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  • 1.
    Andersson, Jonas
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management.
    Hedlund, Patrik
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management.
    Undersökning om handhållna laserskannrar vid detaljmätning: En jämförelse mellan multistationen Leica Nova MS50 och den handhållna laserskannern FARO Freestyle X2016Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Terrestrial laser scanners (TLS) have been common in geodetic measurements for over 10 years. The technology is developing rapidly and specialized instruments are launched constantly. One type of these specialized TLS instruments are hand-held laser scanners. They are designed primarily to generate point clouds of spaces and small objects where the traditional tripod mounted laser scanner has difficulties to scan. When the hand-held laser scanners are relatively new, the research on the instruments is limited, and the lack of standardized control methods. With that in mind it is important to study the instruments. In this thesis the hand-held laser scanner FARO Freestyle X was investigated on how well the handheld laser scanning technology really is and what limitations the instruments have. This was done by comparing point clouds from FARO Freestyle X with reference point cloud generated by Leica's multi-station MS50. To study the instrument a number of parameters was investigated such as scanning distance, ease of use, time and performance. These parameters were considered to be sufficient basis for conclusions about the instrument's advantages/disadvantages and limitations.

    The result of the point cloud comparison from the short distance showed deviations around 10 mm and then increase to few centimeters at longer distances. Volume limitation control showed no differences compared to the scanning from short distance. This means that moving the instrument does not affect the results significantly. The instrument's Achilles' heel is the noise that occurs when scanning from longer distances, about 30 mm deviations. Even the type of object affects the noise. The noise on the wall showed the greatest deviation while the noise on the table indicated the lowest results. The repeatability showed good results visually and had similar deviations. The instrument has a good ability to recreate objects when the resolution test demonstrates good performance. Main advantage of the instrument is its effective documentation of smaller objects, but also some larger areas where the uncertainty of centimeter-level is required. The ease of use can be described as good and the colored point clouds takes visualization to a new level. The results of the study show that the hand-held laser scanners can, potentially, challenge the traditional laser scanner.

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    Undersökning om handhållna laserskannrar vid detaljmätning
  • 2.
    Bagherbandi, Mohammad
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences. KTH.
    Shirazian, Masoud
    Shahid Rajaee Teacher Training University (SRTTU), Tehran, Iran.
    Geodetic Control Networks: Challenges and Solutions: Essesntial Tools for Deformation and Environmental Monitoring2022In: GIM International - The Worldwide Magazine for Geomatics, ISSN 1566-9076, Vol. 36, no 7, p. 31-33Article in journal (Refereed)
    Abstract [en]

    What are the key challenges in establishing precise geodetic control networks? This is one of the most important tasks of geodesists and land surveyors, since geodetic control networks are essential for the deformation and environmental monitoring of dams, tunnels, high towers, landslides and bridges, among others. This article discusses the main challenges relating to vertical angles and provides some recommendations for how they can be overcome.

  • 3.
    Buck, Sine
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management.
    Determining the best location for a nature-like fishway in Gavle River, Sweden2013Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The construction of dams and hydro-power stations are some of the most common anthropogenic changes of watercourses and rivers. While being important to humans and society by providing electricity, these obstructions of watercourses can have severe consequences for the aquatic ecosystems. One consequence is that dams often hinder the important movement of migrating fish species between habitats. This can lead to decline and even extinction of important fish populations. To prevent these negative effects, a number of different fish passage systems, including nature-like fishways, have been developed. Nature-like fishways mimic natural streams in order to function as a natural corridor for a wide range of species. Planning and construction of a nature-like fishway is a complex task that often involves many different interests. In the present study a combination of multi-criteria decision analysis and least-cost path analysis is used for determining the best location for a nature-like fishway past Strömdalen dam in Gavleån, Sweden. An anisotropic least-cost path algorithm is applied on a friction-layer and a digital elevation model, and the least-cost path for a nature-like fishway is determined. The results show that the method is useful in areas of varying topography and steep slopes. However, because low slope is a very important factor when constructing a nature-like fishway, slope becomes the dominating factor in this analysis at the expense of e.g. distance to roads. Combining the methods with results from biological studies of fish behavior and detailed hydrological modelling would provide a very strong tool for the planning of nature-like fishways.

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  • 4.
    Gräns, Sandra
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Land management, GIS.
    Östblom, Simon
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Land management, GIS.
    Utvärdering av Inspect a Surface: En applikation i fältmjukvaran Leica Captivate2018Independent thesis Basic level (degree of Bachelor), 180 HE creditsStudent thesis
    Abstract [en]

    The technical development of terrestrial laser scanning has quickly proceeded in geodetic measurement since the millennium shift. Its success has made TLS well established on the market as a method of scanning and its field of applications has expanded. Leica Geosystems is an international company in the field of surveying and measurement instruments. They have developed a new multistation, Leica Nova MS60 with the field software Leica Captivate. In addition to the software the application Inspect a Surface allows surveyors to evaluate obtained point clouds in the field. The application serves the purpose of controlling an object by comparing a pointcloud with a defined reference. The company is interested of such a study to be made on their products, as it has not been conducted before. The main purpose of the study is to determine to what extent the field software Leica Captivate with Inspect a Surface in a Leica Nova MS60 manages with traditional post processing in external software. Scanning in indoor and outdoor environment was performed on objects common on construction sites, such asfacade, wall, floor, and cylindrical objects with varying radius and material segments. The horizontal and vertical surfaces were tested against measured reference points and interpolated reference points. Scanning data for cylinders was obtained by MS60 and Leica Scan Station C10 for a visual control of the phenomenon “mixed pixels”. In Leica Cyclone, a cylinder was fitted on each segment in order to determine radius deviation from reference and compare the results from each instrument. A hypothesis test was also conducted.

    The study shows that surfaces had equivalent results in all softwares. The error source mixed pixels influenced pointclouds from MS60 and C10 in varying degree. The error source was occurred most frequenlty on the aluminum and wallpaper segment which were close to the floor. Cylinder fitting on point cloud from, MS60 and C10 deviates millimeters from each other and the reference, apart from a few bigger deviations, the aluminum-segment for instance. The conclusion is that the application is satisfactory for post processing in the field. Scanning of cylinders leads to the conclusion thad mixed pixels occurs for MS60 more than C10 only if a surface is behind the cylinder. On the contrary, mixed pixels occur on C10 if there is free space behind the cylinder. Using MS60 for scanning of cylindrical object turns out to be satisfactory.

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  • 5.
    Gustafsson, Amanda
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Land management, GIS.
    Wängborg, Olov
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Land management, GIS.
    Mätosäkerhet vid digital terrängmodellering med handhållen laserskanner: Undersökning av den handhållna laserskannern ZEB-REVO2018Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    A digital terrain model (DTM) represent exclusively the earth surface. There are several methods which can be utilized to create DTMs, where laser scanning have become a common used method. Airborne laser scanning (ALS) is often used since the method can cover a large area in a relatively short time. However a disadvantage with ALS is that the data collection, for a wooded area, can be inadequate due to penetration difficulties for some laser beams. For that reason a handheld laser scanner (HLS) can be an alternative since measurements can be done fast and does not need the same extensive planning. Earlier studies mention HLS to have several advantages but can still not yet be compared with terrestrial laser scanning (TLS) concerning the measurements uncertainty. There are, however, no studies that investigates how measurements with HLS stands against FLS. The purpose with the study is to evaluate the ability to use measurements from HLS to create a DTM for a wooded area in comparison with ALS.

    This is done by comparing the different uncertainties for each DTM. In the study the acquisition of HLS laser data was collected with the instrument ZEB-REVO and the ALS laser data was received from Lantmäteriet (cadastral mapping and surveying authority in Sweden). After the data acquisition a DTM were created from each data set (method). The DTMs were then compared to control profiles, which have been measured with total station. From the comparison with the control profiles average height deviation and standard deviation were calculated for each DTM. The result shows that the DTM created from ALS data received an average height deviation of 0,055 m for the whole area with a standard deviation of 0,046 m. Corresponding result for the DTM created from HLS data were calculated, at best, to 0,043 m in average height deviation and 0,034 m in standard deviation. The study shows that the methods HLS and ALS gave equivalent result regarding the comparison with the control profiles, however HLS gave a generally lower value for standard deviation. Furthermore ZEB-REVO with its processing program GeoSLAM was considered to be very easy and user friendly. The area (approx. 2000 m2) for the study was scanned within only 10 min. The conclusion which were drawn from the obtained result was that measurements with HLS can generate an equivalent DTM, concerning the uncertainty, as measurements with FLS. Thereby HLS can be a complementing method but still FLS is seen as an effective method.

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  • 6.
    Gustafsson, Claes
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    Evaluation of SLAM based mobile laser scanning and terrestrial laser scanning in the Kiruna mine: A comparison between the Emesent Hovermap HF1 mobile laser scanner and the Faro Laser Scanner Focus3D X 330 terrestrial laser scanner2023Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The mining industry has over the last few decades seen a drastic increase in the usage of laser scanning technologies as a way of creating 3D maps of the mines being exploited. Underground mapping in places such as mines has become more prevalent as the technology has progressed and made it easier to generate highly detailed point clouds faster. A newer and faster method of generating point clouds is using a simultaneous localization and mapping (SLAM) based mobile laser scanner (MLS). With the help of complex algorithms, it enables instant point cloud registration and allows for continuous mapping of the surrounding environment while tracking the device location without needing a connection to GPS. As the accuracy and speed of SLAM based MLS continues to improve, its use is becoming far more widespread within the mining industry. Although studies have been conducted previously investigating the differences in quality between SLAM based MLS and terrestrial laser scanners (TLS), there is still a need for further studies conducted in mining environments. This case study aims to investigate the quality differences between two point clouds generated using an Emesent Hovermap HF1, which is a SLAM based MLS, and a Faro Laser Scanner Focus 3D X 330 TLS. Parameters like root mean square (RMS) were investigated. Volume calculations were carried out for both point clouds and compared to each other as well the calculated volume of a theoretical model. To conduct this study data from LKAB’s Kiruna mine was collected and provided by Blå Projekt, Process & GIS AB.

    The result of this study concludes that the Faro TLS is superior in terms of point cloud quality, with five times better RMS values and higher point density than the Hovermap MLS. It also shows that both scanners allowed for accurate volume calculations with only roughly 1% difference in the estimated volumes. The TLS method yielded a much more readable point cloud with clearer visual details than the SLAM based MLS method. This may however be a result of SLAM drift since no loop closure was performed when collecting the MLS data which otherwise could’ve minimized the errors. It was concluded that due to the amount of data processing required and the longer work time of TLS, SLAM based MLS is a method that is worth further development as it provides unparalleled flexibility, safety improvements and work time efficiency.

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  • 7.
    Gustafsson, Nora
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    Klasson, Andreas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    Förändringsanalys för detektering av stormfälld skog i satellitbilder från Sentinel 22020Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    En av Sveriges största industrier är skogsindustrin. Att sköta stora skogsinnehav medför vissa svårigheter, t.ex. så kan i händelse av en storm kan delar av skogen bli vindfälld. Det är då viktigt att upptäcka och ta bort de fallna träden eftersom det annars kan leda till granbarkborrangrepp. En metod för att upptäcka den vindfällda skogen är att ta flygbilder över området, vilket kan bli både dyrt och tidsödande. Därför testas i denna studie detektering av stormfälld skog i Sentinel 2 bilder. Sentinel 2 har valts ut eftersom den har både en hög spatial- och temporal upplösning samt att bilderna är tillgängliga gratis. Tidigare studier på området har använt satellitbilder med en lägre spatial upplösning eller data från andra typer av fjärranalys. De flesta av dessa metoder är ganska komplexa eller väldigt specifika för ett särskilt fall. Metoden som tas fram i denna studie ska vara enkel att implementera även för personer utan någon djupare kunskap inom fjärranalys. Bilddifferens med olika index såsom NDVI, NDMI och GreenNDVI testas. Även oövervakad klassificering testas. Noggrannheten har utvärderats med två-stegs metoden med en noggrannhet på 85 % men även en konfusionsmatris tillämpas för att utvärdera noggrannheten av områden där ingen förändring inträffat. Bilddifferens med NDVI och GreenNDVI klarar två-stegs testet när ett statistiskt bestämt tröskelvärde används, NDVI får högst användarnoggrannhet. Felmatrisen visar dock att det finns många stormfällen i ytorna som blivit klassade som ingen förändring, den oövervakade klassificeringen får inte det problemet i samma utsträckning. Bilddifferens i NDVI med statistiskt bestämt tröskelvärde bedöms vara den mest effektiva metoden för att detektera stormfälld skog.

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  • 8.
    Johnson, Hugo
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    Langerbeck, Axel
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    GIS-baserad multikriterieanalys för placering av små modulära reaktorer i Sveriges fjärde elområde2023Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    With the current situation of increased tension in Europe, inadequate electricity production, and a move towards more electrified societies, there has arisen a need for sustainable energy sources. Many countries have started investing in small modular reactors (SMR) instead of large-scale nuclear power plants as they can be mass-produced and are easy to build, making them cost-effective. This study focused on the most optimal location for SMRs within the fourth electrical bidding zone, disregarding section 17-chapter 6a§ of the Swedish Environmental Code. Bidding zone four was chosen as it produces the least amount of electricity and has the largest deficit. This was done using a multicriteria analysis (MCA) and a subsequent sensitivity analysis with a total of six restriction criteria and nine factors considering guidelines taken from Swedish legislation, previous studies on the subject, and the International Atomic Energy Agency (IAEA). To evaluate the placement interviews and questionnaires with four different people with different areas of expertise in nuclear power were carried out as a basis for the average weighting. The Analytic Hierarchy process (AHP) where used to evaluate the factors relative weights to each other. An average MCA map was made to determine the most optimal location based on the average weighting and a separate map for the different experts' own weightings. This was followed by a sensitivity analysis using one factor at a time (OAT) method, and by eliminating a factor to determine how the most optimal location changes, and the percentage of how much the area changes between the different models. The results show that the most optimal site to place an SMR is around Barsebäck where there was a large-scale nuclear power plant previously. One can conclude that the sensitivity analysis is robust and is not significantly impacted by changes.

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  • 9.
    Kjell, Johan
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    Nilsen, Filip
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    Att förebygga översvämningar med hjälp av konceptet Sponge city: En fallstudie av Hemlingby i Gävle2023Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Climate change is predicted to cause an increase in cloudbursts and heavy precipitation, which makes urban flooding an issue that needs to be dealt with. The term Sponge city is a theory that intends to deal with urban flooding and worsening water quality in urban areas with absorption. The study area Hemlingby is an area that has been prone to flooding before, for instance on the 17–18 of August 2021. The area is located about 3 km from the city center Gävle with Hemlingbybäcken running north through the study area.

    The study was performed in several parts, the first was to use the GIS tool ArcMap 10.8 and hydraulic software CAESAR-lisflood 1.8 to investigate which areas are considered sensitive. In ArcMap 10.8, a bluespot map was created to estimate how much water is needed to fill different areas of Hemlingby, and in CAESAR-lisflood 1.8, the flood inundation area was mapped based on different water flow scenarios. Subsequently, two site visits were made to the study area to photograph and validate the results from the GIS analyses. Based on the GIS analyses, an interview with the municipality of Gävle and an extensive literature analysis, measures were identified that suited both the concept and the study area.

    The results show what affects the drainage in Hemlingby and how it could be improved through the use of Sponge city. Hemlingbybäcken, which is easily flooded by large water flows, and the topography of the area are factors that have been identified as particularly problematic for the study area's drainage. To show how the area could be planned after the Sponge city concept, proposals for both types of measure and location have been presented, also restrictions and how similar concepts can be applied in other areas are presented.

    Given that the frequency and intensity of future cloud bursts are not known, there is no answer as to whether the measures presented in the study would stop the study area from being flooded in the future. Especially when data and statistics from previous rainfall were missing, the area's exact reaction to a cloud burst could not be analyzed. On the other hand, it is possible to determine from the analyzes in the method that the study area was not adapted to the type of downpour it was affected by. Therefore, measures aimed at Hemlingbybäcken become significant as the topography or soil type of the area is much more difficult to influence. In order to investigate exactly what impact the proposed measures would have on Hemlingby, further studies need to be carried out to map both the collection capacity and the impact on Hemlingbybäcken the proposal has.

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  • 10.
    Lian, En Suan Mung
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences.
    Identifiering av optimala platser för återvinningscentral med hjälp av multikriterieanalys och fjärranalys2019Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    People tend to move to urban areas to study, find jobs, and get better opportunities. The population of big cities has increased, and it will also increase even more. Therefore, urban planning or community planning is important and one of the most important areas is waste management where waste from households is managed. In order to build waste management facilities as recycling centers, one needs to plan carefully, and environmental thinking is important. In order to locate optimal places, you need GIS technology. With the help of this technique, it is possible to make analysis and create maps that can, for example, be included in the master plan and the detail plan. The site provision is the most important thing in developing of planning stage before one can start with other processes because misplacement can cause problems like environment issues, security problems for the inhabitants and financial loss for the authority or the state for adjustments and relocations. At pre-sent, there are not many technical solutions that would facilitate location determina-tion.In poor countries, there is a lack of functioning waste management and many throw trashes everywhere. The study therefore has focus in developing countries where re-cycling centers need to be built. The purpose of the work is to find optimal places for recycling centers with GIS solutions.In the study, remote sensing and multi-criteria analysis were performed to find the optimal places for recycling centers. Supervised classification was used to extract classes. Data from Open Street Map was retrieved to supplement data for missing factors. The AHP method was performed to weight the factors. The weighted linear combination method was used to calculate the result. The work gave positive results and the solution will be useful for developing a detailed plan and overview plan for recycling centers. The method will be useful, which is the goal of this work, but im-proved data and more analysis of factors are needed.

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    Identifiering av optimala platser för åter-vinningscentral med hjälp av multikriterieanalys och fjärranalys
  • 11.
    Liu, Xintao
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Urban and regional planning/GIS-institute. KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Samhällsplanering och miljö, Geoinformatik och Geodesi.
    The Principle of Scaling of Geographic Space and its Application in Urban Studies2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Geographic space is the large-scale and continuous space that encircles the earth and in which human activities occur. The study of geographic space has drawn attention in many different fields and has been applied in a variety of studies, including those on cognition, urban planning and navigation systems. A scaling property indicates that small objects are far more numerous than large ones, i.e., the size of objects is extremely diverse. The concept of scaling resembles a fractal in geometric terms and a power law distribution from the perspective of statistical physics, but it is different from both in terms of application. Combining the concepts of geographic space and scaling, this thesis proposes the concept of the scaling of geographic space, which refers to the phenomenon that small geographic objects or representations are far more numerous than large ones. From the perspectives of statistics and mathematics, the scaling of geographic space can be characterized by the fact that the sizes of geographic objects follow heavy-tailed distributions, i.e., the special non-linear relationships between variables and their probability.

    In this thesis, the heavy-tailed distributions refer to the power law, lognormal, exponential, power law with an exponential cutoff and stretched exponential. The first three are the basic distributions, and the last two are their degenerate versions. If the measurements of the geographic objects follow a heavy-tailed distribution, then their mean value can divide them into two groups: large ones (a low percentage) whose values lie above the mean value and small ones (a high percentage) whose values lie below. This regularity is termed as the head/tail division rule. That is, a two-tier hierarchical structure can be obtained naturally. The scaling property of geographic space and the head/tail division rule are verified at city and country levels from the perspectives of axial lines and blocks, respectively.

    In the study of geographic space, the most important concept is geographic representation, which represents or partitions a large-scale geographic space into numerous small pieces, e.g., vector and raster data in conventional spatial analysis. In a different context, each geographic representation possesses different geographic implications and a rich partial knowledge of space. The emergence of geographic information science (GIScience) and volunteered geographic information (VGI) greatly enable the generation of new types of geographic representations. In addition to the old axial lines, this thesis generated several types of representations of geographic space: (a) blocks that were decomposed from road segments, each of which forms a minimum cycle such as city and field blocks (b) natural streets that were generated from street center lines using the Gestalt principle of good continuity; (c) new axial lines that were defined as the least number of individual straight line segments mutually intersected along natural streets; (d) the fewest-turn map direction (route) that possesses the hierarchical structure and indicates the scaling of geographic space; (e) spatio-temporal clusters of the stop points in the trajectories of large-scale floating car data.

    Based on the generated geographic representations, this thesis further applies the scaling property and the head/tail division rule to these representations for urban studies. First, all of the above geographic representations demonstrate the scaling property, which indicates the scaling of geographic space. Furthermore, the head/tail division rule performs well in obtaining the hierarchical structures of geographic objects. In a sense, the scaling property reveals the hierarchical structures of geographic objects. According to the above analysis and findings, several urban studies are performed as follows: (1) generate new axial lines based on natural streets for a better understanding of urban morphologies; (2) compute the fewest-turn and shortest map direction; (3) identify urban sprawl patches based on the statistics of blocks and natural cities; (4) categorize spatio-temporal clusters of long stop points into hotspots and traffic jams; and (5) perform an across-country comparison of hierarchical spatial structures.

    The overall contribution of this thesis is first to propose the principle of scaling of geographic space as well as the head/tail division rule, which provide a new and quantitative perspective to efficiently reduce the high degree of complexity and effectively solve the issues in urban studies. Several successful applications prove that the scaling of geographic space and the head/tail division rule are inspiring and can in fact be applied as a universal law, in particular, to urban studies and other fields. The data sets that were generated via an intensive geo-computation process are as large as hundreds of gigabytes and will be of great value to further data mining studies.

  • 12.
    Miao, Yufan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management.
    Exploring Spatio-Temporal Patterns of Volunteered Geographic Information: A Case Study on Flickr Data of Sweden2013Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This thesis aims to seek interesting patterns from massive amounts of Flickr data in Sweden with pro- posed new clustering strategies. The aim can be further divided into three objectives. The first one is to acquire large amount of timestamped geolocation data from Flickr servers. The second objective is to develop effective and efficient methods to process the data. More specifically, the methods to be developed are bifold, namely, the preprocessing method to solve the “Big Data” issue encountered in the study and the new clustering method to extract spatio-temporal patterns from data. The third one is to analyze the extracted patterns with scaling analysis techniques in order to interpret human social activities underlying the Flickr Data within the urban envrionment of Sweden.

    During the study, the three objectives were achieved sequentially. The data employed for this study was vector points downloaded through Flickr Application Programming Interface (API). After data ac- quisition, preprocessing was performed on the raw data. The whole dataset was firstly separated by year based on the temporal information. Then data of each year was accumulated with its former year(s) so that the evovling process can be explored. After that, large datasets were splitted into small pieces and each piece was clipped, georeferenced, and rectified respectively. Then the pieces were merged together for clustering. With respect to clustering, the strategy was developed based on the Delaunay Triangula- tion (DT) and head/tail break rule. After that, the generated clusters were analyzed with scaling analysis techniques and spatio-temporal patterns were interpreted from the analysis results. It has been found that the spatial pattern of the human social activities in the urban environment of Sweden generally follows the power-law distribution and the cities defined by human social activities are evolving as time goes by.

    To conclude, the contributions of this research are threefold and fulfill the objectives of this study, respectively. Firstly, large amount of Flickr data is acquired and collated as a contribution to other aca- demic researches related to Flickr. Secondly, the clustering strategy based on the DT and head/tail break rule is proposed for spatio-temporal pattern seeking. Thirdly, the evolving of the cities in terms of human activities in Sweden is detected from the perspective of scaling. Future work is expected in major two aspects, namely, data and data processing. For the data aspect, the downloaded Flickr data is expected to be employed by other studies, especially those closely related to human social activities within urban environment. For the processing aspect, new algorithms are expected to either accelerate the processing process or better fit machines with super computing capacities.

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  • 13.
    Milutinovic, Goran
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Computer science.
    Ahonen-Jonnarth, Ulla
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Decision, Risk and Policy Analysis.
    Seipel, Stefan
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Computer science. Department of Information Technology, Uppsala University, Uppsala, Sweden.
    GISwaps: A New Method for Decision Making in Continuous Choice Models Based on Even Swaps2018In: International Journal of Decision Support System Technology, ISSN 1941-6296, E-ISSN 1941-630X, Vol. 10, no 3, p. 57-78Article in journal (Refereed)
    Abstract [en]

    This article describes how continuous GIS-MCDM problems are commonly managed by combining some weighting method based on pairwise comparisons of criteria with an aggregation method. The reliability of this approach may be questioned, though. First, assigning weights to criteria, without taking into consideration the actual consequences or values of the alternatives, is in itself controversial. Second, the value functions obtained by this approach are in most cases linear, which is seldom the case in reality. The authors present a new method for GIS-MCDM in continuous choice models based on Even Swaps. The method is intuitive and easy to use, based on value trade-offs, and thus not relying on criteria weighting. Value functions obtained when using the method may be linear or non-linear, and thereby are more sensitive to the characteristics of the decision space. The performed case study showed promising results regarding the reliability of the method in GIS-MCDM context.

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  • 14.
    Ohrzén, Susanna
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management.
    Westlund, My
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management.
    Möjligheten att använda terrester laserskanning och fotobaserad skanning vid utredning av trafikolyckor2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Det sker dagligen olyckor i trafiken runt om i världen och för att göra vägarna säkrare krävs utredning om vad som orsakar olyckorna. I Sverige sker idag dokumentation av olycksplatsen enbart med bilder och skisser i 2D. Att i stället ha en dokumentation i 3D över olycksplatsen gör det lättare att i efterhand studera och analysera vad som skett på platsen. Dokumentation i 3D kan göras med flera metoder, och i denna studie har terrester laserskanning samt s.k. fotobaserad skanning som baseras på bildmatchning testats och utvärderats för dokumentation av trafikolyckor.

    För att testa respektive metod placerades två bilar mot varandra för att simulera en krocksituation. Först laserskannades bilarna med en multistation, Leica MS50, från fyra stationer med upplösning på 10 mm på 50 m i horisontal- och vertikalled. För att testa olika upplösningar laserskannades även bakluckan på den ena bilen från två stationer med en upplösning på 5 mm respektive 15 mm. Den fotobaserade skanningen utfördes med en digitalkamera, Nikon D7000, där bilderna togs runt om bilarna från tre olika vyer med övertäckning på minst 70 % mellan bilderna. Efter skanning importerades laserskanningsdata till programvaran GEO och bilderna från den fotobaserade skanningen till programvaran Agisoft PhotoScan för bearbetning. En 3D-modell skapades även utifrån den fotobaserade skanningen.

    Resultatet av laserskanningen gav ett tydligt och jämnt punktmoln med endast ett fåtal felaktiga punkter. Bilarnas glasrutor gav dock inga returer vilket resulterade i att inga punkter skapades på glasrutornas ytor. Resultatet av den fotobaserade skanningen gav ett relativt tydligt och översiktligt punktmoln men med flertalet felaktiga punkter. Den ena bilen, som var vit, genererade fler felaktiga punkter p.g.a. dålig textur jämfört med den andra bilen, som var röd.

    Laserskanning är en mycket användbar metod för dokumentation av trafikolyckor eftersom metoden är relativt snabb och ger en korrekt avbildning av olycksplatsen. Den fotobaserade skanningen bedöms inte vara helt tillförlitlig eftersom den har flera brister i punktmolnet. Det kan vara gynnsamt för Polisen eller Trafikverket att investera i laserskanning eftersom dokumentation i 3D ger en tydlig överblick av olycksplatsen samtidigt som detaljer kan studeras, vilket är fördelaktigt i utredningssyfte.

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    Bilaga A
  • 15.
    Olhans, Linnéa
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Land management, GIS.
    Leksandsbrons deformationsövervakning med geodetiska metoder2018Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    For different reasons there are movements in structures, which leads to deformations. To monitor deformations, the changes have to be monitored on a regular basis. Monitoring can take place in different ways. When doing this, a core network based on good quality reference points, should be available. The core network provides a basis for deformation measurements and allows the instrument to predict a suitable location before measuring of the structure.

    In 2014, the consultancy company Sweco, commissioned by Leksands municipality, made deformation measurements of Leksandsbron, an old arch bridge from 1925, situated in Leksand, Dalecarlia. The intention was to investigate the sustainability of the bridge, but it was not possible to draw any conclusions from the measurements from 2014. The purpose of this study is to give suggestions on how the core network from Sweco could be developed.

    The completion was performed by a simulation in SBG Geo Software where some known points from Sweco were chosen as a reference and new points were graphically placed in terms of quality, reliability, geometry and economic aspects in three scenarios. A core network can look in many different ways theoretically, but practically, and especially at bridge measurements, there are limitations. By

    network adjustment of the proposals it could be clarified, which network was the best one to use for the survey of the bridge. The result of the completion was that the best suited proposal also was the one best suited to the surroundings, nature and visibility of the bridge

    The best suggestion was used for the bridge measurement with Sweco´s deformation measurement as a reference. The survey of the core network and the points of the bridge was performed by the Trimble S7 total station. With network adjustment the coordinates and assurances were calculated and the differences were compared to Sweco points to see if any deformation had occurred. The result showed that two of Sweco´s points and some of the bridge points have been exposed to deformation.

    The deformation has also been analyzed for the deviations of the core network points and the bridge points by using t-student significance test of a confidence interval of 95%. If the deviation is within the range it´s considered that the point has not moved and if the deviation is outside the range it´s considered that the point has moved. The significance test showed that the same points that had been exposed to deformation in the network adjustment, also were significant in the t-student test, which confirms that the points have moved.

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  • 16.
    Ottekrall, Carl-Johan
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management.
    Hedberg, Andreas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management.
    Utvärdering av husgrunders sättningar i centrala Gävle: mätningar, analyser och upprättande av rutiner för fortsatt övervakning2011Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Between the years 1985 to 2005, the municipality of Gävle surveyed a number of buildings in the central parts of Gävle. The purpose of these surveys was to monitor the movements of the buildings. Now, in 2011, some of the surveys are repeated and compared with the municipality's surveys as above. In addition to repeated surveys, the thesis also describes procedures and methods for future surveys to be carried out by Högskolan i Gävle (HiG for short). Point sketches of the surveyed levelling studs were produced and their position was entered into a separate GIS layer.

    For the collection of new data the instrument Leica Wild NA3000 with invar rods was used. The surveys were executed in closed loops around the objects and reconnected at the starting point. This facilitated the use observation equations for the least squares method. In order to eliminate the need for an external height system the relative height differences were used. For establishing the point sketches and GIS layer, the studs were inspected visually and photographed. After this the information and images were added according to a template extracted (and slightly adapted) from "Handbok till mätningskungörelsen".

    The results show that there are movements in all three objects. These were smaller further away from Gavleån. The largest movements were in one of the objects near the river, where significant differences in movements were detected. The procedures established for the repeated surveys are based on specifications from the SIS Technical Specifications and the "Handbok till mätningskungörelsen".

    In the process a number of problems were detected, such as missing information in the data supplied by the municipality of Gävle such as the lengths of sights and traverses. The data had also only an indication of the accuracy of the results, which was reported to be 0.5 mm. This meant that the least squares method was rejected for the older the data for the benefit of control under Guide to Uncertainty in Measurements (GUM for short) type B. The traffic in the central part of Gävle also led to some problems with vibrations in the equipment. The method of measurement was changed from analog instruments with plane plate micrometer to digital instruments. Since changes and movements have been found in the objects, it is interesting to continue the monitoring. For the continued surveys it is our hope that annual updates of the data will continue to further enhance transparency in how land and buildings move. If more objects placed around the city will be added, one of the additional products could be a clearer model of how the whole area is moving. There is also a municipality project where the quayside from Gavleån and out to the beach of Gävle is surveyed every year to check for movements. This could also be included in the ongoing surveys each year.

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  • 17.
    Owemyr, Pär
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management.
    Lundgren, Jonas
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management.
    Noggrannhetskontroll av laserdata för ny nationell höjdmodell2010Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The new national elevation model is a project undertaken by the National Land Survey at the request of the government since 2009 and is expected to be completed in 2016. Data collection is performed by means of airborne laser scanning. The purpose of this study is to verify the accuracy of laser data to be used for the production of new national height model in Sweden. Accuracy assessment was con-ducted in the area Årsunda – Ockelbo (south-north) and Storvik – Forsbacka (west-east). Quality as-surance of laser data/Digital elevation model (DEM) has been an important issue in airborne laser scanning through the years. The accuracy assessment was conducted using measurement of profiles according to Technical Specification SIS-TS 21145:2007 “Engineering survey for construction works – Statistical test of digital terrain model”. The terrain types investigated is asphalt, coniferous forest, grass surface, clear cut forest, deciduous forest, bog and grassland. TerraScan software was used for accuracy assessment of laser data and measurements of reference points. National Land Survey has announced that RMS should not exceed 0.2 m in open, flat and well-defined surfaces. This demand is met for all land types. The accuracy of laser data is influenced by the variation of the elevations and the density of the vegetation. Further studies are needed for comparison of different degrees of terrain roughness in similar terrain types.

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  • 18.
    Sigurdsson, Andreas
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    Lehr, Amadeus
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Computer and Geospatial Sciences, Geospatial Sciences.
    Volymberäkning från punktmoln skapatgenom Structure from Motion medbildunderlag från mobilkamera2021Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The technology of smartphones and the development of software for digitalphotogrammetric services have developed rapidly, which has made it possibleto easily create 3D models.The purpose of this study is to investigate whether it is possible with the helpof image data from a mobile phone to be able to calculate the volume ofobjects such as e.g. gravel piles and ditches. The technology used is anautomatic image adjustment algorithm called Structure from Motion (SfM).From a series of digital photos, which cover the object from different anglesand depths, SfM can identify common points in the photos and intertwinethese into a point cloud that can be used to create a 3D model. Based on the3D model, a volume determination can then be made from the AgisoftMetashape software.This study performed a number of different tests to evaluate Structure fromMotion with image data from a smartphone for volume calculation. Someobjects have been filmed with different types of phones and then compared toterrestrial laser scanning (TLS) which is a common method of collecting datafor volume calculation. The volume calculations have been made for bothpositive and negative volumes. The method has only used referencemeasurements from measuring tapes in the field. This means that no advancedmeasuring equipment has been used. A light test was performed to see howdifferent light conditions during the data collection can affect the dataprocessing and volume calculation. By calculating differences in volumebetween the 3D models, a result will be produced.The results from 3D modeling created with data from SfM give a volumedifferences in the comparison with terrestrial laser scanning between 2.2%and 6.8%. These results are from a small stone wall and a ditch used in thestudy, the difference corresponds to 0.031 m3and 15.086 m3. The negativevolume that was calculated, ie. the ditch, is the object that gives the largestdeviation in volume, partly between the different mobile phones, partlycompared to TLS. The method gives an indication that there is a greatopportunity to be able to streamline the work process for volume calculationas the method does not require special measurement tools or special priorknowledge which can save both time and money. 

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  • 19.
    Tenzer, Robert
    et al.
    The Department of Land Surveying and Geo-Informatics, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong.
    Foroughi, Ismael
    Department of Geodesy and Geomatics, University of New Brunswick, Canada.
    Sjöberg, Lars E.
    Division of Geodesy and Satellite Positioning, Royal Institute of Technology (KTH), Stockholm, Sweden.
    Bagherbandi, Mohammad
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Land management, GIS. Division of Geodesy and Satellite Positioning, Royal Institute of Technology (KTH), Stockholm, Sweden.
    Hirt, Christian
    Institute for Astronomical and Physical Geodesy and Institute for Advanced Study, Munich, Germany.
    Pitoňák, Martin
    New Technologies for the Information Society (NTIS), Faculty of Applied Sciences, University of West Bohemia, 301, Czech Republic.
    Definition of Physical Height Systems for Telluric Planets and Moons2018In: Surveys in geophysics, ISSN 0169-3298, E-ISSN 1573-0956, Vol. 39, no 3, p. 313-335Article, review/survey (Refereed)
    Abstract [en]

    In planetary sciences, the geodetic (geometric) heights defined with respect to the reference surface (the sphere or the ellipsoid) or with respect to the center of the planet/moon are typically used for mapping topographic surface, compilation of global topographic models, detailed mapping of potential landing sites, and other space science and engineering purposes. Nevertheless, certain applications, such as studies of gravity-driven mass movements, require the physical heights to be defined with respect to the equipotential surface. Taking the analogy with terrestrial height systems, the realization of height systems for telluric planets and moons could be done by means of defining the orthometric and geoidal heights. In this case, however, the definition of the orthometric heights in principle differs. Whereas the terrestrial geoid is described as an equipotential surface that best approximates the mean sea level, such a definition for planets/moons is irrelevant in the absence of (liquid) global oceans. A more natural choice for planets and moons is to adopt the geoidal equipotential surface that closely approximates the geometric reference surface (the sphere or the ellipsoid). In this study, we address these aspects by proposing a more accurate approach for defining the orthometric heights for telluric planets and moons from available topographic and gravity models, while adopting the average crustal density in the absence of reliable crustal density models. In particular, we discuss a proper treatment of topographic masses in the context of gravimetric geoid determination. In numerical studies, we investigate differences between the geodetic and orthometric heights, represented by the geoidal heights, on Mercury, Venus, Mars, and Moon. Our results reveal that these differences are significant. The geoidal heights on Mercury vary from − 132 to 166 m. On Venus, the geoidal heights are between − 51 and 137 m with maxima on this planet at Atla Regio and Beta Regio. The largest geoid undulations between − 747 and 1685 m were found on Mars, with the extreme positive geoidal heights under Olympus Mons in Tharsis region. Large variations in the geoidal geometry are also confirmed on the Moon, with the geoidal heights ranging from − 298 to 461 m. For comparison, the terrestrial geoid undulations are mostly within ± 100 m. We also demonstrate that a commonly used method for computing the geoidal heights that disregards the differences between the gravity field outside and inside topographic masses yields relatively large errors. According to our estimates, these errors are − 0.3/+ 3.4 m for Mercury, 0.0/+ 13.3 m for Venus, − 1.4/+ 125.6 m for Mars, and − 5.6/+ 45.2 m for the Moon.

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