Semantic 3D city models describe city entities by objects with thematic and spatial attributes and their interrelationships. Today, more and more cities worldwide are representing their 3D city models according to the CityGML standard issued by the Open Geospatial Consortium (OGC). Various application areas of 3D city models such as urban planning or architecture require that authorities or stakeholders manage parallel alternative versions of city models and their evolution over time, which is currently not supported by the CityGML standard 2.0. In this paper, we propose a concept and a data model extending CityGML by denoting versions of models or model elements as planning alternatives. We support transitions between these versions to manage history or evolution of the city models over time. This approach facilitates the interoperable integration and exchange of different versions of a 3D city model within one dataset, including a possibly complex history of a repository. Such an integrated dataset can be used by different software systems to visualize and work with all the versions. The versions and version transitions in our proposed data model are bi-temporal in nature. They are defined as separate feature types, which allow the users to manage versioning and to perform queries about versions using an OGC Web Feature Service. We apply this data model to a use case of planning concurrent versions and demonstrate it with example instance data. The concept is general in the sense that it can be directly applied to other GML-based application schemas including the European INSPIRE data themes and national standards for topography and cadasters like the British Ordnance Survey Mastermap or the German cadaster standard ALKIS.
h i g h l i g h t s • Primitive extraction: detect primitive which corresponds locally to the 3D mesh. • Adjacency relation determination: define the relationship between primitives. • Wire construction: based on the intersection curves between neighboring primitives. • B-Rep creation: that works even in the case of an outline on a periodic surface.
Studying and planning urban evolution is essential to understanding the past and designing the cities of the future and can be facilitated by providing means for sharing, visualizing, and navigating in cities, on the web, in space and in time. Standard formats, methods, and tools exist for visualizing large-scale 3D cities on the web. In this article, we go further by integrating the temporal dimension of cities to geospatial web delivery standard formats. In doing so, we enable interactive visualization of large-scale timeevolving 3D city models on the web. A key characteristic of this article lies in the proposed four-step generic approach. First, we design a generic conceptual model of standard formats for delivering 3D cities on the web. Then, we formalize and integrate the temporal dimension of cities to this generic conceptual model. After that, we specify the conceptual model into the 3D Tiles standard at logical and technical specification levels, resulting in an extension of 3D Tiles for delivering time-evolving 3D city models on the web. Finally, we propose an open-source implementation, experiments, and an evaluation of the propositions and visualization rules. We also give access to reproducibility notes allowing researchers to replicate all the experiments.
CityGML is a recent standard developed to describe, store and exchange virtual city models. Numerous software programmes have been proposed to construct, edit, modify and visualize city models, but visualisation in a web browser is still challenging. In this paper we propose a framework based on standards for visualising a large amount of 3D city data. CityGML files are processed automatically to provide a city model composed of geometries, textures and semantics. Exchanges follow the pending Open Geospatial standard named 3D portrayal. In this paper, we also demonstrate that a solution where semantics and geometries are exchanged together is possible. An effort has been made to show that an approach based on progressive textures may also be possible.
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International audienceWe present a new photoclinometric reconstruction method based on the deformation of a 3D mesh. The optimization process of our method relies on a maximum likelihood estimation with a density function measuring discrepancies between observed images and the correspondingsynthetic images calculated from the progressively deformed 3D mesh. An input mesh is necessary and can be obtained from other methods or created by implementing a multiresolution scheme. We present a 3D shape model of an asteroid obtained by this method and compare it with the models obtained with two high-resolution 3D reconstruction techniques, stereophotogrammetry, and stereophotoclinometry
International audienceDue to the advances in computer graphics and improved network speed it is now possible to navigate in3D virtual world in real time. Until now, technologies employed require to install standalone application orplugins on navigators. The arrival of HTML 5 brings news solutions to visualize 3D data in a browser withWebGL. Several globe projects have proven that such technologies can be employed. Unfortunately, demonstrationsare often based on proprietary formats to exchange or to store data. In this work, we propose touse CityGML: a standard provided by the Open Geospatial Consortium. CityGML files are imported in ourEnvironment Editor. With several tools that we present in this paper, data are processed and stored. A clientserver application is also presented to permit the visualization of geometry and semantic in a navigato
International audienceToday, many cities have at their disposal a digital model useful in many applications such as decision making in urban planning. 3D data representing objects in the city such as land and buildings often comes from successive acquisition campaigns. Unfortunately, digital models of cities can have many versions of the same area. Having tools to detect changes becomes a necessity. It is then possible to highlight any differences between multiple versions of the same area in 3D. A second application can be related to the possibility of making a temporal representation by taking into account the detected changes. In this paper, we propose a set of tools to detect changes. The use case is done on buildings. Our method is based on CityGML and cadastre files. The output is a CityGML file containing a representation of the evolution over time of the objects in the city
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