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  • 1.
    Agha Karimi, Armin
    et al.
    KTH.
    Bagherbandi, Mohammad
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences. KTH.
    Huremuz, Milan
    KTH.
    Multidecadal sea level variability in the Baltic sea and its impact on acceleration estimations2021In: Frontiers in Marine Science, E-ISSN 2296-7745, Vol. 8, article id 702512Article in journal (Refereed)
    Abstract [en]

    Multidecadal sea level variation in the Baltic Sea is investigated from 1900 to 2020 deploying satellite and in situ datasets. As a part of this investigation, nearly 30 years of satellite altimetry data are used to compare with tide gauge data in terms of linear trend. This, in turn, leads to validation of the regional uplift model developed for the Fennoscandia. The role of North Atlantic Oscillation (NAO) in multidecadal variations of the Baltic Sea is also analyzed. Although NAO impacts the Baltic Sea level on seasonal to decadal time scales according to previous studies, it is not a pronounced factor in the multidecadal variations. The acceleration in the sea level rise of the basin is reported as statistically insignificant in recent studies or even decelerating in an investigation of the early 1990s. It is shown that the reason for these results relates to the global warming hiatus in the 1950s−1970s, which can be seen in all eight tide gauges used for this study. To account for the slowdown period, the acceleration in the basin is investigated by fitting linear trends to time spans of six to seven decades, which include the hiatus. These results imply that the sea level rise is accelerated in the Baltic Sea during the period 1900–2020.

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  • 2.
    Bagherbandi, Mohammad
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    A study on the quality of GNSS signals for extracting the sea level height and tidal frequencies utilizing the GNSS-R approach2023Conference paper (Other (popular science, discussion, etc.))
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  • 3.
    Bagherbandi, Mohammad
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    Assessing environmental changes with GNSS reflectometry: An innovative geodetic tool for modelling sea level variations2024In: GIM International, ISSN 1566-9076, no 2Article in journal (Other academic)
    Abstract [en]

    The utilization of remote sensing observations to monitor essential climate variables (ECVs) has become increasingly important in studying their regional and global impacts, as defined by the Global Climate Observing System (GCOS). Understanding the Earth’s surface conditions, including soil moisture runoff, snow, temperature, precipitation, water vapour, radiation, groundwater and sea surface height (SSH), can positively impact the environment and ecosystems. Here, the authors present an overview of how global navigation satellite systems (GNSS) can be employed for environmental monitoring, with a particular focus on sea surface height monitoring. This includes examination of the advantages and disadvantages of utilizing a network of permanent GNSS stations for monitoring sea level rise along shorelines.

  • 4.
    Bagherbandi, Mohammad
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    Farzaneh, Saeed
    Gholamrezaee, Sara
    Parvazi, Kamal
    How accurate are GNSS signals for extracting sea level height and tidal frequencies using GNSS-R technique?2023Conference paper (Refereed)
    Abstract [en]

    Remote sensing observations of Essential Climate Variables (ECVs) provide a means of studying their global and regional impacts. Coastal GNSS stations measure water levels using GNSS Reflectometry (GNSS-R) technique by determining the vertical distance between the antenna and the water surface. In this study, GNSS-R data from four stations over three months were used to estimate sea surface heights (SSH) and assess accuracy using nearest tide gauge observations. Results showed that GNSS signals from GPS, GLONASS, Galileo, and BeiDou were accurate for the SSH estimation. In addition, 145 significant tidal frequencies were extracted using the GNSS-R and tide gauge time series by employing the Least Square Harmonic Estimation (LS-HE) approach. The study demonstrates the usefulness of GNSS-R for tide studies and its potential use alongside tide gauge measurements in coastal locations.

  • 5.
    Bergquist, Arne
    et al.
    Lantmäteriet.
    Brandt, S. Anders
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för samhällsbyggnad.
    Klang, Dan
    Vad är optimal kvalitet på geografisk information som underlag för detaljerad översvämningskartering?2008In: Kart & Bildteknik (Mapping and Image Science), ISSN 1651-792X, no 4, p. 18-20Article in journal (Other (popular science, discussion, etc.))
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  • 6.
    Brandt, S. Anders
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för samhällsbyggnad.
    Betydelse av höjdmodellers kvalitet vid översvämningsmodellering2009In: ULI aktuellt, ISSN 1654-6016, no 1, p. 8-9Article in journal (Other (popular science, discussion, etc.))
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  • 7.
    Brandt, S. Anders
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för samhällsbyggnad.
    Conceptualization of hydraulic and sedimentary processes in downstream reaches during flushing of reservoirs2005In: Proceedings of the XXXI IAHR Congress [Elektronisk resurs]: Water engineering for the future : choices and challenges : COEX Seoul September 11-16, 2005, Seoul: Korea Water Resources Association , 2005, p. 2577-2588Conference paper (Refereed)
    Abstract [en]

    The main focus of this paper is to describe the active hydraulic and sedimentary processes in downstream river reaches during flushing of sediments from reservoirs. During flushing extreme amounts of sediment may be released. Therefore, these processes are different than those downstream from dams and reservoirs not subjected to flushing. Hence, also the effects differ, which knowledge of may be of value for biologists, etc. During flushing of a reservoir a wave will be released to the downstream reaches. This wave can be divided into one water part and one sediment part. Initially they are in phase with each other, but with increased distance downstream from the dam, the transported sediment lags behind the water due to different traveling velocities. The paper treats when and where sedimentation occurs, and how this is related to the different traveling velocities of water and sediment. Also included are discussions on how the downstream effects during flushing differ from non-flushing effects, how visualization of effects can enhance both the analysis and communication with planners, politicians, etc., as well as discussions on how the studies of these effects can benefit from improved field-work methods.

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  • 8.
    Brandt, S. Anders
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Land management, GIS.
    Modeling and visualizing uncertainties of flood boundary delineation: algorithm for slope and DEM resolution dependencies of 1D hydraulic models2016In: Stochastic environmental research and risk assessment (Print), ISSN 1436-3240, E-ISSN 1436-3259, Vol. 30, no 6, p. 1677-1690Article in journal (Refereed)
    Abstract [en]

    As flood inundation risk maps have become a central piece of information for both urban and risk management planning, also a need to assess the accuracies and uncertainties of these maps has emerged. Most maps show the inundation boundaries as crisp lines on visually appealing maps, whereby many planners and decision makers, among others, automatically believe the boundaries are both accurate and reliable. However, as this study shows, probably all such maps, even those that are based on high-resolution digital elevation models (DEMs), have immanent uncertainties which can be directly related to both DEM resolution and the steepness of terrain slopes perpendicular to the river flow direction. Based on a number of degenerated DEMs, covering areas along the Eskilstuna River, Sweden, these uncertainties have been quantified into an empirically-derived disparity distance equation, yielding values of distance between true and modeled inundation boundary location. Using the inundation polygon, the DEM, a value representing the DEM resolution, and the desired level of confidence as inputs in a new-developed algorithm that utilizes the disparity distance equation, the slope and DEM dependent uncertainties can be directly visualized on a map. The implications of this strategy should benefit planning and help reduce high costs of floods where infrastructure, etc., have been placed in flood-prone areas without enough consideration of map uncertainties.

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    Brandt_in press_Modeling and visualizing uncertainties of flood boundary delineation
  • 9.
    Brandt, S. Anders
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för samhällsbyggnad.
    Resolution issues of elevation data during inundation modeling of river floods2005In: Proceedings of the XXXI IAHR Congress [Elektronisk resurs]: Water engineering for the future: choices and challenges. COEX Seoul September 11-16, 2005, Seoul: Korea Water Resources Association , 2005, p. 3573-3581Conference paper (Refereed)
    Abstract [en]

    A case study of the Eskilstuna River in Sweden is presented. This study is carried out within the project KRIS-GIS®, a Swedish initiative of handling crisis situations, including flooding. The purpose is to show how different resolutions in input elevation data affect the resulting inundation maps. Terrain elevation points at the sides of the river were gathered from an airborne laser altimetry survey, and river bed elevations were gathered from an echosounding survey. The terrain model was constructed in ArcView GIS as a triangulated irregular network (TIN), which served as the base for all later modeling. The hydraulic modeling was done as one-dimensional steady flow in HEC-RAS flow routing software. High-resolution elevation data resulted in better inundation delineation than did lowresolution elevation data. If the mean water discharge was used in the modeling and if the river is narrow, a low resolution could even lead to that the river itself would not be marked as inundated. At high water discharges, the river was usually inundated, but there was great uncertainty if the riparian areas really would be flooded or not. With steep side slopes, the delineation of inundation becomes more certain, while at gentler side slopes, the flow is distributed on a larger surface with a risk that the raster cells will be incorrectly marked regarding inundation. Finally, the use of high-resolution elevation data compared with lowresolution data, makes estimates of friction factor, Manning’s n, relatively more important for correct results in inundation studies.

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  • 10.
    Brandt, S. Anders
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för samhällsbyggnad.
    Översvämningsmodellering i GIS: betydelse av höjdmodellers upplösning applicerat på Eskilstunaån - ett delprojekt i KRIS-GIS®2005Report (Other academic)
    Abstract [sv]

    Under senare tid har översvämningar alltmer uppmärksammats av allmänhet, politiker, myndigheter och organisationer. Samtidigt har allt fler insett att det inte är en fråga om en översvämning kommer att ske utan när och hur stor den blir. Detta innebär att översvämningsrisker ständigt måste vara en närvarande del i politikers, planerares och krisberedskapsorganisationers arbete. Ett sätt att vara väl förberedd inför översvämningar är att ta fram översvämningsområden för olika stora vattenflöden. Därför har det inom projektet KRIS-GIS®, beställt och finansierat av Krisberedskapsmyndigheten, gjorts en mer detaljerad specialstudie över översvämningar kring Eskilstunaån. Tillförlitligheten hos framtagna översvämningsområden beror framför allt av två faktorer: korrekt vattenflödessimulering och korrekt beskrivning av terrängen. I denna studie har den endimensionella modellen HEC-RAS använts för flödessimuleringen och för beskrivning av terrängen har en flygburen 3D-laserskanning över området kring Eskilstunaån utförts. Dessutom har ekolodning utförts för att möjliggöra beskrivning av bottentopografin i Eskilstunaån. Samtliga höjddatapunkter kopplades ihop i ett GIS till ett triangulärt oregelbundet nätverk, TIN. Därefter lades sektioner tvärs över vattendraget och omgivande terräng. Dessa tvärsektioner tilldelades höjdvärden från TIN-modellen innan de exporterades till HEC-RAS. Fyra olika vattenföringar simulerades i HEC-RAS: medelvattenföringen på 23,7 m3/s, årsfloden på 70 m3/s, 100-årsflödet på 123 m3/s samt högsta beräknade flödet på 198 m3/s. Dessutom har det gjorts några alternativa körningar med varierande värden på Mannings n, dvs. markfriktion. Efter körningar i HEC-RAS, exporterades resulterande vattennivåer tillbaka till GISet där ett resultatraster skapades, där varje rastercell visades som översvämmad eller ej, och i förekommande fall översvämmat djup. Resultaten av översvämningsanalyserna visar att betydligt säkrare översvämningsprognoser nu kan göras när tillgång till terrängmodeller av hög kvalitet finns. Vid tidigare studier har Lantmäteriets höjddatabas använts, där höjder finns representerade med ett värde per 50-metersruta. Från att terrängmodellen har varit den begränsande faktorn övergår i stället en korrekt beskrivning av markens råhet eller friktion, uttryckt som Mannings n, till att vara den begränsande faktorn. Det rekommenderas därför att differentiera råhetsvärdena beroende på vilken markanvändningstyp som finns längs med vattendraget. Speciellt viktigt är detta i flacka områden. För Eskilstunaåns nordligaste delar är det viktigt att vattennivån i Mälaren bedöms korrekt. För att sprida och kunna dra nytta av resultaten framtagna i KRIS-GIS®-projektet rekommenderas det att färdiga översvämningspolygoner kan användas av kommuner, räddningstjänst osv. i deras arbete. De kan ringa eller automatiskt få information, från t.ex. SMHI eller vattenregleringsföretag, som innehåller upplysningar om förväntade flöden. Motsvarande polygon för förväntat flöde visas i ett GIS och direkt har man lägesbilden klart för sig. Utöver detta har även visualiseringsaspekter behandlats.

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  • 11.
    Brandt, S. Anders
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för samhällsbyggnad.
    Bergquist, Arne
    Lantmäteriet.
    Översvämningskarteringars tillförlitlighet2009In: Kart & Bildteknik (Mapping and Image Science), ISSN 1651-792X, no 4, p. 33-35Article in journal (Other (popular science, discussion, etc.))
    Abstract [sv]

    I ett tidigare nummer av Kart & Bildteknik beskrevs ett pågående forskningsprojekt som försökte ta reda på om det finns en optimal kvalitet på geografisk information som underlag för detaljerad översvämningskartering (Bergquist, Brandt & Klang, 2008). Projektet är nu avslutat och avrapporterat i Brandt (2009) och Klang och Klang (2009). Av resultaten framgår bland annat hur mycket tillförlitligheten av en översvämningskartering minskar med graden av försämrad höjdmodell, vilken utgör ett av de viktigaste underlagen för en översvämningsanalys. I samband med EUs översvämningsdirektiv (Europaparlamentets och rådets direktiv, 2007) föranleder detta en diskussion om vilka översvämningskarteringar som krävs för att uppfylla direktivet.

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  • 12.
    Brandt, S. Anders
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för samhällsbyggnad.
    Jiang, Bin
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för samhällsbyggnad.
    3D geovisualization as a communication and analysis tool in fluvial geomorphology2004In: Geoinformatics 2004: proceedings of the 12th International Conference on Geoinformatics - Geospatial Information Research: Bridging the Pacific and Atlantic, University of Gävle, Sweden, 7-9 June 2004, Gävle: Gävle University Press , 2004, p. 339-346Conference paper (Refereed)
    Abstract [en]

    The fields of hydrology and fluvial geomorphology get more and more attention in the general public. The reason for this is changed climate patterns with increased frequencies of storms and river flooding and as a result changed geomorphology and living conditions for the inhabitants of the area. With the development of 3D geovisualization, hydrological and geomorphological processes can be better simulated and visualized. Thus not only the domain specialists, but also the general public can appreciate very complex hydrological processes and resulting geomorphology. This is of great value since a high frequency of storms and flooding has been a big issue for politicians, planners, and the general public. It is in this sense that 3D geovisualization can be an important tool for analysis and communication. Complex hydrological and geomorphological processes can be effectively simulated and analyzed by the domain specialists while efficient and effective visualization provides a common platform for communication among domain specialists and the general public. This paper will discuss and illustrate these issues using a case study of geomorphology along the Reventazón River, downstream from the Cachí Reservoir in Costa Rica, due to the release of extreme amounts of sediment during flushing of the reservoir.

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  • 13.
    Brandt, S. Anders
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    Lim, Nancy Joy
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    Geodata, översvämningsmodellering och kompetens – Hur kan osäkerhet bidra till ökad resiliens?2022In: Kart och Bildteknik, ISSN 1651-8705, E-ISSN 1651-792X, Vol. 2022, no 2, p. 6-12Article in journal (Other (popular science, discussion, etc.))
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    Brandt_Lim_2022_Geodata_översvämningsmodellering_och_kompetens
  • 14.
    Brandt, S. Anders
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Urban and regional planning/GIS-institute.
    Lim, Nancy Joy
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Urban and regional planning/GIS-institute.
    Importance of river bank and floodplain slopes on the accuracy of flood inundation mapping2012In: River Flow 2012: Volume 2 / [ed] Rafael Murillo Muñoz, Leiden, The Netherlands: CRC Press / Balkema (Taylor & Francis) , 2012, p. 1015-1020Conference paper (Refereed)
    Abstract [en]

    Effective flood assessment and management depend on accurate models of flood events, which in turn are strongly affected by the quality of digital elevation models (DEMs). In this study, HEC-RAS was used to route one specificwater discharge through the main channel of the Eskilstuna River, Sweden. DEMs with various resolutions and accuracies were used to model the inundation. The results showed a strong positive relationship between the quality of theDEMand the extent of the inundation. However, evenDEMswith the highest resolution produced inaccuracies. In another case study, the Testebo River, the model settings could be calibrated, thanks to a surveyed old inundation event. However, even with the calibration efforts, the resulting inundation extents showed varying degrees of deviation from the surveyed flood boundaries. Therefore, it becomes clear that not only does the resolution of the DEM impact the quality of the results; also, the floodplain slope perpendicular to the river flow will impact the modelling accuracy. Flatter areas exhibited the greatest predictive uncertainties regardless of the DEM’s resolution. For perfectly flat areas, uncertainty becomes infinite.

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    Brandt_and_Lim_2012
  • 15.
    Brandt, S. Anders
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Land management, GIS.
    Lim, Nancy Joy
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Land management, GIS.
    Visualising DEM-related flood-map uncertainties using a disparity-distance equation algorithm2016In: IAHS-AISH Proceedings and Reports / [ed] A. H. Schumann, G. Blöschl, A. Castellarin, J. Dietrich, S. Grimaldi, U. Haberlandt, A. Montanari, D. Rosbjerg, A. Viglione, and S. Vorogushyn, Göttingen: Copernicus Publications on behalf of International Association of Hydrological Sciences (IAHS) , 2016, Vol. 373, p. 153-159Conference paper (Refereed)
    Abstract [en]

    The apparent absoluteness of information presented by crisp-delineated flood boundaries can lead tomisconceptions among planners about the inherent uncertainties associated in generated flood maps. Even mapsbased on hydraulic modelling using the highest-resolution digital elevation models (DEMs), and calibrated withthe most optimal Manning’s roughness (n) coefficients, are susceptible to errors when compared to actual floodboundaries, specifically in flat areas. Therefore, the inaccuracies in inundation extents, brought about by thecharacteristics of the slope perpendicular to the flow direction of the river, have to be accounted for. Instead ofusing the typical Monte Carlo simulation and probabilistic methods for uncertainty quantification, an empiricalbaseddisparity-distance equation that considers the effects of both the DEM resolution and slope was used tocreate prediction-uncertainty zones around the resulting inundation extents of a one-dimensional (1-D) hydraulicmodel. The equation was originally derived for the Eskilstuna River where flood maps, based on DEM dataof different resolutions, were evaluated for the slope-disparity relationship. To assess whether the equation isapplicable to another river with different characteristics, modelled inundation extents from the Testebo Riverwere utilised and tested with the equation. By using the cross-sectional locations, water surface elevations, andDEM, uncertainty zones around the original inundation boundary line can be produced for different confidences.The results show that (1) the proposed method is useful both for estimating and directly visualising modelinaccuracies caused by the combined effects of slope and DEM resolution, and (2) the DEM-related uncertaintiesalone do not account for the total inaccuracy of the derived flood map. Decision-makers can apply it to alreadyexisting flood maps, thereby recapitulating and re-analysing the inundation boundaries and the areas that areuncertain. Hence, more comprehensive flood information can be provided when determining locations whereextra precautions are needed. Yet, when applied, users must also be aware that there are other factors that caninfluence the extent of the delineated flood boundary.

  • 16.
    Gholamrezaee, Sara
    et al.
    University of Tehran, Iran.
    Bagherbandi, Mohammad
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    Parvazi, Kamal
    University of Tehran, Iran.
    Farzaneh, Saeed
    University of Tehran, Iran.
    A study on the quality of GNSS signals for extracting the sea level height and tidal frequencies utilizing the GNSS-IR approach2023In: GPS Solutions, ISSN 1080-5370, E-ISSN 1521-1886, Vol. 27, no 2, article id 72Article in journal (Refereed)
    Abstract [en]

    Coastal global navigation satellite system (GNSS) stations equipped with a standard geodetic receiver and antenna enable water level measurement using the GNSS interferometry reflectometry (GNSS-IR) technique. By using GNSS-IR, the vertical distance between the antenna and the reflector surface (e.g., water surface) can be obtained in the vertical (height) reference frame. In this study, the signal-to-noise ratio (SNR) data from four selected stations over three months are used for this purpose. We determined the predominant multipath frequency in SNR data that is obtained using Lomb–Scargle periodogram (LSP) method. The obtained sea surface heights (SSH) are assessed using tide gauge observations regarding accuracy and correlation coefficients. In this study, we investigated daily and hourly GNSS observations and used single frequencies of GPS (L1, L2 and L5), GLONASS (L1 and L2), Galileo (L1, L5, L6, L7 and L8), and BeiDou (L2 and L7) signals to estimate the SSH. The results show that the optimal signals for extracting the SSH are the L1 signal for the GPS, Galileo, and GLONASS systems and the L2 signal for the BeiDou system. The accuracy and correlation parameters for the optimal GPS signal in the daily mode are 2 cm and 0.87, respectively. The same parameters for the optimal GLONASS signal are 4 cm and 0.91. However, the obtained accuracy and correlation coefficients using the best Galileo and BeiDou signals are reduced, i.e., 4 cm and 0.88 using Galileo and 12 cm and 0.52 by employing the Galileo signals, respectively. Our results also show that the GPS L1 signal is more consistent with the tide gauge data. In the following, using the time series derived from the L1 signal and tide gauge readings, the tidal frequencies are extracted and compared using the Least Square Harmonic Estimation (LS-HE) approach. The findings demonstrate that 145 significant tidal frequencies can be extracted using the GNSS-IR time series. The existence of an acceptable correlation between the tidal frequencies of the GNSS-IR and the tide gauge time series indicates the usefulness of the GNSS-IR time series for tide studies. From our results, we can conclude that the GNSS-IR technique can be applied in coastal locations alongside tide gauge measurements for a variety of purposes.

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    fulltext
  • 17.
    Hägg, Linnéa
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    Stenberg Jönsson, Simon
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    Antal tvärsektioners påverkan på djupmodeller producerad av SeaFloor HydroLite ™ enkelstråligt ekolod: En jämförelse mot djupmodeller producerad av Kongsberg EM 2040P MKII flerstråligt ekolod2023Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Hydroacoustic measurements have been conducted for almost two hundred years. It can be compared to topographic measurements on land and shows the appearance of lake or ocean floors. Today, echosounders are used, which is a technique that sends out sound waves into the water to measure the time it takes for the sound to bounce off the bottom and return to the instrument. Sound velocity calculations can then be used to calculate the depth.

    The use of cross-sections is recommended as a data control of single beam echosounder. However, multi beam echosounders only use overlap as control. This study examines how the number of cross-sections affects depth maps created by Seafloor HydroLite TM single beam echosounder. It also investigates the differences between depth maps produced by the SeaFloor HydroLite TM single beam echosounder and the Kongsberg EM 2040 MK11 multi beam echosounder.

    The study area covers 1820 m2 and is located at Forsbackas Harbor in Storsjön, Gävle municipality. A minimum overlap of 50% was used for the surveying with the multi beam echosounder. Five main lines and seven cross-sections were measured using the single beam echosounder. Depth maps with different numbers of cross-sections were created using data from the single beam echosounder. The maps from the single beam echosounder were compared to maps created from the data obtained by the multi beam echosounder to assess the differences and the impact of varying numbers of cross-sections on the depth maps from the single beam echosounder.

    By using the multi beam echosounder as a reference for the depth maps created by the single beam echosounder, the results showed a decrease of 1 cm in RMS value and 2 cm in standard deviation. The comparison between the echosounder systems revealed a difference of around 10 cm in depth values. The conclusions from this study are that cross-sections only marginally improve the quality of depth maps in cases of even and uniform bottom topography but serve an important function in validating the quality of the survey data. Additionally, the SeaFloor HydroLite TM is capable of meeting Order 1b at depths ranging from one to four meters if the requirement for full bottom coverage is not considered. The Seafloor HydroLite TM creates a general overview of the depth map, while the depth models from the Kongsberg EM 2040 MKII provide more detailed information.

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  • 18.
    Khoshlahjeh Azar, Mahdi
    et al.
    K. N. Toosi University of Technology, Tehran, Iran.
    Shami, Siavash
    K. N. Toosi University of Technology, Tehran, Iran.
    Nilfouroushan, Faramarz
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences. Lantmäteriet.
    Salimi, Maryam
    Shahid Beheshti University, Tehran, Iran.
    Bolorfroshan, Mahdieh Ghayoor
    Ferdowsi University of Mashhad, Mashhad, Iran.
    Reshadi, Mir Amir Mohammad
    University of Waterloo, Waterloo, ON, Canada.
    Integrated analysis of Hashtgerd plain deformation, using Sentinel-1 SAR, geological and hydrological data2022In: Scientific Reports, E-ISSN 2045-2322, Vol. 12, article id 21522Article in journal (Refereed)
    Abstract [en]

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

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  • 19.
    Kordi, Maryam
    et al.
    National University of Ireland, National Centre for Geocomputation.
    Brandt, S. Anders
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Urban and regional planning/GIS-institute.
    Effects of increasing fuzziness on analytic hierarchy process for spatial multicriteria decision analysis2012In: Computers, Environment and Urban Systems, ISSN 0198-9715, E-ISSN 1873-7587, Vol. 36, no 1, p. 43-53Article in journal (Refereed)
    Abstract [en]

    Multicriteria decision analysis (MCDA) involves techniques which relatively recently have received great increase in interest for their capabilities of solving spatial decision problems. One of the most frequently used techniques of MCDA is Analytic Hierarchy Process (AHP). In the AHP, decision-makers make pairwise comparisons between different criteria to obtain values of their relative importance. The AHP initially only dealt with crisp numbers or exact values in the pairwise comparisons, but later it has been modified and adapted to also consider fuzzy values. It is necessary to empirically validate the ability of the fuzzified AHP for solving spatial problems. Further, the effects of different levels of fuzzification on the method have to be studied. In the context of a hypothetical GIS-based decision-making problem of locating a dam in Costa Rica using real-world data, this paper illustrates and compares the effects of increasing levels of uncertainty exemplified through different levels of fuzzification of the AHP. Practical comparison of the methods in this work, in accordance with the theoretical research, revealed that by increasing the level of uncertainty or fuzziness in the fuzzy AHP, differences between results of the conventional and fuzzy AHPs become more significant. These differences in the results of the methods may affect the final decisions in decision-making processes. This study concludes that the AHP is sensitive to the level of fuzzification and decision-makers should be aware of this sensitivity while using the fuzzy AHP. Furthermore, the methodology described may serve as a guideline on how to perform a sensitivity analysis in spatial MCDA. Depending on the character of criteria weights, i.e. the degree of fuzzification, and its impact on the results of a selected decision rule (e.g. AHP), the results from a fuzzy analysis may be used to produce sensitivity estimates for crisp AHP MCDA methods.

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    Kordi_and_Brandt_Effects of increasing fuzziness on analytic hierarchy process for spatial multicriteria decision analysis
  • 20.
    Lim, Nancy Joy
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    Brandt, S. Anders
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    Are Feature Agreement Statistics Alone Sufficient to Validate Modelled Flood Extent Quality?: A Study on Three Swedish Rivers Using Different Digital Elevation Model Resolutions2019In: Mathematical problems in engineering (Print), ISSN 1024-123X, E-ISSN 1563-5147, Vol. 2019, article id 9816098Article in journal (Refereed)
    Abstract [en]

    Hydraulic modelling is now, at increasing rates, used all over the world to provide flood risk maps for spatial planning, flood insurance, etc. This puts heavy pressure on the modellers and analysts to not only produce the maps but also information on the accuracy and uncertainty of these maps. A common means to deliver this is through performance measures or feature statistics. These look at the global agreement between the modelled flood area and the reference flood that is used. Previous studies have shown that the feature agreement statistics do not differ much between models that have been based on digital elevation models (DEMs) of different resolutions, which is somewhat surprising since most researchers agree that high-resolution DEMs are to be preferred over poor resolution DEMs. Hence, the aim of this study was to look into how and under which conditions the different feature agreement statistics differ, in order to see when the full potential of high-resolution DEMs can be utilised. The results show that although poor resolution DEMs might produce high feature agreement scores (around F > 0.80), they may fail to provide good flood extent estimations locally, particularly when the terrain is flat. Therefore, when high-resolution DEMs (1 to 5 m) are used, it is important to carefully calibrate the models by the use of the roughness parameter. Furthermore, to get better estimates on the accuracy of the models, other performance measures such as distance disparities should be considered.

  • 21.
    Lim, Nancy Joy
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Land management, GIS.
    Brandt, S. Anders
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Land management, GIS.
    Seipel, Stefan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Computer science. Division of Visual Information and Interaction, Department of Information Technology, Uppsala University, Uppsala, Sweden.
    Visualisation and evaluation of flood uncertainties based on ensemble modelling2016In: International Journal of Geographical Information Science, ISSN 1365-8816, E-ISSN 1365-8824, Vol. 30, no 2, p. 240-262Article in journal (Refereed)
    Abstract [en]

    This study evaluates how users incorporate visualisation of flood uncertainty information in decision-making. An experiment was conducted where participants were given the task to decide building locations, taking into account homeowners’ preferences as well as dilemmas imposed by flood risks at the site. Two general types of visualisations for presenting uncertainties from ensemble modelling were evaluated: (1) uncertainty maps, which used aggregated ensemble results; and (2) performance bars showing all individual simulation outputs from the ensemble. Both were supplemented with either two-dimensional (2D) or three-dimensional (3D) contextual information, to give an overview of the area.The results showed that the type of uncertainty visualisation was highly influential on users’ decisions, whereas the representation of the contextual information (2D or 3D) was not. Visualisation with performance bars was more intuitive and effective for the task performed than the uncertainty map. It clearly affected users’ decisions in avoiding certain-to-be-flooded areas. Patterns to which the distances were decided from the homeowners’ preferred positions and the uncertainties were similar, when the 2D and 3D map models were used side by side with the uncertainty map. On the other hand, contextual information affected the time to solve the task. With the 3D map, it took the participants longer time to decide the locations, compared with the other combinations using the 2D model.Designing the visualisation so as to provide more detailed information made respondents avoid dangerous decisions. This has also led to less variation in their overall responses.

  • 22.
    Lupo Stanghellini, Paola S.
    et al.
    Deptartment of Invertebrate Zoology and Hydrobiology, Natural Science Museum of Trento, Trento, Italy.
    Collentine, Dennis
    University of Gävle, Department of Business Administration and Economics, Ämnesavdelningen för nationalekonomi.
    Stakeholder discourse and water management: implementation of the participatory model CATCH in a Northern Italian alpine sub-catchment2008In: Hydrology and Earth System Sciences, ISSN 1027-5606, E-ISSN 1607-7938, Vol. 12, no 1, p. 317-331Article in journal (Refereed)
    Abstract [en]

    The Water Framework Directive (WFD, directive 2000/60/EC) was created to ensure the sustainable use of water resources in the European Union. A central guideline included throughout the directive is a call for the participation of stakeholders in the management of these resources. Involving stakeholders is an important step to ensure that catchment management plans take into consideration local experience in the development of these plans and the impact of the plans on local interests. This paper describes and analyses the results of a series of workshops to facilitate implementation of the WFD at a catchment level based on the stakeholder participation model, CATCH. To test the usefulness of the CATCH model, developed for water management in a catchment area, a sub-catchment in an alpine valley in the north-east of Italy, the Alta Valsugana in the Province of Trento, was chosen as the setting for a series of workshops. In this valley water is fundamental for activities associated with agriculture, domestic use, energy production, sports and recreation. In the recent past the valley has had serious problems related to water quality and quantity. Implementation of water management plans under the WFD may lead to conflicts within the catchment between different stakeholder interest groups. Including stakeholders in the development of management plans not only follows the guidelines of the WFD but also could result in a more locally adapted and acceptable plan for the catchment. A new stakeholder analysis methodology was developed and implemented in order to identify the relevant stakeholders of the area and then two sets of workshops involving the key stakeholders identified were conducted in Spring 2006. The CATCH meetings were a new experience for the participants, who had to deal with both the principles of the WFD in general and the participation requirement in particular. During the meetings, the CATCH model played a very important role in structuring the participatory process. It provided a general framework consisting of a sequence of steps that helped the participants to reach the goal of the process: the identification and evaluation of measures to improve water management in the catchment. This test of the CATCH model showed it to be a dynamic and flexible tool, useful for structuring and guiding the participation process, without imposing undue restrictions on influencing the outcome of stakeholder participation in a small catchment.

  • 23. Safari, Abdolreza
    et al.
    Kalantarioun, Simin
    Amin, Hadi
    An approach to the spectral analysis of the Jason-2 satellite altimetry observations based on stationary time series, Case study: spectral analysis of instantaneous sea level of the Caspian Sea2015In: Journal of Geomatics and Surveying Technology, ISSN 2322-102X, Vol. 5, no 1, p. 271-285Article in journal (Refereed)
  • 24. Safari, Abdolreza
    et al.
    Kalantarioun, Simin
    Amin, Hadi
    Modeling instantaneous water level changes of Caspian Sea using satellite altimetry observations2015In: Journal of the Earth and Space Physics, ISSN 0378-1046, Vol. 41, no 2, p. 281-299Article in journal (Refereed)
  • 25.
    Schwabe, Joachim
    et al.
    Federal Agency for Cartography and Geodesy (Germany).
    Ågren, Jonas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    Liebsch, Gunter
    Federal Agency for Cartography and Geodesy (Germany).
    Westfeld, Patric
    Federal Maritime and Hydrographic Agency (Germany).
    Hammarklint, Thomas
    Swedish Maritime Administration (Sweden).
    Mononen, Jyrki
    Finnish Transport Agency (Finland).
    Andersen, Ole B
    DTU Space (Denmark).
    The Baltic Sea Chart Datum 2000 (BSCD2000): Implementation of a common reference level in the Baltic Sea2020In: The international hydrographic review, ISSN 0020-6946, no 23, p. 63-83Article in journal (Other academic)
    Abstract [en]

    The Baltic Sea Chart Datum 2000 (BSCD2000) is a geodetic reference system adopted for Baltic Sea hydrographic surveying, hydrographic engineering, nautical charts, navigational publications and water level information. It is based on the common geodetic standards for the height system (EVRS) and the spatial reference system (ETRS89) in Europe. In particular, the zero level of BSCD2000 is in accordance with the Normaal Amsterdams Peil (NAP). BSCD2000 is about to be adopted as unified chart datum by all the countries around the Baltic Sea. It agrees with most national height realizations used on land. BSCD2000 will facilitate effective use of GNSS methods like GPS, GLONASS and Galileo for accurate navigation and hydrographic surveying in the future.

  • 26.
    Thorsteinsson, Russell
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management.
    WATER CONTAMINATION RISK DURING URBAN FLOODS: Using GIS to map and analyze risk at a local scale2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    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.

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