BIM-GIS Interoperability: A reference model for construction permit checking

Marion Kannengiesser Engineering student in geomatics

STUDENT CONTEST 2018

BIM-GIS Interoperability: A reference model for construction permit checking Abstract Nowadays the digital migration is at the origin of many changes in the field of Architecture, Engineering and Construction (AEC). The use of Building Information Modelling (BIM) is becoming frequent and is encouraged mostly because of its benefits regarding collaboration and data sharing at any steps of an architectural project. In a way to improve the treatment of many time consuming procedurals, most of the administration services tend to think about using this technology. Moreover, it would avoid the need of inputting the same information from one unit to another. Digital models produced by the different participants working on a project are a geometric representation but also carry a lot of properties. Those allow obtaining qualitative and quantitative data referring to the constitutive elements of the building.

Since 2015, the State of Geneva and more precisely the department in charge of delivering building permits -called Office des Autorisations de Construire- (OAC) has done many improvements in a way to make the documentary checking faster and easier. Currently the main goal is to develop a workflow that allows to follow the entire process without any paperwork by using a collaborative space. The digital model has to be based on the public restrictions affecting private property. This thesis follows the study realized in 2017 which had for purpose to determine the feasibility of this project. The project of law PL12145 adopted in January 2018 provide a framework for the research and assigned a period of 18 months to develop the digital model.

Keywords: AEC, BIM, FME, GIS, Digital Model, 3D

1. Introduction The field of Architecture, Engineering and Construction (AEC) is experiencing many changes including the introduction of Building Information Modeling (BIM) in most of the architectural projects.

BIM is defined as a means to collaborate at every level of a construction project and appears to be a powerful tool which can simplify the processing of currently non-digital and time-consuming procedures in administrations.

Since 2015, the Canton of Geneva has been working on dematerialization in order to simplify the process of checking building permit applications which is carried out by the Office of Building Authorizations - called Office des Autorisations de Construire (OAC). The plan to integrate BIM into the administration procedure is based on the law PL 12145 adopted in January 2018 by the secretariat of the Grand Council.

2. Context This article refers to the engineering thesis “Convergence BIM-SIG: Une maquette des références pour les permis de construire numériques” (2018) which was initiated by the Direction of the Information for the Territory in the Canton of Geneva – called Direction de l’Information du territoire (DIT). It took place in the "GIS department" (Geographic Information System) of INSER SA (CH). This company is known for its expertise in fields such as infrastructure, environment and land management.

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Marion Kannengiesser Engineering student in geomatics

STUDENT CONTEST 2018

The purpose of this work is to create a BIM model containing all the information necessary for the architect to build his project by respecting the restrictions of public right on the private property – called Restrictions de Droit Public à la Propriété Foncière (RDPPF). In Switzerland, there are currently more than 150 RDPPF, the 17 most important at the federal level must be registered in the cadastre.

Urban planning in Switzerland is, as in any country, defined legally by numerous texts and regulations.

The specificities of the country’s organization make it necessary to consider the rules at different levels of the State’s structure. Indeed, the Confederation decrees the main principles which will be taken over and further deepened by the cantons and then the communes. Moreover, the canton must check the compliance of a construction project with the existing regulations.

The Canton of Geneva own a wide range of 2D, 3D and 4D data covering many topics. The DIT manages the input, update and diffusion of data related to the territory. Nowadays, the DIT coordinates the working group at the origin of the 3Dok charter. This 3D ethics charter, initiated in 2008, aims to ensure the use of 3D data in a deontological and reliable way. At the moment, there is no reference model available in the canton. This work is part of the significant project whose goal is to introduce the BIM architecture within the Information System in Geneva- called Système d’Information et du Territoire de Genève (SITG). This organization is based on a network of public partners that allows the centralization of the territory's data. It also enables the sharing between the different actors of the network and the public via the SITG website. Most of the geo-data are supplied in open source, for free, on the geoportal. Currently, the information system of the OAC is evolving in order to computerise permit applications, including the possibility of working on three-dimensional digital models.

The BIM, coupled with the SITG, would allow an automation of some stages and an overall improvement of the process. The resulting file must provide a template that can be loaded into BIM software and which integrate all the data requested for authorization checking. The model would be ready for use for the architect. The project of law - PL 12145 - was suggested in June 2017 and adopted in January 2018 with the allocation of the third of the budget to the BIM.

3. Main goals In a first place, the DIT’s expectations for this project led to look at the processing chain to be implemented. To answer the needs, a methodology has been defined and a working group was formed to follow the different stages and conduct the first thoughts. It was made possible to identify the following issues to consider before the prototype is made: -

Define the data to be processed and integrated in the model, their potential for development and their extent, i.e. to which public they will be provided.

Define which data can be modeled in 3D, in particular the surface and linear elements.

Find the appropriate containers for the data and their attributes according to IFC file’s specificity.

Evaluate the formats available in the SITG geo-extractor and determine if other should be provided.

Determine the formats and software used to create and control the prototype

The main problematic of this project is the transformation of the geo-data, available in geodatabase format *.gdb, into Industry Foundation Classes (IFC).

4. BIM, GIS and Geo-information The term BIM first appeared in 1986. In 1996, an international consortium, now known as BuildingSMART, created the IFC exchange standard. It has been necessary to wait until the beginning of 2000 before the term BIM popularized. BIM is generally used to represent a 3D building project and

Address Offices in Brussels : Rue du Nord 76, BE – 1000 Bruxelles. Tel +32/2/217.39.72 Fax +32/2/219.31.47 E-mail: maurice.barbieri@clge.eu - www.clge.eu EU-Transparency Register of interest representatives - 510083513941-24

Marion Kannengiesser Engineering student in geomatics

STUDENT CONTEST 2018

all its components. This model can be compared to a digital twin of the building that will evolve according to the changes made by the various contributors. The data integrated within the model can cover dimensions ranging from 2D to 7D. The latter corresponds to the model as built which contains all the information required to maintain the building after the completion of the construction works.

At the scale of the territory, the GIS is well-known and widely used. It provides tools that make it possible to represent data regrouped most of the time within databases (DB). GIS allows a graphic visualization of the DB and are commonly used in administrations.

Smart cities are currently developing and their main objectives are to make social, environmental and cultural aspects interact smoothly in a way to respond to growing urbanization, transport and mobility needs, and to make citizens a central pillar of city. This principle consists of integrating New Information and Communication Technologies (NITC) into cities to create sustainable structures involving public and private actors. Recently, the SITG has redefined its strategy to move towards the Smart Cities and it is with this scope that the State of Geneva set up this project. This leads on the one hand to make GIS and BIM interact, and on the other hand, to create a unique model gathering information from different professionals. It is common to talk about interoperability, but also about City Information Modeling, or CIM, which converges GIS and BIM to produce models on a larger scale than the building. The transition from BIM to GIS has already been studied and put into practice in recent years. It is currently necessary to find which standards are appropriate to solve the difficulties of interactions between the two systems. The BIM is useful to help making decisions as well as manage resources, procedures durations and costs. Combining the works from several actors into the same set of data - which is also updated in real time- makes it possible to consider quickly the potential problems. Furthermore, the use of “Clash detection” allows to complete a resolution as soon as the conflict is detected. On the 1st September 2001 the SITG Law (LSITG) came into effect in order to define the processing of geo-data as well as their control whatever their sources and dimensions are. This law defines the principles of transparency, sharing, organization and use and control of information in Geneva.

Monaco and Singapore are two examples that prove that the use of BIM as part of administrative procedures is put into perspective around the world and solutions already exist. This encourages Switzerland and particularly the Canton of Geneva to take a chance to achieve a long-term, efficient and economical BIM solution.

5. IFC files The IFC format appeared to be the most appropriate format because of its standard status. It is based on the STandard for Exchange of Product (STEP) and developed by BuildingSMART since 1994.

The original idea was to create a neutral format which does not require the use of any particular software. It is possible to open it in any kind of text editor and its interpretation is feasible on software such as NavisWorks, Solibri, Tekla, Revit or ArchiCAD. The different versions of IFC are available in open source and used to exchange data from the different AEC stakeholders by promoting the interoperability of software.

Three kind of information are stored to describe an object which belongs to a class, has several relationships, and is defined by particular properties. The IFC model is therefore a semantic and objectoriented which is decomposed in more than 800 classes of elements. Currently, losses of information are still recorded during transfers between software. Exchanges of data thanks to IFC is not yet fully operational, the problem lies mainly in the fact that two exports are necessary to switch from one software to another. Proceeding methodical data inspection is an essential step to be sure the model correspond to the expectations after the data manipulations.

The Model View Definition (MVD) also called IFC View Definition corresponds to a subset of the IFC schema that allows the exchange of models. These MVD meet the requirements defined in

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Marion Kannengiesser Engineering student in geomatics

STUDENT CONTEST 2018

ISO29481. BuildingSMART currently publishes the following MVD: IFC2x3 Coordination View V2.0, IFC4 Reference View 1.1, and IFC4 Design Transfer View 1.0. Other models are developed outside of BuildingSMART International and are likely to be released in the upcoming years.

An MVD allows specifying exactly what data is needed. The encoding format is mainly mvdXML and can be used in all versions of the IFC. The IFC documentation generator, IFCDOC.exe, is a tool developed by BuildingSMART for reading and writing mvdXML. By including the specification files, this tool provides a way to access the entire IFC hierarchy and manage an IFC file check. It was decided to use the Model View Definition IFC2x3, which seems to be more operational.

It also appears that most of the users in the construction industry remain reluctant to change in favour to IFC4. It is interesting to note that this newer version, which is the result of 6 years of development, is not yet integrated into all software.

6. Data and software Most of the data is available in 2D and needs to be transformed into 3D thanks to the attributes of height and altitude provided for this purpose. The SITG’s geo-extractor allows to obtain data in many formats. The one used for this work was mainly the * .gdb corresponding to geo-databases.

Autodesk's Revit software has been chosen for opening IFC products, while keeping in mind the future adaptation to other software available on the market such as ArchiCAD or Tekla BIMSight. The state of Geneva cannot decree the use of specific software and its proprietary format.

Data transformation has been carried out by FME software whose acronym stands for Feature Manipulation Engine. As its name suggests, it enable to manipulate data. It is a way of extracting, transforming and loading it by switching from one format to another. It appears to be a powerful method of solving interoperability problems. Indeed, more than 300 formats are supported and Safe Software regularly integrates new ones. During this project, two products, FME Workbench for data manipulation and FME Data Inspector for visualization, were used in the 2018 32-bit version.

Before linking IFC files in Revit, it is necessary to use a Viewer to confirm that its content is correct.

BIMVision developed by Datacomp Sp. is interesting because it allows easily and quickly to manipulate the objects, but also to measure distances allowing the control and validation of the model created.

7. Main axes of the study There are numerous issues to consider in order to guarantee the quality and coherence within the files obtained. Most of those are due to the complex hierarchy in IFC files and its particular structure.

It is necessary to define which data can be modeled in 3D and how to translate them in the IFC format.

It is required to transform surfaces and limitations into volumes. For some data layers there is a lack of information such as height and depth which are useful for the transformation into 3D data. The major challenge is to integrate elements that are not currently supported by the IFC and consequently go beyond the usual boundaries of BIM. The model obtained must be representative of the surrounding constraints while remaining refined. The goal is not to create a simple copy of the GIS in IFC format. The solution is to connect GIS and BIM through the object’s unique federal IDs to complete the model if necessary.

It has been chosen to work in two distinct areas, the first one is located in the heart of Geneva, because of its urban character. The second zone, less urbanized, is situated in Veyrier and allows working with forest boundaries, watercourses, existing and projected buildings.

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Marion Kannengiesser Engineering student in geomatics

STUDENT CONTEST 2018

Previous studies carried out by INSER SA have helped to understand the data workflow. The feasibility study from 2017, achieved by the Haute Ecole du Paysage, d’Ingénierie et d’Architecture (Hépia), highlighted the following constraints: -

Existences of inaccuracies in the coordinates due to the need to switch from the Swiss system to the WGS84 (World Geodetic System 1984) The need to create volumes to solve compatibility problems thanks to the Boundary Representation (B-Rep) Solids which consist of a meeting of closed surfaces.

There is a lack of IFC classes to store and represent all the elements

8. Results and prospects There are several issues related to the properties that as to be defined for each object. The mapping between Revit and the IFC file is complicated because it is possible to store Revit objects in IFC classes, but the opposite is almost impossible. Each family is intended to receive objects assigned to the same use, as well as for IFC classes. The major challenge remains to find a correct assignment of objects in existing IFC classes while ensuring that the latter will be correctly linked with Revit family types. Upcoming IFC releases tend to include more classes, not only attached to buildings but taking account on the location area or regarding infrastructures. There is still a shortage for most data in terms of the classes available for legal objects. The parametrization possibilities offered by FME currently hinder the implementation of a reference model. For instance, the Digital Terrain Model (DTM) is generated in FME and affected into the IfcSite class which is defined by BuildingSMART as the “Area where construction works are undertaken”. It would be interesting to use it to create subsites according to the property limits. Nevertheless, it would require an access to the appropriate IFC subclasses which are currently not carried out by FME. Multiple tests on the DTM have highlighted the complexity of dealing with object geometries in order to have a consistent result in Revit. Indeed, it is essential to analyse them in order to make adjustments and corrections to satisfy the requirements of the software.

Various objects not considered as priority have been studied in order to see how classes such as IfcProxy and IfcBuildingElementProxy behave. According to BuildingSMART, the IfcProxy is a container for all types of objects that are not part of the IFC model, while the IfcBuildingElementProxy hosts all elements of a building that do not have a proper class. To fit with the definition of IFC classes, most of the data from the SITG must be sent to IfcProxy. Items in this class are visible in viewers but are not transcribed in Revit. Using this class generates a loss of information and is therefore not a long-term solution. To eliminate the constraints due to the use of IfcProxy for most data, it could be created an IFC Genevois, the IFC-GE. This solution requires the involvement of developers specialized in IFC or a partnership with BuildingSMART directly since its standard status requires compliance with ISO standardization. However, it is difficult to imagine developing a standard for a region of this size. The conclusions underlined regarding the IfcProxy leads to a dead end for the integration of most data layers. Nevertheless, IFC and software are evolving and turning to BIM or even CIM, they are still young and constantly improving. Classes and families adapted for objects external to the building might appear in the upcoming years.

Giving a refined model easily understandable is one of the main goals of the study. The attribution of colours and the way lines are displayed remain problematic and weigh down the model. BIM software is made to design objects whose geometries are not derived from a triangulation and are represented homogeneously by simple faces. The current model includes complex geometry mainly due to the fact that most objects stem from the extrusion of the DTM. The tests performed to add colour to the elements did not lead to satisfactory results on every data. Indeed, this type of model is loaded with a large volume of data and it requires looking at the management of object overlays and their visual appearance.

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Marion Kannengiesser Engineering student in geomatics

STUDENT CONTEST 2018

The different discussions of the project monitoring team led to simplify the building representation as much as possible. Thus, it was requested to create a single volume composed by roofs, walls, bases and basement. Indeed, for the creation of his model, the architect does not need a decomposition of neighboring buildings. All elements are merged and placed in the IfcBuilding class. The latter is supposed to be the container of a set of subcategories containing the geometries. This class seems not to be implemented to contain geometries which may explain why Revit does not recognize the class during the import. The goal of Revit, as well as other BIM software, is to model all components of a building and not a single volume uniting them. The software classifies objects into families if they belong to the IfcElement class that groups classes such as IfcBuildingElement which is a subclass of IfcBuilding. In a way to simplify the representation in the model provided, it seems appropriate to group the elements of a building. However this way of proceeding causes conflicts during the transfer in Revit. Leaving the constitutive elements of the building in their respective classes leads to issues regarding the comprehension and generation of the geometries. No solution was found to overcome these constraints at the end of the study. It should be noted that the representation of buildings is facilitated by directly having 3D data at disposal. This shows the importance of expanding the 3D data catalogue available on the SITG portal.

The tests performed to go from MVD 2x3 to 4 thanks to FME showed that there is a need to revise all the programming since the script writing in IFC 2x3 does not work to create a file in version 4. The IFC 5 will soon arrive and it will therefore be inevitable to adapt to the demand of the various contributors who will use one of these three MVD. Many approaches are still to be explored. For most of the current projects, the lack of maturity of the IFC implies that there is no benefit of hindsight to allow optimal transmission of knowledge. There is a need to deepen the research in order to reach an efficient transfer of the GIS towards the BIM. 9. Conclusion All around the world, cities are tending to use digital processing chains in order to improve efficiency and save time and money. Most official forms can currently be completed online and sent directly to the respective department. In the field of AEC as well as in creation and management of Geodata, the term BIM is becoming more widespread and its use is becoming frequent.

Administrations see this technology as an opportunity to manage their territories and the procedures pertaining to construction projects. In Switzerland, BIM is still underdeveloped but is beginning to gain more and more ground.

This study showed that despite its arrival in the early 2000s, the BIM is still very young and few projects have been made entirely in BIM with the status "Full-BIM". The IFC format has not reached a sufficient maturity for its use to be unhindered. It remains in constant evolution and must be adapted to the increasing demand related to the creation of Smart-Cities. Most software that are dedicated to BIM do not seem ready to handle all the possibilities offered by this format. Currently the major concern is regarding the geometry that does not always load correctly in Revit. By opening the file directly, the elements appear but are often represented in a way which is not understandable.

Moreover, incompatibilities between IFC classes and available families are noted which limits the capabilities given by this format.

Even today, the work focuses on the problem of assigning IFC parameters and mapping elements into an appropriate IFC class. We know that many classes and subclasses exist to obtain rich data and accurate representation. However, few of these parameters are made accessible by FME and we do not yet find a way to integrate them.

Address Offices in Brussels : Rue du Nord 76, BE – 1000 Bruxelles. Tel +32/2/217.39.72 Fax +32/2/219.31.47 E-mail: maurice.barbieri@clge.eu - www.clge.eu EU-Transparency Register of interest representatives - 510083513941-24

Marion Kannengiesser Engineering student in geomatics

STUDENT CONTEST 2018

There is a difference between creating a model under BIM software before exporting it to IFC for sharing, and the creation an IFC file from existing data in another format. The quality of the current model remains unsatisfactory to allow its use in a building permit application process. The various constraints raised in this report tend to show that the production of reference models is a major challenge.

The use of 3D represents the future but there is a need to adapt the rules and norms to frame its use. This would provide a complete 3D base in a way to simplify and ensure an efficient use of the data that will be incorporated into the BIM. BIM needs to be more developed and current projects do not allow to have the necessary perspective to appreciate its entire potential. Most of them are at the experimental stage and are first prototypes. It is necessary to continue to develop this type of full-BIM approach that represent the future in the field of AEC. As well as the work on interoperability and IFC. For Geneva and OAC, the aim is to explore new way for dematerializing procedures using GIS, 3D and possibly BIM.

Address Offices in Brussels : Rue du Nord 76, BE – 1000 Bruxelles. Tel +32/2/217.39.72 Fax +32/2/219.31.47 E-mail: maurice.barbieri@clge.eu - www.clge.eu EU-Transparency Register of interest representatives - 510083513941-24