CityGML Application Domain Extension (ADE): overview of developments <s> Overview of the identified ADEs Supporting applications <s> The Environmental Noise Directive of the European Union 2002/49/EG (END) obligates the EU member states to determine every 5 years the noise emission of major roads and railways, major airports, industrial activity sites and urban agglomerations and to document the results in noise maps. It poses high requirements, as a great number of statewide and ubiquitous geodata and thematic data in the third dimension is necessary (terrain, buildings, roads, railways). To provide these considerable amount of statewide 3D geodata, the state of North Rhine-Westphalia (NRW) follows a modern implementation concept, the sustainable use and enlargement of the Spatial Data Infrastructure GDI NRW. NRW provides for the first time statewide 3D geodata as features in CityGML via OGC Web Feature Services (3D building models in LOD1, ATKIS 3D road and railway data) and the Digital Terrain Model 10m grid via an OGC Web Coverage Service. CityGML is used as sole common exchange format between web services and noise calculation software to solve syntactic and semantic interoperability problems. A CityGML data base is realised, which contains approx. 10 million buildings. ::: ::: This article demonstrates the architecture of geodata provision, the 3D modelling in CityGML, the geodata refinement and interoperability tasks as well as the noise calculation results. <s> BIB001 </s> CityGML Application Domain Extension (ADE): overview of developments <s> Overview of the identified ADEs Supporting applications <s> The cadastral organization in the Netherlands, called the Kadaster, takes responsibility for the registration of land and property. In the current system used by the Kadaster, a piece of land, called a parcel is associated with legal information such as ownership right and ownership boundaries. A parcel may be associated either with a single ownership right or multiple ownership rights. For example, a parcel having a house owned by a single person indicates single ownership right and a parcel having a building with several apartments, each owned by a different person indicate multiple ownership rights. On selecting a parcel, its legal information is produced to the user. However in the case of multiple ownership rights, it is difficult to associate which part of the parcel is owned by which person. To address this issue, the current system produces a scanned image of the floor plans of the given building. These floor plans indicate the ownership rights of each floors. But the information from the scanned images of the floor plans cannot be interpreted by a computer for queries. Hence, there is a need for an alternative method to deal with parcels having multiple ownership rights. This thesis proposes the use of CityGML to visualize and to store cadastral information into buildings having single as well as multiple ownership rights in 3D. CityGML is an XML based, common semantic information model for the representation of 3D city objects. In order to represent legal information into CityGML, this thesis proposes an extension to CityGML for cadastral purposes. It also provides an automated process to represent legal information in extended CityGML. As a result, this thesis presents a proof of concept for a way to represent the multiple ownership rights associated with a given parcel. <s> BIB002 </s> CityGML Application Domain Extension (ADE): overview of developments <s> Overview of the identified ADEs Supporting applications <s> In today’s technologically advanced society the dependency of every citizen and company on working infrastructures is extremely high. Failures of critical infrastructures, such as the Italian blackout in 2003 or the failure of power supply in wide parts of Europe in 2006, demonstrate the strong linkage of networks across borders. However, also infrastructures within the same geographic region but of different types have strong interdependencies and failures in one type of network can have cascading effects onto the other networks. In order to support risk analysis and planning of emergency response actions the modeling of critical infrastructures and their mutual dependencies in 3D space is required. Decision makers need a comprehensive view of the disaster situation to be able to estimate the consequences of their action. For this purpose, a comprehensive understanding and simulation of cascading or looping effects as well as the propagation of the disaster extend is needed. But neither the existing utility networks models nor the international standards for modeling cities or buildings map the mutual interrelationships between different infrastructures or between the city and its infrastructures. <s> BIB003 </s> CityGML Application Domain Extension (ADE): overview of developments <s> Overview of the identified ADEs Supporting applications <s> 3D City models have so far neglected utility networks in built environments, both interior and exterior. Many urban applications, e.g. emergency response or maintenance operations, are looking for such an integration of interior and exterior utility. Interior utility is usually created and maintained using Building Information Model (BIM) systems, while exterior utility is stored, managed and analyzed using GIS. Researchers have suggested that the best approach for BIM/GIS integration is harmonized semantics, which allow formal mapping between the BIM and real world GIS. This paper provides preliminary ideas and directions for how to acquire information from BIM/Industry Foundation Class (IFC) and map it to CityGML utility network Application Domain Extension (ADE). The investigation points out that, in most cases, there is a direct one-to-one mapping between IFC schema and UtilityNetworkADE schema, and only in one case there is one-to-many mapping; related to logical connectivity since there is no exact concept to represent the case in UtilityNetworkADE. Many examples are shown of partial IFC files and their possible translation in order to be represented in UtilityNetworkADE classes. <s> BIB004 </s> CityGML Application Domain Extension (ADE): overview of developments <s> Overview of the identified ADEs Supporting applications <s> Computer games and serious geographic information systems (GIS) share many requirements with regard to storage, exchange, and visualization of geographic data. Furthermore, there is a demand for high-fidelity photo-realistic and non-photo-realistic visualization. This poses at least two questions: Is there a single data format standard suitable for serious GIS-based applications and computer games that supports state-of-the-art visual quality? How can computer games and serious applications benefit from each other, especially platform-wise? In this paper we will investigate both questions by taking a closer look at the CityGML standard in comparison to COLLADA and we will report on our findings in integrating CityGML with mainstream game technology. The main contribution of this paper to the field is a suggested way of integrating an important features of CityGML and Collada for high-quality visualization, i.e. programmable shader effects, and demonstrating the feasibility of employing a game console as a cheap and widely available device for geodata visualization and possibly other geodata-centric applications. <s> BIB005 </s> CityGML Application Domain Extension (ADE): overview of developments <s> Overview of the identified ADEs Supporting applications <s> CityGML is a standard data model for the representation, storage and exchange of 3D city models issued by the OGC (Open Geospatial Consortium). CityGML represents a very attractive solution that combines 3D information and semantic information in a single data model. The efficient visualization of the geometric information contained in the CityGML data model is still an open challenge. A survey of the state of the art shows that current approaches have to be improved. In this paper we introduce a new approach for efficient web visualization of CityGML without plugins based on the use of X3D and web services. The approach has been evaluated with an implementation applied to built heritage at urban scale based on an extended CityGML model. <s> BIB006 </s> CityGML Application Domain Extension (ADE): overview of developments <s> Overview of the identified ADEs Supporting applications <s> In this paper, the database that controls the indoor spatial information for robots and users is referred to as the spatial master database. We designed a data model and a map output model of the spatial master database. Based on the model, a spatial master database service which provides spatial information for robots as well as users is developed. An experimental demonstration at a commercial facility was conducted to show usability of the database. <s> BIB007 </s> CityGML Application Domain Extension (ADE): overview of developments <s> Overview of the identified ADEs Supporting applications <s> Precise and comprehensive knowledge about 3D urban space, critical infrastructures, and belowground features is required for simulation and analysis in the fields of urban and environmental planning, city administration, and disaster management. In order to facilitate these applications, geoinformation about functional, semantic, and topographic aspects of urban features, their mutual dependencies and their interrelations are needed. Substantial work has been done in the modeling and representation of aboveground features in the context of 3D city and building models. However, standardized models such as CityGML and IFC lack a rich information model for multiple and different underground structures. In contrast, existing utility network models are commonly tailored to a specific type of commodity, dedicated to serve as as-built documentation and thus are not suitable for the integrated representation of multiple and different utility infrastructures. Moreover, the mutual relations between networks as well as embedding into 3D urban space are not supported. The Utility Network ADE of CityGML as proposed in 2011 provides the required concepts and classes for the integration of multi-utility networks into the 3D urban environment. While the core model covers only the topological and topographic representation of network entities, the functional and semantic classification of network objects is now introduced in this paper. This paper will show how concepts and classes can be defined to fulfill the requirements of complex analyses and simulation, and how properties of specific networks can be defined with respect to 3D topography but also network connectivity and functional aspects. <s> BIB008 </s> CityGML Application Domain Extension (ADE): overview of developments <s> Overview of the identified ADEs Supporting applications <s> Abstract. In the context of increasing greenhouse gas emission and global demographic change with the simultaneous trend to urbanization, it is a big challenge for cities around the world to perform modifications in energy supply chain and building characteristics resulting in reduced energy consumption and carbon dioxide mitigation. Sound knowledge of energy resource demand and supply including its spatial distribution within urban areas is of great importance for planning strategies addressing greater energy efficiency. The understanding of the city as a complex energy system affects several areas of the urban living, e.g. energy supply, urban texture, human lifestyle, and climate protection. With the growing availability of 3D city models around the world based on the standard language and format CityGML, energy system modelling, analysis and simulation can be incorporated into these models. Both domains will profit from that interaction by bringing together official and accurate building models including building geometries, semantics and locations forming a realistic image of the urban structure with systemic energy simulation models. A holistic view on the impacts of energy planning scenarios can be modelled and analyzed including side effects on urban texture and human lifestyle. This paper focuses on the identification, classification, and integration of energy-related key indicators of buildings and neighbourhoods within 3D building models. Consequent application of 3D city models conforming to CityGML serves the purpose of deriving indicators for this topic. These will be set into the context of urban energy planning within the Energy Atlas Berlin. The generation of indicator objects covering the indicator values and related processing information will be presented on the sample scenario estimation of heating energy consumption in buildings and neighbourhoods. In their entirety the key indicators will form an adequate image of the local energy situation for decision making. An approach for extending the CityGML standard for the explicit storage of these indicators in relation to the according city object will be given by using the concept of CityGML Application Domain Extension (ADE). The aim of this approach is to initiate a discussion process for the specification of a standardized data model extension concerning energy assessment into 3D CityGML models, which facilitates the application of the Energy Atlas decision support concepts within other city models conforming to this standard. <s> BIB009 </s> CityGML Application Domain Extension (ADE): overview of developments <s> Overview of the identified ADEs Supporting applications <s> 3D representations have been recognized as an essential component of Augmented Reality (AR) oriented applications. However, not many examples of AR-oriented applications employ structured 3D data models despite the existence of standard 3D information models like CityGML. One of the reasons for this shortcoming can be explained by lack of a semantic-based modeling method for enriching AR-oriented data models with 3D features. Therefore, a three step procedure is proposed to address this limitation as (1) back-ward engineering of an AR-oriented application to its current data model, (2) enriching the current data model with 3D features, (3) and mapping the enriched model to a standard 3D information model. A notable contribution of this work is that the procedure of data modeling has been subject to the UModelAR meta-model which has brought a complementary standpoint to the employment of 3D geospatial modeling in AR environments. Furthermore, the 3D enriched data model has been mapped to CityGML information model with CityGML Application Domain Extension (ADE) concept. To demonstrate the feasibility of this approach, an operating mobile AR-oriented game has been used for the case study. <s> BIB010 </s> CityGML Application Domain Extension (ADE): overview of developments <s> Overview of the identified ADEs Supporting applications <s> Abstract It is generally acknowledged that immovable property taxes are one of the main revenue sources for local government. The literature emphasizes that the administration of property taxes needs well-developed inventories or registers that provide complete and accurate records of the taxed properties and their legal-economic attributes. This requirement is generally fulfilled by Spatial Data Infrastructures (SDIs) in which the coordinate exchange and sharing of geo-spatial data is provided by separate registers/information systems such as: cadastral systems, building and address registers. Recently, the Open Geospatial Consortium presented a core component of a 3D SDI in the form of an international domain standard for representing, storing and exchanging 3D city models. The CityGML allows the semantic and 3D geometrical representation of physical objects but does not deal with the legal and administrative aspects of the city objects which are required for the process of property taxation. This paper outlines the development of an Application Domain Extension (ADE) for the immovable property taxation domain that expands the CityGML data model with the legal and administrative concepts defined in Turkish Law. The study shows that this ADE could be a 3D national data model for municipal information systems and facilitate a more efficient taxation process, as well as providing data for urban planning, facility management and other municipal services. <s> BIB011 </s> CityGML Application Domain Extension (ADE): overview of developments <s> Overview of the identified ADEs Supporting applications <s> Standardization in spatial data and Cultural Heritage management is one of the main issues in this field of study and the efforts in this direction are twofold, data models and technological development. Regarding the first aspect some preliminary steps towards definition of common vocabularies and conceptual schemas for semantic classification will be analysed and discussed in order to define the open issues and the development strategies. On the side of the modelling languages and data manipulation tools the recent standard definitions and the research efforts are starting to provide a set of application tools for the semantic and spatial data modelling and information retrieving and manipulation. An application of these notions and tools will be performed on an Architectural Heritage case-study and the preliminary results will be exposed. <s> BIB012 </s> CityGML Application Domain Extension (ADE): overview of developments <s> Overview of the identified ADEs Supporting applications <s> The rapid technological evolution, which is characterizing all the disciplines involved within the wide concept of smart cities, becomes a key factor to trigger true user-driven innovation. In this context 3D city models will play an increasingly important role in our daily lives and become an essential part of the modern city information infrastructure (Spatial Data Infrastructure). The goal of this paper is to introduce the i-SCOPE (interoperable Smart City services through an Open Platform for urban Ecosystems) project methodology and implementations together with key technologies and open standards. Based on interoperable 3D CityGML UIMs, the aim of i-Scope is to deliver an open platform on top of which it possible to develop, within different domains, various "smart city" services. Moreover, in i-SCOPE different issues, transcending the mere technological domain, are being tackled, including aspects dealing with social and environmental issues. Indeed several tasks including citizen awareness, crowd source and voluntary based data collection as well as privacy issue concerning involved people should be considered. <s> BIB013 </s> CityGML Application Domain Extension (ADE): overview of developments <s> Overview of the identified ADEs Supporting applications <s> As our urban environments are densifying, it is essential to extend traditional cadastral systems that are based on two dimensional representation of ownership to support 3D. With the need to define property ownership in vertical as well as horizontal dimensions becoming pertinent around the world, a practical solution to represent 3D cadastral data is needed. The Land Administration Domain Model (LADM, ISO 19152) already covers such situations since the spatial unit defined in the Spatial Unit package in LADM can refer to a single volume of space (or multiple volumes of space) besides 2D representations. LADM is a conceptual model that allows land administration objects and relationships to be described. The power of the model is the ability to describe different cadastral systems in different countries or regions in a consistent way. CityGML is an information model and data exchange standard for 3D city model data. It does not contain specifics about land administration. The paper examines how the LADM conceptual model, the representation of legal spaces in particular, can be mapped to and encoded as a CityGML Application Domain Extension (ADE). The CityGML ADE implements a data exchange format but the underlying model could also be used as a starting point to create a database schema for data storage. The paper addresses the modelling issue of integrating different information models that define or refer to the same or overlapping concepts. The possibility to achieve greater integration between ISO19152 and CityGML by including each others concepts in future versions is also discussed. Relating legal features to physical features, a common occurance in practice, is addressed from a data modelling perspective. The paper is intended to stimulate discussion about the topic as well as further development. <s> BIB014 </s> CityGML Application Domain Extension (ADE): overview of developments <s> Overview of the identified ADEs Supporting applications <s> In recent years research interests in 3D geospatial information have been increased to provide location based services and to develop various 3D urban models used in many fields such as urban planning, and disaster management. Especially, due to increasing the scale and complexity of buildings, many researchers have studied to provide the services such as indoor navigation for disaster. In order to manage complicated indoor spatial information efficiently, it is necessary to develop the indoor spatial data model by extending the developed 3D spatial models which have been developed for outdoor space. Although CityGML (City Geography Markup Language) is an international standard model and it supports five Level of Detail for spatial data of urban areas, it is limited to represent and manage indoor facilties in indoor space. In this chapter, we have proposed CityGML Indoor ADE (Application Domain Extensions) applied to implement indoor space and indoor facility management applications. CityGML Indoor ADE is composed of two feature models including indoor space feature model representing space features and indoor facility feature model representing indoor facilities in indoor space. We generate the XML schema of the CityGML Indoor ADE presented by UML diagrams and develop a viewer to visualize the XML documents in order to validate the indoor space feature model. As well, we construct the sample data based on indoor facility feature model to demonstrate the usefulness of the model for indoor facility management applications. <s> BIB015 </s> CityGML Application Domain Extension (ADE): overview of developments <s> Overview of the identified ADEs Supporting applications <s> No widely applicable open information model standard exists until now for large-scale Urban Energy Modelling. Although different data models have been developed for different urban energy tools, they do not offer possibilities of interoperability and exchange between the stakeholders, tools and expert fields. ::: To address this issue, an international group of urban energy simulation developers and users is developing since May 2014 an Application Domain Extension (ADE) Energy for the open urban information model CityGML. ::: This paper introduces the Energy ADE developed and tested by this international urban energy group. Goals, requirements and the modular structure of the CityGML extension are described in detail. <s> BIB016 </s> CityGML Application Domain Extension (ADE): overview of developments <s> Overview of the identified ADEs Supporting applications <s> Different associated properties of city models like building geometries, building energy systems, building end uses, and building occupant behavior are usually saved in different data formats and are obtained from different data sources. Experience has shown that the integration of these data sets for the purpose of energy simulation on city scale is often cumbersome and error prone. A new application domain extension for CityGML has been developed in order to integrate energy-related figures of buildings, thermal volumes, and facades with their geometric descriptions. These energy-related figures can be parameters or results of energy simulations. The applicability of the new application domain extension has been demonstrated for heating energy demand calculation. <s> BIB017 </s> CityGML Application Domain Extension (ADE): overview of developments <s> Overview of the identified ADEs Supporting applications <s> With the advent of energy rating systems and increased energy efficiency requirements for built environment, the assessment of energy performance of new buildings and refurbishment rates of existing buildings have become an important compliance in the building design process. In order to analyse and simulate the effects of energy-efficient measures for buildings, it is essential to establish spatio-semantic information interoperability between the building design and energy modelling softwares. Data interoperability facilitates different domains to interact with the single building model. The geometrical properties of building semantics such as effective areas exposed to total incident radiation were used as indicators for assessment of seasonal solar potential of buildings. The key urban solar potential indicators were identified based on the semantic components of buildings. The CityGML instance document derived from a proposed energy application domain extension (ADE) conceptual schema could be used as... <s> BIB018 </s> CityGML Application Domain Extension (ADE): overview of developments <s> Overview of the identified ADEs Supporting applications <s> European Historic Urban Districts are highly appreciated by their inhabitants and visitors and they can be considered as one of the most valuable collective achievements of the European culture. The preservation of our urban heritage requires the protection of the social context as well as the preservation of the authenticity and integrity of its physical materiality. That means to improve the quality of life of their inhabitants as well as the sustainability of the historic districts. This dissertation analysed the Historic Urban Districts as complex energy and informational systems in order to address the challenge to improve their sustainability and liveability while protecting their cultural values. First, a methodological framework for energy retrofitting in all its phases has been defined based on a strategic information management and from a multiscale perspective. Secondly, a decision making methodology that allows the modelling of the historic city and the selection of the best strategies has been developed. In order to support the whole system a multiscale data model has been designed. Finally, the historic city of Santiago de Compostela has been selected for the implementation. <s> BIB019 </s> CityGML Application Domain Extension (ADE): overview of developments <s> Overview of the identified ADEs Supporting applications <s> Societal drivers including poverty eradication, gender equality, indigenous recognition, adequate housing, sustainable agriculture, food security, climate change response, and good governance, influence contemporary land administration design. Equally, the opportunities provided by technological development also influence design approaches. The Land Administration Domain Model (LADM) attempts to align both: the data model provides a standardised global vocabulary for land administration. As an international standard it can stimulate the development of software applications and may accelerate the implementation of land administration systems that support sustainability objectives. The LADM covers basic information-related components of land administration including those over land, in water, below the surface, and above the ground. The standard is an abstract, conceptual model with three packages related to: parties (people and organisations); basic administrative units, rights, responsibilities, and restrictions (ownership rights); spatial units (parcels, and the legal space of buildings and utility networks) with a sub package for surveying, and representation (geometry and topology). This paper examines the motivation, requirements and goals for developing LADM. Further, the standard itself is described and potential future maintenance. Despite being a very young standard, ‘born’ on 1st December 2012, it is already possible to observe some of the impact of LADM: examples are provided. <s> BIB020 </s> CityGML Application Domain Extension (ADE): overview of developments <s> Overview of the identified ADEs Supporting applications <s> The international standard CityGML defines five levels of detail (LODs) for 3D city models, but only the highest of these (LOD4) supports modelling the indoor geometry of a building, which must be acquired in correspondingly high detail and therefore at a high cost. Whereas simple 3D city models of the exterior of buildings (e.g. CityGML LOD2) can be generated largely automatically, and are thus now widely available and have a great variety of applications, similarly simple models containing their indoor geometries are rare. In this paper we present two contributions: (i) the definition of a level of detail LOD2+, which extends the CityGML LOD2 specification with indoor building geometries of comparable complexity to their exterior geometries in LOD2; and more importantly (ii) a method for automatically generating such indoor geometries based on existing CityGML LOD2 exterior geometries. We validate our method by generating LOD2+ models for a subset of the Rotterdam 3D data set and visually comparing these models to their real counterparts in building blueprints and imagery from Google Street View and Bing Maps. Furthermore, we use the LOD2+ models to compute the net internal area of each dwelling and validate our results by comparing these values to the ones registered in official government data sets. <s> BIB021 </s> CityGML Application Domain Extension (ADE): overview of developments <s> Overview of the identified ADEs Supporting applications <s> Abstract. This paper presents and discusses the first results regarding selection, analysis, preparation and eventual integration of a number of energy-related datasets, chosen in order to enrich a CityGML-based semantic 3D city model of Vienna. CityGML is an international standard conceived specifically as information and data model for semantic city models at urban and territorial scale. The still-in-development Energy Application Domain Extension (ADE) is a CityGML extension conceived to specifically model, manage and store energy-related features and attributes for buildings. The work presented in this paper is embedded within the European Marie-Curie ITN project “CINERGY, Smart cities with sustainable energy systems”, which aims, among the rest, at developing urban decision making and operational optimisation software tools to minimise non-renewable energy use in cities. Given the scope and scale of the project, it is therefore vital to set up a common, unique and spatio-semantically coherent urban data model to be used as information hub for all applications being developed. This paper reports about the experiences done so far, it describes the test area in Vienna, Austria, and the available data sources, it shows and exemplifies the main data integration issues, the strategies developed to solve them in order to obtain the enriched 3D city model. The first results as well as some comments about their quality and limitations are presented, together with the discussion regarding the next steps and some planned improvements. <s> BIB022 </s> CityGML Application Domain Extension (ADE): overview of developments <s> Overview of the identified ADEs Supporting applications <s> This paper illustrates the results of a research project focused on the development of a Web 2.0 system designed to compute and visualize building energy performance large-scale maps. The workflow and the framework include: emerging platform-independent technologies such as WebGL for data presentation, an extended version of the EU-Founded project TABULA/EPISCOPE for building energy parameters estimation and a data model based on CityGML OGC standard. The proposed platform will allow citizens, public administrations and government agencies to perform city-wide analyses on the energy performance of building stocks. To evaluate the accuracy of the model, the simulation results were compared to real data of energy performance of the energy certificates available and the model uncertainties were analyzed. <s> BIB023 </s> CityGML Application Domain Extension (ADE): overview of developments <s> Overview of the identified ADEs Supporting applications <s> For applications of 3D city models such as simulating the impact of failures in supply networks, information on the city objects as well as on the supply networks are required. The CityGML extension UtilityNetworkADE allows for modelling different types of networks, the focus currently being on the representation of topographical and topological aspects. However, for representing supply and disposal tasks, also functional aspects are of relevance, in particular, when no detailed modelling of supply networks is available, but the impact of a failure on a certain region is to be analysed nevertheless. This paper presents three methods complementing the CityGML UtilityNetworkADE by functional aspects regarding the modelling of supply areas, the characterisation of city objects and network features according to functional roles and the representation of the potential and current supply of commodities to city objects. <s> BIB024 </s> CityGML Application Domain Extension (ADE): overview of developments <s> Overview of the identified ADEs Supporting applications <s> Abstract Existing studies on modeling immovable ownership have not explored the internal structure and internal semantic relations of the ownership of condominium units in depth. This paper suggests extending CityGML with legal concepts from the Land Administration Domain Model (LADM) via the application domain extension (ADE) mechanism of the CityGML as a feasible approach for describing the ownership structure of condominium units. Based on legislation in China, a CityGML–LADM ADE model is proposed to precisely present the ownership structure of a condominium unit, which reflects the interrelations of legal objects and their physical counterparts. Finally, the proposed model is validated by two case studies. <s> BIB025 </s> CityGML Application Domain Extension (ADE): overview of developments <s> Overview of the identified ADEs Supporting applications <s> The Open Geospatial Consortium (OGC) CityGML standard offers a Level of Detail (LoD) concept that enables the representation of CityGML features from a very detailed to a less detailed description. Due to a rising application variety, the current LoD concept seems to be too inflexible. Here, we present a multi representation concept (MRC) that enables a user-defined definition of LoDs. Because CityGML is an international standard, official profiles of the MRC are proposed. However, encoding of the defined profiles reveals many problems including mapping the conceptual model to the normative encoding, missing technologies and so on. Therefore, we propose to use the MRC as a meta model for the further definition of an LoD concept for CityGML 3.0. <s> BIB026 </s> CityGML Application Domain Extension (ADE): overview of developments <s> Overview of the identified ADEs Supporting applications <s> Road traffic and industrial noise has become a major source of discomfort and annoyance among the residents in urban areas. More than 44t% of the EU population is regularly exposed to road traffic noise levels over 55 dB, which is currently the maximum accepted value prescribed by the Environmental Noise Directive for road traffic noise. With continuously increasing population and number of motor vehicles and industries, it is very unlikely to hope for noise levels to diminish in the near future. Therefore, it is necessary to monitor urban noise, so as to make mitigation plans and to deal with its adverse effects. The 2002/49/EC Environmental Noise Directive aims to determine the exposure of an individual to environmental noise through noise mapping. One of the most important steps in noise mapping is the creation of input data for simulation. At present, it is done semi-automatically (and sometimes even manually) by different companies in different ways and is very time consuming and can lead to errors in the data. In this paper, we present our approach for automatically creating input data for noise simulations. Secondly, we focus on using 3D city models for presenting the results of simulation for the noise arising from road traffic and industrial activities in urban areas. We implemented a few noise modelling standards for industrial and road traffic noise in CityGML by extending the existing Noise ADE with new objects and attributes. This research is a steping stone in the direction of standardising the input and output data for noise studies and for reconstructing the 3D data accordingly. <s> BIB027 </s> CityGML Application Domain Extension (ADE): overview of developments <s> Overview of the identified ADEs Supporting applications <s> CityGML is an open data model for storage and exchange of 3D city models. It is categorised into thirteen thematic classes, i.e., buildings, tunnels, bridges, etc., lacking the other themes such as indoor routing and positioning. With the amplified use of indoor routing and positioning, the need for prerequisite notion of detailed semantic, as well as geometric information of the 3D building data has grown. We intend to extend the CityGML schema to add attributes of indoor features using the facility of Application Domain Extension (ADE) provided by the OGC CityGML 2.0. In this study, we aim to showcase the formation of Indoor Routing and Positioning ADE along with the process concerning its development, such as the 3D model design, network dataset creation, routing, positioning and Unified Modeling Language based ADE application schema generation. This research would help the users to easily store and exchange 3D city data on which they can perform routing and positioning inside the buildings with enhanced semantic and geometric properties. <s> BIB028 </s> CityGML Application Domain Extension (ADE): overview of developments <s> Overview of the identified ADEs Supporting applications <s> The road towards achievement of the climate protection goals requires, among the rest, a thorough rethinking of the energy planning tools (and policies) at all levels, from local to global. Nevertheless, it is in the cities where the largest part of energy is produced and consumed, and therefore it makes sense to focus the attention particularly on the cities as they yield great potentials in terms of energy consumption reduction and efficiency increase. As a direct consequence, a comprehensive knowledge of the demand and supply of energy resources, including their spatial distribution within urban areas, is therefore of utmost importance. Precise, integrated knowledge about 3D urban space, i.e. all urban (above and underground) features, infrastructures, their functional and semantic characteristics, and their mutual dependencies and interrelations play a relevant role for advanced simulation and analyses. As a matter of fact, what in the last years has proven to be an emerging and effective approach is the adoption of standard-based, integrated semantic 3D virtual city models, which represent an information hub for most of the above-mentioned needs. In particular, being based on open standards (e.g. on the CityGML standard by the Open Geospatial Consortium), virtual city models firstly reduce the effort in terms of data preparation and provision. Secondly, they offer clear data structures, ontologies and semantics to facilitate data exchange between different domains and applications. However, a standardised and omni-comprehensive urban data model covering also the energy domain is still missing at the time of writing (January 2018). Even CityGML falls partially short when it comes to the definition of specific entities and attributes for energy-related applications. Nevertheless, and starting from the current version of CityGML (i.e. 2.0), this article describes the conception and the definition of an Energy Application Domain Extension (ADE) for CityGML. The Energy ADE is meant to offer a unique and standard-based data model to fill, on one hand, the above-mentioned gap, and, on the other hand, to allow for both detailed single-building energy simulation (based on sophisticated models for building physics and occupant behaviour) and city-wide, bottom-up energy assessments, with particular focus on the buildings sector. The overall goal is to tackle the existing data interoperability issues when dealing with energy-related applications at urban scale. The article presents the rationale behind the Energy ADE, it describes its main characteristics, the relation to other standards, and provides some examples of current applications and case studies already adopting it. <s> BIB029 </s> CityGML Application Domain Extension (ADE): overview of developments <s> Overview of the identified ADEs Supporting applications <s> Abstract The demand for improving the energy performance of buildings located in the historic districts of cities is as high as the current demand in other city districts. The need to reduce energy consumption and improve the comfort of inhabitants is compounded by the need to preserve an environment of heritage value. The selection of rehabilitation strategies at urban scale offers significant benefits, but makes the process long and costly. Therefore, methods or tools are necessary to establish a rapid assessment that facilitates strategic decision making and a deeper analysis of a reduced number of alternatives. This paper describes a method that supports decision making regarding the suitability of Energy Conservation Measures (ECMs) in historic districts at early stages. The method considers the improvement of the energy performance of buildings as a positive impact, balanced with the negative impacts that the implementation of ECMs could produce. A CityGML-based urban model allows the automation of a multi-scale assessment for different ECMs and provides possible global energy demand reductions. This method, combined with an economic evaluation, can be used by decision makers for large-scale energy retrofitting. The applicability of the method is demonstrated through implementation in the historic city of Santiago de Compostela. <s> BIB030 </s> CityGML Application Domain Extension (ADE): overview of developments <s> Overview of the identified ADEs Supporting applications <s> Abstract The documentation of cultural heritage is acknowledged as a fundamental instrument to guarantee the monument preservation and promotion, and to educate people towards these aims. The recently evolved potentialities of information technologies and communication (standard data models, ontologies and formats, web technologies) permit the development of digital archives in which the information is also semantically specified in a shared and explicit way, so that it can be universally understood and correctly interpreted. However, some tools are missing for suitably archiving and communicating the architectural heritage information, including the representation potentialities of high-level-of-detail 3D models. A goal of this study is the suitable representation of both the thematic information about architectural heritage and its 3D geometric characteristics in an interoperable and understandable way. For this reason, the existing data models, available for the geometric and cartographic field, and for the cultural heritage domain, were considered. They are distinct standards, and some limits make them incomplete (in the spatial or semantic management). In this study, an extension is proposed of the standard data model CityGML to overcome these limits. CityGML is published by the Open Geospatial Consortium to represent urban objects and permits a multi-scale management of the information useful for the representation of architectural heritage multi-faceted, multi-temporal, complex knowledge. In the paper, the extension is described, and an example of its application on a portion of a highly detailed 3D model of a mediaeval church is presented. <s> BIB031
The primary aim of the ADE concept is to enrich the data model of CityGML supporting specific applications, thus it is not surprising that in practice most of the developed ADEs belong to this category. One of the most mature efforts in this arena is the Energy ADE BIB016 BIB022 BIB029 , jointly developed by several European organisations, mostly universities. This ADE has been incepted with the intention of bridging the gap of an open model standard in the urban energy modelling domain, supporting interoperability between different tools and stakeholders. It extends CityGML by enriching the data model with information required for energy simulations, such as the used energy system, building occupancy, and its physical properties (e.g. material). The model is flexible, taking into account different levels of detail (LODs), and it is modular foreseeing the potential coupling of Energy ADE with other ADEs. The Energy ADE is supported by several implementations and studies BIB022 BIB017 BIB023 BIB018 , and it is established both in an XSD schema and UML class diagram (Fig. 4) . A related effort is the 2011 work of Dalla Costa  , documenting an early proposal for an Energy Efficiency ADE. This ADE enriches CityGML by defining thermal zones for buildings and other information crucial for managing energy efficiency. However, the work appears to remain in its prototype phase, as no subsequent publications could be discovered. An ADE of the same name was introduced in BIB006 (and subsequently it was a subject of the publications  BIB019 ), enabling the modelling of physical properties of materials such as reflectivity and transmittance. The Noise ADE, the exemplary ADE included in CityGML 2.0 [1], has been described in Section Examples hence it will not be described extensively in this section. Other relevant aspects of the Noise ADE to note are that it allows segmenting roads according to noise requirements and modelling train characteristics to understand railway noise BIB001 . It is available in both XSD and UML form. The Noise ADE is also an interesting case to demonstrate the flexibility of the ADE concept. Its schema has been extended by subsequent work of independent researchers BIB027 , indicating that extensions are customisable and extensible per se (since ADEs are extensions, this technically means extending an extension). The researchers identify limitations of the existing ADE for the practices and legislation of noise pollution modelling in the Netherlands, e.g. lack of support for industrial noise and for distinguishing different speeds of vehicles. The work enriches the Noise ADE with new classes and attributes resulting in the Extended Noise ADE, adapting the existing ADE to particular requirements suiting a national context and local legislation. Another interesting example in the noise field is that the same application domain may occasionally be covered by different ADEs (as it is the case in the aforementioned energy application), allowing narrowing down the focus of each. For example, Konde  developed an independent ADE tailored for road traffic noise and concentrated on a particular noise propagation model, without much relation to the Noise ADE. This ADE extends the Building module by including attributes such as reflection correction factors for walls and roofs, which are required by the noise propagation method used. Besides the Noise ADE, the second exemplary ADE included in the CityGML 2.0 standard  is the ADE for Ubiquitous Network Robots Services. This ADE augments CityGML with features necessary for robot navigation, such as floor material and additional information on openings BIB007 . It extends the bldg:Room feature, which is available only in LOD4, doubling as an example of an ADE that is dependent on the LOD. UtilityNetworkADE BIB003 BIB008 BIB024 enables modelling utility networks in CityGML. It tailors the data model including the utilities (e.g. freshwater and electricity) with information on usage, materials, operating parameters, and population depending on the network. It has been used for various purposes, e.g. simulating the cascading impact on population in the event of a failure of the infrastructure BIB009 , facility management and vulnerability assessment  . This ADE is relevant in the context of Building Information Modelling (BIM) since it is possible to transform Industry Foundation Classes (IFC) data containing utilities to this ADE BIB004 . At the time of the submission of this paper, this ADE is a proposed integration to CityGML 3.0. Computer Aided Facility Management (CAFM) ADE  is an instance adapted for facility management. It enriches LOD4 models with additional features about rooms, e.g. ceiling height and window size, which are suited for managing various tasks such as cleaning and costs  . Çagdaş BIB011 proposed an ADE adapted for immovable property taxation, taking into account the legal and administrative aspects which are not covered by CityGML. The Immovable Property Taxation ADE is developed fulfilling the requirements of the Turkish law. It integrates modelling the property units (e.g. parcel) with their components, and legal and economic attributes (e.g. rights), which are required for property taxation and management. The ADE defines several new classes and attributes, e.g. the apartments are modelled as BuildingUsePart. Similarly as the mentioned lack of legal building units, an interesting addition to note is that because parcels do not have a dedicated CityGML representation, a new feature class CadastralParcel has been created within the CityGML LandUse module. Another work related to this application is the one of Dsilva BIB002 who developed an ADE for property administration in the Netherlands. The work enhances the building module of CityGML by including apartments and their properties relevant for cadastre (e.g. ownership rights and number of rooms). A few researchers  BIB025 BIB014 suggest an extension of CityGML with legal concepts found in the Land Administration Domain Model (LADM) BIB020 . For example, Li et al. BIB025 propose an ADE giving consideration to the internal ownership structure of condominium units. The paper includes two examples of datasets from China. Cultural heritage has also been subject of CityGML extensions. The Cultural Heritage ADE is defined both by an UML and XSD, and it has been described in multiple publications BIB006  BIB019 BIB030 . Cultural heritage has been a subject of other unrelated ADEs defined by Costamagna and Spanò BIB012 , Noardo BIB031 , and the BCH (Built Cultural Heritage) Management ADE developed by Zalamea et al.  , indicating particular interest in this application of 3D city models. These ADEs extend the Building module with a class intended for cultural features, allowing modelling monuments including their history, protection status, and condition. Similarly, but focused to a national context, Mohd et al.  developed an ADE for Malaysian heritage houses. Their ADE augments CityGML to support the documentation of heritage houses for their preservation and monitoring of damages. In the frame of the above described project of Prieto et al. BIB006 , a companion ADE to the Cultural Heritage ADE was designed: Intervention ADE includes information on the actors involved in the processes for the maintenance and the rehabilitation of the cultural heritage. Although CityGML's focus in practice is not so much on the interior of buildings, a fair share of ADEs has been developed supporting indoor applications since the LOD4 as defined by the standard falls short with certain applications. Dutta et al. BIB028 developed an ADE for indoor routing and positioning. It adds attributes of indoor features that are of relevance for this application domain. For example, the feature FloorSurface is extended to include routing and positioning attributes. BuildingInstallation is enriched supporting modelling connectors between storeys, such as staircases and elevators. Thanks to this ADE, WiFi routers can be modelled as well, supporting the positioning aspect of this application. Another work focusing on enhancing CityGML for interior features is the Indoor ADE developed in Korea   BIB015 . This ADE provides two feature models extending the Building module: Indoor Space Feature Model and Indoor Facility Feature Model. The former includes space features such as meeting rooms, while the latter is geared towards facilities such as fire hydrants. One of the key features of this ADE is the extension of CityGML supporting storeys, which was discussed by other researchers as well but implemented in different ways BIB021 BIB026 . This ADE is dependent on the LOD of the data, as it is builds on top of standard features available only in LOD4 of CityGML (e.g. Room). Prandi et al. BIB013 developed an ADE supporting multiple services related to smart cities: solar energy, improving mobility of citizens (routing), and noise mapping. This ADE was deployed within the i-SCOPE project (interoperable Smart City services through an Open Platform for urban Ecosystems), with an interesting distinctiveness that it is developed with multiple applications in mind. Examples of features enriched by this ADE are information whether a traffic light is capable of giving audio signals, height of doorsteps, and width of elevator doors. In the water domain, HydroADE  was developed for exchanging dynamic 3D flood information. The ADE is supported by a web visualisation and examples. Zamyadi et al. BIB010 created an ADE for augmented reality (AR). One of the interesting aspects of their work is the extension of the Appearance module to suit augmented reality applications (e.g. denoting the render priority), which is not a common occurrence (the only other related work we identified is an ADE focused on bridging CityGML and a computer graphics format for improving gaming experience BIB005 ). In the related domain, a study by Hasse and Koch  involved extending CityGML with the thematic model of ENC (Electronic Nautical Charts), which they later used with an AR engine to visualise the 3D representation of ENC objects and the corresponding electrical information. Air Quality ADE was developed by Arco et al.  to characterize the existing city objects with air quality values around them so as to identify the main sources of air pollution and the affected areas.