1,720,952 research outputs found
A proposal for an improved transportation model in CityGML
Full text linkCityGML, an OGC standard, is an open data model for virtual 3D city models and includes buildings, roads, terrain, water bodies, etc. While many modules are well-developed (eg buildings, bridges, tunnels), the transportation model is, based on our consultations with various government agencies and municipalities, not sufficient for most transportation applications. We propose in this paper several improvements to the CityGML v2. 0 Transportation module, and to the previous efforts for improving it. Our additions are based on the consultations we had, and on the use-cases that were identified. We argue that the following changes are necessary: A) multi-LoD modelling of roads, B) carriageway representation, C) detailed intersection modelling and, D) introducing waterways as a new sub-class.Urban Data ScienceTransport and Plannin
Knowledge sharing on Q&A fora: challenges of automated interaction analysis
No full textQ\&A fora have developed into a precious tool for online knowledge exchange. Being community-driven, openly accessible and free, getting an answer to a complicated question can nowadays be a matter of minutes. This research investigates the specific case of gis.stackexchange, a technical Q&A forum used by Geographic Information Systems professionals. A central topic is the interaction between users. Based on existing research, an automated approach is elaborated and a big data analysis is performed. Also, a link between the outcomes and self-reflective behaviour found on the community meta forum is established. Factors positively influencing interaction as defined by the approach are identified (implication of the author(s), presence of images and code snippets). Furthermore, weaknesses such as the low share of interactions associated to an alteration (of the original post) are also discussed. These outcomes eventually lead to a series of recommendations for the forum itself and related formats.Applied Sciences | Science Communicatio
A framework for the representation of two versions of a 3D city model in 4D space
No full text3D city models are being increasingly adopted by organisations in order to serve application needs related to urban areas. In order to fulfil the different requirements of various applications, the concept of Level of Detail (LoD) has been incorporated in 3D city models specifications, such as CityGML. Therefore, datasets of different LoDs are being created for the same areas by several organisations for their own use cases. Meanwhile, as time progresses newer versions of existing 3D city models are being created by vendors. Nevertheless, the existing mechanisms for representating multi-LoD data has not been adopted by the users and there has been little effort on the implementation of a mechanism to store multiple revisions of a city model. This results in redundancy of information and the existence of multiple datasets inconsistent with each other. Alternatively, a representation of time or scale as additional dimensions to the three spatial ones has been proposed as a better way to store multiple versions of datasets while retaining information related to the corresponding features between datasets. In this paper, we propose a conceptual framework with initial considerations for the implementation of a 4D representation of two states of a 3D city model. This framework defines both the data structure of such an approach, as well as the methodology according to which two existing 3D city models can be compared, associated and stored with their correspondences in 4D. The methodology is defined as six individual steps that have to be undertaken, each with its own individual requirements and goals that have to be challenged. We, also, provide some examples and considerations for the way those steps can be implemented.Urban Data Scienc
Built Environmental Correlates of Cycling Accidents Involving Fatalities and Serious Injuries in London, UK
No full textIntroduction: Approximately 2,552 individuals were killed or seriously injured through cycling accidents in the Greater London Area between 2010 and 2015. The purpose of this study is to investigate a wide range of built environmental correlates of cycling accidents resulting in KSI so that we can identify potential areas for targeted interventions.Methods: We performed a cross-sectional analysis to examine the association between serious cycling injuries (2010-15), using road segment as the unit of analysis, and a wide range of built environmental characteristics. Multilevel models were used to account for potential spatial clustering.Results: Serious cycling injuries were independently associated with higher commercial and residential densities, higher distance to speed camera, higher bus, car, and 2-wheeled (motorcycle and moped) traffic, and higher density of alcohol outlets. Greenspace was associated with decreased odds of injuries up to the 3rd quartile, but roads adjacent to the highest levels of green space (4th quartile) had increased odds of injuries. Findings from our study point to the potential of urban planning interventions to reduce serious cycling injuries (e.g., speed cameras, improving safety near alcohol outlets and in parks, and recreational areas, etc.). Further research using quasi-experimental approaches is required to evaluate whether the implementation of interventions leads to injury reductions.Urban Data Scienc
Flood damage cost estimation in 3D based on an indicator modelling framework
No full textFlooding and other natural disasters pose risks to cities and residential homes, and these are set to increase in the face of climate change. Single-family residential buildings are of particular interest because they are difficult to insure and often highlight wealth discrepancies in society in the wake of natural disasters. Calculating building replacement cost based on a specific natural disaster is of interest to municipalities and city planners who are working to prepare their cities for potential future costs of recovery. There are models designed by flood modellers, and there are models designed by city planners. This paper presents a novel Indicator Modelling Framework (IMF) by bringing together a model from the flooding domain (HAZUS) and a model from the geospatial application domain (e.g. CityGML) and weaving them together. The weaving process automatically calculates the building replacement cost for buildings based on a flood scenario as well as generates domain-specific metadata. The weaving process capitalizes on the strengths of both models, and future work will focus on weaving between models in other domains.Urban Data Scienc
Shape based classification of seismic building structural types
No full textThis paper investigates automatic prediction of seismic building structural types described by the Global Earthquake Model (GEM) taxonomy, by combining remote sensing, cadastral and inspection data in a supervised machine learning approach. Our focus lies on the extraction of detailed geometric information from a point cloud gained by aerial laser scanning. To describe the geometric shape of a building we apply Shape-DNA, a spectral shape descriptor based on the eigenvalues of the Laplace-Beltrami operator. In a first experiment on synthetically generated building stock we succeed in predicting the roof type of different buildings with accuracies above 80%, only relying on the Shape-DNA. The roof type of a building thereby serves as an example of a relevant feature for predicting GEM attributes, which cannot easily be identified and described by using traditional methods for shape analysis of buildings. Further research is necessary in order to explore the usability of Shape-DNA on real building data. In a second experiment we use real-world data of buildings located in the Groningen region in the Netherlands. Here we can automatically predict six GEM attributes, such as the type of lateral load resisting system, with accuracies above 75% only by taking a buildings footprint area and year of construction into account.Design InformaticsPattern Recognition and Bioinformatic
From road centrelines to carriageways: A reconstruction algorithm
No full textRoads are important for many urban planning applications, such as traffic modelling and delivery vehicle routing. At present, most available datasets represent roads only as centrelines. This is particularily true for OpenStreetMap which provides, among many features, road networks at worldwide coverage. Furthermore, most approaches for creating more detailed networks, such as carriageways or lanes, focus on doing so from sources that are not easy to acquire, such as satellite imagery or LiDAR scans. In this paper we present a methodology to create carriageways based on OpenStreetMap's centrelines and open access areal representations (i.e. polygons) to determine which roads should be represented as two individual carriageways. We applied our methodology in five areas across four different countries with different built environments. We analysed the outcome in a delivery routing problem to evaluate the validity of our results. Our results suggest that this method can be effectively applied to create carriageways anywhere in the world, as long as there is sufficient coverage by OpenStreetMap and an areal representation dataset of roads. Urban Data Scienc
A metadata ADE for CityGML
No full textWhile there exist international standards for geospatial metadata (ISO 19115), these are rarely used in practice for 3D datasets, and one of the OGC standards for 3D city models, CityGML, does not offer a mechanism to store metadata in a structured way. Having metadata in CityGML files, which are in practice often very large and complex, would provide us with the ability to quickly understand the nature of a dataset and to determine if it is relevant for a specific task. Alack of metadata introduces uncertainty into models that are already full of assumptions and estimations. In this paper, we first examine the metadata needs that are specific for 3D geographical datasets and propose ISO 19115compliant categories. We then describe how these can be used within CityGML by defining an Application DomainExtension (ADE), which allows us to store metadata for existing city objects of CityGML, as well as objects in other domain-specific ADEs. Our ADE, its schema in both UML and XSD, and sample datasets is openly accessible, and it can be easily extended to support application specific metadata. In addition the metadata elements have been added to the core of CityJSON. We also offer software to generate automatically many of the metadata categories and we propose coupling it with the source 3D dataset.Urban Data Scienc
A Data Structure to Incorporate Versioning in 3D City Models
No full textA 3D city model should be constantly updated with new versions, either to reflect the changes in its real-world counterpart, or to improve and correct parts of the model. However, the current standards for 3D city models do not support versioning, and existing version control systems do not work well with 3D city models. In this paper, we propose an approach to support versioning of 3D city models based on CityJSON and the concepts behind the Git version control system, including distributed and non-linear workflows. We demonstrate the benefits of our approach in two examples and in our software prototype, which is able to extract a given version of a 3D city model and to display its history.Urban Data Scienc
Generalising 3D Buildings from LoD2 to LoD1
No full textThe increasing popularity of 3D city models in navigation, urban planning, etc.,necessitates application-specific and geometrically accurate and valid models. The concept of Levels of Detail (LoDs) indicate a model’s scale of adherence to its real-world counterpart. Highly detailed datasets often contain errors or require an exorbitant level of computing power. Given the high availability of LoD2 datasets, our research focuses on three considerations for generalising to LoD1: the vertical reference, extrusion vs. downtrusion and floor plan simplification. We present in this paper an initial methodology that produces geometrically accurate LoD1 models with a reduction of over 70% of the original file size.Urban Data Scienc
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