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  • 1.
    Brandt, S. Anders
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för samhällsbyggnad.
    Mårtensson, Stig-Göran
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för samhällsbyggnad.
    Utbildning inom kart- och mätningsteknik2008In: Sveriges kartläggning: tillägg 1998-2007, Gävle: Kartografiska sällskapet , 2008, p. 208-213Chapter in book (Other (popular science, discussion, etc.))
  • 2.
    Ljungberg, Sven-Åke
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för byggnadskvalitet.
    Mejer, Jan-Erik
    Rosqvist, Håkan
    Mårtensson, Stig-Göran
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för samhällsbyggnad.
    Detection and quantification of methane leakage from landfills2009Report (Other academic)
    Abstract [en]

    SGC Rapport 204 Detection and quantification of methane leakage from landfills Sven-Åke Ljungberg, Jan-Erik Meijer, Håkan Rosqvist, Stig-Göran Mårtensson 2009 Landfills make a significant contribution to anthropogenic emission of greenhouse gases through emission of methane. Greater knowledge is needed about how methane leakage occurs and how to calculate its magnitude.The purpose of this project was to detect gas leakage and to measure and quantify methane emission from landfills using modern remote sensing techniques. In this project, a handheld laser instrument and an IR camera were used. The overall objective was to develop cost-effective methods for detecting and quantifying methane emissions from landfills. There are many methods available for measuring the methane concentration in air, both from close-up and from long distances. Combined with the use of a tracer gas, the methane emission from entire landfills can be measured relatively accurately. A number of methods are used to detect leakage from parts of landfill surfaces, but there are few methods for quantifying leakage from sub-zones.The laser instrument used in the project (Siemens AG, CT PS 8 laser system) can detect methane concentrations of ≥10 ppm, and has a maximum range of 30 m that can be extended to 150-200 m using reflective material as a backscatter surface. The concentration of methane is measured in ppm x m and can be stored in logs together with supplementary field data, such as landfill and atmospheric pressure, and weather and radiation conditions, for subsequent analysis after the fieldwork. The IR camera (FLIR ThermaCAM™ GasFindIR LW) has recently been introduced to the market, and was used in the project for detection and visualisation of gas emissions from landfills. The camera produces a thermal image of the gas emission. The thermal image data is stored digitally on a DVD unit connected to the camera.Field measurements with the laser instrument and the IR camera were carried out at seven Swedish landfills and two landfills in France. The investigated surfaces at the Swedish landfills were divided into different zones, such as top surface, slope, crest and toe of slope. The field measurements in France were taken over entire landfills. The methane emission varied between the different landfills in the project, and also between the different landfill zones. The results from repeated field measurements indicated that a landfill with a final cap and a successful gas recovery system produces barely measurable emissions. The weak points at a landfill are generally slopes, including crests and toes of slopes. Where the covering of the waste is inadequate, leakage often occurs at lift joints and in areas where waste protrudes through the cover. Other weak points are deficiencies in the gas recovery system. Leachate systems can lead landfill gas and thereby cause methane leakage.The laser instrument detects point source emission of methane by measuring the methane concentrations above the emission points. The IR camera detects and visualises the occurrence of methane emissions, and can be used to trace emission points and to illustrate the dispersion pattern of methane. Both laser and the IR instrument can be used to determine the exact position of the leakage source. Diffuse emission can only be detected if the emission is large, such as at the tipping face. Both the laser instrument and the IR camera are easy to use. The laser instrument can scan over an area of approximately 1 ha per hour. The smallest measurable point source emission gives a concentration level of approximately 60 ppm, which corresponds to a point source methane emission of the order of 35 – 290 m3 CH4/year.Scanning of the landfill surfaces showed that leakage could stop, increase or slow down. There are many reasons for these dynamics. Wind conditions, air pressure changes, and changes in the moisture content of the covering layer seem to be the most important. Along with wind velocity and variations in atmospheric pressure, moisture content in the ground is an important factor that affects methane emissions from landfill surfaces. Results from field measurements of the same feature/surface at different points in time and with different ground humidity showed that pores in the surface layer close when the moisture content is greater, reducing the landfill gas leakage. The large and sometimes rapid changes make it very difficult to get a picture of the distribution of the methane leakage over the landfill surfaces. Methane emissions were measured in different seasons, and also when the landfill surfaces had snow cover. The results showed that methane is emitted easily through porous snow. The same methane concentrations were recorded for GPS-fixed leakage features with and without snow cover. In the project, the chamber method was used to try to quantify methane leakage detected by the laser instrument. When chamber method results were correlated with the corresponding laser measurements, a relationship was evident. This produced a figure for emission. The relationship between the respective figures from laser and chamber method measurements was used to quantify the detected point source emissions at the French landfills. The total emissions detected with the laser instrument at the two landfills were estimated at 41 and 30 tons of methane respectively per year. These quantified methane emissions from detected points were smaller than the total emissions as reported by the landfill operators. The relationship indicates that it is the diffuse emission of methane that is predominant, and not the point source emission through holes, fissures, etc.If the objective is to produce a reliable measurement of gas emission from a landfill, the combination of laser/chamber method is not probably sufficiently accurate. However, if the objective is, for example, to determine and prioritise where measures should be taken at different landfill surfaces to reduce emission, the combination of laser and the chamber method is very usable. The measurement method tested was application-oriented, and the aim was that the measurements would provide information on which to base the planning and implementation of short- and long-term measures. Manuals were produced for the laser instrument and the IR camera, showing how the two instruments are to be used for detecting methane emissions from landfills.The project demonstrated how the laser instrument could be used by bouncing the beam off a simple reflector. Measurement using a beam path length of up to 200 m is possible. Examples of such applications are measurements over leachate ponds, beside a landfill and on parts of a landfill. Such measurements can give important information about emission conditions that are difficult to measure in any other way.Geoelectrical measurements have several areas of application for landfills, primarily in studies of groundwater pollution. In recent years, interest has also grown in investigating processes inside landfills. Based on results from previous studies, one of the aims of this project was to examine whether three-dimensional evaluation of resistivity measurements could be used to provide better measurements and understanding of the processes below the surface. According to previous studies, landfill gas movements can be visualised through geoelectricity measurements. In the experiment, resistivity was measured along eleven lines in an area 10 m x 10 m on a slope adjacent to a biocell reactor.The resistivity measurements showed results similar to or somewhat lower than the results shown in previous studies. High water content, ion content and high organic content can explain low resistivity, while high gas pressure in the ground partly explains high resistivity. It should also be noted that temperature variations affect resistivity. When the results from the resistivity measurements was compared with results from static chamber measurements and the laser instrument, no clear correlations were observed. The gas movements below the ground surface shown by resistivity measurements at the toe of the slope could not be confirmed with measurements above ground with the laser or static chamber methods. The results from the project show that combinations of laser, IR, chamber method and geo-resistivity measurements are a successful way to describe and map methane emissions from landfills. The mapping of emissions provides precise information useful for planning maintenance or improvement measures on landfill surfaces and gas recovery and leachate systems.

  • 3.
    Mårtensson, Stig-Göran
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för samhällsbyggnad.
    Height Determination by GPS2001Conference paper (Other (popular science, discussion, etc.))
    Abstract [en]

    This paper focus on the problems related with height determination by GPS. Based on experiences in Sweden, the paper and the attached copies of transparancies explain at what accuracy we are today, how the accuracy can be improved and what we can expect in the future from remote positioning systems.

  • 4.
    Mårtensson, Stig-Göran
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för samhällsbyggnad. University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management.
    Height Determination by GPS: Accuracy with Respect to Different Geoid Models in Sweden2002In: Proceedings of the XXII FIG International Congress, Washington, D.C., USA, 2002, p. 106-113Conference paper (Refereed)
    Abstract [en]

    In this paper different gravimetric geoid models have been evaluated: on a regional basis utilising the Swedish GPS reference network SWEPOS; and locally, in a specific research area utilising the results from a GPS campaign conducted in the area.

    The research area is situated in central Sweden having a size of approximately 100x300 km. In the area GPS measurements (with average baseline length of 13 km) have been conducted at well established benchmarks with known orthometric heights.

    To find out if a geometric geoid model, based on the GPS measurements, would be a better height corrector surface for the research area than the gravimetric geoid models, such a model has been computed with geostatistical methods, i.e. universal kriging. The model has been experimentally evaluated utilising a Swedish GPS campaign called RIX95.

    It was found, when the geometric geoid model is used, that the absolute accuracy of GPS levelling is ±14 mm and the relative accuracy ±10 mm (on a 10 km long baseline). It is concluded that the geometric geoid model is the best height corrector surface for the research area among the studied models.

  • 5.
    Mårtensson, Stig-Göran
    et al.
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för samhällsbyggnad.
    Brandt, S. Anders
    University of Gävle, Department of Technology and Built Environment, Ämnesavdelningen för samhällsbyggnad.
    University Exchange Programme and Master's Programme for ALAGaC Employees: Report No. MN 3-4 in the project Capacity Building in Human Resource Development in Order to Strengthen the Land Administration Sector of Mongolia, Mongolia 18 – 27 November 20052005Report (Other (popular science, discussion, etc.))
  • 6.
    Mårtensson, Stig-Göran
    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.
    Reshetyuk, Yuriy
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Urban and regional planning/GIS-institute.
    Fotogrammetriskt uppsving med obemannade flygplan (UAV)2013In: SINUS, no 3, p. 14-16Article in journal (Other (popular science, discussion, etc.))
    Abstract [sv]

    På Högskolan i Gävle har under vårterminen 2013 fyra examensarbeten genomförts för att undersöka möjligheter och problem med användandet av obemannade flygfarkoster för fotogrammetriska ändamål. Studenterna har läst det treåriga lantmätarprogrammet med teknisk inriktning, som liksom alla högskoleprogram, avslutas med ett examensarbete. De här fyra grupperna har haft ett gemensamt intresse, nämligen UAS, och deras undersökningar refereras i artikeln nedan. Men först en kort beskrivning av UAS.

  • 7.
    Mårtensson, Stig-Göran
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Land management, GIS.
    Reshetyuk, Yuriy
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Land management, GIS.
    Height uncertainty in digital terrain modelling with unmanned aircraft systems2017In: Survey review - Directorate of Overseas Surveys, ISSN 0039-6265, E-ISSN 1752-2706, Vol. 49, no 355, p. 312-318Article in journal (Refereed)
    Abstract [en]

    The purpose of this paper is to investigate the height uncertainty of digital terrain models (DTMs) generated from unmanned aircraft system (UAS) surveys over different surface types – asphalt, gravel and grass. The data used in the study was acquired during two UAS flights performed in spring 2014 with a fixed wing aircraft and two different cameras, from the flying height of about 100 m, and it was processed in different software suites – Agisoft PhotoScan, RapidStation and RapidTerrain. The results show that it is possible to achieve the height uncertainty (expressed as a Root Mean Square Error) in a DTM of below 0.02 m on asphalt surfaces and below 0.04 m on gravel and grass surfaces, provided an overcast sky.

  • 8.
    Mårtensson, Stig-Göran
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Land management, GIS.
    Reshetyuk, Yuriy
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Land management, GIS.
    Noggrann och kostnadseffektiv uppdatering av DTM med UAS för BIM2015Report (Other academic)
    Abstract [sv]

    Byggnadsinformationsmodellering (BIM) är ett begrepp som avser att ge en effektiv byggprocess genom digital representation av både fysiska och funktionella aktiviteter i ett byggprojekt. I en vid bemärkelse kan BIM användas i hela byggprocessen, från planering, projektering och byggande till förvaltning, renovering och slutlig destruktion. I en mer snäv bemärkelse används BIM enbart för digitala modeller (Volk m.fl., 2013), som i den här rapporten, där fokus ligger på framställning av digitala terrängmodeller (DTM) för exempelvis byggprocessens planering och/eller projektering.

  • 9.
    Mårtensson, Stig-Göran
    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.
    Reshetyuk, Yuriy
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Urban and regional planning/GIS-institute.
    Jivall, Lotti
    Lantmäteriet,Geodesy Division.
    Measurement uncertainty in network RTK GNSS-based positioning of a terrestrial laser scanner2012In: Journal of Applied Geodesy, ISSN 1862-9024, Vol. 6, no 1, p. 25-32Article in journal (Refereed)
    Abstract [en]

    This paper reports on investigation of measurement uncertainty in positioning of a terrestrial laser scanner with network RTK (Real-Time Kinematic) service provided by SWEPOS®, Swedish national network of permanent reference stations for GNSS (Global Navigation Satellite System). To simulate measurements by a scanner, a rotating flat bar fixed to a prism base, attached to a tribrach, was used. The tests have been carried out with both a rotating GNSS antenna (placed at different distances from the centre of rotation – radii) and a stationary antenna, under different time intervals (1–5 min). The results show that it is possible to achieve a standard uncertainty of less than 10 mm in plane and 16 mm in height, independently of the observation time and radius. Hence, network RTK can be used with advantage for precise direct georeferencing of point clouds, not only for determination of the position of the scanner, but also its orientation.

  • 10.
    Reshetyuk, Yuriy
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Land management, GIS.
    Mårtensson, Stig-Göran
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Land management, GIS.
    Generation of highly accurate digital elevation models with unmanned aerial vehicles2016In: Photogrammetric Record, ISSN 0031-868X, E-ISSN 1477-9730, Vol. 1, no 154, p. 143-165Article in journal (Refereed)
    Abstract [en]

    In order to investigate the possibilities for the generation of digital elevation models with a height uncertainty of 20 mm or less using unmanned aerial vehicles, a survey with a fixed-wing aircraft was carried out over a gravel quarry in Gävle, Sweden. At flying heights of about 80 and 160 m, the resulting imagery had ground sample distances of 24 and 50 mm, respectively. The data was processed in two different software suites – computer-vision-based PhotoScan and photogrammetric RapidStation/RapidTerrain. The results show that PhotoScan was more effective in flat terrain, with height uncertainties of 10 and 17 mm compared with 30 to 40 mm for RapidTerrain, whereas the latter had a clear advantage over undulating terrain.

  • 11.
    Reshetyuk, Yuriy
    et al.
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Land management, GIS.
    Mårtensson, Stig-Göran
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Land management, GIS.
    Noggrann och kostnadseffektiv uppdatering av DTM med laserskanning för BIM – Läget 20152016Report (Other academic)
    Abstract [sv]

    Syftet med det här projektet har varit att undersöka utbudet av befintliga UAS för laserskanning, studera erfarenheter av deras tillämpning inom 3D-kartering, samt bedöma deras potential för framställning av DTM för byggnadsinformationsmodellering (BIM). Med tanke på teknikens snabba utveckling bör den här rapporten ses mer eller mindre som en ”ögonblicksbild” av ”UAS-laserskanningslandskapet” i slutet av 2015.

  • 12.
    Reshetyuk, Yuriy
    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.
    Mårtensson, Stig-Göran
    University of Gävle, Faculty of Engineering and Sustainable Development, Department of Industrial Development, IT and Land Management, Urban and regional planning/GIS-institute.
    Terrestrial laser scanning for detection of landfill gas: a pilot study2014In: Journal of Applied Geodesy, ISSN 1862-9024, Vol. 8, no 1, p. 87-96Article in journal (Refereed)
    Abstract [en]

    Methane built up in landlls as a result of breaking down of organic materials can be a renewable energy source if it is taken advantage of. The aim of research presented in this paper is to detect landll gas (that contains methane) by means of terrestrial laser scanning. The hypothesis is that where no surface leakage has been reported, the landll gas will expand or migrate. Therefore, it is possible to detect it through repeated scanning of the same area and comparison of Digital Terrain Models (DTMs) generated from the point clouds. Only the most signicant movements, i.e. vertical, are of interest in this case. During September–November 2011, a small area at Forsbacka landll in the vicinity of Gävle was scanned 10 times. Epoch-to-epoch comparisons of the resulting DTMs have shown two signicant changes (–27 and +19 mm) in elevation of the surface, and it is not impossible that they are caused by migrating landll gas. The method tested in this study is deemed to be rigorous and accurate for detecting small-scale swell-shrink behaviour of the ground surface (in our case a landll surface). However, both data processing and interpretation of the results have been considerably complicated by presence of low vegetation (weeds) on the study site, which was di-cult to lter away completely from the data. Based on our pilot study, we recommend that a larger area and a longer period of time are chosen to give basis for more grounded conclusions about presence of landll gas.

     

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