Urban scholars have studied street networks in various ways, but there are data availability and consistency limitations to the current urban planning/street network analysis literature. To address these challenges, this article presents OSMnx, a new tool to make the collection of data and creation and analysis of street networks simple, consistent, automatable and sound from the perspectives of graph theory, transportation, and urban design. OSMnx contributes five significant capabilities for researchers and practitioners: first, the automated downloading of political boundaries and building footprints; second, the tailored and automated downloading and constructing of street network data from OpenStreetMap; third, the algorithmic correction of network topology; fourth, the ability to save street networks to disk as shapefiles, GraphML, or SVG files; and fifth, the ability to analyze street networks, including calculating routes, projecting and visualizing networks, and calculating metric and topological measures. These measures include those common in urban design and transportation studies, as well as advanced measures of the structure and topology of the network. Finally, this article presents a simple case study using OSMnx to construct and analyze street networks in Portland, Oregon.

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OSMnx: New Methods for Acquiring, Constructing, Analyzing, and Visualizing Complex Street Networks

In the last decades, 3D city models appear to have been predominantly used for visualisation; however, today they are being increasingly employed in a number of domains and for a large range of tasks beyond visualisation. In this paper, we seek to understand and document the state of the art regarding the utilisation of 3D city models across multiple domains based on a comprehensive literature study including hundreds of research papers, technical reports and online resources. A challenge in a study such as ours is that the ways in which 3D city models are used cannot be readily listed due to fuzziness, terminological ambiguity, unclear added-value of 3D geoinformation in some instances, and absence of technical information. To address this challenge, we delineate a hierarchical terminology (spatial operations, use cases, applications), and develop a theoretical reasoning to segment and categorise the diverse uses of 3D city models. Following this framework, we provide a list of identified use cases of 3D city models (with a description of each), and their applications. Our study demonstrates that 3D city models are employed in at least 29 use cases that are a part of more than 100 applications. The classified inventory could be useful for scientists as well as stakeholders in the geospatial industry, such as companies and national mapping agencies, as it may serve as a reference document to better position their operations, design product portfolios, and to better understand the market.

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Applications of 3D City Models: State of the Art Review

CityGML is the international standard of the Open Geospatial Consortium (OGC) for the representation and exchange of 3D city models It defines the three-dimensional geometry, topology, semantics and appearance of the most relevant topographic objects in urban or regional contexts These definitions are provided in different, well-defined Levels-of-Detail (multiresolution model) The focus of CityGML is on the semantical aspects of 3D city models, its structures, taxonomies and aggregations, allowing users to employ virtual 3D city models for advanced analysis and visualization tasks in a variety of application domains such as urban planning, indoor/outdoor pedestrian navigation, environmental simulations, cultural heritage, or facility management This is in contrast to purely geometrical/graphical models such as KML, VRML, or X3D, which do not provide sufficient semantics CityGML is based on the Geography Markup Language (GML), which provides a standardized geometry model Due to this model and its well-defined semantics and structures, CityGML facilitates interoperable data exchange in the context of geo web services and spatial data infrastructures Since its standardization in 2008, CityGML has become used on a worldwide scale: tools from notable companies in the geospatial field provide CityGML interfaces Many applications and projects use this standard CityGML is also having a strong impact on science: numerous approaches use CityGML, particularly its semantics, for disaster management, emergency responses, or energy-related applications as well as for visualizations, or they contribute to CityGML, improving its consistency and validity, or use CityGML, particularly its different Levels-of-Detail, as a source or target for generalizations This paper gives an overview of CityGML, its underlying concepts, its Levels-of-Detail, how to extend it, its applications, its likely future development, and the role it plays in scientific research Furthermore, its relationship to other standards from the fields of computer graphics and computer-aided architectural design and to the prospective INSPIRE model are discussed, as well as the impact CityGML has and is having on the software industry, on applications of 3D city models, and on science generally

CityGML – Interoperable semantic 3D city models

The OpenStreetMap (OSM) project is a prime example in the field of Volunteered Geographic Information (VGI). Worldwide, several hundred thousand people are currently contributing information to the ―free‖ geodatabase. However, the data contributions show a geographically heterogeneous pattern around the globe. Germany counts as one of the most active countries in OSM; thus, the German street network has undergone an extensive development in recent years. The question that remains is this: How does the street network perform in a relative comparison with a commercial dataset? By means of a variety of studies, we show that the difference between the OSM street network for car navigation in Germany and a comparable proprietary dataset was only 9% in June 2011. The results of our analysis regarding the entire street network showed that OSM even exceeds the information provided by the proprietary dataset by 27%. Further analyses show on what scale errors can be reckoned with in the topology of the street network, and the completeness of turn restrictions and street name information. In addition to the analyses conducted over the past few years, projections have additionally been made about the point in time by which the OSM dataset for Germany can be considered ―complete‖ in relative comparison to a commercial dataset.

The Street Network Evolution of Crowdsourced Maps: OpenStreetMap in Germany 2007-2011

Tracking tourists in the digital age

Generating web-based 3D City Models from OpenStreetMap: The current situation in Germany

The creation of Spatial Data Infrastructures (SDI) has been an important and actively studied topic in geoscience research for years. It is also regarded in politics and by decision makers as leveraging technology for reducing thr time and cost of geo services for internal usage as well as for public information services. In Europe, the new INSPIRE (Infrastructure for Spatial Information in Europe) directive 2007/2/EC provides general rules for implementating national spatial data infrastructures for environmental policies. SDIs must rely on open standards specified by the Open Geospatial Consortium (CSW, WMS, WFS, WCS, WPS, OpenLS, etc.)

Towards 3D Spatial Data Infrastructures (3D-SDI) based on open standards — experiences, results and future issues

In order to generate 3D worlds in an automated way it is important to solve the problem of integrating existing 2D and 3D data automatically. We explain some of the issues of this problem in this paper. We also introduce mechanisms for automated generation of integrated 3D geo-data sets, as well as a prototype that implements these. It is necessary to distinguish the different problems and methods for the generation of buildings and other man made structures on the one hand and digital elevation models and land use areas on the other.Using the integrated data and the developed algorithms we work on a strategy for the dynamic generation of 3D tour animations through a virtual city and landscape model that is optimized for a specific tour. We introduce components that allow the generation of a virtual 3D-tour through our demonstration region - the city of Heidelberg - by the automated integration of 2D and 3D data sources to a 3D model. The user is presented with an interactive animation of a 3D scene of a dynamically calculated tour through the hybrid 3D model of Heidelberg focusing on the area around the tour.

Generation of VRML city models for focus based tour animations: integration, modeling and presentation of heterogeneous geo-data sources

In this paper, we describe an approach for efficiently streaming large and highly detailed 3D city models, which is based on open standards and open source developments. This approach meets both the rendering performance requirements in WebGL enabled web browsers and the requirements by 3D Geographic Information Systems regarding data structuring, geo-referencing and accessibility of feature properties. 3D city models are assumed to be available as CityGML data sets due to its widespread adoption by public authorities. The Cesium.js open source virtual globe is used as a platform for embedding custom 3D assets. glTF and related formats are used for efficiently encoding 3D data and for enabling streaming of large 3D models. In order to fully exploit the capabilities of web browsers and standard internet protocols, a series of filtering and data processing steps must be performed, which are described in this paper.

Using glTF for streaming CityGML 3D city models

In this paper we show how to efficiently integrate traditional GIS data into terrain models in order to generate complete 3D maps with little overhead for textures. The results meet the requirements for the Web 3D Service (W3DS), a proposal for the standardization for delivering 3D web maps. Our approach is designed to create fully vectorized 3D scenes that deliver the best possible quality and do not require dynamic texture generation and handling. We describe the mesh operations for integrating polygonal GIS data like forests, parks, buildings blocks, or streets into the terrain mesh and compare the results with a texture based approach.

Arne Schilling

Papers

Generating web-based 3D City Models from OpenStreetMap: The current situation in Germany

Towards 3D Spatial Data Infrastructures (3D-SDI) based on open standards — experiences, results and future issues

Generation of VRML city models for focus based tour animations: integration, modeling and presentation of heterogeneous geo-data sources

Using glTF for streaming CityGML 3D city models

Vector based mapping of polygons on irregular terrain meshes for web 3d map services