This paper demonstrates how Linked Data can be used to provide a semantically rich connection between the domains of Building Information Modeling (BIM) and Geographic Information Systems (GIS). Expertise from both domains is necessary for the planning of infrastructure projects such as roads, tunnels, bridges, and railways, as these projects usually require the consideration of widely diverging scales. As BIM and GIS rely on different types of data modeling standards, a conversion between the data models will inevitably result in data loss. To overcome this problem, we propose to utilize the concept of Linked Data which allows the original data to coexist and provide coherence by establishing references between the corresponding entities of both standards. The approach is illustrated using exemplary models of shield tunnels in both, the IFC and the CityGML format.

The administration of modern cities is a complex task involving various disciplines. To satisfy their specific needs regarding planning and decision making, all of them require a virtual representation of the city. Semantic 3D city models offer a reliable and increasingly available virtual representation of real world objects in an urban context. They serve as an integration platform for information and applications around the city system, because data from different domains can be linked to the same objects representing real world urban objects. This work gives an overview on the current state of applications based on semantic 3D city models and how they can be categorized. Three use cases are explained in detail. Based on city models according to the CityGML standard, first a tool for estimating the solar irradiation on roofs and facades is introduced. By the combination of a transition model, sun position calculation, and an approximation of the hemisphere the direct, diffuse and global irradiation as well as the SkyViewFactor are computed. Second, an application for the simulation of detonations in urban space is presented. The city model is converted to a field-based representation for running a Computational Fluid Dynamics (CFD) simulation. By storing logical links between the object and the field-based representation of the city model, information exchange between the simulation tool and the city models is realized. The third application demonstrates the estimation of the energy demand of buildings based on official statistical data and the simulation of refurbishment measures. All three applications use a cloudbased 3D web client for visualization of the city model and the application results including interactive analysis capabilities.

Commission IV, WG IV/7KEY WORDS: Collaborative planning, integration of 3D modeling and simulation, multi-scale modelling, mobile computer vision. ABSTRACT:Computer-aided collaborative and multi-scale 3D planning are challenges for complex railway and subway track infrastructure projects in the built environment. Many legal, economic, environmental, and structural requirements have to be taken into account. The stringent use of 3D models in the different phases of the planning process facilitates communication and collaboration between the stake holders such as civil engineers, geological engineers, and decision makers. This paper presents concepts, developments, and experiences gained by an interdisciplinary research group coming from civil engineering informatics and geo-informatics banding together skills of both, the Building Information Modeling and the 3D GIS world. New approaches including the development of a collaborative platform and 3D multi-scale modelling are proposed for collaborative planning and simulation to improve the digital 3D planning of subway tracks and other infrastructures. Experiences during this research and lessons learned are presented as well as an outlook on future research focusing on Building Information Modeling and 3D GIS applications for cities of the future.

Abstract. A range of different and increasingly accessible acquisition methods, the possibility for frequent data updates of large areas, and a simple data structure are some of the reasons for the popularity of three-dimensional (3D) point cloud data. While there are multiple techniques for segmenting and classifying point clouds, capabilities of common data formats such as LAS for providing semantic information are mostly limited to assigning points to a certain category (classification). However, several fields of application, such as digital urban twins used for simulations and analyses, require more detailed semantic knowledge. This can be provided by semantic 3D city models containing hierarchically structured semantic and spatial information. Although semantic models are often reconstructed from point clouds, they are usually geometrically less accurate due to generalization processes. First, point cloud data structures / formats are discussed with respect to their semantic capabilities. Then, a new approach for integrating point clouds with semantic 3D city models is presented, consequently combining respective advantages of both data types. In addition to elaborate (and established) semantic concepts for several thematic areas, the new version 3.0 of the international Open Geospatial Consortium (OGC) standard CityGML also provides a PointCloud module. In this paper a scheme is shown, how CityGML 3.0 can be used to provide semantic structures for point clouds (directly or stored in a separate LAS file). Methods and metrics to automatically assign points to corresponding Level of Detail (LoD)2 or LoD3 models are presented. Subsequently, dataset examples implementing these concepts are provided for download.

ABSTRACT:Semantic 3D city models play an important role in solving complex real-world problems and are being adopted by many cities around the world. A wide range of application and simulation scenarios directly benefit from the adoption of international standards such as CityGML. However, most of the simulations involve properties, whose values vary with respect to time, and the current generation semantic 3D city models do not support time-dependent properties explicitly. In this paper, the details of solar potential simulations are provided operating on the CityGML standard, assessing and estimating solar energy production for the roofs and facades of the 3D building objects in different ways. Furthermore, the paper demonstrates how the time-dependent simulation results are better-represented inline within 3D city models utilizing the so-called Dynamizer concept. This concept not only allows representing the simulation results in standardized ways, but also delivers a method to enhance static city models by such dynamic property values making the city models truly dynamic. The dynamizer concept has been implemented as an Application Domain Extension of the CityGML standard within the OGC Future City Pilot Phase 1. The results are given in this paper.