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  • 1.
    Amin, Hadi
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för datavetenskap och samhällsbyggnad, Samhällsbyggnad.
    Sjöberg, Lars
    Division of Geodesy and satellite positioning, KTH.
    Bagherbandi, Mohammad
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för datavetenskap och samhällsbyggnad, Samhällsbyggnad.
    A global vertical datum defined by the conventional geoid potential and the Earth ellipsoid parameters2019Ingår i: Journal of Geodesy, ISSN 0949-7714, E-ISSN 1432-1394, Vol. 93, nr 10, s. 1943-1961Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The geoid, according to the classical Gauss–Listing definition, is, among infinite equipotential surfaces of the Earth’s gravity field, the equipotential surface that in a least squares sense best fits the undisturbed mean sea level. This equipotential surface, except for its zero-degree harmonic, can be characterized using the Earth’s global gravity models (GGM). Although, nowadays, satellite altimetry technique provides the absolute geoid height over oceans that can be used to calibrate the unknown zero-degree harmonic of the gravimetric geoid models, this technique cannot be utilized to estimate the geometric parameters of the mean Earth ellipsoid (MEE). The main objective of this study is to perform a joint estimation of W0, which defines the zero datum of vertical coordinates, and the MEE parameters relying on a new approach and on the newest gravity field, mean sea surface and mean dynamic topography models. As our approach utilizes both satellite altimetry observations and a GGM model, we consider different aspects of the input data to evaluate the sensitivity of our estimations to the input data. Unlike previous studies, our results show that it is not sufficient to use only the satellite-component of a quasi-stationary GGM to estimate W0. In addition, our results confirm a high sensitivity of the applied approach to the altimetry-based geoid heights, i.e., mean sea surface and mean dynamic topography models. Moreover, as W0 should be considered a quasi-stationary parameter, we quantify the effect of time-dependent Earth’s gravity field changes as well as the time-dependent sea level changes on the estimation of W0. Our computations resulted in the geoid potential W0 = 62636848.102 ± 0.004 m2 s−2 and the semi-major and minor axes of the MEE, a = 6378137.678 ± 0.0003 m and b = 6356752.964 ± 0.0005 m, which are 0.678 and 0.650 m larger than those axes of GRS80 reference ellipsoid, respectively. Moreover, a new estimation for the geocentric gravitational constant was obtained as GM = (398600460.55 ± 0.03) × 106 m3 s−2.

  • 2.
    Bagherbandi, Mohammad
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad, Samhällsbyggnad, GIS. KTH Royal Institute of Technology, Stockholm, Sweden.
    Bai, Yongliang
    School of Geosciences, China University of Petroleum (East China), Qingdao, China.
    Sjöberg, Lars
    KTH Royal Institute of Technology, Stockholm, Sweden.
    Tenzer, Robert
    NTIS - New Technologies for the Information Society, Faculty of Applied Sciences, University of West Bohemia, Plzeň, Czechia.
    Abrehdary, Majid
    KTH Royal Institute of Technology, Stockholm, Sweden.
    Miranda, Silvia
    Departamento de Geofísica y Astronomía, FCEFN Universidad Nacional de San Juan, San Juan, Argentina.
    Sanchez, Juan M. Alcacer
    Departamento de Geofísica y Astronomía, FCEFN Universidad Nacional de San Juan, San Juan, Argentina.
    Effect of the lithospheric thermal state on the Moho interface: a case study in South America2017Ingår i: Journal of South American Earth Sciences, ISSN 0895-9811, E-ISSN 1873-0647, Vol. 76, s. 198-207Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Gravimetric methods applied for Moho recovery in areas with sparse and irregular distribution of seismic data often assume only a constant crustal density. Results of latest studies, however, indicate that corrections for crustal density heterogeneities could improve the gravimetric result, especially in regions with a complex geologic/tectonic structure. Moreover, the isostatic mass balance reflects also the density structure within the lithosphere. The gravimetric methods should therefore incorporate an additional correction for the lithospheric mantle as well as deeper mantle density heterogeneities. Following this principle, we solve the Vening Meinesz-Moritz (VMM) inverse problem of isostasy constrained by seismic data to determine the Moho depth of the South American tectonic plate including surrounding oceans, while taking into consideration the crustal and mantle density heterogeneities. Our numerical result confirms that contribution of sediments significantly modifies the estimation of the Moho geometry especially along the continental margins with large sediment deposits. To account for the mantle density heterogeneities we develop and apply a method in order to correct the Moho geometry for the contribution of the lithospheric thermal state (i.e., the lithospheric thermal-pressure correction). In addition, the misfit between the isostatic and seismic Moho models, attributed mainly to deep mantle density heterogeneities and other geophysical phenomena, is corrected for by applying the non-isostatic correction. The results reveal that the application of the lithospheric thermal-pressure correction improves the RMS fit of the VMM gravimetric Moho solution to the CRUST1.0 (improves ∼ 1.9 km) and GEMMA (∼1.1 km) models and the point-wise seismic data (∼0.7 km) in South America.

  • 3.
    Bagherbandi, Mohammad
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad, Samhällsbyggnad/GIS-Institutet.
    Sjöberg, Lars E.
    Royal Institute of Technology (KTH), Stockholm, Sweden.
    Improving gravimetric–isostatic models of crustal depth by correcting for non-isostatic effects and using CRUST2.02013Ingår i: Earth-Science Reviews, ISSN 0012-8252, E-ISSN 1872-6828, Vol. 117, s. 29-39Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    The principle of isostasy is important in different fields of geosciences. Using an isostatic hypothesis for estimating the crustal thickness suffers from the more or less incomplete isostatic model and that the observed gravity anomaly is not only generated by the topographic/isostatic signal but also by non-isostatic effects (NIEs). In most applications of isostatic models the NIEs are disregarded. In this paper, we study how some isostatic models related with Vening Meinez's isostatic hypothesis can be improved by considering the NIE. The isostatic gravity anomaly needs a correction for the NIEs, which varies from as much as 494 mGal to − 308 mGal. The result shows that by adding this correction the global crustal thickness estimate improves about 50% with respect to the global model CRUST2.0, i.e. the root mean square differences of the crustal thickness of the best Vening Meinesz type and CRUST2.0 models are 6.9 and 3.2 km before and after improvement, respectively. As a result, a new global model of crustal thickness using Vening Meinesz and CRUST2.0 models is generated. A comparison with an independent African crustal depth model shows an improvement of the new model by 6.8 km vs. CRUST2.0 (i.e. rms differences of 3.0 and 9.8 km, respectively). A comparison between oceanic lithosphere age and the NIEs is discussed in this study, too. One application of this study can be to improve crustal depth in areas where CRUST2.0 data are sparse and bad and to densify the resolution vs. the CRUST2.0 model. Other applications can be used to infer the viscosity of the mantle from the NIEs signal to study various locations around the Earth for understanding complete, over- and under-compensations of the topography.

  • 4.
    Bagherbandi, Mohammad
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad, Samhällsbyggnad/GIS-Institutet. KTH, Geodesy & Geoinformatics, Stockholm, Sweden.
    Tenzer, Robert
    School of Geodesy and Geomatics, Wuhan University, Wuhan, China.
    Geoid-to-Quasigeoid Separation Computed Using the GRACE/GOCE Global Geopotential Model GOCO02S: A Case Study of Himalayas and Tibet2013Ingår i: Terrestrial, Atmospheric and Oceanic Science, ISSN 1017-0839, E-ISSN 2223-8964, Vol. 24, nr 1, s. 59-68Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The geoid-to-quasigeoid correction has been traditionally computed approximately as a function of the planar Bouguer gravity anomaly and the topographic height. Recent numerical studies based on newly developed theoretical models, however, indicate that the computation of this correction using the approximate formula yields large errors especially in mountainous regions with computation points at high elevations. In this study we investigate these approximation errors at the study area which comprises Himalayas and Tibet where this correction reaches global maxima. Since the GPS-leveling and terrestrial gravity datasets in this part of the world are not (freely) available, global gravitational models (GGMs) are used to compute this correction utilizing the expressions for a spherical harmonic analysis of the gravity field. The computation of this correction can be done using the GGM coefficients taken from the Earth Gravitational Model 2008 (EGM08) complete to degree 2160 of spherical harmonics. The recent studies based on a regional accuracy assessment of GGMs have shown that the combined GRACE/GOCE solutions provide a substantial improvement of the Earth’s gravity field at medium wavelengths of spherical harmonics compared to EGM08. We address this aspect in numerical analysis by comparing the gravity field quantities computed using the satellite-only combined GRACE/GOCE model GOCO02S against the EGM08 results. The numerical results reveal that errors in the geoid-to-quasigeoid correction computed using the approximate formula can reach as much as ~1.5 m. We also demonstrate that the expected improvement of the GOCO02S gravity field quantities at medium wavelengths (within the frequency band approximately between 100 and 250) compared to EGM08 is as much as ±60 mGal and ±0.2 m in terms of gravity anomalies and geoid/quasigeoid heights respectively.

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  • 5.
    Bagherbandi, Mohammad
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad, Samhällsbyggnad/GIS-Institutet.
    Tenzer, Robert
    Wuhan University, China.
    Sjöberg, Lars
    Royal Institute of Technology (KTH), Stockholm, Sweden.
    Novak, Pavel
    University of West Bohemia, Plzen, Czech Republic.
    Improved global crustal thickness modeling based on the VMM isostatic model and non-isostatic gravity correction2013Ingår i: Journal of Geodynamics, ISSN 0264-3707, E-ISSN 1879-1670, Vol. 66, s. 25-37Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In classical isostatic models for a gravimetric recovery of the Moho parameters (i.e., Moho depths and density contrast) the isostatic gravity anomalies are usually defined based on the assumption that the topographic mass surplus and the ocean mass deficiency are compensated within the Earth’s crust. As acquired in this study, this assumption yields large disagreements between isostatic and seismic Moho models. To assess the effects not accounted for in classical isostatic models, we conduct a number of numerical experiments using available global gravity and crustal structure models. First, we compute the gravitational contributions of mass density contrasts due to ice and sediments, and subsequently evaluate respective changes in the Moho geometry. Residual differences between the gravimetric and seismic Moho models are then used to predict a remaining non-isostatic gravity signal, which is mainly attributed to unmodeled density structures and other geophysical phenomena. We utilize three recently developed computational schemes in our numerical studies. The apparatus of spherical harmonic analysis and synthesis is applied in forward modeling of the isostatic gravity disturbances. The Moho depths are estimated globally on a 1 arc-deg equiangular grid by solving the Vening-Meinesz Moritz inverse problem of isostasy. The same estimation model is applied to evaluate the differences between the isostatic and seismic models. We demonstrate that the application of the ice and sediment density contrasts stripping gravity corrections is essential for a more accurate determination of the Moho geometry. We also show that the application of the additional non-isostatic correction further improves the agreement between the Moho models derived based on gravity and seismic data. Our conclusions are based on comparing the gravimetric results with the CRUST2.0 global crustal model compiled using results of seismic surveys.

  • 6.
    Bagherbandi, Mohammad
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad, Samhällsbyggnad/GIS-Institutet. KTH.
    Tenzer, Robert
    Royal Institute of Technology (KTH), Stockholm, Sweden .
    Sjöberg, L.E.
    Wuhan University, Wuhan, China .
    Moho depth uncertainties in the Vening-Meinesz Moritz inverse problem of isostasy2014Ingår i: Studia Geophysica et Geodaetica, ISSN 0039-3169, E-ISSN 1573-1626, Vol. 58, nr 2, s. 227-248Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We formulate an error propagation model based on solving the Vening Meinesz-Moritz (VMM) inverse problem of isostasy. The system ofobservation equations in the VMM model defines the relation between theisostatic gravity data and the Moho depth  by means of a second-order Fredholm integralequation of the first kind. The corresponding error model (derived in aspectral domain) functionally relates the Moho depth errors with the commissionerrors of used gravity and topographic/bathymetric models. The error model alsoincorporates the non-isostatic bias which describesthe disagreement, mainly of systematic nature, between the isostatic andseismic models. The error analysis is conducted at the study area of theTibetan Plateau and Himalayas with the world largest crustal thickness. TheMoho depth uncertainties due to errors of the currently available globalgravity and topographic models are estimated to be typically up to 1-2 km,provided that the GOCE gravity gradient observables improved themedium-wavelength gravity spectra. The errors due to disregarding sedimentarybasins can locally exceed ~2 km. The largest errors (which cause a systematic bias betweenisostatic and seismic models) are attributed to unmodeled mantleheterogeneities (including thecore-mantle boundary) and other geophysical processes. These errors aremostly less than 2 km under significant orogens (Himalayas, Ural), but canreach up to ~10 km under the oceanic crust.

  • 7.
    Bekele, Yared
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad.
    GIS Based Factor Identification for the Change in Occurrence of Genista pilosa: a Case Study in Southern Sweden2012Självständigt arbete på avancerad nivå (magisterexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    This study has the objective of identifying the possible environmental constraints that has role for the continuous loss of heathland plant Genista pilosa. The study has assessed different environmental settings where the plant occurs by way of overlaying analysis based on multiple spatial data sets. Thereafter empirical change detection analyses on the land use of the study area have been performed on the GIS environment by combining temporal based remotely sensed spatial data. The result was then analyzed using land use dynamicity model and the rates of change on each land use type are identified. Expansion of human activity, especially the spreading of agricultural land and urbanization, is found to be the most determinant factor for the dramatic loss of the plant. Finally serious attention for the protection of the plant is recommended by mentioning the possible problem that would occur due to a loss of biodiversity.

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    GIS-Based Factor Identification for the Change in Occurrence of Genista pilosa a Case Study in Southern Sweden
  • 8.
    Carpenter, Angela
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för industriell ekonomi, industridesign och maskinteknik, Industriell ekonomi. Högskolan i Gävle, Centrum för logistik och innovativ produktion.
    Lozano, Rodrigo
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för industriell ekonomi, industridesign och maskinteknik, Industriell ekonomi. Högskolan i Gävle, Centrum för logistik och innovativ produktion.
    Introduction, chapter summary, and conclusions from the book2020Ingår i: European port cities in transition: Moving towards more sustainable sea transport hubs, Springer, 2020, s. 1-17Kapitel i bok, del av antologi (Övrigt vetenskapligt)
  • 9.
    Carpenter, Angela
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för industriell ekonomi, industridesign och maskinteknik, Industriell ekonomi. Högskolan i Gävle, Centrum för logistik och innovativ produktion.
    Lozano, Rodrigo
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för industriell ekonomi, industridesign och maskinteknik, Industriell ekonomi. Högskolan i Gävle, Centrum för logistik och innovativ produktion.
    Proposing a framework for anchoring sustainability relationships between ports and cities2020Ingår i: European port cities in transition: Moving towards more sustainable sea transport hubs, Springer, 2020, s. 37-51Kapitel i bok, del av antologi (Övrigt vetenskapligt)
  • 10.
    Eklundh, Lars
    et al.
    Lunds universitet.
    Ågren, Jonas
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för datavetenskap och samhällsbyggnad, Samhällsbyggnad.
    Olsson, Håkan
    Sveriges Lantbruksuniversitet.
    Harrie, Lars
    Lunds universitet.
    Klang, Dan
    Insamling av geografiska data2019Ingår i: Geografisk informationsbehandling: Teori, metoder och tillämpningar / [ed] Lars Harrie, Studentlitteratur AB, 2019, 7, s. 85-126Kapitel i bok, del av antologi (Övrig (populärvetenskap, debatt, mm))
    Abstract [sv]

    Det här kapitlet fokuserar på att förklara de grundläggande principerna för insamling av geografiska data, och vi lägger tonvikten på fjärranalys och geodetiska metoder. Fjärranalys innefattar olika tekniker som fotogrammetri, laserskanning och analys av bilder från mark, flyg och satelliter. Geodetiska datainsamling används för att mäta in koordinater för objekt på marken och innefattar satellitbaserade tekniker såväl som användning av fältinstrument. Olika tekniker, avseende både fjärranalys och geodesi, används i olika situationer beroende på krav på noggrannhet och innehåll, och kompletterar därför varandra. Vi börjar med att beskriva satellitfjärranalys som kan täcka stora områden med relativt begränsad detaljeringsgrad, beskriver sedan flygbilder och laserskanning där detaljnivån ökar, för att till sist beskriva de geodetiska metoderna för noggranna mätningar på marknivå.

  • 11.
    Engfeldt, Andreas
    et al.
    Lantmäteriet.
    Olsson, Per-Anders
    Lantmäteriet.
    Steffen, Holger
    Lantmäteriet.
    Lidberg, Martin
    Lantmäteriet.
    Ågren, Jonas
    Lantmäteriet.
    Sekowski, Marcin
    Institute of Geodesy and Cartography, Poland.
    Krynski, Jan
    Institute of Geodesy and Cartography, Poland.
    Bryskhe, Henrik
    Lantmäteriet.
    Nielsen, Jens Emil
    Danish Technical University, Denmark.
    Strykowski, Gabriel
    Danish Technical University, Denmark.
    RG 2000 – the New Gravity Reference Frame of Sweden2019Ingår i: Geophysica, ISSN 0367-4231, E-ISSN 2324-0741, Vol. 54, nr 1, s. 69-92Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The increased need for improved geoid models for Global Navigation Satellite Systems (GNSS) height determination calls for additional gravity observations and quality assurance of existing data. In this perspective, a modern gravity system and the renovation of an already existing high order gravity network is considered as a moderate strategic investment which provides a firm foundation for further activities. Here the new gravity reference frame RG 2000 for Sweden is presented. RG 2000 is realized by absolute gravity observations at 109 stations. The absolute points are connected via old and new relative gravity observations, including another 216 points. Points and observations have been chosen so that good overlap with the older Swedish reference frames, RG 62 and RG 82, is achieved, allowing to evaluate the older frames and transformations between them. RG 2000 is based on a zero permanent tide system with epoch 2000.

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  • 12.
    Findler, Florian
    et al.
    Vienna University of Economics and Business, Vienna, Austria.
    Schönherr, Norma
    Vienna University of Economics and Business, Vienna, Austria.
    Lozano, Rodrigo
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för industriell ekonomi, industridesign och maskinteknik, Industriell ekonomi. Högskolan i Gävle, Centrum för logistik och innovativ produktion.
    Reider, Daniela
    Vienna University of Economics and Business, Vienna, Austria.
    Martinuzzi, André
    Vienna University of Economics and Business, Vienna, Austria.
    The impacts of higher education institutions on sustainable development: a review and conceptualization2019Ingår i: International Journal of Sustainability in Higher Education, ISSN 1467-6370, E-ISSN 1758-6739, Vol. 20, nr 1, s. 23-38Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    Purpose

    This paper aims to conceptualize impacts of higher education institutions (HEIs) on sustainable development (SD), complementing previous literature reviews by broadening the perspective from what HEIs do in pursuit of SD to how these activities impact society, the environment and the economy.

    Design/methodology/approach

    The paper provides a systematic literature review of peer-reviewed journal articles published between 2005 and 2017. Inductive content analysis was applied to identify major themes and impact areas addressed in the literature to develop a conceptual framework detailing the relationship between HEIs’ activities and their impacts on SD.

    Findings

    The paper identifies six impact areas where direct and indirect impacts of HEIs on SD may occur. The findings indicate a strong focus on case studies dealing with specific projects and a lack of studies analyzing impacts from a more holistic perspective.

    Practical implications

    This systematic literature review enables decision-makers in HEIs, researchers and educators to better understand how their activities may affect society, the environment and the economy, and it provides a solid foundation to tackle these impacts.

    Social implications

    The review highlights that HEIs have an inherent responsibility to make societies more sustainable. HEIs must embed SD into their systems while considering their impacts on society.

    Originality/value

    This paper provides a holistic conceptualization of HEIs’ impacts on SD. The conceptual framework can be useful for future research that attempts to analyze HEIs’ impacts on SD from a holistic perspective.

  • 13.
    Fobbe, Lea
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för industriell ekonomi, industridesign och maskinteknik, Industriell ekonomi. Högskolan i Gävle, Centrum för logistik och innovativ produktion.
    Lozano, Rodrigo
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för industriell ekonomi, industridesign och maskinteknik, Industriell ekonomi. Högskolan i Gävle, Centrum för logistik och innovativ produktion.
    Carpenter, Angela
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för industriell ekonomi, industridesign och maskinteknik, Industriell ekonomi. Högskolan i Gävle, Centrum för logistik och innovativ produktion.
    Proposing a holistic framework to assess sustainability performance in seaports2020Ingår i: European port cities in transition: Moving towards more sustainable sea transport hubs, Springer, 2020, s. 149-168Kapitel i bok, del av antologi (Övrigt vetenskapligt)
  • 14.
    Jiang, Bin
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad, Samhällsbyggnad/GIS-Institutet.
    Jia, Tao
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad, Samhällsbyggnad/GIS-Institutet.
    Agent-based simulation of human movement shaped by the underlying street structure2011Ingår i: International Journal of Geographical Information Science, ISSN 1365-8816, E-ISSN 1365-8824, Vol. 25, nr 1, s. 51-64Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Relying on random and purposive moving agents, we simulated human movement in large street networks. We found that aggregate flow, assigned to individual streets, is mainly shaped by the underlying street structure, and that human moving behavior (either random or purposive) has little effect on the aggregate flow. This finding implies that given a street network, the movement patterns generated by purposive walkers (mostly human beings) and by random walkers are the same. Based on the simulation and correlation analysis, we further found that the closeness centrality is not a good indicator for human movement, in contrast to a long-standing view held by space syntax researchers. Instead we suggest that Google's PageRank and its modified version (weighted PageRank), betweenness and degree centralities are all better indicators for predicting aggregate flow.

  • 15.
    Jiang, Bin
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad, Samhällsbyggnad/GIS-Institutet.
    Liu, Xintao
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad, Samhällsbyggnad/GIS-Institutet.
    Automatic generation of the axial lines of urban environments to capture what we perceive2010Ingår i: International Journal of Geographical Information Science, ISSN 1365-8816, E-ISSN 1365-8824, Vol. 24, nr 4, s. 545-558Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Based on the concepts of isovists and medial axes, we developed a set of algorithms that can automatically generate axial lines for representing individual linearly stretched parts of open space of an urban environment. Open space is the space between buildings where people can freely move around. The generation of the axial lines has been a key aspect of space syntax research, conventionally relying on hand-drawn axial lines of an urban environment, often called axial map, for urban morphological analysis. Although various attempts have been made towards an automatic solution, few of them can produce the axial map that consists of the least number of longest visibility lines, and none of them really works for different urban environments. Our algorithms provide a better solution than existing ones. Throughout this article, we have also argued and demonstrated that the axial lines constitute a true skeleton, superior to medial axes, in capturing what we perceive about the urban environment.

  • 16.
    Jiang, Bin
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad, Samhällsbyggnad/GIS-Institutet.
    Liu, Xintao
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad, Samhällsbyggnad/GIS-Institutet.
    Computing the fewest-turn map directions based on the connectivity of natural roads2011Ingår i: International Journal of Geographical Information Science, ISSN 1365-8816, E-ISSN 1365-8824, Vol. 25, nr 7, s. 1069-1082Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this article, we introduce a novel approach to computing the fewest-turn map directions or routes based on the concept of natural roads. Natural roads are joined road segments that perceptually constitute good continuity. This approach relies on the connectivity of natural roads rather than that of road segments for computing routes or map directions. Because of this, the derived routes possess the fewest turns. However, what we intend to achieve are the routes that not only possess the fewest turns but are also as short as possible. This kind of map direction is more effective and favored by people because they bear less cognitive burden. Furthermore, the computation of the routes is more efficient because it is based on the graph encoding the connectivity of roads, which is substantially smaller than the graph of road segments. We experimented on eight urban street networks from North America and Europe to illustrate the above-stated advantages. The experimental results indicate that the fewest-turn routes possess fewer turns and shorter distances than the simplest paths and the routes provided by Google Maps. For example, the fewest-turn-and-shortest routes are on average 15% shorter than the routes suggested by Google Maps, whereas the number of turns is just half as much. This approach is a key technology behind FromToMap.org – a web mapping service using openstreetmap data.

  • 17.
    Jiang, Bin
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad, Samhällsbyggnad/GIS-Institutet.
    Yao, Xiaobai
    University of Georgia, Athens, GA, USA.
    Geospatial analysis and modeling of urban structure and dynamics: an overview2010Ingår i: The GeoJournal Library, 2010, Volume 99, Part 1 / [ed] Bin Jiang and Xiaobai Yao, Berlin: Springer , 2010, s. 3-11Kapitel i bok, del av antologi (Övrigt vetenskapligt)
  • 18.
    Lim, Nancy Joy
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad, Samhällsbyggnad, GIS.
    Modelling, mapping and visualisation of flood inundation uncertainties2018Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    Översvämningskartor som visar utbredningen av förutspådda översvämningar för vissa extrema händelser har stor användning i all typ av samhällsplanering, samt fungerar som informationsmaterial för allmänheten. Men, de produktionsprocesser som dessa kartor genomgår (inkluderande olika data, metoder, modeller och beslut från de personer som genererar dessa) och som innefattar både geografiska informationssystem (GIS) och hydraulisk modellering, påverkar kartornas innehåll, vilket även återspeglas i de slutliga kartornas utseende. En skarp översvämningsgräns, som är det vanliga sättet att visa gränsen i översvämningskartor, är därför antagligen inte det bästa sättet att representera utbredningen. Sådana gränser ger en falsk trygghet i att dessa kartor är korrekta och att översvämningsutbredningen är absolut, trots att hela processen att producera dem innebär osäkerheter. Denna studie försöker därför undersöka hur översvämningskartering påverkas av osäkerheter i modelleringsprocesser och hur dessa osäkerheter kan representeras, visualiseras och kommuniceras i kartorna. Dessutom försöker studien utvärdera hur olika användare förstår, använder och uppfattar översvämningskartor som innehåller osäkerhetsinformation.

    Tre huvudmetoder har använts i denna studie: osäkerhetsmodellering och analys, kart- och geovisualiseringsutveckling samt användarstudier. Resultaten visar att översvämningsgränserna påverkades både av de digitala höjdmodellernas upplösning (cellstorlek) och markens friktion, representerat av Mannings 𝑛, men också av markens topografi. För att kvantifiera skillnaderna mellan modell och referensöversvämningsyta och därefter kunna välja den mest optimala modellen användes olika valideringsmetoder. Dessa lider dock också av olika brister, vilket gör att resultaten varierar beroende på den valideringsmetod som används.

    I denna studie föreslås flera sätt att visualisera osäkerheter baserat på resultaten från osäkerhetsmodellering och karaktären av osäkerhetsinformation. Dessa utgörs av kartor med divergerande färgramp (sk. dual-ended colour maps), sekventiella kartor (som framhäver graden av säkerhet, respektive osäkerhet), binära kartor, överlagring av översvämningsgränser från olika modeller samt värdestaplar. Olika karteringsmetoder och visuella variabler användes för att representera informationen. Resultat från en användarstudie visade att dessa, samt utformningen av den grafiska representationen, underlättade förståelsen av informationen. Beroende på uppgiften finns det visualisering som är lättare eller svårare att förstå för kartanvändarna. Varje visualisering hade också för- och nackdelar med att kommunicera översvämningsosäkerhetsinformation. En annan viktig aspekt som kom fram i studien var hur användarnas bakgrund påverkar beslutsfattandet när de använde de olika kartorna. Användarnas vilja att ta risker berodde inte bara på kartan, utan också på deras uppfattning av risken i sig. Sammantaget visade det sig emellertid att osäkerhetskartorna är användbara för planeringsuppgifter.

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  • 19.
    Lin, Yue
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad.
    A Comparison Study on Head/tail Breaks and Topfer’s Method for Model-based Map Generalization on Geographic Features in Country and City Levels2015Självständigt arbete på avancerad nivå (magisterexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Map generalization is a traditional cartographical issue which should be particularly considered in today’sinformation age. The aim of this study is to find some characteristics about head/tail breaks which worksas generalization method compared with the well known Topfer’s method. A questionnaire survey wasconducted to let 30 users choose either of the series maps of both methods and the reason(s) for thatchoice. Also to test their understanding of the series maps histograms were added for them to match.Afterwards the sample results were analyzed using both univariate and bivariate analysis approaches. Itshows that the head/tail breaks method was selected by 58%, compared with 38.7% of Topfer’s method,because of its simplicity. By checking the correctness of histogram question it also shows that those whowell understood answers choose the head/tail breaks rather than the Topfer’s method. However in somecases, where the amount of geographical features is relatively small, Topfer’s method is more selectedbecause of its informative characteristic and similar structure to the original map. It was also found that inthe comparison the head/tail breaks is more advantageous in line feature type generalization than in arealfeature type. This is probably because Topfer’s method changes its minority selection rule to half selectionin line feature type, whereas the head/tail breaks keeps the scaling property. Any difference between thetwo tested scales, Finland level and Helsinki level, is not found in this comparison study. However, futurework should explore more regarding this and other issues.

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  • 20.
    Lozano, Rodrigo
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för industriell ekonomi, industridesign och maskinteknik, Industriell ekonomi. Högskolan i Gävle, Centrum för logistik och innovativ produktion.
    Bridging aims and delivery of higher education for sustainable development: Using pedagogical approaches to fulfil competences2019Konferensbidrag (Refereegranskat)
  • 21.
    Lozano, Rodrigo
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för industriell ekonomi, industridesign och maskinteknik, Industriell ekonomi. Högskolan i Gävle, Centrum för logistik och innovativ produktion.
    Drivers for and barriers to Corporate Sustainability2019Konferensbidrag (Övrigt vetenskapligt)
  • 22.
    Lozano, Rodrigo
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för industriell ekonomi, industridesign och maskinteknik, Industriell ekonomi. Högskolan i Gävle, Centrum för logistik och innovativ produktion.
    Impulsores de la sostenibilidad corporativa [Corporate sustainability drivers]2019Konferensbidrag (Övrigt vetenskapligt)
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  • 23.
    Lozano, Rodrigo
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för industriell ekonomi, industridesign och maskinteknik, Industriell ekonomi. Högskolan i Gävle, Centrum för logistik och innovativ produktion. Organisational Sustainability, Ltd, Cardiff, UK.
    Sustainable business models: providing a more holistic perspective2018Ingår i: Business Strategy and the Environment, ISSN 0964-4733, E-ISSN 1099-0836, Vol. 27, nr 8, s. 1159-1166Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Corporate sustainability has recently been challenging traditional business models that have been based on value proposition, creation and capture. There has been a steady increase in publications using the term “sustainable business models”; however, there have been few that have theoretically defined or characterized the term, and in most cases, they just apply the term. Seven peer‐reviewed papers were selected that aimed to define and explain sustainable business models and that have been widely cited. The papers were analyzed by assessing the elements and activities covered using the corporate sustainability framework, and by comparing them against four approaches to explain organizations. The paper proposes a definition and framework for more sustainable business models aimed at integrating organizational approaches, the company system, stakeholders, change and sustainability dimensions, thus providing a more holistic and systemic approach to discourses on sustainable business models.

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  • 24.
    Lozano, Rodrigo
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för industriell ekonomi, industridesign och maskinteknik, Industriell ekonomi. Högskolan i Gävle, Centrum för logistik och innovativ produktion. Organisational Sustainability, Cardiff, UK.
    Barreiro-Gen, Maria
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för industriell ekonomi, industridesign och maskinteknik, Industriell ekonomi. Högskolan i Gävle, Centrum för logistik och innovativ produktion.
    Analysing the incorporation of sustainable development into European Higher Education Institution's curricula2019Ingår i: Engineering Education towards Sustainability: Approaches for Institutionalization and Teaching Implementation: Second Internacional Conference on Engineering Education for the 21st Century – ICEE21C 2019 / [ed] Guraya, T., Cabedo, L., Bilbao: Universidad del País Vasco / Euskal Herriko Unibertsitatea , 2019, s. 51-56Konferensbidrag (Övrigt vetenskapligt)
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    bilaga
  • 25.
    Lozano, Rodrigo
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för industriell ekonomi, industridesign och maskinteknik, Industriell ekonomi. Högskolan i Gävle, Centrum för logistik och innovativ produktion.
    Carpenter, Angela
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för industriell ekonomi, industridesign och maskinteknik, Industriell ekonomi. Högskolan i Gävle, Centrum för logistik och innovativ produktion.
    Sammalisto, Kaisu
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för industriell ekonomi, industridesign och maskinteknik, Industriell ekonomi. Högskolan i Gävle, Centrum för logistik och innovativ produktion.
    Analysing organisational change management in seaports: Stakeholder perception, communication, drivers for, and barriers to sustainability at the Port of Gävle2020Ingår i: European port cities in transition: Moving towards more sustainable sea transport hubs, Springer, 2020Kapitel i bok, del av antologi (Övrigt vetenskapligt)
  • 26.
    Lozano, Rodrigo
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad, Industriell ekonomi. Högskolan i Gävle, Centrum för logistik och innovativ produktion.
    Findler, Florian
    Schönherr, Norma
    Stacherl, Barbara
    Making the Invisible Visible: Impact Assessment in Higher Education2018Ingår i: Proceedings of the International Association for Business and Society: Proceedings of the Twenty-Ninth Annual Meeting, 2018Konferensbidrag (Refereegranskat)
  • 27.
    Märdla, Silja
    et al.
    Tallinn University of Technology, Estonia.
    Ellmann, Artu
    Tallinn University of Technology, Estonia.
    Ågren, Jonas
    Lantmäteriet.
    Sjöberg, Lars
    KTH.
    Regional geoid computation by least squares modified Hotine’s formula with additive corrections2018Ingår i: Journal of Geodesy, ISSN 0949-7714, E-ISSN 1432-1394, Vol. 92, nr 3, s. 253-270Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Geoid and quasigeoid modelling from gravity anomalies by the method of least squares modification of Stokes’s formula with additive corrections is adapted for the usage with gravity disturbances and Hotine’s formula. The biased, unbiased and optimum versions of least squares modification are considered. Equations are presented for the four additive corrections that account for the combined (direct plus indirect) effect of downward continuation (DWC), topographic, atmospheric and ellipsoidal corrections in geoid or quasigeoid modelling. The geoid or quasigeoid modelling scheme by the least squares modified Hotine formula is numerically verified, analysed and compared to the Stokes counterpart in a heterogeneous study area. The resulting geoid models and the additive corrections computed both for use with Stokes’s or Hotine’s formula differ most in high topography areas. Over the study area (reaching almost 2 km in altitude), the approximate geoid models (before the additive corrections) differ by 7 mm on average with a 3 mm standard deviation (SD) and a maximum of 1.3 cm. The additive corrections, out of which only the DWC correction has a numerically significant difference, improve the agreement between respective geoid or quasigeoid models to an average difference of 5 mm with a 1 mm SD and a maximum of 8 mm.

  • 28.
    Märdla, Silja
    et al.
    Tallinn University of Technology, Estonia.
    Ågren, Jonas
    Lantmäteriet.
    Strykowsky, Gabriel
    Technical University of Denmark.
    Oja, Tönis
    Estonian Land Board.
    Ellmann, Artu
    Tallinn University of Technology, Estonia.
    Forsberg, René
    Technical University of Denmark.
    Bilker-Koivula, Mirjam
    Land Survey of Finland.
    Omang, Ove
    Norwegian Mapping Authority.
    Parseliunas, Eimuntas
    Vilinius Gediminas Technical Univesity, Lithuania.
    Liepins, Ivars
    Latvian Geospatial Information Agency.
    From discrete gravity survey data to a high-resolution gravity field representation in the Nordic-Baltic region2017Ingår i: Marine Geodesy, ISSN 0149-0419, E-ISSN 1521-060X, Vol. 40, nr 6, s. 416-453Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The deduction of a regularly spaced gravity anomaly grid from scattered survey data is studied, addressing mainly two aspects: reduction of gravity to anomalies and subsequent interpolation by various methods. The problem is illustrated in a heterogeneous study area and contrasting test areas including mountains, low terrains, and a marine area. Provided with realistic error estimates, Least Squares Collocation interpolation of Residual Terrain Model anomalies yields the highest quality gravity grid. In most cases, the Bouguer reduction and other interpolation methods tested are equally viable. However, spline-based interpolation should be avoided in marine areas with trackwise survey data.

  • 29.
    Novák, Pavel
    et al.
    University of West Bohemia, Plzeň, Czech Republic.
    Tenzer, Robert
    National School of Surveying, Division of Sciences, University of Otago, Dunedin, New Zealand.
    Eshagh, Mehdi
    Royal Institute of Technology, Stockholm, Sweden.
    Bagherbandi, Mohammad
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad, Samhällsbyggnad/GIS-Institutet.
    Evaluation of gravitational gradients generated by Earth's crustal structures2013Ingår i: Computers & Geosciences, ISSN 0098-3004, E-ISSN 1873-7803, Vol. 51, s. 22-33Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Spectral formulas for the evaluation of gravitational gradients generated by upper Earth’s mass components are presented in the manuscript. The spectral approach allows for numerical evaluation of global gravitational gradient fields that can be used to constrain gravitational gradients either synthesised from global gravitational models or directly measured by the spaceborne gradiometer on board of the GOCE satellite mission. Gravitational gradients generated by static atmospheric, topographic and continental ice masses are evaluated numerically based on available global models of Earth’s topography, bathymetry and continental ice sheets. CRUST2.0 data are then applied for the numerical evaluation of gravitational gradients generated by mass density contrasts within soft and hard sediments, upper, middle and lower crust layers. Combined gravitational gradients are compared to disturbing gravitational gradients derived from a global gravitational model and an idealised Earth’s model represented by the geocentric homogeneous biaxial ellipsoid GRS80. The methodology could be used for improved modelling of the Earth’s inner structure.

  • 30.
    Sahlin, Eva A.U.
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad, Samhällsbyggnad/GIS-Institutet.
    Glasser, Neil F.
    Institute of Geography and Earth Sciences, Aberystwyth University, Wales.
    The Geomorphological Map of Wales and its use in Geoconservation Assessment (poster)2011Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    A geomorphological map is probably the most comprehensive way of illustrating the landform distribution, surface form, material, age, and the processes responsible for the landscape look. As such geomorphological maps are invaluable in the fields of geoconservation assessment, evaluation and management. It is therefore an oddity, as well as an inconvenience, that there is no systematic landform inventory or mapping of the geomorphology that is comparable to the surveys undertaken for geology or soils in the UK. For that purpose the project of “Developing a Geomorphological Map of Wales” was initiated by the Countryside Council for Wales (CCW) as part of a PhD project investigating the Quaternary glaciations of Wales.

    To develop a mapping methodology suitable for the Welsh landscape, three contrasting areas were selected to provide a wide range of geomorphological features. Aerial photography, satellite imagery, digital elevation models, and field investigations of landform/sediment associations, formed the foundation for landform interpretation, which were compiled in a GIS.

    Geomorphological maps of Cadair Idris, and the Central and North Cambrian Mountains were produced, scale 1:10 000 – 1:25 000. The maps form an extensive inventory of the geomorphological geodiversity, and were used for providing data to palaeoglaciological reconstructions and making geoconservation recommendations to the CCW. The recommended sites are of regional interest; their rareness, distinct morphology, interesting research and educational value makes them worthy of RIGS (Regional Important Geodiversity Sites) protection.

    A Geomorphological Map of Wales has the potential for wider practical, scientific and educational benefits, such as for governmental bodies, local authority planners, tourism, researchers, teachers, landowners and land managers. Without a full account of all the geomorphological components of a landscape, there can be no full understanding of the landscape history or the various landforming processes. Important geodiversity sites may be overlooked, badly managed or lost before their full potential are realised.

  • 31.
    Sjöberg, Lars
    et al.
    Division of Geodesy and Satellite Positioning KTH.
    Abrehdry, Majid
    Division of Geodesy and Satellite Positioning.
    Bagherbandi, Mohammad
    Division of Geodesy and Satellite Positioning KTH.
    The observed geoid height versus Airy's and Pratt's isostatic models using matched asymptotic expansions2014Ingår i: Acta Geodaetica et Geophysica Hungarica, ISSN 1217-8977, E-ISSN 1587-1037, Vol. 49, nr 4, s. 473-490Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Isostasy is a key concept in geodesy and geophysics. The classical isostatic models of Airy/Heiskanen and Pratt/Hayford imply that the topographic mass surplus and ocean mass deficit are balanced by mountain roots and anti-roots in the former model and by density variations in the topography and the compensation layer below sea bottom in the latter model. In geophysics gravity inversion is an essential topic where isostasy comes to play. The main objective of this study is to compare the prediction of geoid heights from the above isostatic models based on matched asymptotic expansion with geoid heights observed by the Earth Gravitational Model 2008. Numerical computations were carried out both globally and in several regions, showing poor agreements between the theoretical and observed geoid heights. As an alternative, multiple regression analysis including several non-isostatic terms in addition to the isostatic terms was tested providing only slightly better success rates. Our main conclusion is that the geoid height cannot generally be represented by the simple formulas based on matched asymptotic expansions. This is because (a) both the geoid and isostatic compensation of the topography have regional to global contributions in addition to the pure local signal considered in the classical isostatic models, and (b) geodynamic phenomena are still likely to significantly blur the results despite that all spherical harmonic low-degree (below degree 11) gravity signals were excluded from the study.

  • 32.
    Sjöberg, Lars
    et al.
    Royal Institute of Technology (KTH), Stockholm, Sweden .
    Bagherbandi, Mohammad
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad, Samhällsbyggnad/GIS-Institutet.
    A study on the Fennoscandian post-glacial rebound as observed by present-day uplift rates and gravity field model GOCO02S2013Ingår i: Acta Geodaetica et Geophysica Hungarica, ISSN 1217-8977, E-ISSN 1587-1037, Vol. 48, nr 3, s. 317-331Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Repeated absolute gravity measurements in Fennoscandia have revealed that the on-going post-glacial rebound can be regarded as a pure viscous flow of mantle mass of density 3390 kg/m3 towards the central part of the region caused by a gravity/uplift rate of −0.167 μGal/mm. Our model estimates the rebound induced rates of changes of surface gravity and geoid height to have peaks of −1.9 μGal/yr and 1.6 mm/yr, respectively, the former being consistent with absolute gravity observations. The correlation coefficient of the spherical harmonic representations of the geoid height and uplift rate for the spectral windows between degrees 10 and 70 is estimated to −0.99±0.006, and the maximum remaining land uplift is estimated to the order of 80 m. Both the (almost) linear increase of relaxation time with degree and the linear relation between geoid height and uplift rate support a model with mass flow in the major part of the mantle and disqualify the model with a flow in a thin channel below the crust. The mean viscosity of the flow in the central uplift region is estimated to 4×1021 Pa s.

  • 33.
    Sjöberg, Lars E.
    et al.
    Royal Institute of Technology, Stockholm, Sweden.
    Bagherbandi, Mohammad
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad, Samhällsbyggnad, GIS. Royal Institute of Technology, Stockholm, Sweden.
    Isostasy - Geodesy2016Ingår i: Encyclopedia of Geodesy / [ed] Grafarend, Erik, Springer , 2016Kapitel i bok, del av antologi (Övrigt vetenskapligt)
    Abstract [en]

    Isostasy (Greek isos “equal,” stasis “stand still”) is a term in geology, geophysics, and geodesy to describe the state of mass balance (equilibrium) between the Earth’s crust and upper mantle. It describes a condition to which the mantle tends to balance the mass of the crust in the absence of external forces.

  • 34.
    Tenzer, Robert
    et al.
    The Key Laboratory of Geospace Environment and GeodesySchool of Geodesy and Geomatics, Wuhan UniversityWuhanChina.
    Bagherbandi, Mohammad
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för datavetenskap och samhällsbyggnad, Samhällsbyggnad. Division of Geodesy and Satellite Positioning.
    Comparative Study of the Uniform and Variable Moho Density Contrast in the Vening Meinesz-Moritz’s Isostatic Scheme for the Gravimetric Moho Recovery2014Ingår i: IGFS 2014, Proceedings of the 3rd International Gravity Field Service (IGFS), Shanghai, China, 30 June - 6 July 2014 / [ed] Shuanggen Jin, Riccardo Barzaghi, Springer, 2014, s. 199-207Konferensbidrag (Refereegranskat)
    Abstract [en]

    In gravimetric methods for a determination of the Moho geometry, the constant value of the Moho density contract is often adopted. Results of gravimetric and seismic studies, however, showed that the Moho density contrast varies significantly. The assumption of a uniform density contrast thus might yield large errors in the estimated Moho depths. In this study we investigate these errors by comparing the Moho depths determined globally for the uniform and variable models of the Moho density contrast. These two gravimetric results are obtained based on solving the Vening Meinesz-Moritz’s inverse problem of isostasy. The uniform model of the Moho density contrast is defined individually for the continental and oceanic lithosphere to better reproduce the reality. The global data of the lower crust and upper mantle retrieved from the CRUST1.0 seismic crustal model are used to define the variable Moho density contrast. This seismic model is also used to validate both gravimetric solutions. Results of our numerical experiment reveals that the consideration of the variable Moho density contrast improves the agreement between the gravimetric and seismic Moho models; the RMS of differences is 5.4 km (for the uniform density contrast) and 4.7 km (for the variable density contrast).

  • 35.
    Tenzer, Robert
    et al.
    National School of Surveying, University of Otago, Dunedin, New Zealand.
    Bagherbandi, Mohammad
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad, Samhällsbyggnad/GIS-Institutet.
    Reformulation of the Vening-Meinesz Moritz Inverse Problem of Isostasy for Isostatic Gravity Disturbances2012Ingår i: International Journal of Geosciences, ISSN 2156-8359, E-ISSN 2156-8367, Vol. 3, nr 5A, s. 918-929Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The isostatic gravity anomalies have been traditionally used to solve the inverse problems of isostasy. Since gravity measurements are nowadays carried out together with GPS positioning, the utilization of gravity disturbances in various regional gravimetric applications becomes possible. In global studies, the gravity disturbances can be computed using global geopotential models which are currently available to a relatively high accuracy and resolution. In this study we facilitate the definition of the isostatic gravity disturbances in the Vening-Meinesz Moritz inverse problem of isostasy for finding the Moho depths. We further utilize uniform mathematical formalism in the gravimetric forward modelling based on methods for a spherical harmonic analysis and synthesis of gravity field. We then apply both mathematical procedures to determine globally the Moho depths using the isostatic gravity disturbances. The results of gravimetric inversion are finally compared with the global crustal seismic model CRUST2.0; the RMS fit of the gravimetric Moho model with CRUST2.0 is 5.3 km. This is considerably better than the RMS fit of 7.0 km obtained after using the isostatic gravity anomalies.

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  • 36.
    Tenzer, Robert
    et al.
    University of Otago.
    Bagherbandi, Mohammad
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad, Samhällsbyggnad/GIS-Institutet.
    Cheinway, Hwang
    Chang, Emmy Tsui-Yu
    Moho Interface Modeling Beneath the Himalayas, Tibet and Central Siberia Using GOCO02S and DTM2006.02013Ingår i: Terrestrial, Atmospheric and Oceanic Science, ISSN 1017-0839, E-ISSN 2223-8964, Vol. 24, nr 4, s. 581-590Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We apply a newly developed method to estimate the Moho depths and density contrast beneath the Himalayas, Tibet and Central Siberia. This method utilizes the combined least-squares approach based on solving the inverse problem of isostasy and using the constraining information from the seismic global crustal model (CRUST2.0). The gravimetric forward modeling is applied to compute the isostatic gravity anomalies using the global geopotential model (GOCO02S) and the global topographic/bathymetric model (DTM2006.0). The estimated Moho depths vary between 60 - 70 km beneath most of the Himalayas and Tibet and reach the maxima of ~79 km. The Moho depth under Central Siberia is typically 50 - 60 km. The Moho density contrast computed relative to the CRUST2.0 lower crustal densities has the maxima of ~300 kg m-3 under Central Tibet. It substantially decreases to 150 - 250 kg m-3 under Himalayas and north Tibet. The estimated Moho density contrast under central Siberia is within 100 - 200 kg m-3.

  • 37.
    Tenzer, Robert
    et al.
    Wuhan University, China, Hubei, China.
    Bagherbandi, Mohammad
    Division of Geodesy and Satellite Positioning, KTH.
    Sjöberg, Lars
    Division of Geodesy and Satellite Positioning KTH.
    Novak, Pavel
    University of West Bohemia, Czech Republic, Plzeň, República Checa.
    Isostatic crustal thickness under the Tibetan Plateau and Himalayas from satellite gravity gradiometry data2015Ingår i: Earth Sciences Research Journal, ISSN 1794-6190, E-ISSN 2339-3459, Vol. 19, nr 2Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The global gravity and crustal models are used in this study to determine the regional Moho model. For this purpose, we solve the Vening Meinesz-Moritz's (VMM) inverse problem of isostasy defined in terms of the isostatic gravity gradient. The functional relation between the Moho depth and the second-order radial derivative of the VMM isostatic potential is formulated by means of the (linearized) Fredholm integral equation of the first kind. Methods for a spherical harmonic analysis and synthesis of the gravity field and crustal structure models are applied to evaluate the gravity gradient corrections and the respective corrected gravity gradient, taking into consideration major known density structures within the Earth's crust (while mantle heterogeneities are disregarded). The resulting gravity gradient is compensated isostatically based on applying the VMM scheme. The VMM inverse problem for finding the Moho depths is solved iteratively. The regularization is applied to stabilize the ill-posed solution. The global geopotential model GOCO-03s, the global topographic/bathymetric model DTM2006.0 and the global crustal model CRUST1.0 are used to generate the VMM isostatic gravity gradient with a spectral resolution complete to a spherical harmonic degree of 250. The VMM inverse scheme is used to determine the regional isostatic crustal thickness beneath the Tibetan Plateau and Himalayas (compiled on a 1x1 arc-deg grid). The differences between the isostatic and seismic Moho models are modeled and subsequently corrected for by applying the non-isostatic correction. Our results show that the regional gravity gradient inversion can model realistically the relative Moho geometry, while the solution contains a systematic bias. We explain this bias by more localized information on the Earth's inner structure in the gravity gradient field compared to the potential or gravity fields.

  • 38.
    Ågren, Jonas
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för datavetenskap och samhällsbyggnad, Samhällsbyggnad.
    Hauska, Hans
    Kungliga Tekniska Högskolan.
    Referenssystem och kartprojektioner2019Ingår i: Geografisk informationsbehandling: Teori, metoder och tillämpningar / [ed] Lars Harrie, Studentlitteratur AB, 2019, 7, s. 59-84Kapitel i bok, del av antologi (Övrig (populärvetenskap, debatt, mm))
    Abstract [sv]

    I ett geografiskt informationssystem hanteras geografiska objekt med kända lägen. För att ange ett läge behövs en fast referens, relativt vilken objektets position kan anges. Man behöver därför ett referenssystem, som är ett koordinatsystem vars axlar har lagts fast i förhållande till jordens yta. Det är mycket viktigt att objekten i ett geografiskt informationssystem är bestämda i ett väldefinierat referenssystem. Referenssystem och koordinatsystem behandlas inom ämnesområdet geodesi, som är vetenskapen om jordens uppmätning. 

    Kapitlet börjar med en övergripande diskussion i avsnitt 3.2, som förklarar vad ett referenssystem är och motiverar varför det behövs som grund för inmätning av geografiska objekt. I avsnitt 3.3 behandlas därefter de vanligaste typerna av koordinatsystem. För att trycka en karta på papper eller för presentation på en dataskärm behövs ett plant koordinatsystem. Detta ställer till problem eftersom jorden är rund och inte platt. För att avbilda den buktiga jordytan på ett plan används en kartprojektion. Grunderna för sådana kartprojektioner förklaras i avsnitt 3.4. Referenssystem tas därefter upp i avsnitt 3.5. Genom hela kapitlet ligger tyngdpunkten på att förklara de viktigaste referenssystemen, koordinatsystemen och kartprojektionerna som används i Sverige. Kapitlet avslutas i avsnitt 3.6. med att diskutera några viktiga grundprinciper för transformationer mellan olika koordinat- och referenssystem.

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