Change search
Refine search result
4567 301 - 321 of 321
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 301.
    YANG, CAN
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Multi-Agent Simulation to Study Sustainable Travel Behaviors in Stockholm County2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

     In this master thesis, multiagent simulation was implemented with MATSim to study the change would take place on travel behaviors in Stockholm County when all residents travel in a sustainable way under a predefined emission limit. In this multiagent simulation, individual person was simulated as agent with attributes, daily travel plans and behaviors. The attributes contained home location, workplace locations, and some socioeconomic attributes, which were assigned according to the demographic data and travelling statistics data collected. Two trips, morning commuting from home to workplace and evening commuting from workplace to home, were simulated while the daily travel plans included travelling by car, public transit, bike and working at home. Each day, the person was set to select a travel plan based on socioeconomic attributes, his current greenhouse gas emission and a monthly emission limit. The selected plan was then executed and his emission was updated. In the model, a working population of 771614 people in Stockholm County was used and one month period with 21 working days was simulated. Totally four monthly emission limits were tested: 30kg, 37kg, 50kg, and infinity representing the current scenario. The research shows that multiagent simulation is effective in simulating individual travel behaviors. The results suggest that under current scenario car is the most frequently selected travel mode accounting for 32%, followed by public transit 31%. There are about 12% of people working at home and 25% travelling by bike. Nearly 1 percent fails to select a plan because of the plan selection setting. When emission limit is set, the percentage of people changing travel behaviors is 21.2%, 25.8% and 29.9% under the emission limit 50kg, 37kg and 30kg respectively. Most of them would abort from car and public transit to bike, public transit or even failing to keep their emission under the limit. The percentage of people changing plan to bike is 9.4%, 11.8%, 13.4% under the three limits 50kg, 37kg and 30kg respectively while the percentage of people changing plan to public transit or failure is 10.2%, 12.5% and 15.2%. The result also shows that when 37kg limit is set, the people having problems with keeping their emission under the limit are mainly distributed at three regions: Stockholm City, some cities in southwest and northeast of Stockholm County, where there would also be more demand for public transit service. The people changing plans to bike are mainly  distributed  in  Stockholm  City  area,  where  sustainable  travel  behavior  should  be promoted

  • 302.
    Yousif, Osama
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Change Detection Using Multitemporal SAR Images2013Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Multitemporal SAR images have been used successfully for the detection of different types of environmental changes. The detection of urban change using SAR images is complicated due to the special characteristics of SAR images—for example, the existence of speckle and the complex mixture of the urban environment. This thesis investigates the detection of urban changes using SAR images with the following specific objectives: (1) to investigate unsupervised change detection, (2) to investigate reduction of the speckle effect and (3) to investigate spatio-contextual change detection. Beijing and Shanghai, the largest cities in China, were selected as study areas. Multitemporal SAR images acquired by ERS-2 SAR (1998~1999) and Envisat ASAR (2008~2009) sensors were used to detect changes that have occurred in these cities.

    Unsupervised change detection using SAR images is investigated using the Kittler-Illingworth algorithm. The problem associated with the diversity of urban changes—namely, more than one typology of change—is addressed using the modified ratio operator. This operator clusters both positive and negative changes on one side of the change-image histogram. To model the statistics of the changed and the unchanged classes, four different probability density functions were tested. The analysis indicates that the quality of the resulting change map will strongly depends on the density model chosen. The analysis also suggests that use of a local adaptive filter (e.g., enhanced Lee) removes fine geometric details from the scene.

    Speckle suppression and geometric detail preservation in SAR-based change detection, are addressed using the nonlocal means (NLM) algorithm. In this algorithm, denoising is achieved through a weighted averaging process, in which the weights are a function of the similarity of small image patches defined around each pixel in the image. To decrease the computational complexity, the PCA technique is used to reduce the dimensionality of the neighbourhood feature vectors. Simple methods to estimate the dimensionality of the new space and the required noise variance are proposed. The experimental results show that the NLM algorithm outperformed traditional local adaptive filters (e.g., enhanced Lee) in eliminating the effect of speckle and in maintaining the geometric structures in the scene. The analysis also indicates that filtering the change variable instead of the individual SAR images is effective in terms of both the quality of the results and the time needed to carry out the computation.

    The third research focuses on the application of Markov random field (MRF) in change detection using SAR images. The MRF-based change detection algorithm shows limited capacity to simultaneously maintain fine geometric detail in urban areas and combat the effect of speckle noise. This problem has been addressed through the introduction of a global constraint on the pixels’ class labels. Based on NLM theory, a global probability model is developed. The iterated conditional mode (ICM) scheme for the optimization of the MAP-MRF criterion function is extended to include a step that forces the maximization of the global probability model. The experimental results show that the proposed algorithm is better at preserving the fine structural detail, effective in reducing the effect of speckle, less sensitive to the value of the contextual parameter, and less affected by the quality of the initial change map compared with traditional MRF-based change detection algorithm.

  • 303.
    Yousif, Osama A.
    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), Urban Planning and Environment, Geoinformatics (closed 20110301). KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatics.
    Ban, Yifang
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatics.
    Object-based change detection in urban areas using multitemporal high resolution SAR images with unsupervised thresholding algorithms2016In: Remote Sensing and Digital Image Processing, Springer, 2016, p. 89-105Chapter in book (Refereed)
    Abstract [en]

    With the recent launches of optical and SAR systems that are capable of producing images in very high resolution, the quantification of temporal changes can be achieved with unprecedented level of details. However, very high resolution data presents new challenges and difficulties such as the strong intensity variations within land cover classes thus the noisy appearance of change map generated by pixelbased change detection. This has led to the development of object-based approaches that utilize image segmentation. For unsupervised change detection, on the other hand, automatic thresholding algorithms provided a simple yet effective technique to produce a binary change map. Thresholding techniques have been used successfully for pixel-based change detection using medium resolution SAR images. They have also been used for object-based change detection using high resolution optical imagery. However, they have not been tested in the context of object-based change detection using high resolution SAR images. Therefore, this chapter investigates the potential of several thresholding techniques for object-based unsupervised detection of urban changes using high resolution SAR images. To avoid the creation of sliver polygons, the multidate image segmentation strategy is adopted to produce image objects that are spectrally, spatially, and temporally homogeneous. A change image is generated by comparing objects multitemporal mean intensities using the modified ratio operator. To threshold the change image and generate a binary change map, three thresholding algorithms, i.e., the Kittler-Illingworth algorithm, the Otsu method, and the outlier detection technique, are tested and compared. Two multitemporal datasets consisting of TerraSAR-X images acquired over Beijing and Shanghai are used for evaluation. Quantitative and qualitative analyses reveal that the three algorithms achieved similar results. The three algorithms achieved Kappa coefficients around 0.6 for the Beijing dataset and 0.75 for the Shanghai datasets. The analysis also reveals the limitation of the mathematical comparison operator in accentuating the difference between the changed and the unchanged class, thus calls for the development of more sophisticated object-based change image generation mechanisms capable of reflecting all types of changes in the complex urban environment.

  • 304.
    Yousif, Osama
    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.
    Improving SAR-Based Urban Change Detection by Combining MAP-MRF Classifier and Nonlocal Means Similarity Weights2014In: IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, ISSN 1939-1404, E-ISSN 2151-1535, Vol. 7, no 10, p. 4288-4300Article in journal (Refereed)
    Abstract [en]

    In remote sensing change detection, Markov random field (MRF) has been used successfully to model the prior probability using class-labels dependencies. MRF has played an important role in the detection of complex urban changes using optical images. However, the preservation of details in urban change analysis turns out to be a highly complex task if multi-temporal SAR images with their speckle are to be used. Here, the ability of MRF to preserve geometric details and to combat speckle effect at the same time becomes questionable. Blob-region phenomenon and fine structures removal are common consequences of the application of traditional MRF-based change detection algorithm. To overcome these limitations, the iterated conditional modes (ICM) framework for the optimization of the maximum a posteriori (MAP-MRF) criterion function is extended to include a nonlocal probability maximization step. This probability model, which characterizes the relationship between pixels' class-labels in a nonlocal scale, has the potential to preserve spatial details and to reduce speckle effects. Two multitemporal SAR datasets were used to assess the proposed algorithm. Experimental results using three density functions [i.e., the log normal (LN), generalized Gaussian (GG), and normal distributions (ND)] have demonstrated the efficiency of the proposed approach in terms of detail preservation and noise suppression. Compared with the traditional MRF algorithm, the proposed approach proved to be less-sensitive to the value of the contextual parameter and the chosen density function. The proposed approach has also shown less sensitivity to the quality of the initial change map when compared with the ICM algorithm.

  • 305.
    Yousif, Osama
    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.
    Improving Urban Change Detection from Multitemporal SAR Images Using PCA-NLM2013In: IEEE Transactions on Geoscience and Remote Sensing, ISSN 0196-2892, E-ISSN 1558-0644, Vol. 51, no 4, p. 2032-2041Article in journal (Refereed)
    Abstract [en]

    Multitemporal synthetic aperture radar (SAR) images have been increasingly used in change detection studies. However, the presence of speckle is the main disadvantage of this type of data. To reduce speckle, many local adaptive filters have been developed. Although these filters are effective in reducing speckle in homogeneous areas, their use is often accompanied with the degradation of spatial details and fine structures. In this paper, we investigate a nonlocal means (NLM) denoising algorithm that combines local structures with a global averaging scheme in the context of change detection using multitemporal SAR images. First, the ratio image is logarithmically scaled to convert the multiplicative noise model to an additive model. A multidimensional change image is then constructed using image neighborhood feature vectors. Principle component analysis is then used to reduce the dimensionality of the neighborhood feature vectors. Recursive linear regression combined with fitting-accuracy assessment strategy is developed to determine the number of significant PC components to be retained for similarity weight computation. An intuitive method to estimate the unknown noise variance (necessary to run the NLM algorithm) based on the discarded PC components is also proposed. The efficiency of the method has been assessed using two different bitemporal SAR datasets acquired in Beijing and Shanghai, respectively. For comparison purposes, the algorithm is also tested against some of the most commonly used local adaptive filters. Qualitative and quantitative analyses of the algorithm have demonstrated the efficiency of the algorithm in recovering the noise-free change image while preserving the complex structures in urban areas.

  • 306.
    Yuan, Zhengwu
    et al.
    Chongqing University of Posts and Telecommunications / College of Computer Science and Technology.
    Jiang, Yanli
    Chongqing University of Posts and Telecommunications / College of Computer Science and Technology.
    Gidofalvi, Gyözö
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Geographical and Temporal Similarity Measurement on Location-based Social Networks2013In: Proceedings of the Second ACM SIGSPATIAL International Workshop on Mobile Geographic Information Systems / [ed] Chi-Yin Chow and Shashi Shekhar, New York, NY, USA: Association for Computing Machinery (ACM), 2013, p. 30-34Conference paper (Refereed)
    Abstract [en]

    Using "check-in" data gathered from location-based social networks, this paper proposes to measure the similarity of users by considering the geographical and the temporal aspect of their geographical and temporal aspects of their "check-ins". Temporal neighborhood is added to support the time dimension on the basis of the traditional DBSCAN clustering algorithm, which determines the similarity among users at different scales using the classical Vector Space Model (VSM) with vectors composed of the amount of visits in different cluster area. The spatio-temporal similarity of the user behaviors are obtained through overlapping the different weighted user similarity values. The experimental results show that the proposed approach is effective in measuring user similarity in location-based social networks.

  • 307.
    Zaheer, Muhammad
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Kinematic orbit determination of low Earth orbiting satellites, using satellite-to-satellite tracking data and comparison of results with different propagators2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The GPS data from Challenging Mini-satellite Payload (CHAMP) is used for its orbit determination for the epoch day of January 1st 2002.  The orbit of CHAMP is computed from the GPS data and ionospheric effects are removed by frequency combination.

    Further, the orbits of CHAMP for the same epoch day are computed using the satellite tool kit (STK) employing simplified general perturbations (SGP4) and a high precision orbit propagator (HPOP). Results from both techniques (GPS computed orbit and STK computed orbit) are compared.

    Furthermore, orbits computed using GPS data are also compared with jet propulsion laboratory’s published CHAMP spacecraft orbit and we have found that root mean square difference in ECEF position X component is below 0.01km other than some spikes at poles. The standard deviation of the difference in ECEF position X coordinate is 11.7m.

    The accuracy of our computed satellite positions (using GPS data) is about 12 metres for other than polar areas. However there are some occasional spikes, especially at poles, having maximum errors (about 0.055 km).

  • 308.
    Zaheer, Muhammad
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Kinematic orbit determination of low Earth orbiting satellites, using satellite-to-satellite tracking data and comparison of results with different propagators2014Independent thesis Advanced level (degree of Master (Two Years)), 80 credits / 120 HE creditsStudent thesis
    Abstract [en]

    GPS data from Challenging Mini-satellite Payload (CHAMP) is used for its orbit determination for the epoch day of January 1st 2002.  The orbit of CHAMP is computed from the GPS data and ionospheric effects are removed by frequency combination.

    Further, the orbits of CHAMP for the same epoch day are computed using the satellite tool kit (STK) employing simplified general perturbations (SGP4) and a high precision orbit propagator (HPOP).

    Furthermore, orbits computed using GPS data are also compared with jet propulsion laboratory’s published CHAMP spacecraft orbit and we have found that root mean square difference in ECEF position X component is below 0.01km other than some spikes at poles. The standard deviation of the difference in ECEF position X coordinate (JPL results – GPS computed results) is 11.7m. Since JPL computed orbits are considered as true orbits of CHAMP with accuracy of centimeter level (https://gipsy-oasis.jpl.nasa.gov/). Therefore this difference can also be referred as observed error in GPS computed orbits. Considering above discussion, we can expect that accuracy of our computed satellite positions (using GPS data) is about 12 metres for other than poles area. However there are some occasional spikes, especially at poles, having maximum errors (about 0.055 km).

  • 309.
    Zhang, Qian
    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.
    Analysis of landscape dynamics in Shanghai using landscape metrics: effects of spatial resolution2008In: XXI Congress of International Society for Photogrammetry and Remote Sensing. july, 2008. Beijing, China, 2008Conference paper (Refereed)
    Abstract [en]

    It is increasingly evident that urban sprawl leads to dramatic changes in landscape patterns and thus changes in ecosystem functioning. Analysis of the landscape patterns and their dynamic under urbanization is of great importance for sustainable development, especially in cities with significant changes like Shanghai. The objective of this research is to illustrate the landscape dynamic under the urbanization process in a selected test area of Shanghai in 1991, 1998 and 2007 using multitemtopal remote sensing and landscape metrics; and to determine the optimal resolution suitable for this case study. Preliminary results show that it is a quick and executable way to assessing the impact of urban sprawl on landscape dynamic using remote sensing data and landscape matrices; and the optimal resolution for the case study is 10-30 meters.

     

  • 310.
    Zhang, Qian
    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.
    Monitoring impervious surface sprawl in Shanghai using tasseled cap transformation of landsat data2010Conference paper (Other academic)
    Abstract [en]

    Transformation from non-impervious surface to impervious surface changes the landscapes and also changes the ecological and environmental conditions. Detecting impervious surface growth is vital to monitoring urban development and supporting sustainable city planning. The objective of this research is to conduct detection of impervious surface sprawl using tasseled cap transformation within the conceptual framework of Vegetation-Impervious surface-Soil (V-I-S) model. Landsat-3 MSS images on August 4, 1979 and Gap-filled Landsat-7 ETM+ images on May 22, 2009, covering the Greater Shanghai Area, were used in the case study. The results demonstrated that direct change detection using variables derived from tasseled cap transformation was effective for monitoring impervious surface sprawl. The variables derived from tasseled cap transformation have the potential to link to the components of the V-I-S model. The Greater Shanghai Area experienced high-speed impervious surface sprawl over the past 30 years at the average speed of 38.84km2/year.

  • 311.
    Zhang, Qian
    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.
    Hu, Yunfeng
    Institute of Geographic Science and Natural Resorces Research, Chinese Academy of Sciences, China.
    Liu, Jiyuan
    Institute of Geographic Science and Natural Resources Research, Chinese Academy of Sciences, China.
    The Trajectories of Urban Land and Industrial Land in Shanghai over the Past 30 Years2009In: 2009 JOINT URBAN REMOTE SENSING EVENT, VOLS 1-3, New York: IEEE , 2009, p. 1022-1028Conference paper (Refereed)
    Abstract [en]

    With regional economy development and the changes of urban development strategies, Shanghai experienced a distinct land use change process during the past 30 year. To explore the spatial pattern and temporal dynamics of urban land and industrial land over the past years, two independent datasets from multitemporal satellite images based on interpretation with computer-aids and object-oriented classification methods were employed in this study. Preliminary study indicated that Shanghai's urban land experienced continuous increases over the past 30 years. The total urban area of Shanghai increased from 146.1km(2) to 1121.3km(2) during 1979-2007, with an annual urban expansion area of 34.8km(2) per year. The rate of urban expansion, however, was not homogeneous spatially and temporally. The expanded area in the Puxi region was 5.23 times of its original area while that of Pudong region was 19.94 times of its original area. Within the extent of 1979's urban land distribution, the told area of industrial land and warehouses way 14.7 km(2) in 1966 and 16.8 km(2) in 2007, with the ratio of the industrial land to the whole territory increased from 10.1% to 11.5% The sizes of industrial land patches within the boundary decreased with the total industrial land area and the number of industrial patches increased. Moreover, the average size of industrial land in the Pudong region (1.6-2.0ha) was larger than that in the Puxi region (1.1-1.8ha). The trajectories of urban land and industrial land in Shanghai can he well explained by the policies of the national and the local government.

  • 312.
    Zhang, Qian
    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.
    Liu, Jiyuan
    Institute of Geographic Science and Natural Resources Research, Chinese Academy of Sciences, China.
    Hu, Yunfeng
    Institute of Geographic Science and Natural Resorces Research, Chinese Academy of Sciences, China.
    Simulating urban development scenarios using Markov-Cellular automata: a case study of greater Shanghai area, China2009In: Computers, Environment and Urban Systems, ISSN 0198-9715, E-ISSN 1873-7587Article in journal (Refereed)
    Abstract [en]

    The objective of this paper is to provide a comparative analysis of urban simulations under different scenarios. The objective of this paper is to provide a comparative analysis of urban simulations under different scenarios. Specifically, this research investigates the Markov-Cellular Automata (Markov-CA) model under different development schemes for simulations of the urban expansion scenarios of Greater Shanghai Area (GSA) in 2015 and 2025 in support of sustainable urban development. In this study, multitemporal land cover dataset, derived from remotely sensed images from 1995, 2000 and 2005 were used for simulation and validation. The scenarios of urban expansion patterns of GSA in 2015 and 2025 under three different schemes, i.e., Non-Scheme (NS), Service Oriented Center scheme (SOC) and Manufacture Dominant Center scheme (MDC), were simulated and comparatively analyzed with the aid of landscape metrics. The results demonstrated that GSA will experience less urban sprawl and retain a better environment in 2025 if the service orientated development policy is given priority. If favorable policy for MDC is adopted, however, there will be a lot of manufacturing industries gathering in GSA and more agricultural lands will be encroached. Through this study, the combined approach using remote sensing data, GIS spatial analysis environment and urban simulation model with landscape metrics and scenario analysis proved to be effective to understand, represent and predict the spatial-temporal dynamics of urban evolution, and Markov-CA model is a useful tool for simulating the scenarios of future urban developments, even though there are some issues that need to be investigated in the future, such as the construction of localized schemes, and the incorporation of political, social, economic and cultural factors. Specifically, this research investigates the Markov-Cellular Automata (Markov-CA) model under different development schemes for simulations of the urban expansion scenarios of Greater Shanghai Area (GSA) in 2015 and 2025 in support of sustainable urban development. In this study, multitemporal land cover dataset, derived from remotely sensed images from 1995, 2000 and 2005 were used for simulation and validation. The scenarios of urban expansion patterns of GSA in 2015 and 2025 under three different schemes, i.e., Non-Scheme (NS), Service Oriented Center scheme (SOC) and Manufacture Dominant Center scheme (MDC), were simulated and comparatively analyzed with the aid of landscape metrics. The results demonstrated that GSA will experience less urban sprawl and retain a better environment in 2025 if the service orientated development policy is given priority. If favorable policy for MDC is adopted, however, there will be a lot of manufacturing industries gathering in GSA and more agricultural lands will be encroached. Through this study, the combined approach using remote sensing data, GIS spatial analysis environment and urban simulation model with landscape metrics and scenario analysis proved to be effective to understand, represent and predict the spatial-temporal dynamics of urban evolution, and Markov-CA model is a useful tool for simulating the scenarios of future urban developments, even though there are some issues that need to be investigated in the future, such as the construction of localized schemes, and the incorporation of political, social, economic and cultural factors.

  • 313.
    Zhang, Qian
    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.
    Liu, Jiyuan
    Hu, Yunfeng
    Simulation and analysis of urban growth scenarios for the Greater Shanghai Area, China2011In: Computers, Environment and Urban Systems, ISSN 0198-9715, E-ISSN 1873-7587, Vol. 35, no 2, p. 126-139Article in journal (Refereed)
    Abstract [en]

    This research investigates the potential of an integrated Markov chain analysis and cellular automata model to better understand the dynamics of Shanghai's urban growth. The model utilizes detailed land cover categories to simulate and assess landscape changes under three different scenarios, i.e., baseline, Service Oriented Center, and Manufacturing Dominant Center scenarios. In the study, multi-temporal land use datasets, derived from remotely-sensed images from 1995, 2000, and 2005, were used for simulation and validation. Urban growth patterns and processes were then analyzed and compared with the aid of landscape metrics. This research represents the first scenario-based simulations of the future growth of Shanghai, and is one of the few studies to use landscape metrics to analyze urban scenario-based simulation results with detailed land use categories. The results indicate that the future expansion of both high-density and low-density residential/commercial zones is always located around existing built-up urban areas or along existing transportation lines. In contrast to the baseline and Service Oriented Center scenarios, industrial land under the Manufacturing Dominant Center scenario in 2015 and 2025 will form industrial parks or industrial belts along the transportation channels from Shanghai to Nanjing and Hangzhou. The study's approach, which combines scenario-based urban simulation modeling and landscape metrics, is shown to be effective in representing, understanding, and predicting the spatial-temporal dynamics and patterns of urban evolution, including urban expansion trends. (C) 2010 Elsevier Ltd. All rights reserved.

  • 314.
    Zhang, Qian
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Hu, Y.
    Liu, J.
    Liu, Y.
    Ren, W.
    Li, J.
    Identification of urban clusters in China based on assessment of transportation accessibility and socio-economic indicators2011In: Acta Geographica Sinica, ISSN 1520-7412, E-ISSN 1786-0091, Vol. 66, no 6, p. 761-770Article in journal (Refereed)
    Abstract [en]

    Urban clusters are the expected products of high levels of industry and urbanization in a country, as well as being the basic units of participation in global competition. With respect to China, urban clusters are regarded as the dominant formation for boosting the China's urbanization process. However, to date, there is no coincident, efficient, and credible methodological system and set of techniques to identify Chinese urban clusters. This research investigates the potential of an computerized identification method supported by geographic information techniques to provide a better understanding of the distribution of China's urban clusters. The identification method is executed based on a geographic information database, a digital elevation model, and socio-economic data with the aid of ArcInfo Macro Language programming. In the method, preliminary boundaries are identified according to transportation accessibility, and final identifications are achieved from limiting city numbers, population, and GDP in a region with the aid of the rasterized socio-economic dataset. The results show that the method identifies nine Chinese urban clusters, i.e., Pearl River Delta, Lower Yangtze River Valley, Beijing-Tianjin-Hebei Region, Northeast China, Middle Yangtze River Valley, Central China Plains, Western Taiwan Strait, Guanzhong and Chengdu-Chongqing urban clusters. This research represents the first study involving the computerized identification of China's urban clusters. Moreover, compared to other related studies, the study's approach, which combines transportation accessibility and socio-economic characteristics, is shown to be a distinct, effective and reliable way of identifying urban clusters.

  • 315.
    Zhang, Qian
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geoinformatik och Geodesi.
    Yunfeng, Hu
    Jiyuan, Liu
    Yue, Liu
    Wangbing, Ren
    Jun, Li
    A quantitative assessment of the distribution and extent of urban clusters in China2012In: Journal of Geographical Sciences, ISSN 1009-637X, Vol. 22, no 1, p. 137-151Article in journal (Refereed)
    Abstract [en]

    Urban clusters are the expected products of high levels of industry and urbanization in a country, as well as being the basic units of participation in global competition. With respect to China, urban clusters are regarded as the dominant formation for boosting the Chinese urbanization process. However, to date, there is no coincident, efficient, and credible methodological system and set of techniques to identify Chinese urban clusters. This research investigates the potential of a computerized identification method supported by geographic information techniques to provide a better understanding of the distribution of Chinese urban clusters. The identification method is executed based on a geographic information database, a digital elevation model, and socio-economic data with the aid of ArcInfo Macro Language programming. In the method, preliminary boundaries are identified according to transportation accessibility, and final identifications are achieved from limiting city numbers, population, and GDP in a region with the aid of the rasterized socio-economic dataset. The results show that the method identifies nine Chinese urban clusters, i.e., Pearl River Delta, Lower Yangtze River Valley, Beijing-Tianjin-Hebei Region, Northeast China Plain, Middle Yangtze River Valley, Central China Plains, Western Taiwan Strait, Guanzhong and Chengdu-Chongqing urban clusters. This research represents the first study involving the computerized identification of Chinese urban clusters. Moreover, compared to other related studies, the study's approach, which combines transportation accessibility and socio-economic characteristics, is shown to be a distinct, effective and reliable way of identifying urban clusters.

  • 316.
    Zhao, Yueming
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    GPS/IMU Integrated System for Land Vehicle Navigation based on MEMS2011Licentiate thesis, monograph (Other academic)
    Abstract [en]

    The Global Positioning System (GPS) and an Inertial Navigation System (INS)are two basic navigation systems. Due to their complementary characters in manyaspects, a GPS/INS integrated navigation system has been a hot research topic inthe recent decade. Both advantages and disadvantages of each individual systemare analyzed.

    The Micro Electrical Mechanical Sensors (MEMS) successfully solved theproblems of price, size and weight with the traditional INS. Therefore they arecommonly applied in GPS/INS integrated systems. The biggest problem ofMEMS is the large sensor errors, which rapidly degrade the navigationperformance in an exponential speed. By means of different methods, i.e.autoregressive model, Gauss-Markov process, Power Spectral Density and AllanVariance, we analyze the stochastic errors within the MEMS sensors. Real testson a MEMS based inertial measurement unit for each method are carried out. Theresults show that different methods give similar estimates of stochastic errorsources. These error coefficients can be used further in the Kalman filter for betternavigation performance and in the Doppler frequency estimate for fasteracquisition after the GPS signal outage.

    Three levels of GPS/IMU integration structures, i.e. loose, tight and ultra tightGPS/IMU navigation, are introduced with a brief analysis of each character. Theloose integration principles are given with detailed equations as well as the basicINS navigation principles.

    The Extended Kalman Filter (EKF) is introduced as the basic data fusionalgorithm, which is also the core of the whole navigation system to be presented.The kinematic constraints of land vehicle navigation, i.e. velocity constraint andheight constraint, are presented. These physical constraints can be used asadditional information to further reduce the navigation errors. The theoreticalanalysis of the Kalman filter with constraints are given to show the improvementon the navigation performance. As for the outliers in practical applications, theequivalent weight is introduced to adaptively reduce the influence on positioningaccuracy.

    A detailed implementation process of the GPS/IMU integration system is given.Based on the system model, we show the propagation of position standard errorswith the tight integration structure under different scenarios. Even less than 4observable satellites can contribute to the integrated system. Especially 2 satellitescan maintain the orientation errors at a reasonable level due to the benefit of thetight integration. A real test with loose integration structure is carried out, and theEKF performance as well as the physical constraints are analyzed in detail. Also atest with random outliers at the resolution level is carried out to show theeffectiveness of the equivalent weight. Finally some suggestions on future researchare proposed.

  • 317.
    Zhao, Yueming
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Key Technologies in Low-cost Integrated Vehicle Navigation Systems2013Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Vehicle navigation systems incorporate on-board sensors/signal receivers and provide necessary positioning and guidance information for land, marine, airborne and space vehicles. Among different navigation solutions, the Global Positioning System (GPS) and an Inertial Navigation System (INS) are two basic navigation systems. Due to their complementary characters in many aspects, a GPS/INS integrated navigation system has been a hot research topic in recent decades. Both advantages and disadvantages of each individual system and their combination are analysed in this thesis.

    The Micro Electrical Mechanical Sensors (MEMS) successfully solved the problems of price, size and weight with traditional INS, and hence are widely applied in GPS/INS integrated systems. The main problem of MEMS is the large sensor errors, which rapidly degrade the navigation performance in an exponential speed. By means of different methods, such as autoregressive model, Gauss-Markov process, Power Spectral Density and Allan Variance, we analyse the stochastic errors within the MEMS sensors. The test results show that different methods give similar estimates of stochastic error sources. An equivalent model of coloured noise components (random walk, bias instability and ramp noise) is given.

    Three levels of GPS/IMU integration structures, i.e. loose, tight and ultra-tight GPS/IMU navigation, are introduced with a brief analysis of each character. The loose integration principles are presented with detailed equations as well as the INS navigation principles. The Extended Kalman Filter (EKF) is introduced as the data fusion algorithm, which is the core of the whole navigation system. Based on the system model, we show the propagation of position standard errors with the tight integration structure under different scenarios. Even less than 4 observable GNSS satellites can contribute to the integrated system, especially for the orientation errors. A real test with loose integration is carried out, and the EKF performance is analysed in detail.

    Since the GPS receivers are normally working with a digital map, the map matching principle and its link-choosing problem are briefly introduced. This problem is proposed to be solved by the lane detection from real-time images. The procedures for the lane detection based on image processing are presented. The test on high ways, city streets and pathways are successfully carried out, and analyses with possible solutions are given for some special failure situations.

    To solve the large error drift of the IMU, we propose to support the IMU orientation with camera motion estimation from image pairs. First the estimation theory and computer vision principles are briefly introduced. Then both point and line matches algorithms are given. Finally the L1-norm estimator with balanced adjustment is proposed to deal with possible mismatches (outliers). Tests and comparisons with the RANSAC algorithm are also presented.

    For the latest trend of MEMS chip sensors, their industry and market are introduced. To evaluate the MEMS navigation performance, we augment the EKF with an equivalent coloured noise model, and the basic observability analysis is given. A realistic simulated navigation test is carried out with single and multiple MEMS sensors, and a sensor array of 5-10 sensors are recommended according to the test results and analysis. Finally some suggestions for future research are proposed.

  • 318.
    Zhao, Yueming
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Horemuz, Milan
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Sjöberg, Lars E.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Stochastic modelling and analysis of IMU sensor errors2011In: Archives of Photogrammetry, Cartography and Remote Sensing, ISSN 2083-2214, Vol. 22, p. 437-449Article in journal (Refereed)
    Abstract [en]

    The performance of a GPS/INS integration system is greatly determined by the ability of stand-alone INS system to determine position and attitude within GPS outage. The positional and attitude precision degrades rapidly during GPS outage due to INS sensor errors. With advantages of low price and volume, the Micro Electrical Mechanical Sensors (MEMS) have been wildly used in GPS/INS integration. Moreover, standalone MEMS can keep a reasonable positional precision only a few seconds due to systematic and random sensor errors. General stochastic error sources existing in inertial sensors can be modelled as (IEEE STD 647, 2006) Quantization Noise, Random Walk, Bias Instability, Rate Random Walk and Rate Ramp. Here we apply different methods to analyze the stochastic sensor errors, i.e. autoregressive modelling, Gauss-Markov process, Power Spectral Density and Allan Variance. Then the tests on a MEMS based inertial measurement unit were carried out with these methods. The results show that different methods give similar estimates of stochastic error model parameters. These values can be used further in the Kalman filter for better navigation accuracy and in the Doppler frequency estimate for faster acquisition after GPS signal outage.

  • 319.
    Zhu, Rui
    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.
    GPS-based Crowd Sourced Intelligent Traffic Information Hub2013In: Proceedings of the 26th International Cartographic Conference / [ed] Manfred F. Buchroithner, ICC International Cartographic Association , 2013, p. 669-670Conference paper (Refereed)
    Abstract [en]

    Congestion is a major problem in most metropolitan areas and given the increasing rate of urbanization it is likely to be an even more serious problem in the rapidly expanding mega cities. Some well know negative effects of congestion include: 1) the economic losses and quality of life degradation that result from the increased and unpredictable travel times, 2) the increased level of carbon footprint that vehicles idling in congestions leave behind, and 3) the increased number of traffic accidents that are direct results of the stress and fatigue of drivers that are stuck in congestion.

    One possible method to combat congestion is provide intelligent traffic management systems that can in a timely manner inform drivers about current or predicted traffic congestion that is relevant to them on their journeys. This this extent, the present paper proposes a scalable, grid-based intelligent traffic information hub that facilitates the manual definition and/or automatic detection of abnormal traffic condition events, e.g., accidents or congestion, and in advance informs drivers about events that will likely be relevant to them on their journey, thereby allowing the divers or their onboard navigation units to alter their paths as needed.

    The proposed system achieves the above described functionality through the following methodology. The system, without loss of generality, adopts a grid-based discretization of space, which by changing the resolution of the grid allows the system to scale in terms of it computation cost and the geographical level of detail of traffic information that it manages. The system derives traffic information from the continuous stream of grid-based position and speed reports that it receives from the vehicles. In particular, the system in an online fashion 1) summarizes Current (grid-based) Traffic Flow Statistics (CTFS), i.e., it records for each grid cell g from each neighboring grid cell n, the mean and standard deviation of the speeds of the vehicles that are currently located in g and have entered g from n; and 2) efficiently incorporates the CTFS into compressed Historical (grid-based) Traffic Flow Statistics (HTFS) using incremental statistics. Simultaneously, using a sliding window model, the system also 1) maintains the Recent (grid-based) Trajectories (RT) of the vehicles; 2) extracts Recent (gridbased) Mobility Statistics (RMS), i.e., it records for each destination grid cell d, for each neighboring grid cell n of g, and for each possible source grid cell s, the number of vehicles that (i) are currently in d, (ii) have entered d from n, and (iii) have a RT that has passed through s; and 3) efficiently incorporates the RMS into compressed Historical (grid-based) Mobility Statistics (HMS) using incremental statistics. To capture the temporal variability in traffic flow and mobility patterns at different scales, the system through temporal domain projections maintains day-of-week and hour-ofday based aggregations of HTFS and RMS. Then, the system classifies a grid cell g to be congested from the direction of a neighboring grid cell n if the current mean speed of vehicles that entered the grid cell g from the direction of n is below the normal according to the temporally relevant HFS. Finally, based on the temporally relevant HMS, the system sends out congestion notifications to vehicles that are likely to be effected in the future part of their journey by these congestions, i.e., the system sends out a congestion notification (g,n) to a vehicle v that is currently located in some grid cell s from which the likelihood of v moving to g through n within the prediction horizon is above a user-defined threshold.

    Extensive empirical evaluations on large sets of realistically simulated trajectories of vehicles illustrate that the above described methodology and its simple SQL-based implementation in a relational database system is scalable and effective. In particular, the execution time of- and the space used by the system scales linearly with the input size (number of concurrently moving vehicles) and the method’s mutually dependent parameters (grid resolution r and RT length 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, running on a single personal computer, can manage the described congestion detection and one-minute-ahead notification tasks within real-time requirements for 15 thousand and 2.5 million concurrently moving vehicles for spatio-temporal resolutions (r=62.5m, l=17) and (r=4km,l=2), respectively. Finally, the proposed method, for all spatio-temporal resolutions and prediction horizons, significantly outperforms in terms of notification accuracy the grid-based baseline method, which sends non-directional congestion notifications based on the recent linear movement tendencies of vehicles. 

  • 320.
    Ågren, Jonas
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics. Lantmäteriet Swedish Mapping, Sweden.
    Engberg, L. E.
    Alm, L.
    Dahlström, F.
    Engfeldt, A.
    Lidberg, M.
    Improving the Swedish quasigeoid by gravity observations on the ice of Lake Vänern2014In: International Association of Geodesy Symposia, 2014, p. 171-177Conference paper (Refereed)
    Abstract [en]

    One of the key activities in Geodesy 2010, the Swedish strategic plan for geodetic activities during the period 2011–2020, is the restoration of the gravity network and data in order to improve the accuracy of the national quasigeoid model. One weak point has been that very few gravity observations have been available over Lake Vänern, Sweden’s largest lake. During the extremely cold winters 2010 and 2011, the ice became sufficiently thick to make ice observation of gravity. The main purpose of this paper is to present the 2011 ice gravity campaign, summarise the experiences made and investigate how much the new ice observations improve the computed quasigeoid model in the area. This is investigated under the assumption that a modern Earth Gravitational Model based on GRACE and GOCE is used. It is found that new ice measurements improve the quasigeoid with a RMS of about 2–3 cm in and around the lake with a maximum improvement of 7 cm.

  • 321.
    Österman, Anna
    KTH, School of Architecture and the Built Environment (ABE), Urban Planning and Environment, Geodesy and Geoinformatics.
    Map visualization in ArcGIS, QGIS and MapInfo2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Mapproduction, also called cartography, is one of the processes of visualrepresentation of reality. This practice has for a long time been of hugeinterest to humanity and was initially a handcraft[2]. Today most maps areproduced with the help of computers and are often the last step of a GISanalysis – the way the result is presented. This makes knowledge of mapproduction important and relevant when working with different GIS analysis. Thereare several GIS programs on the market, both free and commercial software.ArcGIS is one of the most common programs used by companies when producing mapsand is often used in universities for teaching. However, there are otherprograms on the market. Two examples of these are QGIS and MapInfo. QGIS isfree open source software and MapInfo is licensed software like ArcGIS. Theobjectives of this thesis are to explore and learn the steps of map productionin these programs and to look at how interchangeable the programs are in mapediting. This is examined by trying to create the same map and map series inthe three programs. From the process and result an evaluation schema is createdto present the functionality as well as a discussion to raise the pros and consof the programs. The result of creating a simple map shows that it is possibleto create the same map in all three programs, except from some minordifferences. When looking at the evaluations schema it is clear that theprograms have almost the same functionality. The biggest difference is thatboth ArcGIS and QGIS have a tool for generating an atlas while MapInfo lacksthis functionality. What the evaluation schema does not show is the differencesin how user-friendly the programs are. This is further narrated in the discussionpart of the report where the pros and cons are reported. The conclusion is thatArcGIS and QGIS are much alike when it comes to producing maps while MapInfoworks differently and are harder to get used to. The result gives a goodindication of which programs to choose and what type of functionality thatexists, though a more profound study could have been done where more types ofmaps were created for more reliable results.

4567 301 - 321 of 321
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf