| 1. |
- Bin, Jiang, 1965-, et al.
(författare)
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Automatic generation of the axial lines of urban environments to capture what we perceive
- 2010
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Ingår i: International Journal of Geographical Information Science. - London : Taylor & Francis Group. - 1365-8816 .- 1365-8824 .- 1362-3087. ; 24:4, s. 545-558
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Tidskriftsartikel (refereegranskat)abstract
- Based on the concepts of isovists and medial axes, we developed a set of algorithms that can automatically generate axial lines for representing individual linearly stretched parts of open space of an urban environment. Open space is the space between buildings, where people can freely move around. The generation of the axial lines has been a key aspect of space syntax research, conventionally relying on hand-drawn axial lines of an urban environment, often called axial map, for urban morphological analysis. Although various attempts have been made towards an automatic solution, few of them can produce the axial map that consists of the least number of longest visibility lines, and none of them really works for different urban environments. Our algorithms provide a better solution than existing ones. Throughout this paper, we have also argued and demonstrated that the axial lines constitute a true skeleton, superior to medial axes, in capturing what we perceive about the urban environment.
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| 2. |
- Bin, Jiang, 1965-, et al.
(författare)
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Computing the fewest-turn map directions based on the connectivity of natural roads
- 2011
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Ingår i: International Journal of Geographical Information Science. - London : Taylor & Francis Group. - 1365-8816 .- 1365-8824 .- 1362-3087. ; 25:7, s. 1069-1082
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we introduced a novel approach to computing the fewest-turn map directions or routes based on the concept of natural roads. Natural roads are joined road segments that perceptually constitute good continuity. This approach relies on the connectivity of natural roads rather than that of road segments for computing routes or map directions. Because of this, the derived routes posses the fewest turns. However, what we intend to achieve are the routes that not only possess the fewest turns, but are also as short as possible. This kind of map direction is more effective and favorable by people, because they bear less cognitive burden. Furthermore, the computation of the routes is more efficient, since it is based on the graph encoding the connectivity of roads, which is significantly smaller than the graph of road segments. We made experiments applied to eight urban street networks from North America and Europe in order to illustrate the above stated advantages. The experimental results indicate that the fewest-turn routes posses fewer turns and shorter distances than the simplest paths and the routes provided by Google Maps. For example, the fewest-turn-and-shortest routes are on average 15% shorter than the routes suggested by Google Maps, while the number of turns is just half as much. This approach is a key technology behind FromToMap.org - a web mapping service using openstreetmap data.
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| 3. |
- Shirazian, Masoud, et al.
(författare)
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Network-Aided Reduction of Slope Distances in Small-Scale Geodetic Control Networks
- 2021
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Ingår i: Journal of Surveying Engineering. - : ASCE-The American Society of Civil Engineers. - 0733-9453 .- 1943-5428. ; 147:4
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Tidskriftsartikel (refereegranskat)abstract
- Most of the human-made infrastructures (e.g., dams) need very precise geodetic networks and constant monitoring to detect risks of failure and to plan civil engineering maintenance works. The combination of different measurements helps in determining displacements with high precision; therefore, the risk of damages is reduced. In this paper, we present a new approach, which considers a special geodetic observation strategy as a method to significantly reduce the volume of operations of a precise geodetic network and changes the designing concept of such networks. Decrease in data collection time and cost while keeping or increasing the quality of control networks has been one of the most important goals of any network designer. This paper proposes a method exploiting network properties to convert slope distances to the horizontal ones to be used in the classic terrestrial geodetic two-dimensional (2D) networks. We have evaluated the proposed method in different dam geodetic control networks in Iran. The network adjustment results show the acceptable performance of the presented method compared with the methods that are currently in use.
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| 4. |
- Bagherbandi, Mohammad
(författare)
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Deformation monitoring using different least squares adjustment methods : A simulated study
- 2016
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Ingår i: KSCE Journal of Civil Engineering. - : Springer. - 1226-7988 .- 1976-3808. ; 20:2, s. 855-862
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Tidskriftsartikel (refereegranskat)abstract
- This study aims to investigate the ability of different least squares adjustment techniques for detecting deformation. A simulated geodetic netwo rk is used for this purpose. The observations are collected using the Total Station instrument in three epochs and different least squares adjustment methods are used to analyze the simulated network. The applied methods are adjustment-byelement, using variance-covariance components and Tikhonov regularization. For numerical computation, we utilized exist geodetic network around the simulated network and the deformation (changes in the simulated network) imposes to the object using a simulator in each epoch. The obtained results demonstrate that more accurate outcome for detection of small deformation is possible by estimating variance-covariance components. The difference of the estimated and the simulated deformations in the best scenario, i.e., applying variance-covariance components, is 0.2 and 0.1 mm in x and y directions. In comparison with adjustment by element and Tikhonov regularization methods the differences are 1.1 and 0.1 in x direction and 1.4 and 1.1 mm in y direction, respectively. In addition, it is also possible to model the deformation and therefore it can be seen that how the calculated displacement will affect the result of deformation modelling. It has been demonstrated that determining reasonable variance-covariance components is very important to estimate realistic deformation model and monitoring the geodetic networks.
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| 5. |
- Bagherbandi, Mohammad, et al.
(författare)
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Effect of the lithospheric thermal state on the Moho interface : a case study in South America
- 2017
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Ingår i: Journal of South American Earth Sciences. - : Elsevier BV. - 0895-9811 .- 1873-0647. ; 76, s. 198-207
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Tidskriftsartikel (refereegranskat)abstract
- Gravimetric methods applied for Moho recovery in areas with sparse and irregular distribution of seismic data often assume only a constant crustal density. Results of latest studies, however, indicate that corrections for crustal density heterogeneities could improve the gravimetric result, especially in regions with a complex geologic/tectonic structure. Moreover, the isostatic mass balance reflects also the density structure within the lithosphere. The gravimetric methods should therefore incorporate an additional correction for the lithospheric mantle as well as deeper mantle density heterogeneities. Following this principle, we solve the Vening Meinesz-Moritz (VMM) inverse problem of isostasy constrained by seismic data to determine the Moho depth of the South American tectonic plate including surrounding oceans, while taking into consideration the crustal and mantle density heterogeneities. Our numerical result confirms that contribution of sediments significantly modifies the estimation of the Moho geometry especially along the continental margins with large sediment deposits. To account for the mantle density heterogeneities we develop and apply a method in order to correct the Moho geometry for the contribution of the lithospheric thermal state (i.e., the lithospheric thermal-pressure correction). In addition, the misfit between the isostatic and seismic Moho models, attributed mainly to deep mantle density heterogeneities and other geophysical phenomena, is corrected for by applying the non-isostatic correction. The results reveal that the application of the lithospheric thermal-pressure correction improves the RMS fit of the VMM gravimetric Moho solution to the CRUST1.0 (improves ∼ 1.9 km) and GEMMA (∼1.1 km) models and the point-wise seismic data (∼0.7 km) in South America.
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| 6. |
- Bagherbandi, Mohammad, Professor, et al.
(författare)
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Geodetic Control Networks: Challenges and Solutions : Essesntial Tools for Deformation and Environmental Monitoring
- 2022
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Ingår i: GIM International - The Worldwide Magazine for Geomatics. - : Geomares. - 1566-9076. ; 36:7, s. 31-33
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Tidskriftsartikel (refereegranskat)abstract
- What are the key challenges in establishing precise geodetic control networks? This is one of the most important tasks of geodesists and land surveyors, since geodetic control networks are essential for the deformation and environmental monitoring of dams, tunnels, high towers, landslides and bridges, among others. This article discusses the main challenges relating to vertical angles and provides some recommendations for how they can be overcome.
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| 7. |
- Jiang, Bin, et al.
(författare)
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Scaling of geographic space from the perspective of city and field blocks and using volunteered geographic information
- 2012
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Ingår i: International Journal of Geographical Information Science. - : Taylor & Francis. - 1365-8816 .- 1365-8824 .- 1362-3087. ; 26:2, s. 215-229
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Tidskriftsartikel (refereegranskat)abstract
- Scaling of geographic space refers to the fact that for a large geographic area its small constituents or units are much more common than the large ones. This paper develops a novel perspective to the scaling of geographic space using large street networks involving both cities and countryside. Given a street network of an entire country, we decompose the street network into individual blocks, each of which forms a minimum ring or cycle such as city blocks and field blocks. The block sizes demonstrate the scaling property, i.e., far more small blocks than large ones. Interestingly, we find that the mean of all the block sizes can easily separate between small and large blocks- a high percentage (e.g., 90%) of smaller ones and a low percentage (e.g., 10%) of larger ones. Based on this regularity, termed as the head/tail division rule, we propose an approach to delineating city boundaries by grouping the smaller blocks. The extracted city sizes for the three largest European countries (France, Germany and UK) exhibit power law distributions. We further define the concept of border number as a topological distance of a block far from the outmost border to map the center(s) of the country and the city. We draw an analogy between a country and a city (or geographic space in general) with a complex organism like the human body or the human brain to further elaborate on the power of this block perspective in reflecting the structure or patterns of geographic space.
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| 8. |
- Jouybari, Arash, et al.
(författare)
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Numerical Analysis of GNSS Signal Outage Effect on EOPs Solutions Using Tightly Coupled GNSS/IMU Integration : A Simulated Case Study in Sweden
- 2023
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Ingår i: Sensors. - : MDPI AG. - 1424-8220. ; 23:14
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Tidskriftsartikel (refereegranskat)abstract
- The absence of a reliable Global Navigation Satellite System (GNSS) signal leads to degraded position robustness in standalone receivers. To address this issue, integrating GNSS with inertial measurement units (IMUs) can improve positioning accuracy. This article analyzes the performance of tightly coupled GNSS/IMU integration, specifically the forward Kalman filter and smoothing algorithm, using both single and network GNSS stations and the post-processed kinematic (PPK) method. Additionally, the impact of simulated GNSS signal outage on exterior orientation parameters (EOPs) solutions is investigated. Results demonstrate that the smoothing algorithm enhances positioning uncertainty (RMSE) for north, east, and heading by approximately 17-43% (e.g., it improves north RMSE from 51 mm to a range of 42 mm, representing a 17% improvement). Orientation uncertainty is reduced by about 60% for roll, pitch, and heading. Moreover, the algorithm mitigates the effects of GNSS signal outage, improving position uncertainty by up to 95% and orientation uncertainty by up to 60% using the smoothing algorithm instead of the forward Kalman filter for signal outages up to 180 s.
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| 9. |
- Liu, Xintao, 1976-
(författare)
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The Principle of Scaling of Geographic Space and its Application in Urban Studies
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Geographic space is the large-scale and continuous space that encircles the earth and in which human activities occur. The study of geographic space has drawn attention in many different fields and has been applied in a variety of studies, including those on cognition, urban planning and navigation systems. A scaling property indicates that small objects are far more numerous than large ones, i.e., the size of objects is extremely diverse. The concept of scaling resembles a fractal in geometric terms and a power law distribution from the perspective of statistical physics, but it is different from both in terms of application. Combining the concepts of geographic space and scaling, this thesis proposes the concept of the scaling of geographic space, which refers to the phenomenon that small geographic objects or representations are far more numerous than large ones. From the perspectives of statistics and mathematics, the scaling of geographic space can be characterized by the fact that the sizes of geographic objects follow heavy-tailed distributions, i.e., the special non-linear relationships between variables and their probability.In this thesis, the heavy-tailed distributions refer to the power law, lognormal, exponential, power law with an exponential cutoff and stretched exponential. The first three are the basic distributions, and the last two are their degenerate versions. If the measurements of the geographic objects follow a heavy-tailed distribution, then their mean value can divide them into two groups: large ones (a low percentage) whose values lie above the mean value and small ones (a high percentage) whose values lie below. This regularity is termed as the head/tail division rule. That is, a two-tier hierarchical structure can be obtained naturally. The scaling property of geographic space and the head/tail division rule are verified at city and country levels from the perspectives of axial lines and blocks, respectively.In the study of geographic space, the most important concept is geographic representation, which represents or partitions a large-scale geographic space into numerous small pieces, e.g., vector and raster data in conventional spatial analysis. In a different context, each geographic representation possesses different geographic implications and a rich partial knowledge of space. The emergence of geographic information science (GIScience) and volunteered geographic information (VGI) greatly enable the generation of new types of geographic representations. In addition to the old axial lines, this thesis generated several types of representations of geographic space: (a) blocks that were decomposed from road segments, each of which forms a minimum cycle such as city and field blocks (b) natural streets that were generated from street center lines using the Gestalt principle of good continuity; (c) new axial lines that were defined as the least number of individual straight line segments mutually intersected along natural streets; (d) the fewest-turn map direction (route) that possesses the hierarchical structure and indicates the scaling of geographic space; (e) spatio-temporal clusters of the stop points in the trajectories of large-scale floating car data.Based on the generated geographic representations, this thesis further applies the scaling property and the head/tail division rule to these representations for urban studies. First, all of the above geographic representations demonstrate the scaling property, which indicates the scaling of geographic space. Furthermore, the head/tail division rule performs well in obtaining the hierarchical structures of geographic objects. In a sense, the scaling property reveals the hierarchical structures of geographic objects. According to the above analysis and findings, several urban studies are performed as follows: (1) generate new axial lines based on natural streets for a better understanding of urban morphologies; (2) compute the fewest-turn and shortest map direction; (3) identify urban sprawl patches based on the statistics of blocks and natural cities; (4) categorize spatio-temporal clusters of long stop points into hotspots and traffic jams; and (5) perform an across-country comparison of hierarchical spatial structures.The overall contribution of this thesis is first to propose the principle of scaling of geographic space as well as the head/tail division rule, which provide a new and quantitative perspective to efficiently reduce the high degree of complexity and effectively solve the issues in urban studies. Several successful applications prove that the scaling of geographic space and the head/tail division rule are inspiring and can in fact be applied as a universal law, in particular, to urban studies and other fields. The data sets that were generated via an intensive geo-computation process are as large as hundreds of gigabytes and will be of great value to further data mining studies.
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| 10. |
- Milutinovic, Goran, et al.
(författare)
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GISwaps: A New Method for Decision Making in Continuous Choice Models Based on Even Swaps
- 2018
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Ingår i: International Journal of Decision Support System Technology. - : IGI Global. - 1941-6296 .- 1941-630X. ; 10:3, s. 57-78
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Tidskriftsartikel (refereegranskat)abstract
- This article describes how continuous GIS-MCDM problems are commonly managed by combining some weighting method based on pairwise comparisons of criteria with an aggregation method. The reliability of this approach may be questioned, though. First, assigning weights to criteria, without taking into consideration the actual consequences or values of the alternatives, is in itself controversial. Second, the value functions obtained by this approach are in most cases linear, which is seldom the case in reality. The authors present a new method for GIS-MCDM in continuous choice models based on Even Swaps. The method is intuitive and easy to use, based on value trade-offs, and thus not relying on criteria weighting. Value functions obtained when using the method may be linear or non-linear, and thereby are more sensitive to the characteristics of the decision space. The performed case study showed promising results regarding the reliability of the method in GIS-MCDM context.
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