Moreover, the GNSS derived velocities and the LOS temporal variations measured on the nearby corner reflectors are useful to transform the relative ground motions estimated with InSAR to an absolute geodetic reference frame.

  • 49.
    Nilfouroushan, Faramarz
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences. Lantmäteriet, Gävle.
    Gido, Nureldin
    Lantmäteriet, Gävle.
    Olsson, Per-Anders
    Lantmäteriet, Gävle.
    Gedara, Chrishan Puwakpitiya
    Lantmäteriet, Gävle.
    Activity Report: Contributions from Lantmäteriet to the InSAR-Sweden Project2023Report (Other academic)
    Abstract [en]

    The two-year Swedish Ground Motion Service (InSAR-Sweden) project was started in 2021 and made a collaboration between the Geological Survey of Norway (NGU) and several Swedish organizations, including Lantmäteriet. During the project, the InSAR-based ground motion service has been developed by NGU using Sentinel-1 data (2015–2021) and the Persistent Scatterer Interferometry (PSI) technique and is freely available for interested users. There were different working groups in the project and Lantmäteriet has contributed mostly to working group WP#3 which is the “validation of deformation data”.We used the PSI results of previous studies for Uppsala and Gävle cities to validate the newly launched InSAR-Sweden ground motion service. We compared the deformation localization and Line of Sight (LOS) displacement time series at some deforming locations. Although the number and acquisition dates of Sentinel-1 data and the parameters used for PSI processing differ between Uppsala, Gävle and InSAR-Sweden, the cross-checked results demonstrate good agreement between corresponding studies regarding the localization and rate of subsidence in those two cities over a period of five years.During the project, Lantmäteriet installed several types of radar corner reflectors (CR) in different locations in Sweden. These corner reflectors are passive devices which provide precise measurement points and can be installed at desired locations. These devices can be used to measure temporal LOS changes and consequently the ground movements precisely using the InSAR technique. The plan is to continue and complement the national geodetic infrastructure with at least 20 passive reflectors which are collocated with permanent GNSS stations and/or tide gauges. Among others, these co-located permanent GNSS stations and corner reflectors can potentially contribute to the development and validation of the national (InSAR-Sweden) and European ground motion (EGMS) services. Moreover, the co-location helps to transform the relative ground motions estimated with InSAR to an absolute geodetic reference frame.In this activity report, we provide a brief introduction to SAR corner reflectors and their applications, and we explain our progress in installing such reflectors in Sweden. We also present our preliminary results from our data analysis. Moreover, we explain our cross-checking of the results obtained from InSAR-Sweden with the InSAR-based studies conducted for Uppsala and Gävle cities.

  • 50.
    Nilfouroushan, Faramarz
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    Gido, Nureldin
    Lantmäteriet.
    Olsson, Per-Anders
    Lantmäteriet.
    Puwakpitiya Gedara, Chrishan
    Lantmäteriet.
    Active and passive radar corner reflectors co-located with permanent GNSS stations in Sweden: Installation and performance2023Conference paper (Refereed)
    Abstract [en]

    Artificial corner reflectors (CRs), passive (which have no electronic parts), or active ones, so called electronic CR (ECR) or compact transponders (CAT), are devices which reflect the radar signal back to the SAR satellites and provide measurement points at desired locations. Using, such devices we can measure temporal Line of sight (LOS) changes of the CRs using the InSAR technique and for example monitor the ground movements precisely.

    Since January 2020, Lantmäteriet, the Swedish mapping, cadastral and land registration authority, has installed three ECRs and several types of passive reflectors (different shape and size, planned for C-band Sentinel-1 satellites) in different locations in Sweden. So far, ECRs are still functioning with no electronic failure. However, from the ESA Geodetic SAR project (https://eo4society.esa.int/projects/sar-hsu/) we experienced that the ECRs electronic characteristics are different, so individual calibrations maybe required by the manufacturer. In addition, thermal effects may also cause problems for measurements with ECRs. Therefore, instead of installing more ECRs, we switched to passive ones which have no electronics and have already shown their high-quality performance in different studies. So far, we have installed ten CRs in different locations and the goal is to continue and complement the national geodetic infrastructure of Sweden with at least twenty passive reflectors which are co-located with permanent GNSS stations. Among others, these co-located corner reflectors can potentially contribute to the development of the national and European ground motion services in future updates. Moreover, the co-location helps to map the relative ground motions estimated with InSAR to an absolute geodetic reference frame

    Among different tests and performance analysis of such reflectors, we did multipath analysis to investigate if our corner reflectors cause any multipath error on nearby GNSS stations.  We looked at the coordinate time series of the twin GNSS stations at two locations, Visby and Sveg. The installed corner reflector, double back-flipped squared, in Sveg is about 6 m away from the GNSS stations whereas, in Visby, the twin corner reflectors, ascending and descending, are about 20 meters away and have a trihedral squared trimmed shape. The daily GNSS coordinate time series for three components before and after installation of the corner reflectors didn’t show any significant jump in the time series and the coordinate variations are in the range of expected mm-level variations for all stations.

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