Future City Pilot-1: Using IFC/CityGML in Urban Planning Engineering Report

The Future Cities Pilot is an OGC initiative to demonstrate how cities can benefit from open standards in managing human, physical and natural systems. The first pilot project (FCP1) aimed to show how 3D modeling open standards such as IFC and CityGML can be used in urban planning and management scenarios. The scenarios included 1) the application of IFC and CityGML in land development proposal assessment, 2) the integration of CityGML with dynamic data feeds such as sensor observations and the utility of CityGML in solar energy potential of buildings, and 3) the value of CityGML in modeling urban flooding.

These scenarios were proposed and sponsored by Institut National de l’Information Géographique et Forestière - IGN (France), Ordnance Survey Great Britain (UK), and virtualcitySYSTEMS GmbH (Germany). The pilot participants that developed the solutions for Scenario 1 was University of Melbourne (Australia), for Scenario 2 was Technical University of Munich (Germany), and for Scenario 3 was Remote Sensing Solutions, Inc. (U.S.A).

Scenario 1 involved two objectives. The first objective was to demonstrate that 3D data in IFC and CityGML can provide the land development assessment process with better information than that of 2D spatial data. The second objective was to demonstrate how the conformance with urban planning rules can be enhanced and automated through the adoption of WPS.

This OGC® document addresses the first objective of Scenario 1 in which a land development assessment workflow system that uses 3D data was developed. [OGC 16-16-099], which is an output of FCP1, addresses the second objective of Scenario 1.

All questions regarding this document should be directed to the editor or the contributors:

The future work related to this document are specifications for preparing IFC files to use in urban planning and mapping from IFC to CityGML LoD 2 and LoD 3.

Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. The Open Geospatial Consortium shall not be held responsible for identifying any or all such patent rights.

Recipients of this document are requested to submit, with their comments, notification of any relevant patent claims or other intellectual property rights of which they may be aware that might be infringed by any implementation of the standard set forth in this document, and to provide supporting documentation.

The use of BIM models encoded in IFC will become mandatory for major land development projects. The FCP1’s urban planning requirement, therefore, included the use of BIM in the development approval process. This process included a requirement to automatically validate the proposed development against urban planning rules. In particular, the process was required to use contextual information such as the surrounding city model, cadastre, and road network to facilitate the validation process. Concerning the city models, the process was required to consider mapping IFC to various levels of detail of CityGML including Level of Details (LoD) 2, LoD 3, and LoD 4. The process was also required to provide facilities for human inspection and verification of proposal such that urban planner can view the building project within the existing 3D model of the city and store in databases.

The following dataset was provided for urban planning scenario:

Urban planning systems aim to establish affordable, socially inclusive, environmentally friendly environments for human settlement. Urban planning is an interplay of place, people, and purpose. Planning for where to live, work, and enjoy is therefore inherently a spatial process. The use of geospatial information system in urban planning is now well established. The use of small and large scale geospatial data such as planning zones, green areas, street networks, and property boundaries is an indispensable part of the planning processes for land development.

In urban planning, land development is considered to be a multi-stakeholder process, in which several agencies are involved. The agencies may include privately operated land surveying, land development, or architecture design firms or publicly-funded organizations such as municipalities, road authorities, land registries, or mapping agencies. Each agency plays a unique role in the land development approval process, but the process itself is about preparing development proposals and the application of rules and criteria defined in the regulation, some of which are location-dependent, against the proposals. Where the rules are location-dependent, the agencies use spatial data for assessing land development proposals. Spatial representation of development proposals may be prepared and designed using CAD or GIS software solutions but are often submitted in paper/image formats for assessment.

Some technology inefficiencies are evident in this process. First, even if proposals are submitted as data, the format may not be readily usable by processing agencies (1). Second, the 2D design of even complex high-rise land developments is a norm in representing proposals (2). Third, land development rules are applied in isolation since the responsible agencies usually do not have the infrastructure that enables sharing spatial data (3a) and automating rules (3b).

An open platform design is presented in this report to help with inefficiency 2 by replacing the workflow system that is based on 2D paper/image/CAD drawings with a workflow that uses 3D data. [OGC 16-099], which is part of FCP1, addresses inefficiencies 1 and 3 in a separate report.

The design enables recording and visualization of 3D data in several formats and the ability to transform data from IFC to CityGML . The system architecture involves four layers: User Interface, Logic, Service, and Data (Figure 1). The layers include 11 components including development approval workflow user interface, several database systems capable of managing various data formats, urban planning rules engine, a data transformation engine, and web services for accessing data and processing.

Figure 1: System Architecture

Of significance to this ER, to address inefficiency 2, some components were designed for demonstration including: 1) a web-based client for rendering IFC files; 2) transforming IFC to CityGML; 3) a web-based client for rendering the resulted CityGML and city model of it surroundings.

The components are described as below.

Based on the system architecture, two solutions were put forward for implementation. The first solution was to use only the IFC file and examine if the considered urban planning scenarios can be realized (Solution 1). The second solution was to convert the IFC file to its equivalent in CityGML and then test if the urban planning scenarios can be realized (Solution 2).

BIMServer: The Building Information Model server (BIMserver.org) platform enables creating web based applications for BIM based on the open standard IFC. IFC data are interpreted by a smart core and stored as objects in an underlying database. BIMserver is based on plugins in an open framework. The BIMserver software is free and open source (GNU Affero GPL) (BIMserver, 2017). It can support dynamic collaboration processes in urban planning where several players such as land developers, land registration officers, mapping agencies, and urban planners play a role. It has core server features like revisions, authorization, compare, query, model checking, merging, etc. BIMserver has open interfaces and network protocols (soap, PB, JSON), uses open standards, is built as a plugin framework for easy fine-tuning, has an admin configuration GUI, and developers documentation and SDKs. The core of the software is based on the open standard IFC. Components 1 to 5 of the demonstrator are built on BIMserver and its plug-ins.

52°North Web Processing Service: This component enables the deployment of standardized geo-processing on the web (52°North, 2017). It features a pluggable architecture for processes and data encodings. It is used to implement components 7 and 12 which are about WPS 1, 2, 3 and 4 for automating development assessment proposal. In this project, the WPS version 1.0.0 was used.

GeoServer: It is a software server that allows viewing and editing geospatial data based on OGC standards. In implementing the demonstrator, GeoServer’s Web Feature Service (WFS) capability is used to serve the topographic and cadastral data that was required in WPS based urban planning functions. In this demonstrator, WFS implementation 1.0.0 was used.

3D City Database: It is a free 3D geo database to store, represent, and manage virtual 3D city models on top of a spatial relational database based on CityGML schema (3DCityDB, 2017). In this project, it has been used to store the existing city model of the study area, and the resultant CityGML.

3D City Database Importer/Exporter: It is an application interface for the 3D City Database (3DCityImporterExporter, 2017). This application offers a wide range of configuration options (e.g., based on the schema, feature id, bounding box) to validate and import CityGML files into the 3D City Database. It also allows exporting the content of the database to file format such as KMZ, KML, COLLADA. When exporting, several aspects of the data such as LoD, bounding box, and appearance can be configured. This tool has been extensively used in preparing data for this demonstrator.

3D City Database Web Feature Service: This service allows web-based access to 3D City Database. It is a platform-independent, database-independent service that is provided as a Java WAR and Java libraries that render necessary dependencies for the WFS service (3DCityWFS, 2017). This service was used to access the CityGML data that was required in parameterizing data requirements of WPS 3 and 4.

3D-DB-Web-Map-Client: This is a web client for 3D visualization (3DCityWebClient, 2017). It is based on Cesium Virtual Globe with WebGL as the underlying technology. This component has been customized to visualize the proposed development and surrounding area. It is important to note that the spatial data of interest were converted to KML and KMZ for visualization by 3D-DB-Web-Map-Client.

As described in the conceptual design section, the implementation of the demonstrator considers two solutions. The implementation result of these two solutions are detailed below.

Digital enhancement of cities requires technologies that can record and represent temporal and spatial dynamics of their natural, human, and physical systems.

Collecting, recording and maintaining higher dimensional spatial data such as 3D data of the cities are vital with the growing dominance of multi-storey buildings.

The availability of several open spatial data infrastructure tools for dealing with 3D data has become evident as a result of developing this demonstrator. The open infrastructure tools that are utilized in this project are freely available, well supported, and more importantly, developed on open standards such as IFC, CityGML, WPS, and WFS. Such advancement in the open platforms development paints a promising future for the fast adoption of open standards in cities that use numerous and diverse technology for digital enhancement.

This report documents the potential applications of IFC and CityGML in urban planning using a case study. While the case study successfully used the CityGML file format in meeting the requirement of urban planning, it was also confirmed that IFC, after generalization, can be used in geographically constrained scenarios such as urban planning. It was demonstrated that IFC could be a source for CityGML. Recommendations for IFC to be an effective source for CityGML are as follows.

This project demonstrated that the international open 3D standards such as CityGML and IFC, to a large extent, are interoperable such that the data from one format can be transformed without loss of much details to another format.

However, several challenges were identified that could constitute the future work for the Future City Pilot project. The future work can consider the following interoperability considerations.

This level of interoperability is significant as a design in the AEC industry that is based on IFC can provide valuable data for downstream disciplines of built environments such as city administration, emergency management, and facilities management. While this demonstrator was undertaken in the context of land development proposal assessment, the potential of 3D open models such as IFC and CityGML can be further demonstrated in other application domains such as urban heat island analysis, building management systems, evacuation of high-rise buildings, and search and rescue requirements of public safety agencies.

Some of these application domains need indoor (e.g. building management systems) or outdoor (e.g. urban heat island) only representation of built environments and the current level of interoperability between IFC and CityGML mostly can address these applications' requirements.

However, some of the other domains' requirements (e.g., emergency response) go beyond the interoperability between the data models. In these domains, it is the seamless representation of indoors and outdoors of built environment that is critical, not simply the ability to transform data from one model to another.