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  • 251.
    Tenzer, Robert
    et al.
    Department of Land Surveying and Geo-Informatics, Hong Kong Polytechnic University, Hong Kong, China.
    Chen, Wenjin
    Department of Geodesy and Geomatics, Wuhan University, Wuhan, China.
    Baranov, Alexey
    Schmidt Institute of Physics of the Earth, Russian Academy of Sciences, Moscow, Russian Federation; Institute of Earthquake Prediction Theory and Mathematical Geophysics, Russian Academy of Sciences, Moscow, Russian Federation.
    Bagherbandi, Mohammad
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad, Samhällsbyggnad, GIS. Division of Geodesy and Geoinformatics, Royal Institute of Technology (KTH), Stockholm, Sweden.
    Gravity maps of Antarctic lithospheric structure from remote-sensing and seismic data2018Ingår i: Pure and Applied Geophysics, ISSN 0033-4553, E-ISSN 1420-9136, Vol. 175, nr 6, s. 2181-2203Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Remote-sensing data from altimetry and gravity satellite missions combined with seismic information have been used to investigate the Earth’s interior, particularly focusing on the lithospheric structure. In this study, we use the subglacial bedrock relief BEDMAP2, the global gravitational model GOCO05S, and the ETOPO1 topographic/bathymetric data, together with a newly developed (continental-scale) seismic crustal model for Antarctica to compile the free-air, Bouguer, and mantle gravity maps over this continent and surrounding oceanic areas. We then use these gravity maps to interpret the Antarctic crustal and uppermost mantle structure. We demonstrate that most of the gravity features seen in gravity maps could be explained by known lithospheric structures. The Bouguer gravity map reveals a contrast between the oceanic and continental crust which marks the extension of the Antarctic continental margins. The isostatic signature in this gravity map confirms deep and compact orogenic roots under the Gamburtsev Subglacial Mountains and more complex orogenic structures under Dronning Maud Land in East Antarctica. Whereas the Bouguer gravity map exhibits features which are closely spatially correlated with the crustal thickness, the mantle gravity map reveals mainly the gravitational signature of the uppermost mantle, which is superposed over a weaker (long-wavelength) signature of density heterogeneities distributed deeper in the mantle. In contrast to a relatively complex and segmented uppermost mantle structure of West Antarctica, the mantle gravity map confirmed a more uniform structure of the East Antarctic Craton. The most pronounced features in this gravity map are divergent tectonic margins along mid-oceanic ridges and continental rifts. Gravity lows at these locations indicate that a broad region of the West Antarctic Rift System continuously extends between the Atlantic–Indian and Pacific–Antarctic mid-oceanic ridges and it is possibly formed by two major fault segments. Gravity lows over the Transantarctic Mountains confirms their non-collisional origin. Additionally, more localized gravity lows closely coincide with known locations of hotspots and volcanic regions (Marie Byrd Land, Balleny Islands, Mt. Erebus). Gravity lows also suggest a possible hotspot under the South Orkney Islands. However, this finding has to be further verified.

  • 252. Tenzer, Robert
    et al.
    Chen, Wenjin
    Tsoulis, Dimitrios
    Bagherbandi, Mohammad
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad, Samhällsbyggnad, GIS. Royal Institute of Technology (KTH), Stockholm, Sweden .
    Sjöberg, Lars E.
    Novák, Pavel
    Jin, Shuanggen
    Analysis of the Refined CRUST1.0 Crustal Model and its Gravity Field2015Ingår i: Surveys in geophysics, ISSN 0169-3298, E-ISSN 1573-0956, Vol. 36, nr 1, s. 139-165Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    The global crustal model CRUST1.0 (refined using additional global datasets of the solid topography, polar ice sheets and geoid) is used in this study to estimate the average densities of major crustal structures. We further use this refined model to compile the gravity field quantities generated by the Earth's crustal structures and to investigate their spatial and spectral characteristics and their correlation with the crustal geometry in context of the gravimetric Moho determination. The analysis shows that the average crustal density is 2,830 kg/m3, while it decreases to 2,490 kg/m3 when including the seawater. The average density of the oceanic crust (without the seawater) is 2,860 kg/m3, and the average continental crustal density (including the continental shelves) is 2,790 kg/m3. The correlation analysis reveals that the gravity field corrected for major known anomalous crustal density structures has a maximum (absolute) correlation with the Moho geometry. The Moho signature in these gravity data is seen mainly at the long-to-medium wavelengths. At higher frequencies, the Moho signature is weakening due to a noise in gravity data, which is mainly attributed to crustal model uncertainties. The Moho determination thus requires a combination of gravity and seismic data. In global studies, gravimetric methods can help improving seismic results, because (1) large parts of the world are not yet sufficiently covered by seismic surveys and (2) global gravity models have a relatively high accuracy and resolution. In regional and local studies, the gravimetric Moho determination requires either a detailed crustal density model or seismic data (for a combined gravity and seismic data inversion). We also demonstrate that the Earth's long-wavelength gravity spectrum comprises not only the gravitational signal of deep mantle heterogeneities (including the core-mantle boundary zone), but also shallow crustal structures. Consequently, the application of spectral filtering in the gravimetric Moho determination will remove not only the gravitational signal of (unknown) mantle heterogeneities, but also the Moho signature at the long-wavelength gravity spectrum. 

  • 253.
    Thorsteinsson, Russell
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad.
    WATER CONTAMINATION RISK DURING URBAN FLOODS: Using GIS to map and analyze risk at a local scale2014Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Water contamination during urban flood events can have a negative impact on human health and the environment. Prior flood studies lack investigation into how GIS can map and analyze this at a large scale (cadastral) level. This  thesis  focused on how GIS can  help map and analyze water contamination risk in urban  areas  using  LiDAR  elevation  data,  at  a  large-scale  (cadastral)  level,  and  symbology  and  flood classification  intervals  specifically  selected  for  contamination  risk.  This  was  done  by  first  completing a literature review about past research and studies  of similar scope. Based on  the findings, a method to map and analyze water contamination risk during sea-based flood scenarios was tested in the Näringen district of Gävle, Sweden. This study area was investigated and flood contamination risk maps were produced  for two different  flood scenarios which illustrated  which properties are vulnerable to flooding and at what depth, what their contamination risk is, and if they are hydrologically connected to the ocean.  The findings from this investigation  are that this method of examining water contamination risk could be useful to planning officials who are in charge of policies relating to land-use. These findings could help guide landuse  or  hazardous  material  storage  regulations  or  restrictions.  To  further  research  in  this  topic,  it  is recommended  that  similar  studies  are  performed  that  use  a  more  detailed  land-use  map  which  has information  on  what  type  and  quantity  of  possible  contaminants  are  stored  on  individual  properties. Furthermore, flood modeling should be employed in place of the flood mapping which was conducted in this thesis.

  • 254.
    Twumasi, Ebenezer
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Byggvetenskap - byggnadsmateriallära.
    Norberg, Peter
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Byggvetenskap - byggnadsmateriallära.
    Sjöström, Christer
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Byggvetenskap - byggnadsmateriallära.
    Tailored Precipitated Silica Adsorbents for the Built Environment2011Ingår i: XII DBMC: 12th International Conference on Durability of Building Materials and Components (Vol. 4): Michael A. Lacasse, Vasco Peixoto de Freitas, Helena Corvacho, Porto: FEUP Edições , 2011, , s. 8Konferensbidrag (Refereegranskat)
    Abstract [en]

    The paper provides a review of the synthesis and adsorptive properties of a novel class of precipitated silica materials. To enhance or tailor the adsorption efficiency, various trapping chemicals (potassium hydroxide, potassium permanganate) or co-adsorbents (coconut activated carbon) are incorporated in the structure of the substrate material. Further, it discusses the applicability and performance over time of the material as adsorbents for removal of hydrogen sulphide, sulphur dioxide and toluene contaminants which are potentially hazardous to sensitive equipment and more importantly, human health. Chemical substances in the air are an unavoidable by-product of most human endeavours within industry and transportation. The need for adsorbents to combat Airborne Molecular Contamination (AMC) follows from the continued intensification of the global environmental movement as well as the rapid industrialisation of developing countries. The removal performance of modified precipitated silica adsorbent shows that the new adsorbent can be tailored to remove low concentrations of sulphur dioxide, hydrogen sulphide and toluene contaminants at indoor environment conditions. The results further shows that the new precipitated silica adsorbent impregnated with 8 wt% KOH shows better performance than commercial alumina impregnated with 8 wt% KMnO4.The adsorbent material may find interesting and efficient uses as passive sinks for pollutants incorporated into more traditional building products such as acoustic baffles or as ingredients in various coatings. The filter material is environmentally friendly and consists of benign chemicals that are abundant worldwide. Performance over time aspects, re-use and recycling of exhausted filter materials are key issues addressed.

  • 255. Vajedian, Sanaz
    et al.
    Motagh, Mahdi
    Nilfouroushan, Faramarz
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Mineralogi, petrologi och tektonik.
    Response to Sowter, A.; Cigna, F. On the Use of the ISBAS Acronym in InSAR Applications. Comment on Vajedian, S.; Motagh, M.; Nilfouroushan, F. StaMPS Improvement for Deformation Analysis in Mountainous Regions: Implications for the Damavand Volcano and Mosha Fault in Alborz. Remote Sens. 2015, 7, 8323–83472015Ingår i: Remote Sensing, ISSN 2072-4292, E-ISSN 2072-4292, Vol. 7, nr 9, s. 11324-11325Artikel i tidskrift (Refereegranskat)
  • 256.
    Vajedian, Sanaz
    et al.
    Department of Surveying and Geomatics Engineering, University of Tehran, Tehran, Iran.
    Motagh, Mahdi
    GFZ German Research Center for Geosciences, Potsdam, Germany; Department of Surveying and Geomatics Engineering, University of Tehran, Tehran, Iran.
    Nilfouroushan, Faramarz
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    STaMPS improvement for deformation analysis in mountainous regions: Implications for Damavand volcano and Mosha fault in Alborz2015Ingår i: Remote Sensing, ISSN 2072-4292, E-ISSN 2072-4292, Vol. 7, nr 7, s. 8323-8347Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Interferometric Synthetic Aperture Radar (InSAR) capability to detect slow deformation over terrain areas is limited by temporal decorrelation, geometric decorrelation and atmospheric artefacts. Multitemporal InSAR methods such as Persistent Scatterer (PS-InSAR) and Small Baseline Subset (SBAS) have been developed to deal with various aspects of decorrelation and atmospheric problems affecting InSAR observations. Nevertheless, the applicability of both PS-InSAR and SBAS in mountainous regions is still challenging. Correct phase unwrapping in both methods is hampered due to geometric decorrelation in particular when using C-band SAR data for deformation analysis. In this paper, we build upon the SBAS method implemented in StaMPS software and improved the technique, here called ISBAS, to assess tectonic and volcanic deformation in the center of the Alborz Mountains in Iran using both Envisat and ALOS SAR data. We modify several aspects within the chain of the processing including: filtering prior to phase unwrapping, topographic correction within three-dimensional phase unwrapping, reducing the atmospheric noise with the help of additional GPS data, and removing the ramp caused by ionosphere turbulence and/or orbit errors to better estimate crustal deformation in this tectonically active region. Topographic correction is done within the three-dimensional unwrapping in order to improve the phase unwrapping process, which is in contrast to previous methods in which DEM error is estimated before/after phase unwrapping. Our experiments show that our improved SBAS approach is able to better characterize the tectonic and volcanic deformation in the center of the Alborz region than the classical SBAS. In particular, Damavand volcano shows an average uplift rate of about 3 mm/year in the year 2003–2010. The Mosha fault illustrates left-lateral motion that could be explained with a fault that is locked up to 17–18 km depths and slips with 2–4 mm/year below that depth.

  • 257.
    Vestøl, Olav
    et al.
    Statens Kartverk, Norge.
    Ågren, Jonas
    Lantmäteriet.
    Steffen, Holger
    Lantmäteriet.
    Kierulf, Halfdan
    Oslo Universitet, Norge.
    Tarasov, Lev
    Memorial University of Newfoundland, Canada.
    NKG2016LU: a new land uplift model for Fennoscandia and the Baltic Region2019Ingår i: Journal of Geodesy, ISSN 0949-7714, E-ISSN 1432-1394, Vol. 93, nr 9, s. 1759-1779Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present the official land uplift model NKG2016LU of the Nordic Commission of Geodesy (NKG) for northern Europe. The model was released in 2016 and covers an area from 49° to 75° latitude and 0° to 50° longitude. It shows a maximum absolute uplift of 10.3 mm/a near the city of Umeå in northern Sweden and a zero-line that follows the shores of Germany and Poland. The model replaces the NKG2005LU model from 2005. Since then, we have collected more data in the core areas of NKG2005LU, specifically in Norway, Sweden, Denmark and Finland, and included observations from the Baltic countries as well. Additionally, we have derived an underlying geophysical glacial isostatic adjustment (GIA) model within NKG as an integrated part of the NKG2016LU project. A major challenge is to estimate a realistic uncertainty grid for the model. We show how the errors in the observations and the underlying GIA model propagate through the calculations to the final uplift model. We find a standard error better than 0.25 mm/a for most of the area covered by precise levelling or uplift rates from Continuously Operating Reference Stations and up to 0.7 mm/a outside this area. As a check, we show that two different methods give approximately the same uncertainty estimates. We also estimate changes in the geoid and derive an alternative uplift model referring to this rising geoid. Using this latter model, the maximum uplift in Umeå reduces from 10.3 to 9.6 mm/a and with a similar reduction ratio elsewhere. When we compare this new NKG2016LU with the former NKG2005LU, we find the largest differences where the GIA model has the strongest influence, i.e. outside the area of geodetic observation. Here, the new model gives from − 3 to 4 mm/a larger values. Within the observation area, similar differences reach − 1.5 mm/a at the northernmost part of Norway and − 1.0 mm/a at the north-western coast of Denmark, but generally within the range of − 0.5 to 0.5 mm/a.

  • 258.
    Wang, Mian
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad.
    Extending geographic information systems to urban morphological analysis with a space syntax approach2012Självständigt arbete på avancerad nivå (magisterexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Branches of complexity theory have been widely employed in geographic information systems (GIS) to explore phenomena that appear in urban environments. Among these, space syntax, as an urban morphological application of complexity theory, has attracted increasing attention in recent years.

    Accordingly, many computer-based tools have been developed to realize related analysis spatially, especially those that can be integrated as functions with GIS. In this thesis, a space syntax tool – Axwoman – is redeveloped and tested as an extension of ESRI ArcGIS Desktop in order to fulfill certain specific needs in urban morphological analysis. It is primarily used to calculate all space syntax measures for several urban systems and to explore the relationships between these measures. To meet the needs for this new version of Axwoman, several functions have been updated and changed, for drawing, coloring, and classifying axial lines as maps for visual thinking; ticking overpasses and excluding them from computing space syntax parameters; and integrating AxialGen and Axwoman.

    In accordance with this, several case studies have been performed on the urban street networks in large cities. In this paper, Stockholm was chosen as the study object at both the urban level and the building level. After the scaling analysis and time efficiency analysis, the results are also interpreted from a structural point of view and in terms of how the function of space is subject to its morphological structure. Finally, the connectivity of axial lines (a spatial measurement in space syntax theory) was found to follow a power-law distribution.

    Through this work, the new edition of Axwoman generating satisfactory outputs, the research have proved that the connectivity of axial lines follows a lognormal distribution or a power-law-like distribution, which is one of the heavy-tailed distributions. In addition, it was have found that axial lines better for capture the underlying urban morphologies showed in their study on redefining the generated axial lines from street center lines. Moreover, fewer longest axial lines will show up on the maps, just as coincidental as the shape of mental maps, which proved that the axial line representations can be a powerful tool for urban studies.

  • 259.
    Wang, Zhu
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad.
    A Comparison Study on Urban Morphology of Beijing and Shanghai2013Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    With time going by, urban morphological structures of Beijing and Shanghai have dramatic changes during last decades. These changes often ignored by citizen, but have big influence for human daily life. And the changes of urban morphologies should be easily recognized by citizen. There are many previous comparative studies between these two Chinese cities, and these studies focus on types of areas, such as environment, traffic, city planning and cultures etc.. There are also many comparative studies about using space syntax theory and geometrical statistics to study urban morphologies. However, there are not direct comparison urban morphological study between Beijing and Shanghai, which from multiple perspectives. In order to gain a better understanding of urban morphologies, this thesis take street networks of two Chinese cites as a research object, based on space syntax theory, as well the combination of traditional geometrical statistics, comparative analysis methods to systematic quantitative analyze and comparative study the different street networks of urban space in Beijing and Shanghai. This project work analyzes hierarchy of axial lines, which automatically generated from street networks, to do a morphological comparison from topological perspective. And it analyzes frequency distribution of axial lines’ included angles and length of axial lines to study urban morphologies from geometrical perspective. Results in the project seem to empirical study that, the well-connected streets are minority part, which all most distributed in the sample cities’ ring structures and center areas. Street networks constitute an obvious regular grid pattern of Beijing and a curves pattern of Shanghai. Based on the hierarchical levels of street networks, research samples have same hierarchical levels but without the same number of street lines. The included angles of axial lines have an exceptionally sharply peaked bimodal distribution for both cities and number of most connected street’s length do not increase so much from ring1 to ring6 for Beijing, but they have much change for Shanghai.

  • 260.
    Wu, Jie
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad.
    Zhou, Lina
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad.
    GIS-Based Multi-Criteria Analysis for Hostital Selection in Haidian District of Beijing2012Självständigt arbete på avancerad nivå (magisterexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    China has the largest population and the fastest growing economy in the world. The general public's demand for health is rising promptly with the improvement of the living standard. However, the limited and unbalanced medical resource have caused the prominent problem of the society, even in the capital city of Beijing, the new hospital constructions with rational allocation is iminent and significant. Along with the technology development and Internet popularization, GIS approaches and related products has been widely used in the people's daily life. The main focus of this paper is to select a site for building a new hospital in Haidian District of Beijing using GIS-based Multi-Criteria Analysis (MCA). With Analytical Hieraichy Process(AHP) and Rank Order Method (ROM) for the weight setting on factor criteria, necessity tests and sensitivity tests are applied to check which criteria are really necessary and how the results are sensitive to their weight change. The optimal site located in Wenquan Town (E: 116.182, N:40.039) is screened from several candidate sites usin Google Earth maps, which makes the ultimate result more convincing and practical. It can be concluded that GIS-based MCA with necessity and sensitivity tests proposes a novel and useful reference to other site selection decision makers, and also provides constructive tools for the public asministration to set up efficent databases for decision makers to carry out spatial analyses. To make it more maneuverable and practical, a further research on th improvement of this method will have a promising future. 

  • 261.
    Wu, Sirui
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad.
    A study on Extraction of Natural Cities from the Nightlight Imagery Using Head/tail breaks method2013Självständigt arbete på grundnivå (kandidatexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    With the high development of economic and demand for city research, an issue of detecting city boundaries plays an extremely important role in urbanization that promotes the progress of human civilization. Some critical applications such as land use, urban planning and city sprawl have been constantly discussed, which rely on the acquisition of city areas. For the better acquisition of city areas, choosing a proper method to capture city boundaries becomes significant where it greatly improves the value of city study. Although conventional data can be used to define the city boundaries, some drawbacks still exist when measuring the city boundaries in a global scale.

    Remote sensing (RS) data of nightlight imagery (2010) by Defense Meteorological Satellite Program’s Operational Linescan System (DMSP/OLS) acquired from National oceanic and atmospheric administration's National Geoscience Data Center (NOAA/NOGA) is applied to extract the city boundaries in fifty countries, of which these countries are chosen followed by the Gross Domestic Product that are ranked in top 50. In this case, the data distribution of nightlight imagery followed by heavy-tailed distribution. Head/tail break algorithm poses a possibility of calculating reasonable threshold and extracting the natural cities with the help of software based on the Geomatics information system (GIS). An extended study of power law is made by using of power law estimator from previous studies to check whether the extracted natural cities can match the power law distribution.

    Result shows that combination of the nightlight imagery data and the head/tail break is capable of extracting the city boundaries and a set of possible thresholds with visual inspection by using the head/tail break are executed. There is only one country, namely Belgium, cannot be processed due to its data properties. Result also address how well the natural cities of the fifty countries can be extracted in terms of visual inspection, among the chosen cities, 33 of countries boundaries can be better matched and 13 countries can fundamentally match the city boundaries. Meanwhile, an extended study of power law is provided and four countries have to be found that do not follow the power law distribution. From the result obtained, the study expects that integration of support data will efficiently increase the accuracy of extraction and more useful information can be acquired in further study. On the other hand, a comparative study of threshold decision needs to be verified, put it differently, whether using head/tail break with visual inspection on extracted city boundaries is helpful or not.

  • 262.
    Wu, Sirui
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad.
    Zipf's Law for Natural Cities Extracted from Location-Based Social Media Data2015Självständigt arbete på avancerad nivå (magisterexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Zipf’s law is one of the empirical statistical regularities found within many natural systems, ranging from protein sequences of immune receptors in cells to the intensity of solar flares from the sun. Verifying the universality of Zipf’s law can provide many opportunities for us to further seek the commonalities of phenomena that possess the power law behavior. Since power law-like phenomena, as many studies have previously indicated, is often interpreted as evidence for studying complex systems, exploring the universality of Zipf’s law is also of potential capability in explaining underlying generative mechanisms and endogenous processes, i.e. self-organization and chaos theory.

    The main purpose of this study was to verify whether Zipf’s law is valid for city sizes, city numbers and population extracted from natural cities. Unlike traditional city boundaries extracted by applying census-imposed and top-down imposed data, which are arbitrary and subjective, the study established the new kind of boundaries of cities, namely, natural cities through using four location-based social media data from Twitter, Brightkite, Gowalla and Freebase and head/tail breaks rule. In order to capture and quantify the hierarchical level for studying heterogeneous scales of cities, ht-index derived from head/tail breaks rule was employed. Furthermore, the validation of Zipf’s law was examined.

    The result revealed that the natural cities had deviations in subtle patterns when different social media data were examined. By employing head/tail breaks method, the result calculated the ht-index and detected that hierarchy levels were not largely influenced by spatial-temporal changes but rather data itself. On the other hand, the study found that Zipf’s law is not universal in the case of using location-based social media data. Compared to city numbers extracted from nightlight imagery, the study found out the reason why Zipf’s law does not hold for location-based social media data, i.e. due to bias of customer behavior. The bias mainly resulted in the emergence of natural cities were much more frequent than others in certain regions and countries so that making the emergence of natural cities was not exhibited objectively. Furthermore, the study showed whether Zipf’s law could be well observed depends not only on the data itself and man-made limitations but also on calculation methods, data precisions and scales and the idealized status of observed data.

  • 263.
    Yang, Frank
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för bygg- energi- och miljöteknik, Miljöteknik.
    Goldman, Mattias
    Forum for reforms, entrepreneurship and sustainability (Fores), Stockholm, Sweden.
    Lagercrantz, Jakob
    The 2030 secretariat, Stockholm, Sweden.
    Sustainable Mobility the Chinese Way: Opportunities for European cooperation and inspiration2018 (uppl. 1)Bok (Refereegranskat)
    Abstract [en]

    The book introduces China's endeavours in sustainable mobility to combat climate change and ease air pollution, including electric vehicles, high-speed rail, shared bikes and cars, etc. Suggestions are given on how Europe and China can learn from each other for a more sustainable world.

  • 264.
    Yao, Xiaobai Angela
    et al.
    Department of Geography, University of Georgia, Athens, USA.
    Huang, Haosheng
    Department of Geography, Universitat Zurich Institut fur Geographie, Zurich, Switzerland.
    Jiang, Bin
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för datavetenskap och samhällsbyggnad, Samhällsbyggnad.
    Krisp, Jukka M.
    University of Augsburg, Augsburg, Germany.
    Representation and analytical models for location-based big data2019Ingår i: International Journal of Geographical Information Science, ISSN 1365-8816, E-ISSN 1365-8824, Vol. 33, nr 4, s. 707-713Artikel i tidskrift (Refereegranskat)
  • 265.
    Yazdanfar, Camellia
    et al.
    Department of Geology, University of Golestan, Iran; Department of Geology, University of Uroumieh, Iran.
    Nemati, Majid
    Department of Geology, Faculty of Science and Earthquake Research Center of Shahid Bahonar University of Kerman, Iran.
    Agh Ataby, Maryam
    Department of Geology, University of Golestan, Iran.
    Roustaei, Mahasa
    Geological Survey of Iran, Iran.
    Nilfouroushan, Faramarz
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad, Samhällsbyggnad, GIS. Geodata Division, Lantmäteriet, Gävle, Sweden.
    Stress transfer, aftershocks distribution and InSAR analysis of the 2005 Dahuieh earthquake, SE Iran2018Ingår i: Journal of African Earth Sciences, ISSN 0899-5362, Vol. 147, nr 86, s. 211-219Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, the authors studied the 2005 Dahuieh Zarand earthquake in SE Iran by combining Coulomb stress changes, InSAR study, locally recorded aftershocks and their spatial correlations, co-seismic slip distributions, Iso-seismal curves, and strong ground motion data. The event (MW 6.4) occurred in Kerman province, SE Iran, on February 22, 2005. The locally recorded aftershocks were used to calculate the Coulomb stress changes and the decay time based on Omori’s law. The decay time of aftershocks calculated by Omori’s law was about 500 days. A great correlation was particularly deduced from the spatial distribution of the aftershocks and areas of increased Coulomb stress for optimal strike slip faults. Moreover, using SAR Interferograms, we determined the postseismic surface deformations. Also, the majority of the coseismic slips occurred in the eastern part, where there was sparsely distributed aftershocks. The deformation maps showed active uplift for at least 300 days after the main shock. We reconciled time decays of the aftershocks with the postseismic uplifts, calculated from InSAR. In our model, which is based on after slip evolution, for one of the postseismic relaxation mechanisms, we found a proper correlation between the aftershock decay time and InSAR displacement maps to define postseismic motions. There is also a reasonable correspondence between the mainshock intensity, the acceleration map, and postseismic ground uplift, estimated by InSAR.

  • 266.
    Zarifi, Zoya
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Geofysik..
    Nilfouroushan, Faramarz
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Geovetenskapliga sektionen, Institutionen för geovetenskaper, Berggrundsgeologi.
    Raeesi, Mohammad
    Department of Earth Science, University of Bergen, Bergen, Norway.
    Crustal stress Map of Iran: Insight from seismic and geodetic computations2014Ingår i: Pure and Applied Geophysics, ISSN 0033-4553, E-ISSN 1420-9136, Vol. 171, nr 17, s. 1219-1236Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We used the focal mechanisms of crustal earthquakes (depth <40 km) in the period 1909-2012 and the available GPS velocities, estimated from the data collected between 1999 to 2011, to estimate the magnitude and directions of maximum principal stress and strain rates in Iran. The Pearson product moment correlation was used to find the correlation between the stress field obtained from the focal mechanism stress inversion and that obtained using the seismic and geodetic strain rates. Our assumption is that stresses in a continuum are produced by tectonic forces and the consequent deformation on the crustal scale. Therefore, the direction of the stress and strain (or strain rate) are ideally be the same. Our results show a strong correlation between the directions of the principal components of stress and strain (rate) obtained using the different data/methods.  Using  weighted average analysis, we present a new stress map for Iran.

  • 267.
    Zutautas, Vaidutis
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad, Samhällsbyggnad, GIS.
    Charcoal Kiln Detection from LiDAR-derived Digital Elevation Models Combining Morphometric Classification and Image Processing Techniques2017Självständigt arbete på avancerad nivå (magisterexamen), 10 poäng / 15 hpStudentuppsats (Examensarbete)
    Abstract [en]

    This paper describes a unique method for the semi-automatic detection of historic charcoal production sites in LiDAR-derived digital elevation models. Intensified iron production in the early 17th century has remarkably influenced ways of how the land in Sweden was managed. Today, the abundance of charcoal kilns embedded in the landscape survives as cultural heritage monuments that testify about the scale forest management for charcoal production has contributed to the uprising iron manufacturing industry. An arbitrary selected study area (54 km2) south west of Gävle city served as an ideal testing ground, which is known to consist of already registered as well as unsurveyed charcoal kiln sites. The proposed approach encompasses combined morphometric classification methods being subjected to analytical image processing, where an image that represents refined terrain morphology was segmented and further followed by Hough Circle transfer function applied in seeking to detect circular shapes that represent charcoal kilns. Sites that have been identified manually and using the proposed method were only verified within an additionally established smaller validation area (6 km2). The resulting outcome accuracy was measured by calculating harmonic mean of precision and recall (F1-Score). Along with indication of previously undiscovered site locations, the proposed method showed relatively high score in recognising already registered sites after post-processing filtering. In spite of required continual fine-tuning, the described method can considerably facilitate mapping and overall management of cultural resources.

  • 268.
    Åberg, Curt
    Högskolan i Gävle-Sandviken.
    En vädur i bäcken: om metoder att lyfta och framleda vatten1990Rapport (Övrigt vetenskapligt)
  • 269.
    Åberg, Curt
    Högskolan i Gävle-Sandviken.
    Landformer i Gävleområdet: genomgång av litteratur i ett omdiskuterat ämne1984Rapport (Övrigt vetenskapligt)
  • 270.
    Åberg, Curt
    Högskolan i Gävle-Sandviken.
    Naturgeografi i vardagsnatur1989Rapport (Övrigt vetenskapligt)
  • 271.
    Åberg, Curt
    Högskolan i Gävle-Sandviken.
    Vädurpumpen i Sverige: utvecklingen 1977-19911991Rapport (Övrigt vetenskapligt)
  • 272.
    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, 7:1, 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.

  • 273.
    Åhlén, Julia
    et al.
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad, Datavetenskap.
    Seipel, Stefan
    Högskolan i Gävle, Akademin för teknik och miljö, Avdelningen för Industriell utveckling, IT och Samhällsbyggnad, Datavetenskap. Uppsala University, Department of Information Technology, Sweden.
    Kautz, Marie-Loise
    Technische Universität, Dresden, Germany.
    Data source evaluation for shoreline deliniation applications2017Ingår i: International Multidisciplinary Scientific GeoConference Surveying Geology and Mining Ecology Management, SGEM: Conference proceedings, 2017, Vol. 17, nr 2-3, s. 849-858Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper proposes an evaluation of data acquired with various sensors and used in coastal water segmentation applications. Correct monitoring of coastal changes in dynamic coastal environments strongly depends on accurate and frequent detection of shoreline position. Automatic shoreline delineation methods are preferable, especially in terms of time, cost, labor intensiveness and difficulties of in-situ measurements. Two main issues have been encountered within this application field, the quality of data and the segmentation algorithms. In this work, potential benefits of various data sources including optical and active sensors for extraction of shorelines have been investigated. The goal with shoreline detection from digital data sources is to obtain information as efficiently as possible and as reliably as necessary. Starting with that observation the paper discusses the effectiveness of coastal information extraction provided different data sources. This question is especially important to address since we observe a fast development of high spatial resolution data acquisition. There are many of segmentation algorithms described in the field of image processing and yet there is currently no single theory or method, no universal segmentation framework, that can be applied on all images to precisely and robustly extract shorelines. Nether there is a uniform standard for the assessment of segmentation results, and this process still largely relies on visual analysis and personal judgment. Out of myriads of image segmentation algorithms, we chose the most frequently and successfully applied within the application field and considering the data sources. In optical sensor data cases, the most frequently used methods are NDWI (Normalized Difference Water Index) and thresholding techniques. We do not aim to create yet another method to segment out the particular objects from remotely sensed data and then tailor it to work efficiently on that data set. Instead, we evaluate the data quality regarding the given application field. The case study is carried out on a 10 km coastal stretch facing the Baltic Sea (Sweden) and belonging to the Municipality of Gävle. In citu measurements were acquired to evaluate the extracted coastal lines and comparisons with reference were performed based on the average mean distance. A conclusion is done regarding the most reliable data source for this particular application of shoreline delineation.

  • 274.
    Åsén Ekstrand, Eva
    et al.
    Högskolan i Gävle, Akademin för utbildning och ekonomi, Avdelningen för humaniora, Media- och kommunikationsvetenskap.
    Findahl, OlleHögskolan i Gävle, Akademin för utbildning och ekonomi, Avdelningen för humaniora, Media- och kommunikationsvetenskap.
    Consuming the Environment 2017: Multidisciplinary approaches to urbanization and vulnerability2018Proceedings (redaktörskap) (Övrigt vetenskapligt)
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