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  • 201.
    Niu, Xin
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Ban, Yifang
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Multitemporal Polarimetric RADARSAT-2 SAR Data for Urban Land Cover Mapping Through a Dictionary-based and a Rule-based Model Selection in a Contextual SEM Algorithm2013In: Canadian journal of remote sensing, ISSN 0703-8992, E-ISSN 1712-7971, Vol. 39, no 2, p. 138-151Article in journal (Refereed)
    Abstract [en]

    This paper presents a dictionary-based and a rule-based model selection approach in an adaptive contextual semi-supervised algorithm for improving urban land cover classification using high-resolution multitemporal RADARSAT-2 polarimetric SAR (PolSAR) data.  Six-date PolSAR data were acquired during June to September, 2008 over the Greater Toronto Area. Contextual information and the capabilities of different PolSAR distribution models were explored by the spatially variant Finite Mixture Model (FMM) with an adaptive Markov Random Field (MRF) in a Stochastic Expectation-Maximization (SEM) algorithm. This algorithm can obtain homogenous results while preserving shape details in the complex urban environment with high accuracy. Commonly used PolSAR distribution models such as Wishart, G0p, Kp and KummerU were compared through the proposed approaches for urban land cover mapping. According to a Goodness-of-fit test based on Mellin transformation, accurate PolSAR distribution model could be selected with the dictionary-based classification. However, the results showed that improvement by the dictionary-based approach was limited. Therefore, further improvements were expected by exploring expert knowledge. The initial results showed that G0p and KummerU performed better for distinguishing between low density built-up areas and forest. G0p, Kp and KummerU are better for the low scattering classes. The Wishart model has superior capacity in separating high density built-up areas and the adjacent roads. Based on such knowledge, a set of rules were developed to integrate the advantages of alternative models. Significant improvement on the overall classification accuracy could be observed by such rule-based approach. The biggest improvement was achieved using HD-Road rule on G0p model with the best overall classification accuracy at 89.99% (kappa: 0.87). This represented 4.1% (kappa: 0.045) improvement over that of G0p without model selection.

  • 202.
    Niu, Xin
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Ban, Yifang
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Multi-temporal RADARSAT-2 polarimetric SAR data for urban land-cover classification using an object-based support vector machine and a rule-based approach2013In: International Journal of Remote Sensing, ISSN 0143-1161, E-ISSN 1366-5901, Vol. 34, no 1, p. 1-26Article in journal (Refereed)
    Abstract [en]

    We have investigated multi-temporal polarimetric synthetic aperture radar (SAR) data for urban land-cover classification using an object-based support vector machine (SVM) in combinations of rules. Six-date RADARSAT-2 high-resolution polarimetric SAR data in both ascending and descending passes were acquired in the rural-urban fringe of the Greater Toronto Area during the summer of 2008. The major land-use/land-cover classes include high-density residential areas, low-density residential areas, industrial and commercial areas, construction sites, parks, golf courses, forests, pasture, water, and two types of agricultural crops. Various polarimetric SAR parameters were evaluated for urban land-cover mapping and they include the parameters from Pauli, Freeman and Cloude-Pottier decompositions, the coherency matrix, intensities of each polarization, and their logarithm forms. The multi-temporal SAR polarimetric features were classified first using an SVM classifier. Then specific rules were developed to improve the SVM classification results by extracting major roads and streets using shape features and contextual information. For the comparison of the polarimetric SAR parameters, the best classification performance was achieved using the compressed logarithmic filtered Pauli parameters. For the evaluation of the multi-temporal SAR data set, the best classification result was achieved using all six-date data (kappa = 0.91), while very good classification results (kappa = 0.86) were achieved using only three-date polarimetric SAR data. The results indicate that the combination of both the ascending and the descending polarimetric SAR data with an appropriate temporal span is suitable for urban land-cover mapping.

  • 203.
    Niu, Xin
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatik och Geodesi.
    Ban, Yifang
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatik och Geodesi.
    Multitemporal RADARSAT-2 polarimetric SAR data for urban cover classification using support vector machine2010In: 30th EARSeL Symposium, Paris, France, June, 2010, 2010, p. 581-588Conference paper (Refereed)
    Abstract [en]

    This research investigates the various RADARSAT-2 polarimetric SAR features for urban land cover classification using object-based method combining with support vector machine (SVM) and ruled-based approach. Six-dates of RADARSAT-2 fine-beam polarimetric SAR data were acquired in the rural-urban fringe of Greater Toronto Area during June to September, 2008. The major landuse/land-cover classes were high-density built-up areas, low-density built-up areas, roads, forests, parks, golf courses, water and several types of agricultural crops. The polarimetric SAR features examined are the parameters from Pauli, Freeman and Cloude-Pottier decompositions as well as the elements from coherence matrix and the intensities and their logarithm form of each channel. For urban land cover classification, SVM is combined with rule-based method for the object-based classification. The image objects containing the multitemporal polarimetric features were classified using the SVM classifier first. The SVM classification results were further refined using a rule-based approach. Rules were built to recognize specific classes defined by the shape features and the spatial relationships within the context. In terms of the effectiveness of different SAR ploarimtric parameters, the results indicated that the processed Pauli feature set could produce best classification result while the use of all the polarimetric features did not produce the best classification result. The raw Pauli parameters could generate similar result as all T elements. The logarithm parameters such as log intensity and processed Pauli parameters perform better than the intensity and raw Pauli respectively. The proposed object-based classification using SVM and rule-based approach yielded higher classification accuracies than the object-based classification using nearest neighbor classifier. 

     

     

     

  • 204.
    Niu, Xin
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Ban, Yifang
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    RADARSAT-2 fine-beam polarimetric and ultra-fine beam SAR data for urban land cover mapping: Comparison and SynergyManuscript (preprint) (Other academic)
    Abstract [en]

    This paper investigates the capabilities of multitemporal RADARSAT-2 fine-beam polarimetric SAR (PolSAR) data and ultra-fine beam C-HH SAR data for the detailed urban land cover mapping using a novel contextual approach. With an adaptive Markov Random Field (MRF) and the spatially variant Finite Mixture Model (FMM), contextual information was effectively explored to improve the mapping accuracy. The results showed that the contextual approach could produce homogenous classification while preserve shape details. Compared with C-HH SAR, PolSAR data were important for identify various urban patterns. Nevertheless, efficiency of the C-HH SAR textures for extraction of the built-up area was observed. Thus we proposed a texture enhancement in FMM to further improve the classification accuracy. Moreover, a rule-based approach employing object features and spatial relationships has been used to extract the road, street and park with reasonable accuracy. Three-date RADARSAT-2 fine-beam PolSAR and three-date ultra-fine beam C-HH SAR data over the Greater Toronto Area were used for the evaluation.  

  • 205.
    Niu, Xin
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatik och Geodesi.
    Ban, Yifang
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatik och Geodesi.
    RADARSAT-2 polarimetric SAR data for urban land cover mapping using spatial- temporal SEM algorithm and mixture models2011In: 6th Joint Urban Remote Sensing Event (JURSE 2011), Munich, Germany, April 2011, 2011, p. 241-244Conference paper (Refereed)
  • 206. Novák, P.
    et al.
    Tenzer, R.
    Eshagh, Mehdi
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Bagherbandi, Mohammad
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Evaluation of gravitational gradients generated by Earth's crustal structures2013In: Computers & Geosciences, ISSN 0098-3004, E-ISSN 1873-7803, Vol. 51, p. 22-33Article in journal (Refereed)
    Abstract [en]

    Spectral formulas for the evaluation of gravitational gradients generated by upper Earth's mass components are presented in the manuscript. The spectral approach allows for numerical evaluation of global gravitational gradient fields that can be used to constrain gravitational gradients either synthesised from global gravitational models or directly measured by the spaceborne gradiometer on board of the GOCE satellite mission. Gravitational gradients generated by static atmospheric, topographic and continental ice masses are evaluated numerically based on available global models of Earth's topography, bathymetry and continental ice sheets. CRUST2.0 data are then applied for the numerical evaluation of gravitational gradients generated by mass density contrasts within soft and hard sediments, upper, middle and lower crust layers. Combined gravitational gradients are compared to disturbing gravitational gradients derived from a global gravitational model and an idealised Earth's model represented by the geocentric homogeneous biaxial ellipsoid GRS80. The methodology could be used for improved modelling of the Earth's inner structure.

  • 207.
    Ohlsson, Kent
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Studie av mätosäkerhet och tidskorrelationer vid mätning med nätverks-RTK i Swepos 35 km-nät2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [sv]

    GNSS-mätning med nätverks-RTK är en satellitbaserad geodetisk mätningsmetod som reducerar inverkande felkällor genom relativ mätning mot ett nät av fasta referensstationer.I Sverige har Lantmäteriet upprättat ett nät av fasta referensstationer kallat Swepos med ca 70 km mellan referensstationerna. En förtätning av Swepos-nätet till ca 35 km mellan referensstationerna pågår och beräknas vara klar 2015. Det finns tidigare studier (Emardson m fl (2009) och Odolinski (2010 a)) kring osäkerheten vid mätning i områden med ca 70 km mellan referensstationerna och vid ett projektanpassat nät med ca 10-20 km mellan referensstationerna. Studierna undersöker också hur lång tid som behöver gå mellan två mätningar för att de ska anses oberoende av varandra (korrelationstid). Detta arbete beräknar standardosäkerhet och korrelationstider vid mätning i det förtätade 35 km-nätet baserat på statiska GNSS-mätningar på olika avstånd från närmaste referensstation samt data från en permanent monitorstation belägen i Växjö.Standardosäkerheten (68% konfidensnivå) för mätningarna, vid förhållandena i denna studie, var vid mätning 0,1 km från närmaste referensstation 3,8 mm i plan och 6,9 mm i höjd (höjd över ellipsoiden). Vid mätning 8,8 km från närmaste referensstation var standardosäkerheten 6,3 mm i plan och 9,6 mm i höjd (höjd över ellipsoiden) och 15,8 km från närmaste referensstation var motsvarande värden 6,3 mm i plan och 10,5 mm i höjd (höjd över ellipsoiden). Detta tyder på att avståndet från närmaste referensstation troligtvis har viss betydelse för standardosäkerheten vid GNSS-mätning med nätverks-RTK. Under förhållandena för mätningarna inom denna studie ökar standardosäkerheten med avståndet till referensstationen. Ökningen av standardosäkerheten verkar dock avta vid längre avstånd till närmaste referensstation.Växjö-monitorn gav klart högre osäkerhetsvärden (11,5 mm i plan och 19,8 mm i höjd) trots liknande avstånd till referensstationen som punkten längst från referensstationen. Detta indikerar att det även finns andra faktorer än just avståndet till närmaste referensstation som påverkar mätosäkerheten.Korrelationstider skattades utifrån månadslånga perioder av monitordata till ca 22-23 minuter för mätning med nätverks-RTK i Swepos 35 km-nät. Detta gäller både plan och höjd men ska ses som en ungefärlig uppskattning av tiden som krävs för att en mätning, vid återbesök av en punkt, ska anses vara oberoende av en tidigare mätning. Tar vi inte hänsyn till tidskorrelationen kan osäkerheten i mätningar nära varandra i tiden underskattas. Mätningar under en kortare tidsperiod med en låg standardosäkerhet, kan i själva verket innehålla en systematisk avvikelse beroende på att mätningarna är korrelerade och därmed påverkade av ett liknande fel.Det ska dock nämnas att det finns en rad andra parametrar som inverkar vid GNSS-mätningar som inte har behandlats i detta arbete, t ex den lokalt omgivande miljön vid mätplatsen, väder-förhållanden och osäkerhet i de lokala referensstationerna. Eventuella användarrelaterade fel, t ex centrings- och horisonteringsfel av antennen liksom osäkerhet vid mätning av antennhöjden, är inte heller inkluderade i de beräknade standardosäkerhetsvärdena.

  • 208.
    Ornum, Mary Joy Silverio
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatik och Geodesi.
    Design of a Flexible Location-Based Services Architecture2010Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 209.
    Parsanezhad, Pouriya
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatik och Geodesi.
    Ranhagen, Ulf
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment.
    Ban, Yifang
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatik och Geodesi.
    Towards an Integrated Web-based Visualization Tool: A Comparative Survey of Visualization Techniques for Enhancing Stakeholders’ Participation in Planning2011In: Proceedings of SIGRAD 2011: Evaluations of Graphics and Visualization — Efficiency, Usefulness, Accessibility, Usability. November 17–18, 2011 KTH, Stockholm, Sweden / [ed] Thomas Larsson, Lars Kjelldahl & Kai-Mikael Jää-Aro, Linköping University Electronic Press, 2011, p. 61-68Conference paper (Refereed)
    Abstract [en]

    Digital visualization tools are widely used in planning nowadays around the world by various contributors to the field and in different planning scales. Visualization facilitates perception of underlying thoughts and objectives of planning alternatives and consequently assists with communication of the plan to different stakeholders. This, in turn, enables them to actively and efficiently participate in the procedure from the very initial stages to the implementation phase thanks to the insight provided by user-friendly visualization tools. Available visualization tools for planning, however, are either not integrated and efficient enough or too resource- or expertise-demanding and thus not entirely fulfilling the qualities mentioned above. This study is a search for a conceptual framework for an integrated web-based visualization tool. Web-accessibility diminishes temporal and spatial distance among the users and planning agents and provides the possibility for more participation in and interaction with planning projects. Within this study, major characteristics of an integrated tool have been investigated through literature, online resources, contacts with experts and practitioners, a survey over off-the-shelf products and comparative analysis of the outcomes. An evaluation cube was initially developed and used as the basis for provision of a set of dual criteria. A selection of visualization tools were examined against those criteria and results were demonstrated visually. Eventually, findings were used to provide a back-casted example of the integrated tool.

  • 210.
    Peppa, Maria Valasia
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Precision analysis of 3D camera2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Three dimensional mapping is becoming an increasingly attractive product nowadays. Many devices like laser scanner or stereo systems provide 3D scene reconstruction. A new type of active sensor, the Time of Flight (ToF) camera obtains direct depth observations (3rd dimensional coordinate) in a high video rate, useful for interactive robotic and navigation applications. The high frame rate combined with the low weight and the compact design of the ToF cameras constitute an alternative solution of the 3D measuring technology. However a deep understanding of the error involved in the ToF camera observations is essential in order to upgrade their accuracy and enhance the ToF camera performance.

    This thesis work addresses the depth error characteristics of the SR4000 ToF camera and indicates potential error models for compensating the impact. In the beginning of the work the thesis investigates the error sources, their characteristics and how they influence the depth measurements. In the practical part, the work covers the above analysis via experiments. Last, the work proposes simple methods in order to reduce the depth error so that the ToF camera can be used for high accuracy applications.  

    An overall result of the work indicates that the depth acquired by the Time of Flight (ToF) camera deviates several centimeters, specifically the SR4000 camera provides 35 cm error size for the working range of 1-8 m. After the error compensation the depth offset fluctuates 15cm within the same working range. The error is smaller when the camera is set up close to the test field than when it is further away.

  • 211.
    Persson, Erik
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatik och Geodesi.
    Olika metoder för positionering och inventering av träd i stadsmiljö2011Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    There are several advantages with establishing a database of the trees of a city. The trees contribute great value ​​to the urban environment and are therefore important to take care of, especially because urban trees often live in a stressed habitat. In order to establish a database of the trees of a city, there are various methods to perform an inventory. The two main areas are field methods and techniques based on remote sensing. The field methods can be divided into terrestrial surveying with a total station and measurement with some kind of hand-held GNSS receiver. The remote methods that are of interest when analyzing trees can be divided into laser scanning and aerial photographic methods. The different methods are described in the report and their possibilities, advantages and disadvantages are investigated.

    The method that over a larger area may be considered to be most effective begins with a laser scanning. From the laser data each tree can be detected and information about tree height and also some information about tree species can be extracted. If more information about the trees is needed, a near-infrared orthophoto can be used. With some manual processing tree species can then be extracted with greater certainty.

    To improve possibilities and accuracy for determining wood affiliation hyper spectral images could be used. These are however not yet implemented in commercial procedures and more research is needed.

    The database obtained from the procedure described above may, decided by demand and budget, be supplemented with field surveys to obtain the desired attributes.

  • 212. Piwowar, Joseph M.
    et al.
    Ban, Yifang
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Foreword to the Special Issue on the Analysis of Multitemporal Remote Sensing Images2014In: IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, ISSN 1939-1404, E-ISSN 2151-1535, Vol. 7, no 8, p. 3187-3189Article in journal (Refereed)
  • 213.
    Prelipcean, Adrian Corneliu
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Capturing travel entities to facilitate travel behaviour analysis: A case study on generating travel diaries from trajectories fused with accelerometer readings2016Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The increase in population, accompanied by an increase in the availability of travel opportunities have kindled the interest in understanding how people make use of the space around them and their opportunities. Understanding the travel behaviour of individuals and groups is difficult because of two main factors: the travel behaviour's wide coverage, which encompasses different research areas, all of which model different aspects of travel behaviour, and the difficulty of obtaining travel diaries from large groups of respondents, which is imperative for analysing travel behaviour and patterns.

    A travel diary allows an individual to describe how she performed her activities by specifying the destinations, purposes and travel modes occurring during a predefined period of time. Travel diaries are usually collected during a large-scale survey, but recent developments show that travel diaries have important drawbacks such as the collection bias and the decreasing response rate. This led to a surge of studies that try to complement or replace the traditional declaration-based travel diary collection with methods that extract travel diary specific information from trajectories and auxiliary datasets.

    With the automation of travel diary generation in sight, this thesis presents a suitable method for collecting data for travel diary automation (Paper I), a framework to compare multiple travel diary collection systems (Paper II), a set of relevant metrics for measuring the performance of travel mode segmentation methods (Paper III), and applies these concepts during different case studies (Paper IV).

  • 214.
    Prelipcean, Adrian Corneliu
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Implementation and evaluation of Space Time Alarm Clock2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Many modern mobile communication devices are equipped with a GPS receiver and anavigation tool. These devices are useful when a user seeks to reach a specified destinationas soon as possible, but may not be so when he/she only needs to arrive at thedestination in time and wants to focus on some activities on the way. To deal with thislatter situation, a method and device called “Space Time Alarm Clock” is presented forhelping the user reach the destination by a specified deadline and inform the user aboutthe consequences of his/her decisions. It does so by continuously and efficiently computinghow much more time the user may stay at his/her current location without failing toreach the destination by the deadline. Furthermore, it determines the possible movementchoices that a user can make with regards to an underlying road network, it computesthe shortest travel time associated with each choice and informs the user about the consequencesof his/her decisions. Advantage of this approach is that it works completelyin the background so that the user‘s en-route activities will never be interfered with. The“Space Time Alarm Clock” was implemented for Stockholm, where it was tested.

  • 215.
    Prelipcean, Adrian Corneliu
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Gidofalvi, Gyözö
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Mobility Collector: Battery Conscious Mobile Tracking2013In: Mobile Ghent 2013, 2013Conference paper (Refereed)
    Abstract [en]

    Tracking and analyzing the location of users to understand, to predict (and ultimately control) the movement of humans (or animals) has been an important part of research in different groups such as human geographers, urban planers, behavioral scientists or movement ecologists. Despite the availability of tracking technology, the above research activities have been limited by: 1)the spatial granularity of tracking data, 2) the willingness of users to share their private 3) the fact that a tracking mobile application drains a user's battery, and last but not least 4) the absence of a generic, configurable, open-source trajectory collector and annotator. Most studies that exceeded this barrier restrict the collection to settings where an obvious “unlimited” power source is available (i.e., taxi cabs and cars). Thus, to combat the aforementioned limitations, this paper describes the features and design of the Mobility Collector, a configurable, open-source, battery conscious Android mobile tracking application and provides a prototype implementation that works uniformly across multiple hardware devices and Android OS versions.According to the official Android developer's web page [weblink], two main parameters are considered when requesting location updates: minTime, which controls the location update interval and minDistance, which is the minimum distance between location updates. The intended advantage of the method, i.e., battery preserving equitime location sampling, is linked to a degradation of spatial data quality. This approach is relevant for the majority of mapping-oriented applications, which require data that is equally distributed in time, but, in the case of tracking services, an implementation that focuses mostly on equidistance sampling can be vital in order to accurately determine and infer activities while being aware of the user's context.The Mobility Collector provides high quality data in a battery conscious manner. On one hand, the custom implementation of the Location Manager class using a linear movement model based on the recent samples, which duty-cycles the parameters dynamically, allows the data to have a high spatial granularity, making it suitable for different tracking settings (Figure 1, Table 1). On the other hand, the battery life is considerably extended by using a motion-enabled alarm, which switches the servicethat gets location updates on and off, thus allowing for any Android phone to be used for data collection without compromising its usability (Figure 2). While using the Mobility Collector, the usability of a phone is approximately 75% of the daily basis usage plan.The Mobility Collector was designed specifically for research purposes and it offers a high degree of extensibility and usability. First, the source-code will be provided for customization and the platform can be configured either as a standalone client application or as part of a client-server architecture. Second, it provides a configurable user-friendly interface for point- and period-based trajectory annotation. Finally, while the configuration can be done manually by modifying the source-code, a web client that takes configuration-specific parameters (i.e., equitime vs. equidistance sampling, sampling frequency, annotations, etc.) and produces a version of the application according to specific needs is available.

  • 216.
    Prelipcean, Adrian Corneliu
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics. KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport and Location Analysis.
    Gidofalvi, Gyözö
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatics.
    Susilo, Yusak
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Transport and Location Analysis.
    Transportation mode detection – an in-depth review of applicability and reliability2016In: Transport reviews, ISSN 0144-1647, E-ISSN 1464-5327Article in journal (Refereed)
    Abstract [en]

    The wide adoption of location-enabled devices, together with the acceptance of services that leverage (personal) data as payment, allows scientists to push through some of the previous barriers imposed by data insufficiency, ethics and privacy skepticism. The research problems whose study require hard-to-obtain data (e.g. transportation mode detection, service contextualisation, etc.) have now become more accessible to scientists because of the availability of data collecting outlets. One such problem is the detection of a user's transportation mode. Different fields have approached the problem of transportation mode detection with different aims: Location-Based Services (LBS) is a field that focuses on understanding the transportation mode in real-time, Transportation Science is a field that focuses on measuring the daily travel patterns of individuals or groups of individuals, and Human Geography is a field that focuses on enriching a trajectory by adding domain-specific semantics. While different fields providing solutions to the same problem could be viewed as a positive outcome, it is difficult to compare these solutions because the reported performance indicators depend on the type of approach and its aim (e.g. the real-time availability of LBS requires the performance to be computed on each classified location). The contributions of this paper are three fold. First, the paper reviews the critical aspects desired by each research field when providing solutions to the transportation mode detection problem. Second, it proposes three dimensions that separate three branches of science based on their main interest. Finally, it identifies important gaps in research and future directions, that is, proposing: widely accepted error measures meaningful for all disciplines, methods robust to new data sets and a benchmark data set for performance validation.

  • 217.
    Prelipcean, Adrian Corneliu
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, System Analysis and Economics.
    Gidofalvi, Gyözö
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics. KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatics.
    Susilo, Yusak Octavius
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, System Analysis and Economics.
    Longest common subsequences: Identifying the stability of individuals’ travel patternsManuscript (preprint) (Other academic)
    Abstract [en]

    There is a strong consensus in the travel behaviour research community that the one day travel diary collection is insufficient to understand the finer aspects of behaviour that transcend attributes such as average trip length, duration, travel modes, etc. While a large body research was done on exploring the spatial, temporal and spatio-temporal travel behavioural patterns, the sequential aspect of behaviour is seldom studied. The consensus of the few papers that have studied travel behaviour variability from a sequential perspective has been to use edit distance and compute the costs of transforming one day of travel activities into another. While useful, this approach generates difficult to understand metrics since it does not directly extract (sub)sequences but computes penalties. This paper provides an alternative for investigating the sequential aspect of travel behaviour that makes use of longest common subsequences to extract the activities that are common to multiple days and / or users. The proposed methodology provides indexes for measuring the inter- and intra-personal stability of a given user base and its usefulness is proved in a case study on travel diaries collected from 51 users for a period of 7 days.

  • 218.
    Prelipcean, Adrian Corneliu
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Gidofalvi, Gyözö
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Susilo, Yusak Octavius
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, System Analysis and Economics.
    Measures of transport mode segmentation of trajectories2016In: International Journal of Geographical Information Science, ISSN 1365-8816, E-ISSN 1365-8824, Vol. 30, no 9, p. 1763-1784Article in journal (Refereed)
    Abstract [en]

    Rooted in the philosophy of point- and segment-based approaches for transportation mode segmentation of trajectories, the measures that researchers have adopted to evaluate the quality of the results (1) are incomparable across approaches, hence slowing the progress in the field and (2) do not provide insight about the quality of the continuous transportation mode segmentation. To address these problems, this paper proposes new error measures that can be applied to measure how well a continuous transportation mode segmentation model performs. The error measures introduced are based on aligning multiple inferred continuous intervals to ground truth intervals, and measure the cardinality of the alignment and the spatial and temporal discrepancy between the corresponding aligned segments. The utility of this new way of computing errors is shown by evaluating the segmentation of three generic transportation mode segmentation approaches (implicit, explicit–holistic, and explicit–consensus-based transport mode segmentation), which can be implemented in a thick client architecture. Empirical evaluations on a large real-word data set reveal the superiority of explicit–consensus-based transport mode segmentation, which can be attributed to the explicit modeling of segments and transitions, which allows for a meaningful decomposition of the complex learning task.

  • 219.
    Prelipcean, Adrian Corneliu
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Gidofalvi, Gyözö
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Susilo, Yusak Octavius
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, System Analysis and Economics.
    Mobility Collector2014In: Journal of Location Based Services, ISSN 1748-9725, Vol. 8, no 4, p. 229-255Article in journal (Refereed)
    Abstract [en]

    Despite the availability of mobile positioning technologies and scientists' interests in tracking, modelling and predicting the movements of individuals and populations, these technologies are seldom efficiently used. The continuous changes in mobile positioning and other sensor technologies overburden scientists who are interested in data collection with the task of developing, implementing and testing tracking algorithms and their efficiency in terms of battery consumption. To this extent, this article proposes an adaptive, battery conscious tracking algorithm that collects trajectory data fused with accelerometer data and presents Mobility Collector, which is a prototype platform that, using the tracking algorithm, can produce highly configurable, off-the-shelf, multi-user tracking systems suitable for research purposes. The applicability of the tracking system is tested within the transport science domain by collecting labelled movement traces and related motion data, i.e. accelerometer data and derived information (number of steps and other useful movement features based on temporal aggregates of the raw readings) to develop and evaluate a method that automatically classifies the transportation mode of users with a 90.8% prediction accuracy.

  • 220.
    Prelipcean, Adrian Corneliu
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Schmid, Falko
    Bremen University.
    Shirabe, Takeshi
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    A Space Time Alarm2015In: Progress in Location-Based Services 2014 / [ed] Georg Gartner,Haosheng Huang, Springer, 2015, p. 187-198Chapter in book (Refereed)
    Abstract [en]

    Many modern mobile communication devices are equipped with a global positioning systems (GPS) receiver and a navigation tool. These devices are useful when a user seeks to reach a specified destination as soon as possible, but may not be so when he/she only needs to arrive at the destination in time and wants to focus on some activities on the way. To deal with this latter situation, a method and device called “Space Time Alarm” is presented for helping the user reach the destination by a specified deadline. It does so by continuously and efficiently computing how much more time the user may stay at his/her current location without failing to reach the destination by the deadline. Advantage of this approach is that it works completely in the background so that the user’s en route activities will not be interfered with.

  • 221.
    Prelipcean, Adrian Corneliu
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, System Analysis and Economics.
    Susilo, Yusak Octavius
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, System Analysis and Economics.
    Gidofalvi, Gyözö
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics. KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatics.
    A series of three case studies on the semi-automation of activity travel diary generation using smarpthones2017In: Proceedings of TRB 2017 Annual Meeting, 2017Conference paper (Refereed)
    Abstract [en]

    The growing need of acquiring data that is useful for travel behaviour analysis led scientists topursue new ways of obtaining travel diaries from large groups of people. The most promising al-ternative to traditional (declarative) travel diary collection methods are those that rely on collectingtrajectories from individuals and then extract travel diary semantics from the trajectories. However,most studies report on routines specific to the post-processing of data, and seldom focus on datacollection. Even the few studies that deal explicitly with data collection describe the final state ofthe collection system, but do not go at the lengths that are required to describe the decision thatwere taken to bring the system to its current state. This leads to a considerable amount of work thatis needed for designing collection systems that are often undocumented, which impedes the reuseof the aforementioned systems. In light of the aforementioned problems, this paper presents a series of three case studies behind the continuous development of MEILI, a travel diary collection,annotation and automation system, in an effort to: 1) illustrate the utility of the developed systemto collect travel diaries, 2) identify how MEILI and other semi-automatic travel diaries collectionsystems can be improved, and 3) propose MEILI as an open source system that has the potentialof being improved into a widely available semi-automated travel diary collection system.

  • 222.
    Prelipcean, Adrian Corneliu
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, System Analysis and Economics.
    Susilo, Yusak Octavius
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, System Analysis and Economics.
    Gidofalvi, Gyözö
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics. KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatics.
    Future directions of research for automatic travel diary collection2018In: Proceedings of the 11th International conference on Transport Survey Methods, 2018Conference paper (Refereed)
    Abstract [en]

    The amount of useful information that can be extracted from travel diaries is matched by the difficulty of obtaining travel diariesin a modern era where the response rate to traditional travel diary collection methods has seen a decrease in most countries.Prompted by this, a body of research has been dedicated to study how travel diaries can be collected via new methods, namelylocation enabled devices such as smartphones, that have a higher penetration rate (in terms of device ownerships and userattachment) and are both easier and cheaper to manage compared to traditional data collection method, e.g. paper-and-pencil,phone, or web-based questionnaires. This paper offers an overview of the current state of travel diary collection, a potentialfuture state and a practical checklist for travel diary collection case studies. A thorough discussion on different pros and cons oftravel diary collection methods and efforts needed for the convergence of methods to collect travel diaries for all demographicsare provided. The practical checklist to aid researchers to organise case studies is based on the authors’ experience and it is meantto raise awareness of difficulties that can be encountered while collecting travel surveys with automated and semi-automatedsystems, and how to overcome them.

  • 223.
    Qin, Yuchu
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    From LiDAR waveform to Urban Land Cover Map: Modeling, Processing and Application2014Doctoral thesis, comprehensive summary (Other academic)
  • 224.
    Qin, Yuchu
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Niu, Z.
    Chen, F.
    Li, B.
    Ban, Yifang
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Object-based land cover change detection for cross-sensor images2013In: International Journal of Remote Sensing, ISSN 0143-1161, E-ISSN 1366-5901, Vol. 34, no 19, p. 6723-6737Article in journal (Refereed)
    Abstract [en]

    Accurate and timely land cover change detection at regional and global scales is necessary for both natural resource management and global environmental change studies. Satellite remote sensing has been widely used in land cover change detection over the past three decades. The variety of satellites which have been launched for Earth Observation (EO) and the large volume of remotely sensed data archives acquired by different sensors provide a unique opportunity for land cover change detection. This article introduces an object-based land cover change detection approach for cross-sensor images. First, two images acquired by different sensors were stacked together and principal component analysis (PCA) was applied to the stacked data. Second, based on the Eigen values of the PCA transformation, six principal bands were selected for further image segmentation. Finally, a land cover change detection classification scheme was designed based on the land cover change patterns in the study area. An image-object classification was implemented to generate a land cover change map. The experiment was carried out using images acquired by Landsat 5 TM and IRS-P6 LISS3 over Daqing, China. The overall accuracy and kappa coefficient of the change map were 83.42% and 0.82, respectively. The results indicate that this is a promising approach to produce land cover change maps using cross-sensor images.

  • 225.
    Qin, Yuchu
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatik och Geodesi.
    Vu, Tuong Thuy
    University of Nottingham, Malaysia Campus.
    Ban, Yifang
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatik och Geodesi.
    Toward an Optimal Algorithm for LiDAR Waveform Decomposition2012In: IEEE Geoscience and Remote Sensing Letters, ISSN 1545-598X, E-ISSN 1558-0571, Vol. 9, no 3, p. 482-486Article in journal (Refereed)
    Abstract [en]

    This letter introduces a new approach for light detection and ranging (LiDAR) waveform decomposition. First, inflection points are identified by the Ramer-Douglas-Peucker curve-fitting algorithm, and each inflection point has a corresponding baseline during curve fitting. Second, according to the spatial relation between the baseline and the inflection point, peaks are selected from the inflection points. The distance between each peak and its baseline and the maximum number of peaks are employed as a criterion to select a "significant" peak. Initial parameters such as width and boundaries of peaks provide restraints for the decomposition; right and left boundaries are estimated via a conditional search. Each peak is fitted by a Gaussian function separately, and other parts of the waveform are fitted as line segments. Experiments are implemented on waveforms acquired by both small-footprint LiDAR system LMS-Q560 and large-footprint LiDAR system Laser Vegetation Imaging Sensor. The results indicate that the algorithm could provide an optimal solution for LiDAR waveform decomposition.

  • 226.
    Qin, Yuchu
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Vu, Tuong Thuy
    Ban, Yifang
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Niu, Zheng
    Range determination for generating point clouds from airborne small footprint LiDAR waveforms2012In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 20, no 23, p. 25935-25947Article in journal (Refereed)
    Abstract [en]

    This paper presents a range determination approach for generating point clouds from small footprint LiDAR waveforms. Waveform deformation over complex terrain area is simulated using convolution. Drift of the peak center position is analyzed to identify the first echo returned by the illuminated objects in the LiDAR footprint. An approximate start point of peak in the waveform is estimated and adopted as the indicator of range calculation; range correction method is proposed to correct pulse widening over complex terrain surface. The experiment was carried out on small footprint LiDAR waveform data acquired by RIEGL LMS-Q560. The results suggest that the proposed approach generates more points than standard commercial products; based on field measurements, a comparative analysis between the point clouds generated by the proposed approach and the commercial software GeocodeWF indicates that: 1). the proposed approach obtained more accurate tree heights; 2). smooth surface can be achieved with low standard deviation. In summary, the proposed approach provides a satisfactory solution for range determination in estimating 3D coordinate values of point clouds, especially for correcting range information of waveforms containing deformed peaks.

  • 227.
    Reda Adinew, Amezene
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Bedada Damtie, Bekele
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Accuracy analysis and Calibration of Total Station based on the Reflectorless Distance Measurement2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Abstract

    Reflectorless EDM technology uses phase measuring or pulsed lasers to measure targets of a reflective and non-reflective nature. Reflectorless distance measurement provides rapid measurement by saving time and labour for surveyors. However, the accuracy of these types of measurements is under question because of the variety of constraints that affect the measurement.

    This paper attempts to show the techniques of total station calibration and to investigate the possible sources of error in reflectorless distance measurement. As a result, the effects of different color targets and angle incidence on distance measurement were checked. The precision of reflectorless distance measurement also investigated. In addition, comparison was made for manual and automatic target recognition measurement. Further experiment was performed on how to calibrate the total station instrument and the performance of the instrument was checked by KTH-TSC software.

    The experiments were evaluated by taking the reflector reading as ‘true value’ to check the accuracy of reflectorless measurement. The effects of colour surfaces on distance measurement have no significant difference. Besides, the result shows that the error in distance increased as the angle of incidence in the target increases. The result also indicates that automatic target recognition mode is the most advisable technique for precise measurement. Finally, an optimal number of seven target points was found for the calculation of prism constant.

  • 228.
    Rehn-Molin, Lotta
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatik och Geodesi.
    Long-term Stability Analysis of Antenna Temperature & Brightness Temperature from ESA's SMOS Satellite2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The European Space Agency’s Soil Moisture and Ocean Salinity (SMOS) satellite is designed to accurately detect the energy of the electromagnetic radiation naturally emitted from Earth, from which the level of soil moisture and ocean salinity content can be derived. Studies of these two geophysical parameters will increase the knowledge of the Earth’s water cycle and improve the understanding of the climate. The single payload of the SMOS satellite is the Microwave Imaging Radiometer by Aperture Synthesis (MIRAS). Researchers at Universitat Politècnica de Catalunya in Barcelona have developed the MIRAS Testing Software which basically translates SMOS raw data into useful data. The data is continuously analyzed and it has been discovered that some parameters of the MIRAS instrument are drifting more than expected.The objective of this Master’s thesis project was to create a long-term stability analyzing tool with which the long-term trends of the MIRAS parameters antenna temperature and brightness temperature can be investigated. The long-term stability analyzing tool has been coded in Matlab and the analysis is based on flight data from January to November 2010. The data has been processed in the MIRAS Testing Software with different inversion and calibration options before it has been used as input to the long-term stability analyzing tool. The main goal of this project was to find out which of the options gave the least drifting and most accurate results.The calibration options that have been studied are the 1-point and 4-point calibration, referring to the number of reference points used in each calibration respectively. The long-term stability analysis of the antenna temperature shows that the 1-point calibration gave more stable results than the 4-point calibration. This was expected since the 4-point calibration makes use of the so called NIR (Noise Injection Radiometer) antennas so a drift in the calibration of the NIRs is added to the uncertainty of the 4-point calibration.The inversion options refer to different approaches of inverting the measured visibility to brightness temperature. The two approaches that have been studied differ from each other by a correction term of the visibility that is included in Approach 3 and not in Approach 5. The long-term stability analysis of the brightness temperature shows that the inversion Approach 5 gave more stable results than the inversion Approach 3, which means the correction term causes instability in the results. If the correction was modified though, Approach 3 could possibly give more stable results which might imply a change of this conclusion.This long-term stability analysis aimed to contribute to the assessment of the stability of the MIRAS instrument, and so it has. This Master’s thesis project’s main contribution to the SMOS project is the demonstration of a new kind of systematic long-term stability analysis, which uses the same set of data when comparing things, in this case different inversion and calibration options. As a consequence of this Master’s thesis project, the SMOS calibration community is now discussing the options for finding metrics that can help to establish the SMOS long-term stability.

  • 229.
    Rodriguez, Raquel Libros
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatik och Geodesi.
    Dorado, Yolanda Perez
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatik och Geodesi.
    Assessing Tsunami Vulnerability using MCE in Phanga, Thailand2009Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 230. Ruelke, A.
    et al.
    Dietrich, R.
    Sjöberg, Lars E.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    The Antarctic regional GPS network densification- status and results2013Conference paper (Refereed)
  • 231.
    Rui, Yikang
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Urban Growth Modeling Based on Land-use Changes and Road Network Expansion2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    A city is considered as a complex system. It consists of numerous interactivesub-systems and is affected by diverse factors including governmental landpolicies, population growth, transportation infrastructure, and market behavior.Land use and transportation systems are considered as the two most importantsubsystems determining urban form and structure in the long term. Meanwhile,urban growth is one of the most important topics in urban studies, and its maindriving forces are population growth and transportation development. Modelingand simulation are believed to be powerful tools to explore the mechanisms ofurban evolution and provide planning support in growth management.

    The overall objective of the thesis is to analyze and model urban growth basedon the simulation of land-use changes and the modeling of road networkexpansion. Since most previous urban growth models apply fixed transportnetworks, the evolution of road networks was particularly modeled. Besides,urban growth modeling is an interdisciplinary field, so this thesis made bigefforts to integrate knowledge and methods from other scientific and technicalareas to advance geographical information science, especially the aspects ofnetwork analysis and modeling.

    A multi-agent system was applied to model urban growth in Toronto whenpopulation growth is considered as being the main driving factor of urbangrowth. Agents were adopted to simulate different types of interactiveindividuals who promote urban expansion. The multi-agent model with spatiotemporalallocation criterions was shown effectiveness in simulation. Then, anurban growth model for long-term simulation was developed by integratingland-use development with procedural road network modeling. The dynamicidealized traffic flow estimated by the space syntax metric was not only used forselecting major roads, but also for calculating accessibility in land-usesimulation. The model was applied in the city centre of Stockholm andconfirmed the reciprocal influence between land use and street network duringthe long-term growth.

    To further study network growth modeling, a novel weighted network model,involving nonlinear growth and neighboring connections, was built from theperspective of promising complex networks. Both mathematical analysis andnumerical simulation were examined in the evolution process, and the effects ofneighboring connections were particular investigated to study the preferentialattachment mechanisms in the evolution. Since road network is a weightedplanar graph, the growth model for urban street networks was subsequentlymodeled. It succeeded in reproducing diverse patterns and each pattern wasexamined by a series of measures. The similarity between the properties of derived patterns and empirical studies implies that there is a universal growthmechanism in the evolution of urban morphology.

    To better understand the complicated relationship between land use and roadnetwork, centrality indices from different aspects were fully analyzed in a casestudy over Stockholm. The correlation coefficients between different land-usetypes and road network centralities suggest that various centrality indices,reflecting human activities in different ways, can capture land development andconsequently influence urban structure.

    The strength of this thesis lies in its interdisciplinary approaches to analyze andmodel urban growth. The integration of ‘bottom-up’ land-use simulation androad network growth model in urban growth simulation is the major contribution.The road network growth model in terms of complex network science is anothercontribution to advance spatial network modeling within the field of GIScience.The works in this thesis vary from a novel theoretical weighted network modelto the particular models of land use, urban street network and hybrid urbangrowth, and to the specific applications and statistical analysis in real cases.These models help to improve our understanding of urban growth phenomenaand urban morphological evolution through long-term simulations. Thesimulation results can further support urban planning and growth management.The study of hybrid models integrating methods and techniques frommultidisciplinary fields has attracted a lot attention and still needs constantefforts in near future.

  • 232.
    Rui, Yikang
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Ban, Yifang
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Nonlinear growth in weighted networks with neighborhood preferential attachment2012In: Physica A: Statistical Mechanics and its Applications, ISSN 0378-4371, E-ISSN 1873-2119, Vol. 391, no 20, p. 4790-4797Article in journal (Refereed)
    Abstract [en]

    We propose a nonlinear growing model for weighted networks with two significant characteristics: (i) the new weights triggered by new edges at each time step grow nonlinearly with time; and (ii) a neighborhood local-world exists for local preferential attachment, which is defined as one selected node and its neighbors. Global strength-driven and local weight-driven preferential attachment mechanisms are involved in our model. We study the evolution process through both mathematical analysis and numerical simulation, and find that the model exhibits a wide-range power-law distribution for node degree, strength, and weight. In particular, a nonlinear degree-strength relationship is obtained. This nonlinearity implies that accelerating growth of new weights plays a nontrivial role compared with accelerating growth of edges. Because of the specific local-world model, a small-world property emerges, and a significant hierarchical organization, independent of the parameters, is observed.

  • 233.
    Rui, Yikang
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Ban, Yifang
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    The influence of street centrality on urban structure in StockholmArticle in journal (Other academic)
  • 234.
    Rui, Yikang
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Ban, Yifang
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Wang, Jiechen
    The effects of neighboring connections on weighted network evolution.Article in journal (Other academic)
  • 235.
    Rui, Yikang
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Ban, Yifang
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Wang, Jiechen
    Haas, Jan
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Exploring the patterns and evolution of self-organized urban street networks through modeling2013In: European Physical Journal B: Condensed Matter Physics, ISSN 1434-6028, E-ISSN 1434-6036, Vol. 86, no 3, p. 74-Article in journal (Refereed)
    Abstract [en]

    As one of the most important subsystems in cities, urban street networks have recently been well studied by using the approach of complex networks. This paper proposes a growing model for self-organized urban street networks. The model involves a competition among new centers with different values of attraction radius and a local optimal principle of both geometrical and topological factors. We find that with the model growth, the local optimization in the connection process and appropriate probability for the loop construction well reflect the evolution strategy in real-world cities. Moreover, different values of attraction radius in centers competition process lead to morphological change in patterns including urban network, polycentric and monocentric structures. The model succeeds in reproducing a large diversity of road network patterns by varying parameters. The similarity between the properties of our model and empirical results implies that a simple universal growth mechanism exists in self-organized cities.

  • 236.
    Rui, Zhu
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Moving Object Trajectory Based Intelligent Traffic Information Hub2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Congestion is a major problem in most metropolitan areas and given the increasingrate of urbanization it is likely to be an even more serious problem in the rapidlyexpanding mega cities. One possible method to combat congestion is to provide in-telligent traffic management systems that can in a timely manner inform drivers aboutcurrent or predicted traffic congestions that are relevant to them on their journeys. Thedetection of traffic congestion and the determination of whom to send in advance no-tifications about the detected congestions is the objective of the present research. Byadopting a grid based discretization of space, the proposed system extracts and main-tains traffic flow statistics and mobility statistics from the grid based recent trajectoriesof moving objects, and captures periodical spatio-temporal changes in the traffic flowsand movements by managing statistics for relevant temporal domain projections, i.e.,hour-of-day and day-of-week. Then, the proposed system identifies a directional con-gestion as a cell and its immediate neighbor, where the speed and flow of the objectsthat have moved from the neighbor to the cell significantly deviates from the histori-cal speed and flow statistics. Subsequently, based on one of two notification criteria,namely, Mobility Statistic Criterion (MSC) and Linear Movement Criterion (LMC),the system decides which objects are likely to be affected by the identified conges-tions and sends out notifications to the corresponding objects such that the numberof false negative (missed) and false positive (unnecessary) notifications is minimized.The thesis discusses the design and DBMS-based implementation of the proposedsystem. Empirical evaluations on realistically simulated trajectory data assess the ac-curacy of the methods and test the scalability of the system for varying input sizes andparameter settings. The accuracy assessment results show that the MSC based systemachieves an optimal performance with a true positive notification rate of 0.67 and afalse positive notification rate of 0.05 when min prob equals to 0.35, which is superiorto the performance of the LMC based system. The execution time of- and the spaceused by the system scales linearly with the input size (number of concurrently movingvehicles) and the methods mutually dependent parameters (grid resolution r and RTlength l) that jointly define a spatio-temporal resolution. Within the area of a large 

    city (40km by 40km), assuming a 60km/h average vehicle speed, the system, runningon a commodity personal computer, can manage the described congestion detectionand three-minute-ahead notification tasks within real-time requirements for 2000 and20000 concurrently moving vehicles for spatio-temporal resolutions (r=100m, l=19)and (r=2km, l=3), respectively.

  • 237.
    Rydén, Magnus
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatik och Geodesi.
    Strategic Placing of Field Hospitals Using Spatial Analysis2011Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Humanitarian help organisations today may benefit on improving their location analysis when placing field hospitals in countries hit by a disasters or catastrophe. The main objective of this thesis is to develop and evaluate a spatial decision support method for strategic placing of field hospitals for two time perspectives, long term (months) and short term (weeks). Specifically, the possibility of combining existing infrastructure and satellite data is examined to derive a suitability map for placing field hospitals. Haut-Katanga in Congo is used as test area where exists a large variety of ground features and has been visited by aid organisations in the past due to epidemics and warzones.

    The method consists of several steps including remote sensing for estimation of population density, a Multi Criteria Evaluation (MCE) for analysis of suitability, and visualization in a webmap.

    The Population density is used as a parameter for an MCE operation to create a decision support map for locating field hospitals. Other related information such as road network, water source and landuse is also taken into consideration in MCE. The method can generate a thematic map that highlights the suitability value of different areas for field hospitals. By using webmap related technologies, these suitability maps are also dynamic and accessible through the Internet.

    This new approach using the technology of dasymetric mapping for population deprival together with an MCE process, yielded a method with the result being both a standalone population distribution and a suitability map for placing field hospitals with the population distribution taken into consideration. The use of dasymetric mapping accounted for higher resolution and the ability to derive new population distributions on demand due to changing conditions rather than using pre-existing methods with coarser resolution and a more seldom update rate.

    How this method can be used in other areas is also analysed. The result of the study shows that the created maps are reasonable and can be used to support the locating of field hospitals by narrowing down the available areas to be considered. The results from MCE are compared to a real field hospital scenario, and it is shown that the proposed method narrows down the localisation options and shortens the time required for planning an operation. The method is meant to be used together with other decision methods which involves non spatial factors that are beyond the scope of this thesis.

  • 238. Sadatipour, S. M. T.
    et al.
    Kiamehr, R.
    Abrehdary, Majid
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatik och Geodesi.
    Sharifi, A. R.
    The Evaluation of Sea Surface Topography Models based on the Combination of the Satellite altimetry and the Global Geoid Models in the Persian Gulf2012In: International Journal of Environmental Research, ISSN 1735-6865, E-ISSN 2008-2304, Vol. 6, no 3, p. 645-652Article in journal (Refereed)
    Abstract [en]

    One of the difficulties in using absolute altitudes is the separation between the mean open sea level and geoid. Theoretically, geoid is the base level in absolute altitudes, but practically, the mean open sea level is used as a base level for absolute altitudes. The difference between these two levels is called as the sea surface topography. In this research, it is dealt the mean sea level modeling by using the observations of three altimeter satellites (i.e. Topex/Poseidon, Jason-1 and GFO) in Persian Gulf and then it is dealt with the evaluation of existing models of the sea surface topography based on the altimeter satellites data and the global geopotential geoid models (i.e. European Improved Gravity model of the Earth by New techniques, Gravity field and steady-state Ocean Circulation Explorer, Earth Gravitational Model 2008. The results of this research indicate that the sea surface topographical model resulting from the EIGEN06C geoid is the most precise model with changes range between -2.482 m and -1.511 m and mean -0.23 m.

  • 239.
    Sandberg, Johan
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatik och Geodesi.
    Challenges within geographical data sharing using OGC-standards regarding the INSPIRE Directive2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 240.
    Shahiruzzaman, Mohammad
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatik och Geodesi.
    Rauf, Adnan
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatik och Geodesi.
    Geostatistical techniques for predicting bird species occurrences2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Habitat loss and fragmentation are major threats to biodiversity. Geostatistical methods, especially kriging, are widely used in ecology. Bird counts data often fail to show normal distribution over an area which is required for most of the kriging methods. Hence choosing an interpolation method without understanding the implications may lead to bias results. United Kingdom’s Exprodat Consulting Ltd had set an Exploratory Spatial Data Analysis (ESDA) workflow for optimising interpolation of petroleum dataset. This workflow was applied in this study to predict capercaillie bird species over whole Sweden. There was no trend found in the dataset. Also the dataset was not spatially auto-correlated. A completely regularized spline surface model was created with RMSE 1.336. Medium to high occurrences (8-16) were found over two very small areas, within Västerbottens county and Västra Götlands county. Low occurrences (1-3) were found all over Sweden. Urban areas like Stockholm city and Malmö city had low occurrences. Another kriging prediction surface was created with RMSE 1.314 to compare the results. There were no prediction values from 5 to 16 in kriging surface. In-depth studies were carried out by selecting three areas. The studies showed that the results of local kriging surfaces did not match with the results of global surface. Uncertainty in GIS may exist at any level. Having low RMSE value does not always mean a good result. Hence ESDA before choosing interpolation method is an effective way. And a post result field investigation could make it more valid.

    Regression analysis is also widely used in ecology and there are certain different methods that are available to be used. Ordinary Least Squares is the first method that was tested upon bird counts data set. Adjusted R-squared value was 0.008616 which indicated that explanatory variables pine, spruce, roads, urban areas and wetlands were just contributing to 0.8% to the dependent variable bird counts. It was also found that there was no linear relationship between dependent and explanatory variables. Logistic regression was the next step as it had the capability to work with nonlinear data also. The Spatial Data Modeller (SDM) tool was used to perform logistic regression in ArcGIS 9.3. Initially results of logistic regression were unexpected, hence focal statistics was performed upon all the independent variables. Logistic regression with these new independent variables generated meaningful results. This time the probability of occurrence of birds had weak positive relationship with all the independent variables. Coefficients of pine, spruce, roads, urban areas and wetlands were found to be 0.39, 0.23, 0.13, 0.24 and 0.14 respectively. Pine and spruce are natural attractors for birds, hence results were quite acceptable. But the overall model performance remained poor. Positive coefficient for roads, urban areas and wetlands may well be due to redundancy in these datasets or observer bias in bird species reporting. IDRISI Andes also came up with almost the same results when logistic regression with same dependent and independent variables was performed. IDRISI Andes output contained the pseudo R-square value, found to be 0.0416. This was an indication of biasness in the dataset also. The results of in-depth studies by selecting three areas also showed that LR with focal statistics were having better results than LR without focal statistics, but the overall performance remained poor. The SDM tool is a good choice for performing logistic regression on small scale datasets due to its limitation. Comparison of results between the two geostatistical methods, interpolation and regression depicts the similarity at discrete places; an unbiased dataset might have resulted in a better comparison of two methods.

  • 241. Shao, Quanqin
    et al.
    Sun, C.
    Liu, J.
    Ban, Yifang
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatik och Geodesi.
    Kuang, W.
    Impact of Urban Expansion on Meteorological Observation Data and Over-estimation to Regional Air Temperature in China2009In: ACTA GEOGRAPHICA SINICA/地理学报, ISSN 0375-5444, Vol. 64, no 11, p. 1292-1302Article in journal (Refereed)
  • 242.
    Shirabe, Takeshi
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    A path that buys time to decide where to go2014In: International Journal of Geographical Information Science, ISSN 1365-8816, E-ISSN 1365-8824, Vol. 28, no 2, p. 314-325Article in journal (Refereed)
    Abstract [en]

    This paper considers the problem of planning a path in a circumstance where its origin is given, but its destination is not specified and is to be selected from among a set of candidate destinations during a trip. A situation like this may be experienced by a group of people who have different preferred destinations, as well as by an individual who is simply indecisive about where to go. To resolve such an uncertainty, one may stay at the origin until he decides on a destination, or choose to proceed on some path that does not overly deviate from a shortest path, whichever destination is eventually chosen, and make a decision on the way. The latter action is sensible when the risk of traveling longer is outweighed by the benefit of buying more time for a better destination decision. The problem of finding such a time-buying path is formulated and a simple algorithm is developed for its solution. Some extensions and applications are also discussed.

  • 243.
    Shirabe, Takeshi
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Prescriptive modeling with map algebra for multi-zone allocation with size constraints2012In: Computers, Environment and Urban Systems, ISSN 0198-9715, E-ISSN 1873-7587, Vol. 36, no 5, p. 456-469Article in journal (Refereed)
    Abstract [en]

    Map algebra is a methodology for organizing and processing digital cartographic data in a geographic information system (GIS). While its capabilities to describe patterns existing (or hidden) in data have been well studied, its capabilities to prescribe new patterns in response to specific requirements have not been much explored. The latter, prescriptive capabilities help planners address a class of spatial problems called " cartographic allocation" (. Tomlin, 1990), which concerns allocation of subsets (or zones) of a cartographic space to certain uses according to one or more criteria. Taking a school districting problem as an example, this paper introduces a systematic approach to designing a map algebraic procedure for a cartographic allocation problem with capacity constraints. It is found that a classical trial-and-error heuristic can be refined to a more formal approximation method and serve as a good alternative to other solution methods when the problem involves a large number of spatial units as is often the case with a raster-based GIS.

  • 244.
    Shirazian, Masoud
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Quality description in GPS precise point positioning2013Doctoral thesis, monograph (Other academic)
    Abstract [en]

    GPS processing, like every processing method for geodetic applications, relies upon least-squares estimation. Quality measures must be defined to assure that the estimates are close to reality. These quality measures are reliable provided that, first, the covariance matrix of the observations (the stochastic model) is well defined and second, the systematic effects are completely removed (i.e., the functional model is good).

    In the GPS precise point positioning (PPP) the stochastic and functional models are not as complicated as in the differential GPS processing. We will assess the quality of the GPS Precise Point Positioning in this thesis by trying to define more realistic standard deviations for the station position estimates.

    To refine the functional model from systematic errors, we have 1) used the phase observations to prevent introducing any hardware bias to the observation equations, 2) corrected observations for all systematic effects with amplitudes of more than 1cm, 3) used undifferenced observations to prevent having complications (e.g. linearly related parameters) in the system of observation equations.

    To have a realistic covariance matrix for the observations we have incorporated the ephemeris uncertainties into the system of observation equations.

    Based on the above-mentioned issues a PPP processing method is designed and numerically tested on the real data of some of the International GNSS Service stations. The results confirm that undifferenced stochastic-related properties (e.g. degrees of freedom) can be reliable means to recognize the parameterization problem in differenced observation equations. These results also imply that incorporation of the satellite ephemeris uncertainties might improve the estimates of the station positions.

    The effect of troposphere on the GPS data is also focused in this thesis. Of particular importance is the parameterization problem of the wet troposphere in the observation equations.

  • 245.
    Shirazian, Masoud
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatik och Geodesi.
    Remarks on the quality of GPS precise point positioning using phase observations2012Licentiate thesis, monograph (Other academic)
    Abstract [en]

    GPS processing, like every processing method for geodetic applications, relies upon least-squares estimation. Quality measures must be defined to assure that the estimates are close to reality. These quality measures are reliable provided that, first, the covariance matrix of the observations (the stochastic model) is well defined and second, the systematic effects are completely removed (i.e., the functional model is good).

    In the GPS precise point positioning (PPP) the stochastic and functional models are not as complicated as in the differential GPS processing. We will assess the quality of the GPS Precise Point Positioning in this thesis.

    To refine the functional model from systematic errors, we have 1) used the phase observations to prevent introducing any hardware bias to the observation equations, 2) corrected observations for all systematic effects with amplitudes of more than 1cm, 3) used undifferenced observations to prevent having complications (e.g. linearly related parameters) in the system of observation equations.

    To have a realistic covariance matrix for the observations we have incorporated the ephemeris’ uncertainties into the system of observation equations.

    The above-mentioned technique is numerically tested on the real data of some of the International GNSS Service stations. The results confirm that undifferenced stochastic-related properties (e.g. degrees of freedom) can be reliable means to recognize the parameterization problem in differenced observation equations. These results also imply that incorporation of the satellite ephemeris uncertainties might improve the estimates of the station positions.

  • 246.
    Shirazian, Masoud
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatik och Geodesi.
    Sjöberg, Lars E.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatik och Geodesi.
    Horemuz, Milan
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatik och Geodesi.
    A remark on the GNSS differenced phase ambiguity parameters2011In: Acta Geodaetica et Geophysica Hungarica, ISSN 1217-8977, E-ISSN 1587-1037, Vol. 46, no 4, p. 431-440Article in journal (Refereed)
    Abstract [en]

    In the global navigation satellite system (GNSS) carrier phase data processing, cycle slips are limiting factors and affect the quality of the estimators in general. When differencing phase observations, a problem in phase ambiguity parameterization may arise, namely linear relations between some of the parameters. These linear relations must be considered as additional constraints in the system of observation equations. Neglecting these constraints, results in poorer estimators. This becomes significant when ambiguity resolution is in demand. As a clue to detect the problem in GNSS processing, we focused on the equivalence of using undifferenced and differenced observation equations. With differenced observables this equivalence is preserved only if we add certain constraints, which formulate the linear relations between some of the ambiguity parameters, to the differenced observation equations. To show the necessity of the additional constraints, an example is made using real data of a permanent station from the network of the international GNSS service (IGS). The achieved results are notable to the GNSS software developers.

  • 247.
    Sjoberg, Lars E.
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatik och Geodesi.
    Bagherbandi, Mohammad
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatik och Geodesi.
    Quasigeoid-to-geoid determination by EGM082012In: Earth Science Informatics, ISSN 1865-0473, Vol. 5, no 2, p. 87-91Article in journal (Refereed)
    Abstract [en]

    We present a method to estimate the difference between quasigeoid and geoid heights globally from the Earth Gravitational Model EGM08 and a related topographic model. The numerical computations with the standard topographic density of 2.67 g/cm(3) show that the maximum and minimum of the separations are estimated to 5.47 m and -0.11 m on the Tibet plateau and in the Indian Ocean, respectively. These estimates do not consider possible topographic density variations, which result in topographic bias changes proportional to the topographic elevation squared. Assuming such density changes of 10% from the standard value, the separation may change up to 5 dm.

  • 248.
    Sjöberg, Lars E.
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatik och Geodesi.
    Eshagh, Mehdi
    Islamic Azad University.
    A theory on geoid modelling by spectral combination of data from satellite gravity gradiometry, terrestrial gravity and an Earth Gravitational Model2012In: Acta Geodaetica et Geophysica Hungarica, ISSN 1217-8977, E-ISSN 1587-1037, Vol. 47, no 1, p. 13-28Article in journal (Refereed)
    Abstract [en]

    In precise geoid modelling the combination of terrestrial gravity data and an Earth Gravitational Model (EGM) is standard. The proper combination of these data sets is of great importance, and spectral combination is one alternative utilized here. In this method data from satellite gravity gradiometry (SGG), terrestrial gravity and an EGM are combined in a least squares sense by minimizing the expected global mean square error. The spectral filtering process also allows the SGG data to be downward continued to the Earth's surface without solving a system of equations, which is likely to be ill-conditioned. Each practical formula is presented as a combination of one or two integral formulas and the harmonic series of the EGM. Numerical studies show that the kernels of the integral part of the geoid and gravity anomaly estimators approach zero at a spherical distance of about 5 degrees. Also shown (by the expected root mean square errors) is the necessity to combine EGM08 with local data, such as terrestrial gravimetric data, and/or SGG data to attain the 1-cm accuracy in local geoid determination.

  • 249.
    Sjöberg, Lars
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Abrehdary, Majid
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Bagherbandi, Mohammad
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    The observed geoid height versus Airy's and Pratt's isostatic models using matched asymptotic expansions2014In: Acta Geodaetica et Geophysica, ISSN 2213-5812, Vol. 49, no 4, p. 473-490Article in journal (Refereed)
    Abstract [en]

    Isostasy is a key concept in geodesy and geophysics. The classical isostatic models of Airy/Heiskanen and Pratt/Hayford imply that the topographic mass surplus and ocean mass deficit are balanced by mountain roots and anti-roots in the former model and by density variations in the topography and the compensation layer below sea bottom in the latter model. In geophysics gravity inversion is an essential topic where isostasy comes to play. The main objective of this study is to compare the prediction of geoid heights from the above isostatic models based on matched asymptotic expansion with geoid heights observed by the Earth Gravitational Model 2008. Numerical computations were carried out both globally and in several regions, showing poor agreements between the theoretical and observed geoid heights. As an alternative, multiple regression analysis including several non-isostatic terms in addition to the isostatic terms was tested providing only slightly better success rates. Our main conclusion is that the geoid height cannot generally be represented by the simple formulas based on matched asymptotic expansions. This is because (a) both the geoid and isostatic compensation of the topography have regional to global contributions in addition to the pure local signal considered in the classical isostatic models, and (b) geodynamic phenomena are still likely to significantly blur the results despite that all spherical harmonic low-degree (below degree 11) gravity signals were excluded from the study.

  • 250.
    Sjöberg, Lars
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatik och Geodesi.
    Bagherbandi, Mohammad
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatik och Geodesi.
    A method of estimating the Moho density contrast with a tentative application of EGM08 and CRUST2.02011In: ACTA GEOPHYSICA, ISSN 1895-6572, Vol. 59, no 3, p. 502-525Article in journal (Refereed)
    Abstract [en]

    Based on Vening Meinez-Moritz global inverse isostatic problem, the Moho density contrast is formulated as that of finding a solution of a Fredholm integral equation of the first kind. We present solutions to this equation by combining global models of gravity (EGM08), topography (DTM2006) and seismic crust (CRUST2.0) to a resolution of 2A degrees x2A degrees. The test computations yielded Moho density contrasts ranging from 81.5 kg/m3 (in Pacific) to 988 kg/m(3) (Tibet), with averages of 678 +/- 78 and 334 +/- 108 kg/m(3) for continental and oceanic regions, respectively, and a global average of 448 +/- 187 kg/m(3). Estimated Moho depths range from 8 to 75 km with continental and oceanic averages of 36.6 +/- 5.3 km and 12.9 +/- 5.8 km, respectively, and a global average of 21 +/- 12.5 km. This article has its emphasis on the new theory, while significant corrections to computational results are expected in a forthcoming study, where the isostatic gravity anomaly will be reduced for several disturbing signals.

234567 201 - 250 of 322
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