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  • 1. Abrehdary, M.
    et al.
    Sjoberg, Lars E.
    KTH, School of Architecture and the Built Environment (ABE), Real Estate and Construction Management, Geodesy and Satellite Positioning.
    Sampietro, D.
    Contribution of satellite altimetry in modelling Moho density contrast in oceanic areas2019In: Journal of Applied Geodesy, ISSN 1862-9016, E-ISSN 1862-9024, Vol. 13, no 1, p. 33-40Article in journal (Refereed)
    Abstract [en]

    The determination of the oceanic Moho (or crust-mantle) density contrast derived from seismic acquisitions suffers from severe lack of data in large parts of the oceans, where have not yet been sufficiently covered by such data. In order to overcome this limitation, gravitational field models obtained by means of satellite altimetry missions can be proficiently exploited, as they provide global uniform information with a sufficient accuracy and resolution for such a task. In this article, we estimate a new Moho density contrast model named MDC2018, using the marine gravity field from satellite altimetry in combination with a seismic-based crustal model and Earth's topographic/bathymetric data. The solution is based on the theory leading to Vening Meinesz-Moritz's isostatic model. The study results in a high-accuracy Moho density contrast model with a resolution of 1° × 1° in oceanic areas. The numerical investigations show that the estimated density contrast ranges from 14.2 to 599.7 kg/m 3 with a global average of 293 kg/m 3 . In order to evaluate the accuracy of the MDC2018 model, the result was compared with some published global models, revealing that our altimetric model is able to image rather reliable information in most of the oceanic areas. However, the differences between this model and the published results are most notable along the coastal and polar zones, which are most likely due to that the quality and coverage of the satellite altimetry data are worsened in these regions.

  • 2.
    Abrehdary, M.
    et al.
    Univ West HV, Div Math Comp & Surveying Engn, SE-46186 Trollhattan, Sweden..
    Sjöberg, L. E.
    KTH, School of Architecture and the Built Environment (ABE), Real Estate and Construction Management, Geodesy and Satellite Positioning. Univ West HV, Div Math Comp & Surveying Engn, SE-46186 Trollhattan, Sweden..
    Recovering Moho constituents from satellite altimetry and gravimetric data for Europe and surroundings2019In: Journal of Applied Geodesy, ISSN 1862-9016, E-ISSN 1862-9024, Vol. 13, no 4, p. 291-303Article in journal (Refereed)
    Abstract [en]

    In this research, we present a local Moho model, named MOHV19, including Moho depth and Moho density contrast (or shortly Moho constituents) with corresponding uncertainties, which are mapped from altimetric and gravimetric data (DSNSC08) in addition to seismic tomographic (CRUST1.0) and Earth topographic data (Earth2014) to a resolution of 1 degrees x 1 degrees based on a solution of Vening Meinesz-Moritz' theory of isostasy. The MOHV19 model covers the area of entire European plate along with the surrounding oceans, bounded by latitudes (30 degrees N-82 degrees N) and longitudes (40 degrees W-70 degrees E). The article aims to interpret the Moho model resulted via altimetric and gravimetric information from the geological and geophysical perspectives along with investigating the relation between the Moho depth and Moho density contrast. Our numerical results show that estimated Moho depths range from 7.5 to 57.9 km with continental and oceanic averages of 41.3 +/- 4.9 km and 21.6 +/- 9.2 km, respectively, and an overall average of 30.9 +/- 12.3 km. The estimated Moho density contrast ranges from 60.2 to 565.8 kg/m(3), with averages of 421.8 +/- 57.9 and 284.4 +/- 62.9 kg/m(3) for continental and oceanic regions, respectively, with a total average of 350.3 +/- 91.5 kg/m(3). In most areas, estimated uncertainties in the Moho constituents are less than 3 km and 40 kg/m(3), respectively, but they reach to much more significant values under Iceland, parts of Gulf of Bothnia and along the Kvitoya Island. Comparing the Moho depths estimated by MOHV19 and those derived by CRUST1.0, MDN07, GRAD09 and MD19 models shows that MOHV19 agree fairly well with CRUST1.0 but rather poor with other models. The RMS difference between the Moho density contrasts estimated by MOHV19 and CRUST1.0 models is 49.45 kg/m(3).

  • 3.
    Ahnlén, Fredrik
    KTH, School of Architecture and the Built Environment (ABE), Real Estate and Construction Management, Geodesy and Satellite Positioning.
    Automatic Detection of Low Passability Terrain Features in the Scandinavian Mountains2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    During recent years, much focus have been put on replacing time consuming manual mappingand classification tasks with automatic methods, having minimal human interaction. Now it ispossible to quickly classify land cover and terrain features covering large areas to a digital formatand with a high accuracy. This can be achieved using nothing but remote sensing techniques,which provide a far more sustainable process and product. Still, some terrain features do not havean established methodology for high quality automatic mapping.The Scandinavian Mountains contain several terrain features with low passability, such asmires, shrub and stony ground. It would be of interest to anyone passing the land to avoid theseareas. However, they are not sufficiently mapped in current map products.The aim of this thesis was to find a methodology to classify and map these terrain featuresin the Scandinavian Mountains with high accuracy and minimal human interaction, using remotesensing techniques. The study area chosen for the analysis is a large valley and mountain sidesouth-east of the small town Abisko in northern Sweden, which contain clearly visible samplesof the targeted terrain features. The methodology was based on training a Fuzzy Logic classifierusing labeled training samples and descriptors derived from ortophotos, LiDAR data and currentmap products, chosen to separate the classes from each other by their characteristics. Firstly,a set of candidate descriptors were chosen, from which the final descriptors were obtained byimplementing a Fisher score filter. Secondly a Fuzzy Inference System was constructed usinglabeled training data from the descriptors, created by the user. Finally the entire study area wasclassified pixel-by-pixel by using the trained classifier and a majority filter was used to cluster theoutputs. The result was validated by visual inspection, comparison to the current map productsand by constructing Confusion Matrices, both for the training data and validation samples as wellas for the clustered- and non-clustered results.The results showed that

  • 4.
    Alizadeh Khameneh, Mohammad Amin
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Real Estate and Construction Management, Geodesy and Satellite Positioning. WSP Civils, Department of Geographic Information and Asset Management.
    Eshagh, Mehdi
    University West, Department of Engineering Science.
    Jensen, Anna B. O.
    KTH, School of Architecture and the Built Environment (ABE), Real Estate and Construction Management, Geodesy and Satellite Positioning.
    Optimization of Deformation Monitoring Networks using Finite Element Strain Analysis2018In: Journal of Applied Geodesy, ISSN 1862-9016, E-ISSN 1862-9024, Vol. 12, no 2Article in journal (Refereed)
    Abstract [en]

    An optimal design of a geodetic network can fulfill the requested precision and reliability of the network, and decrease the expenses of its execution by removing unnecessary observations. The role of an optimal design is highlighted in deformation monitoring network due to the repeatability of these networks. The core design problem is how to define precision and reliability criteria. This paper proposes a solution, where the precision criterion is defined based on the precision of deformation parameters, i.e. precision of strain and differential rotations. A strain analysis can be performed to obtain some information about the possible deformation of a deformable object. In this study, we split an area into a number of three-dimensional finite elements with the help of the Delaunay triangulation and performed the strain analysis on each element. According to the obtained precision of deformation parameters in each element, the precision criterion of displacement detection at each network point is then determined. The developed criterion is implemented to optimize the observations from the Global Positioning System (GPS) in Skåne monitoring network in Sweden. The network was established in 1989 and straddled the Tornquist zone, which is one of the most active faults in southern Sweden. The numerical results show that 17 out of all 21 possible GPS baseline observations are sufficient to detect minimum 3 mm displacement at each network point.

  • 5.
    Amin, Hadi
    et al.
    Faculty of Engineering and Sustainable Development, The University of Gävle.
    Sjöberg, Lars
    KTH, School of Architecture and the Built Environment (ABE), Real Estate and Construction Management, Geodesy and Satellite Positioning. Faculty of Engineering and Sustainable Development, University of Gävle.
    Bagherbandi, Mohammad
    KTH, School of Architecture and the Built Environment (ABE), Real Estate and Construction Management, Geodesy and Satellite Positioning. Faculty of Engineering and Sustainable Development, The University of Gävle.
    A global vertical datum defined by the conventional geoid potential and the Earth ellipsoid parameters2019In: Journal of Geodesy, ISSN 0949-7714, E-ISSN 1432-1394Article in journal (Refereed)
    Abstract [en]

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

  • 6.
    Baranov, Alexey
    et al.
    Russian Acad Sci, Schmidt Inst Phys Earth, Moscow 119991, Russia.;Russian Acad Sci, Inst Earthquake Predict Theory & Math Geophys, Moscow 119991, Russia..
    Bagherbandi, Mohammad
    KTH, School of Architecture and the Built Environment (ABE), Real Estate and Construction Management, Geodesy and Satellite Positioning.
    Tenzer, Robert
    Hong Kong Polytech Univ, Dept Land Surveying & Geoinformat, Hong Kong, Peoples R China..
    Combined Gravimetric-Seismic Moho Model of Tibet2018In: GEOSCIENCES, ISSN 2076-3263, Vol. 8, no 12, article id UNSP 461Article in journal (Refereed)
    Abstract [en]

    Substantial progress has been achieved over the last four decades to better understand a deep structure in the Himalayas and Tibet. Nevertheless, the remoteness of this part of the world still considerably limits the use of seismic data. A possible way to overcome this practical restriction partially is to use products from the Earth's satellite observation systems. Global topographic data are provided by the Shuttle Radar Topography Mission (SRTM). Global gravitational models have been derived from observables delivered by the gravity-dedicated satellite missions, such as the Gravity Recovery and Climate Experiment (GRACE) and the Gravity field and steady-state Ocean Circulation Explorer (GOCE). Optimally, the topographic and gravity data should be combined with available results from tomographic surveys to interpret the lithospheric structure, including also a Moho relief. In this study, we use seismic, gravity, and topographic data to estimate the Moho depth under orogenic structures of the Himalayas and Tibet. The combined Moho model is computed based on solving the Vening Meinesz-Moritz (VMM) inverse problem of isostasy, while incorporating seismic data to constrain the gravimetric solution. The result of the combined gravimetric-seismic data analysis exhibits an anticipated more detailed structure of the Moho geometry when compared to the solution obtained merely from seismic data. This is especially evident over regions with sparse seismic data coverage. The newly-determined combined Moho model of Tibet shows a typical contrast between a thick crustal structure of orogenic formations compared to a thinner crust of continental basins. The Moho depth under most of the Himalayas and the Tibetan Plateau is typically within 60-70 km. The maximum Moho deepening of similar to 76 km occurs to the south of the Bangong-Nujiang suture under the Lhasa terrane. Local maxima of the Moho depth to similar to 74 km are also found beneath Taksha at the Karakoram fault. This Moho pattern generally agrees with the findings from existing gravimetric and seismic studies, but some inconsistencies are also identified and discussed in this study.

  • 7.
    Börjesson, Alexandra
    KTH, School of Architecture and the Built Environment (ABE), Real Estate and Construction Management, Geodesy and Satellite Positioning.
    Automatic Generation of Levels of Detail: A Study on the Swedish National Road Database2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    When creating a map, the amount of data and which geographical information chosen to bepresented are decided based on the purpose of the map. Trafikverket is responsible for theNational Road Database that is a reference road network with a large amount of dataconnected to it. The database is built at a carriageway level where several links can be usedto represent a single road. In this thesis the database has been studied as well as thepossibilities to create an automatic workflow that creates a generalisation to road level. Someapplications and analyses that use this database are requesting input data of a higher level ofdetail. It is also found important from a cartographic point of view. Possibilities to create alinear referencing for the data between the different levels was studied as well, to make theupdates between the levels easier and not having the need to maintain two differentdatabases. It would make it possible to inherit attributes and the generic features connectedto the network.The first fully automated workflow for a generalisation of an entire map was developed in theNetherlands in 2014. Several other agencies in Sweden and Norway are currently working ongeneralisations as well and using different approaches. Statens Vegvesen, which is theNational Road Agency in Norway, has already implemented the different levels of detail intheir road database. Lantmäteriet currently has a project where their goal is to create a fullyautomated map to easily change to a larger scale.After studying the programs used in other generalisations and which programs Trafikverketnormally use, FME and ArcGIS were chosen to be used in this thesis. A small study area waschosen, and the proper data was collected from the National Road Database. The study wasconducted by a set of experiments and trying different parameter values in order to obtain asatisfactory result.Three different areas where studied, where the goal was to find a sequence of functions thatsuccessfully generalised all the areas. The areas were parallel roads, complex intersectionsand roundabouts. The result consists of a suggested workflow, but alterations hade to bemade manually since it was not possible to find a fully automated generalisation for the areachosen. Therefore, a set of functions and tools that could be developed were collected as wellin the end to make a more automated workflow possible.The result found in this thesis show that if the cartographic generalisations are more studiedand examined it should be possible to get a more automated workflow to create ageneralisation between the different level of detail. However, it might be difficult to get theworkflow fully automated due to the complexity of the intersections.

  • 8.
    Eshagh, Mehdi
    et al.
    Univ West, Dept Engn Sci, Trollhattan, Sweden..
    Johansson, Filippa
    Univ West, Dept Engn Sci, Trollhattan, Sweden..
    Karlsson, Lenita
    Univ West, Dept Engn Sci, Trollhattan, Sweden..
    Horemuz, Milan
    KTH, School of Architecture and the Built Environment (ABE), Real Estate and Construction Management, Geodesy and Satellite Positioning.
    A case study on displacement analysis of Vasa warship2018In: Journal of Geodetic Science, ISSN 2081-9919, E-ISSN 2081-9943, Vol. 8, no 1, p. 43-54Article in journal (Refereed)
    Abstract [en]

    Monitoring deformation of man-made structures is very important to prevent them from a risk of collapse and save lives. Such a process is also used for monitoring change in historical objects, which are deforming continuously with time. An example of this is the Vasa warship, which was under water for about 300 years. The ship was raised from the bottom of the sea and is kept in the Vasa museum in Stockholm. A geodetic network with points on the museum building and the ship's body has been established and measured for 12 years for monitoring the ship's deformation. The coordinate time series of each point on the ship and their uncertainties have been estimated epoch-wisely. In this paper, our goal is to statistically analyse the ship's hull movements. By fitting a quadratic polynomial to the coordinate time series of each point of the hull, its acceleration and velocity are estimated. In addition, their significance is tested by comparing them with their respective estimated errors after the fitting. Our numerical investigations show that the backside of the ship, having highest elevation and slope, has moved vertically faster than the other places by a velocity and an acceleration of about 2 mm/year and 0.1 mm/year(2), respectively and this part of the ship is the weakest with a higher risk of collapse. The central parts of the ship are more stable as the ship hull is almost vertical and closer to the floor. Generally, the hull is moving towards its port and downwards.

  • 9.
    Gido, Nureldin A. A.
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Real Estate and Construction Management, Geodesy and Satellite Positioning. Univ Gavle, Fac Engn & Sustainable Dev, SE-80176 Gavle, Sweden..
    Bagherbandi, Mohammad
    KTH, School of Architecture and the Built Environment (ABE), Real Estate and Construction Management, Geodesy and Satellite Positioning. Univ Gavle, Fac Engn & Sustainable Dev, SE-80176 Gavle, Sweden..
    Sjoberg, Lars E.
    KTH, School of Architecture and the Built Environment (ABE), Real Estate and Construction Management, Geodesy and Satellite Positioning. Univ Gavle, Fac Engn & Sustainable Dev, SE-80176 Gavle, Sweden..
    Tenzer, Robert
    Hong Kong Polytech Univ, Dept Land Surveying & Geoinformat, Kowloon, Hong Kong, Peoples R China..
    Studying permafrost by integrating satellite and in situ data in the northern high-latitude regions2019In: Acta Geophysica, ISSN 1895-6572, E-ISSN 1895-7455, Vol. 67, no 2, p. 721-734Article in journal (Refereed)
    Abstract [en]

    There is an exceptional opportunity of achieving simultaneous and complementary data from a multitude of geoscience and environmental near-earth orbiting artificial satellites to study phenomena related to the climate change. These satellite missions provide the information about the various phenomena, such as sea level change, ice melting, soil moisture variation, temperature changes and earth surface deformations. In this study, we focus on permafrost thawing and its associated gravity change (in terms of the groundwater storage), and organic material changes using the gravity recovery and climate experiment (GRACE) data and other satellite- and ground-based observations. The estimation of permafrost changes requires combining information from various sources, particularly using the gravity field change, surface temperature change, and glacial isostatic adjustment. The most significant factor for a careful monitoring of the permafrost thawing is the fact that this process could be responsible for releasing an additional enormous amount of greenhouse gases emitted to the atmosphere, most importantly to mention carbon dioxide (CO2) and methane that are currently stored in the frozen ground. The results of a preliminary numerical analysis reveal a possible existence of a high correlation between the secular trends of greenhouse gases (CO2), temperature and equivalent water thickness (in permafrost active layer) in the selected regions. Furthermore, according to our estimates based on processing the GRACE data, the groundwater storage attributed due to permafrost thawing increased at the annual rates of 3.4, 3.8, 4.4 and 4.0cm, respectively, in Siberia, North Alaska and Canada (Yukon and Hudson Bay). Despite a rather preliminary character of our results, these findings indicate that the methodology developed and applied in this study should be further improved by incorporating the in situ permafrost measurements.

  • 10.
    Gido, Nureldin A. A.
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Real Estate and Construction Management, Geodesy and Satellite Positioning. Univ Gävle.
    Bagherbandi, Mohammad
    KTH, School of Architecture and the Built Environment (ABE), Real Estate and Construction Management, Geodesy and Satellite Positioning. Univ Gävle.
    Sjöberg, Lars E.
    KTH, School of Architecture and the Built Environment (ABE), Real Estate and Construction Management, Geodesy and Satellite Positioning. Univ Gävle.
    A gravimetric method to determine horizontal stress field due to flow in the mantle in Fennoscandia2019In: GEOSCIENCES JOURNAL, ISSN 1226-4806, Vol. 23, no 3, p. 377-389Article in journal (Refereed)
    Abstract [en]

    Mass changes and flow in the Earth's mantle causes the Earth's crust not only to move vertically, but also horizontally and to tilt, and produce a major stress in the lithosphere. Here we use a gravimetric approach to model sub-lithosphere horizontal stress in the Earth's mantle and its temporal changes caused by geodynamical movements like mantle convection in Fennoscandia. The flow in the mantle is inferred from tectonics and convection currents carrying heat from the interior of the Earth to the crust. The result is useful in studying how changes of the stress influence the stability of crust. The outcome of this study is an alternative approach to studying the stress and its change using forward modelling and the Earth's viscoelastic models. We show that the determined horizontal stress using a gravimetric method is consistent with tectonics and seismic activities. In addition, the secular rate of change of the horizontal stress, which is within 95 kPa/year, is larger outside the uplift dome than inside.

  • 11.
    Hugosson, Alice
    KTH, School of Architecture and the Built Environment (ABE), Real Estate and Construction Management, Geodesy and Satellite Positioning.
    Visualization of 3D Real Properties in Sweden2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    It is a high demand of land in the society today, especially in urbanized areas. Values of land are increasing, and the cities get more complex constructions and relations between ownership.Since the 1st of January 2004 it is possible to form real properties that are limited both horizontally and vertically. This is called three-dimensional real properties a property spaces and is defined in the Swedish Land Code and the Real Property Act. The purpose is to separate land and buildings with different functions on different levels to achieve a more efficient use of land.The aim in this thesis is to investigate current legislation and recommendations for presentation of 3D real properties and their rights, restrictions and responsibilities (RRRs) and how these are presented in cadastral dossiers today. Further, the thesis addresses the question of how a 3D cadastral model should be visualized, which level of detail should be implemented in the model and which input data is required. The thesis has been conducted by studying literature, documents and laws, creating a 3D model and by study and evaluate cadastral dossiers for 3D property formation.The current legislation for property formation declares that if a property boundary cannot be marked in the ground, it should be presented by “enough accuracy” in maps and drawings. As a complement to this there are also a textual description of the vertical and horizontal extent of the property. The results of the study show that the intelligibility of the 3D extension in cadastral dossiers for 3D property formation can be improved. One way to improve this is to use standardized 3D models which can make it easier to interpret the relations between real property boundaries, RRRs, the construction and other features of interest. But to create a 3D model that presents the accurate cadastral relationships can be very time consuming and requires a lot of data. To solve this, a concept for standardized 3D models in three levels of detail is proposed. The concept covers a general, schematic and detailed model. The models require different types and amount of data and need different amount of work to create. A general visualization concept for these models are also proposed.A conclusion that can be drawn, is that standards and requirements for presentation of the extent of 3D real properties and RRRs is are missing today. It is hard to interpret the legal situation in current cadastral dossiers for 3D property formation, if this could be presented in a better way it could lead to more efficient processes and better understanding by both professionals and laymen. Another conclusion is that how 3D real properties and RRRs are formed varies a lot, from simple volumes to more complex situation related to construction details. This makes it hard to create one type of 3D cadastral model that covers all types of 3D real property situations.

  • 12.
    Håkansson, Martin
    KTH, School of Architecture and the Built Environment (ABE), Real Estate and Construction Management, Geodesy and Satellite Positioning.
    Characterization of GNSS observations from a Nexus 9 Android tablet2019In: GPS Solutions, ISSN 1080-5370, E-ISSN 1521-1886, Vol. 23, no 1, article id UNSP 21Article in journal (Refereed)
    Abstract [en]

    Global navigation satellite system (GNSS) raw data were made available in the application programming interface (API) starting from version 7.0 of the Android operating system. This opens possibilities for precise positioning with Android devices, as externally generated GNSS corrections can now be included in the positioning estimation in a convenient way. The Nexus 9 tablet is a good candidate for an early assessment of the raw GNSS observables and the corresponding derived precise positions, as it also supports many of the optional features and observation types presented by the API, including carrier phase observations which play an important role in many precise positioning techniques. It is known from the previous studies that poor handling of multipath in smartphones and tablets is a big challenge when it comes to precise GNSS positioning with these kinds of devices. Hence, this study assesses the raw GNSS observations and the calculated precise positions of the Nexus 9 tablet in two experimental setups with different multipath impacts. In addition, various biases of the observations are determined, some of which is not present on high-grade geodetic receivers. The analysis is done for GPS and GLONASS, which are supported by the Nexus 9 tablet. The study shows that multipath plays an important role for the expected accuracy of the calculated precise positions, both due to the induced error on the measurements, and due to loss of lock of the GNSS signals, which significantly affects precise positioning from carrier-phase measurements. Position accuracy ranges from just below 1m to a few decimeters between the experimental setups with moderate and low levels of multipath respectively, for positioning based on carrier-phase observations. It is, furthermore, demonstrated that consideration of code inter-system biases and code inter-frequency biases of the Nexus 9 tablet are crucial for differential GNSS with multiple GNSS systems and when GLONASS observations are used in the positioning solutions. Besides these expected biases, also other less expected behaviors were discovered in the Nexus 9 GNSS observations, including various drifts for the code and phase observations. This study also proposes some strategies to handle these.

  • 13.
    Jansson, Patric
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Real Estate and Construction Management, Geodesy and Satellite Positioning. Trafikverket.
    Lundgren, Liselotte
    Lidingö kommun.
    A Comparison of Different Methods Using GNSS RTK to Establish Control Points in Cadastral Surveying2018Report (Refereed)
    Abstract [en]

    The purpose of this report is to compare different methods using Global Navigation Satellite System Real Time Kinematic (GNSS RTK) to establish control points to be used for the establishing of a free total station (in the next step). The objectives are to evaluate quality measures for different methods for multiple occupations and the averaging method “180-seconds”. The quality measures used in the study is expanded uncertainty (U95; with 95% level of confidence) and maximum deviation from the true value (“risk”), i.e. the maximum horizontal distance from the mean.From the results in this study, it is clear that it is not only the number of occupations that matters, also the length of the observation periods is important in order to minimize the risk. Extending from one occupation to two (or more) in order to be ‘safe’ is to give a false sense of security.Janssen et al. (2012) stated that an observation window of 1-2 minutes reduces the effects of extreme outliers as much as possible in the shortest time frame. They also concluded that averaging for a longer period than 1-2 minutes does not appear to provide any significant further improvement. In our study, however, increasing the observation window from 1-2 to 3 minutes, are motivated by a decrease in risk (cf. Appendix 1). Further, 180 seconds seem like an eternity for RTK users in the field; consequently, they will use supporting legs for their antenna pole. Using a shorter averaging time (60-120 s), this is not always obvious for the user. Consequently, extending the observation window to 3 minutes is motivated by a decrease in risk and a decrease in centering error. Therefore, the recommendation is to use observation periods of at least 180 seconds (3 min) of data. This is according to the recommendations given in Edwards et al. (2010).There is a trade-off between the recommendation of using as many observations as possible, i.e. at least two occupations with at least 3 minutes length of every observation periods, and productivity. This task must be carefully balanced by the surveyor in a case-by-case evaluation.Regarding productivity, averaging over 180 seconds of data at only one occupation seems to be a proper balance for cadastral surveying. According to this study it is not significantly worse than the mean of the eleven different multiple occupations methods in this study.

  • 14. Ouassou, M.
    et al.
    Jensen, Anna B. O.
    KTH, School of Architecture and the Built Environment (ABE), Real Estate and Construction Management, Geodesy and Satellite Positioning.
    Network real-time kinematic data screening by means of multivariate statistical analysis2019In: SN Applied Science, ISSN 2523-3963, Vol. 1, no 512Article in journal (Refereed)
    Abstract [en]

    We introduce a novel approach to the computation of network real-time kinematic (NRTK) data integrity, which can be used to improve the position accuracy for a rover receiver in the field. Our approach is based on multivariate statistical analysis and stochastic generalized linear model (SGLM). The new approach has an important objective of alarming GNSS network RTK carrier-phase users in case of an error by introducing a multi-layered approach. The network average error corrections and the corresponding variance fields are computed from the data, while the squared Mahalanobis distance (SMD) and Mahalanobis depth (MD) are used as test statistics to detect and remove data from satellites that supply inaccurate data. The variance-covariance matrices are also inspected and monitored to avoid the Heywood effect, i.e. negative variance generated by the processing filters. The quality checks were carried out at both the system and user levels in order to reduce the impact of extreme events on the rover position estimates. The SGLM is used to predict the user carrier-phase and code error statistics. Finally, we present analyses of real-world data sets to establish the practical viability of the proposed methods.

  • 15.
    Sjoberg, Lars E.
    KTH, School of Architecture and the Built Environment (ABE), Real Estate and Construction Management, Geodesy and Satellite Positioning.
    On the geoid and orthometric height vs. quasigeoid and normal height2018In: Journal of Geodetic Science, ISSN 2081-9919, E-ISSN 2081-9943, Vol. 8, no 1, p. 115-120Article in journal (Refereed)
    Abstract [en]

    The geoid, but not the quasigeoid, is an equipotential surface in the Earth's gravity field that can serve both as a geodetic datum and a reference surface in geophysics. It is also a natural zero-level surface, as it agrees with the undisturbed mean sea level. Orthometric heights are physical heights above the geoid, while normal heights are geometric heights (of the telluroid) above the reference ellipsoid. Normal heights and the quasigeoid can be determined without any information on the Earth's topographic density distribution, which is not the case for orthometric heights and geoid. We show from various derivations that the difference between the geoid and the quasigeoid heights, being of the order of 5 m, can be expressed by the simple Bouguer gravity anomaly as the only term that includes the topographic density distribution. This implies that recent formulas, including the refined Bouguer anomaly and a difference between topographic gravity potentials, do not necessarily improve the result. Intuitively one may assume that the quasigeoid, closely related with the Earth's surface, is rougher than the geoid. For numerical studies the topography is usually divided into blocks of mean elevations, excluding the problem with a non-star shaped Earth. In this case the smoothness of both types of geoid models are affected by the slope of the terrain, which shows that even at high resolutions with ultra-small blocks the geoid model is likely as rough as the quasigeoid model. In case of the real Earth there are areas where the quasigeoid, but not the geoid, is ambiguous, and this problem increases with the numerical resolution of the requested solution. These ambiguities affect also normal and orthometric heights. However, this problem can be solved by using the mean quasigeoid model defined by using average topographic heights at any requested resolution. An exact solution of the ambiguity for the normal height/quasigeoid can be provided by GNSS-levelling.

  • 16.
    Sjöberg, Lars E.
    KTH, School of Architecture and the Built Environment (ABE), Real Estate and Construction Management, Geodesy and Satellite Positioning.
    Topographic effects in geoid determinations2018In: Geosciences (Switzerland), ISSN 2076-3263, Vol. 8, no 4, article id 143Article in journal (Refereed)
    Abstract [en]

    Traditionally, geoid determination is applied by Stokes’ formula with gravity anomalies after removal of the attraction of the topography by a simple or refined Bouguer correction, and restoration of topography by the primary indirect topographic effect (PITE) after integration. This technique leads to an error of the order of the quasigeoid-to-geoid separation, which is mainly due to an incomplete downward continuation of gravity from the surface to the geoid. Alternatively, one may start from the modern surface gravity anomaly and apply the direct topographic effect on the anomaly, yielding the no-topography gravity anomaly. After downward continuation of this anomaly to sea-level and Stokes integration, a theoretically correct geoid height is obtained after the restoration of the topography by the PITE. The difference between the Bouguer and no-topography gravity anomalies (on the geoid or in space) is the “secondary indirect topographic effect”, which is a necessary correction in removing all topographic signals. In modern applications of an Earth gravitational model (EGM) in geoid determination a topographic correction is also needed in continental regions. Without the correction the error can range to a few metres in the highest mountains. The remove-compute-restore and Royal Institute of Technology (KTH) techniques for geoid determinations usually employ a combination of Stokes’ formula and an EGM. Both techniques require direct and indirect topographic corrections, but in the latter method these corrections are merged as a combined topographic effect on the geoid height. Finally, we consider that any uncertainty in the topographic density distribution leads to the same error in gravimetric and geometric geoid estimates, deteriorating GNSS-levelling as a tool for validating the topographic mass distribution correction in a gravimetric geoid model.

  • 17.
    Sun, Jing
    KTH, School of Architecture and the Built Environment (ABE), Real Estate and Construction Management, Geodesy and Satellite Positioning.
    The Integration of 3D Geodata and BIM Data in 3D City Models and 3D Cadastre2019Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The initial geographic information system (GIS) and building information modelling (BIM) are designed and developed independently in order to serve different purposes and use. Within the prolific increase and growing maturity of three-dimensional (3D) technology, both 3D geodata and BIM data can specify semantic data and model 3D buildings that are prominent for the 3D city models and 3D cadastre. 3D geodata can be collected from geodetic surveying methods such as total station, laser scanning and photogrammetry and generate 3D building models by CityGML format for macro analysis on city scale. BIM data has significant advantages in planning, designing, modelling and managing building information, which contains rich details of building elements. Additionally, BIM helps and supports to exchange and share complex information through life-cycle project. Because there are some overlaps between them, the integration of BIM and 3D city models is mutually beneficial for representing comprehensive 3D building models.

    This thesis is a summary and compilation of two papers, where one is a review paper published in Journal of Spatial Science, and the other is a research paper currently under review in ISPRS International Journal of Geo-Information. The first paper designed and implemented a methodology to formalize the integration of BIM data into city models (CityGML models) that were generated from BIM data and from ALS/footprint data based on the proposed common modelling guidelines. The geometric results of the CityGML models were compared and evaluated visually and quantitatively. The second paper proposed a general framework for sharing and integrating cadastral information with BIM and 3D GIS together with general requirements. Based on the requirements and framework, the case study focused on how to represent and visualize 3D cadastral boundaries legally and technically by integrating BIM at building level and CityGML at city level. Both the Industry Foundation Classes (IFC) model and the CityGML model were connected to Land Administration Domain Model (LADM) at the conceptual level using Unified Modeling Language (UML) models and on database level.

    The findings of the first paper include investigation of BIM data as a qualified source on the geometric aspects in order to satisfy the need for a more rapid update process of 3D city models, and the second paper shows that the proposed framework and requirements perform well for generating 3D cadastral model in the real-world case study.

  • 18.
    Sun, Jing
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Real Estate and Construction Management, Geodesy and Satellite Positioning.
    Mi, Siying
    Department of Physical Geography and Ecosystem Science, Lund University, 223 62 Lund, Sweden.
    Olsson, Perola
    Department of Physical Geography and Ecosystem Science, Lund University, 223 62 Lund, Sweden.
    Paulsson, Jenny
    KTH, School of Architecture and the Built Environment (ABE), Real Estate and Construction Management, Real Estate Planning and Land Law.
    Harrie, Lars
    Department of Physical Geography and Ecosystem Science, Lund University, 223 62 Lund, Sweden.
    Utilizing BIM and GIS for Representation and Visualization of 3D Cadastre2019In: ISPRS International Journal of Geo-Information, ISSN 2220-9964Article in journal (Other academic)
    Abstract [en]

    The current three-dimensional (3D) property units are in most countries registered using two-dimensional (2D) documentation and textual descriptions. This approach has limitations of representing the actual extent of complicated 3D property units and also to provide an overview of the 3D cadastre in e.g. city centers. To improve the representation and visualization of the 3D cadastre we could utilize 3D digital models. To facilitate this several requirements needs to be considered such as organizations, legal rules, coordinate reference systems and height systems, data standards, geometry and users. In this study, we formulate these requirements and then develop a framework for integration of 3D cadastre and 3D digital models. The basic idea is that cadastral information (stored the in Land Administration Domain Model, LADM) are integrated with Building Information Modelling (BIM) on building level for accurate representation of legal boundaries and with Geographic Information System (GIS) on city level for visualization of 3D cadaster in urban environments. The framework is implemented and evaluated against the requirements in a practical case study in Sweden. The conclusion is that the integration of the cadastral information and BIM/GIS is possible on both conceptual level and data level which will facilitate that organizations dealing with cadastral information (cadastral units), BIM models (architecture, engineering and construction companies) and GIS (surveying units on e.g. municipality level) can exchange information; this facilitates better representation and visualization of 3D cadastral boundaries.

  • 19.
    Sun, Jing
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Real Estate and Construction Management, Geodesy and Satellite Positioning.
    Olsson, Perola
    Department of Physical Geography and Ecosystem Science, Lund University, Lund, Sweden.
    Eriksson, Helen
    Department of Physical Geography and Ecosystem Science, Lund University, Lund, Sweden ; Geodata division, Lantmäteriet, Gävle, Sweden.
    Harrie, Lars
    Department of Physical Geography and Ecosystem Science, Lund University, Lund, Sweden.
    Evaluating the geometric aspects of integrating BIM data into city models2019In: Journal of Spatial Science, ISSN 1449-8596Article in journal (Refereed)
    Abstract [en]

    Airborne Laser Scanning (ALS) is used to acquire three-dimensional(3D) city model data over large areas. However, because of the longALS update cycle, building information models (BIM) could be utilizedto maintain city models. In this study, we designed, implemented, andevaluated a methodology to formalize the integration of BIM data intocity models. CityGML models were created from BIM data and ALS/footprint data based on common modelling guidelines. Both CityGMLbuilding models are modelled in a similar way and the relative differencesbetween the models are on the order of decimetres.

  • 20.
    Tenzer, Robert
    et al.
    Hong Kong Polytech Univ, Dept Land Surveying & Geoinformat, 181 Chatham Rd South, Kowloon, Hong Kong, Peoples R China..
    Chen, Wenjin
    Wuhan Univ, Dept Geodesy & Geomat, Wuhan, Hubei, Peoples R China..
    Baranov, Alexey
    Russian Acad Sci, Schmidt Inst Phys Earth, Moscow, Russia.;Russian Acad Sci, Inst Earthquake Predict Theory & Math Geophys, Moscow, Russia..
    Bagherbandi, Mohammad
    KTH, School of Architecture and the Built Environment (ABE), Real Estate and Construction Management, Geodesy and Satellite Positioning.
    Gravity Maps of Antarctic Lithospheric Structure from Remote-Sensing and Seismic Data2018In: Pure and Applied Geophysics, ISSN 0033-4553, E-ISSN 1420-9136, Vol. 175, no 6, p. 2181-2203Article in journal (Refereed)
    Abstract [en]

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

  • 21.
    Uggla, Gustaf
    KTH, School of Architecture and the Built Environment (ABE), Real Estate and Construction Management, Geodesy and Satellite Positioning.
    Automatic extraction of roadside objects from mobile mapping data2019In: Article in journal (Refereed)
  • 22.
    Uggla, Gustaf
    KTH, School of Architecture and the Built Environment (ABE), Real Estate and Construction Management, Geodesy and Satellite Positioning.
    Classification and object reconstruction in point clouds using semantic segmentation and transfer learning2019Conference paper (Refereed)
  • 23.
    Uggla, Gustaf
    KTH, School of Architecture and the Built Environment (ABE), Real Estate and Construction Management, Geodesy and Satellite Positioning.
    Connecting digital and physical representations through semantics and geometry2019Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The fields of geodesy and building information modeling (BIM) meet each other in the intersection between the physical and the digital world. Within the construction industry, the role of geodesy has typically been to describe the position of assets and to transform the geometries of those assets between coordinate systems suitable for design and coordinate systems with a known relation to the Earth. This is not changed by the introduction of BIM but rather emphasized by it, as higher degrees of automation and prefabrication increases the need for strict and non-distorting transformations. The objectoriented aspects of BIM require that captured geodata can be semantically classified and that objects can be reconstructed and extracted from the geodata. In this landscape, geodesy is the bridge between model and reality, connecting the two worlds through both semantics and geometry. This thesis is a comprehensive summary of three papers within these two topics. The first paper describes the geometric transformations required throughout the life cycle of a built asset and assesses the georeferencing capabilities of the open BIM standard Industry Foundation Classes (IFC). The second and third paper propose and showcase a methodology where image-based deep learning is used to extract roadside objects from mobile mapping data. The findings of the first paper include suggestions for how IFC can be improved in order to facilitate better georeferencing, and the second and third paper show that the proposed methodology performs well in comparison to a manual classification.

  • 24.
    Uggla, Gustaf
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Real Estate and Construction Management, Geodesy and Satellite Positioning.
    Horemuz, Milan
    KTH, School of Architecture and the Built Environment (ABE), Real Estate and Construction Management, Geodesy and Satellite Positioning.
    Geographic capabilities and limitations of Industry Foundation Classes2018In: Automation in Construction, ISSN 0926-5805, E-ISSN 1872-7891, Vol. 96, p. 554-566Article in journal (Refereed)
    Abstract [en]

    Infrastructure design is conducted in a 3D Cartesian coordinate system with the assumption that the Earth is flat and that the scale is constant over the entire project area. Map projections are commonly used to georeference the designed geometries before constructing them on the surface of the Earth. The scale in a map projection varies depending on the position in the map plane, which leads to scale distortions between the designed geometries and the geometries staked out for construction. These distortions are exaggerated for large longitudinal projects such as the construction of roads and railroads because the construction site spans a larger area. Building Information Modeling (BIM) is increasing in popularity as a way to manage information within a construction project. Its use is more widespread in the building industry, but it is currently being adopted by the infrastructure industry as well. The open BIM standard IFC (Industry Foundation Classes) has recently developed support for alignment geometries, and full support for disciplines such as road and railroad construction is underway. This study tests whether the current IFC standard can facilitate georeferencing with sufficiently low distortion for the construction of infrastructure. This is done by performing georeferencing using three different methods, all using the information provided in the IFC schema, and by calculating the scale distortions caused by the different methods. It is concluded that the geographic capabilities of the IFC schema could be improved by adding a separate scale factor for the horizontal plane and support for object-specific map projections.

  • 25.
    Uggla, Gustaf
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Real Estate and Construction Management, Geodesy and Satellite Positioning.
    Horemuz, Milan
    KTH, School of Architecture and the Built Environment (ABE), Real Estate and Construction Management, Geodesy and Satellite Positioning.
    Georeferencing Methods for IFC2018In: Proceedings - 2018 Baltic Geodetic Congress, BGC-Geomatics 2018, Institute of Electrical and Electronics Engineers Inc. , 2018, p. 207-211Conference paper (Refereed)
    Abstract [en]

    Building Information Modelling (BIM) is becoming a standard tool for information management throughout the life cycle of a construction project. Elements in BIM are designed in a Cartesian coordinate system (Engineering system) with no direct relation to the project's geographic location. Accurate georeferencing of BIM data is required both for construction and integration with Geographic Information Systems (GIS), as improperly treated or neglected scale distortions can lead to costly delays in construction as problems requiring ad hoc solutions may arise on site Industry Foundation Classes (IFC) is an open BIM standard developed by buildingSMART, and the current version IFC 4 has recently been extended with IFC Alignment, which includes support for alignment geometries used for infrastructure design. This paper investigates the geographic capabilities of IFC 4 and its extension IFC Alignment. The study identifies a lack of support for non-uniform scale factors and object-specific map projections as the largest weaknesses.

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