The development of the next major version 3.0 of the international OGC standard CityGML is nearing its end. CityGML 3.0 will come up with a variety of new features and revisions of existing modules that will increase the usability of CityGML for more user groups and areas of application. This includes a new space concept, a revised level-of-detail (LOD) concept, the representation of time-dependent properties, the possibility to manage multiple versions of cities, the representation of city objects by point clouds, an improved modelling of constructions, the representation of building units and storeys, an improved representation of traffic infrastructure as well as a clear separation of the conceptual model and the data encodings that allow for providing further encoding specifications besides GML. This paper gives an overview of these new and revised concepts, and illustrates their application through selected use cases. KeywordsCityGML 3.0 · 3D city models · Space concept Zusammenfassung CityGML 3.0: Neue Funktionen eröffnen neue Anwendungen. Die Entwicklung der nächsten Hauptversion 3.0 des internationalen OGC-Standards CityGML nähert sich dem Ende. CityGML 3.0 wird mit einer Vielzahl an neuen Funktionen und der Überarbeitung bestehender Module aufwarten, die die Benutzerfreundlichkeit von CityGML für weitere Benutzergruppen und Anwendungsbereiche verbessern. Dazu gehören ein neues Space-Konzept, ein überarbeitetes Level-of-Detail (LOD)-Konzept, die Darstellung von zeitabhängigen Eigenschaften, die Möglichkeit, mehrere Versionen von Stadtmodellen gleichzeitig zu verwalten, die Darstellung von Stadtobjekten durch Punktwolken, eine verbesserte Modellierung von sonstigen Bauwerken, die Darstellung von Gebäudeeinheiten und Etagen, eine verbesserte Darstellung der Verkehrsinfrastruktur sowie eine klare Trennung des konzeptuellen Modells von der Datenhaltung, die es erlaubt, neben GML weitere Datenformate bereitzustellen. Dieser Artikel gibt einen Überblick über die neuen und überarbeiteten Konzepte und veranschaulicht ihre Anwendung anhand ausgewählter Beispiele.

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.

Typically, smart city projects involve complex distributed systems having multiple stakeholders and diverse applications. These applications involve a multitude of sensor and IoT platforms for managing different types of timeseries observations. In many scenarios, timeseries data is the result of specific simulations and is stored in databases and even simple files. To make well-informed decisions, it is essential to have a proper data integration strategy, which must allow working with heterogeneous data sources and platforms in interoperable ways. In this paper, we present a new lightweight web service called InterSensor Service allowing to simply connect to multiple IoT platforms, simulation specific data, databases, and simple files and retrieving their observations without worrying about data storage and the multitude of different APIs. The service encodes these observations “on-the-fly” according to the standardized external interfaces such as the OGC Sensor Observation Service and OGC SensorThings API. In this way, the heterogeneous observations can be analyzed and visualized in a unified way. The service can be deployed not only by the users to connect to different sources but also by providers and stakeholders to simply add further interfaces to their platforms realizing interoperability according to international standards. We have developed a Java-based implementation of the InterSensor Service, which is being offered free as open source software. The service is already being used in smart city projects and one application for the district Queen Elizabeth Olympic Park in London is shown in this paper.

ABSTRACT:Smart cities provide effective integration of human, physical and digital systems operating in the built environment. The advancements in city and landscape models, sensor web technologies, and simulation methods play a significant role in city analyses and improving quality of life of citizens and governance of cities. Semantic 3D city models can provide substantial benefits and can become a central information backbone for smart city infrastructures. However, current generation semantic 3D city models are static in nature and do not support dynamic properties and sensor observations. In this paper, we propose a new concept called Dynamizer allowing to represent highly dynamic data and providing a method for injecting dynamic variations of city object properties into the static representation. The approach also provides direct capability to model complex patterns based on statistics and general rules and also, real-time sensor observations. The concept is implemented as an Application Domain Extension for the CityGML standard. However, it could also be 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.

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