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 Caroline Tasse Branch Manager of Vectuel Middle East Email: c.tasse@vectuel.com  The advantage of 3D in high definition is its ability to understand a city, its areas, its functioning and its dynamics as they are on the ground. This article talks about the power of 3D interactive in decision-making and in territory governance 3D technology has evolved over the years from being purely a technical tool to a multi-pronged tool for all the stakeholders in the area of governance. The main advantage of 3D in high definition is its ability to understand a city, its areas, its functioning and its dynamics. A powerful tool for decision- making, 3D interactive enables a user to be fully aware of the impact of a project in an existing environment. 3D technology is playing an increasing role in territory management for two reasons. The first one is the technological availability of computers (hardware) and software to ingest 3D databases in high definition: which involves more data to store and to visualise, better display capacities, more powerful calculation tools, etc. The second reason is the diversification and the increase of proven needs among the stakeholders of territory governance. In the past 3D technology was mainly used by engineers in the field of GIS. Today, it has opened up to other requirements and needs like architecture, communication, town planning, security, Internet, GIS, design and transport. Among these, priority is to serve urbanism and architecture purposes and this requires high definition data. We cannot create the simulation of an architectural building with low quality 3D environment that provides poor rendering. Thus 3D technology has incorporated the management and updating of 3D high definition database. CityGML, an OGC standard, answered this expectation by normalising levels of modelling, from basic and external modelling (boxes) to high detail and inside modelling of buildings. No software can meet all business needs. So, it is essential to distinguish the creation of data from its use and to emphasise the interoperability of this data in order for all territory stakeholders to be able to work with it. 3D modelling aims to open 3D data not only to different businesses but also to diverse interlocutors. Thus 3D interactive, also called virtual reality, is a powerful tool for decisionmaking and communication between all players in the territory of governance, as well as to the general public. What is 3D data in high definition? Today, 3D technology represents different realities interpreted by diverse levels of details according the application. CityGML has standardised these levels of details. It is a common information model for representing 3D urban projects enabling the storage and exchange of virtual 3D city models. The first level of details, called LoD0, refers to the modelling of the relief (DTM) textured with true orthophotography. It is used for display on visualisation tools such as Google Earth. The second level of details LoD1 represents the very basic shape of buildings, like a box or cube. These data are used for technical calculations such as wave propagation, aerodynamics, etc. Realism becomes a part of 3D modelling from LoD2, thanks to the modelling of the roof superstructures and to the dressing of the facades with aerial imagery. With this, a fly through gives low definition realism and 3D modelling may be used as communication purposes such as on Google Earth, for instance.  The two following levels, LoD3 and LoD4, keep increasing the quality and the 3D definition of the modelling. With LoD3, the facades are dressed with pictures taken from the street and the details of the facades (balcony, arch, etc. are modelled more finely. 
LoD3 serves the
purposes of urbanism
and architecture for
analysis of the urban
environment at
paedestrian level and
for project simulation.The level of realism is incredibly astonishing and enables the export of data into virtual reality. Finally, LoD4 is the inside modelling of the building that meets, for example, security requirements. The 3D data has been enriched to meet other requirements of the stakeholders of territory management. 3D data interoperable and upgradable The need of territory governance is to have diverse and high definition data at the disposal of all stakeholders. It is essential to differentiate 3D georeferenced data from its uses. By creating 3D georeferenced database in high definition (LoD3 andD4 data), architects, town planner and external services provider have the possibility to collect the data they need to work on a project. The 3D modelling in high definition is especially dedicated to three core businesses of territory governance. Firstly, urbanism/town planning and architecture will be able to edit construction rules, to preserve the visibility from and on the future projects, to simulate future developments and assess their impacts in the existing environment, etc. Secondly, GIS will have, at its disposal, more detailed data for more specific calculations dedicated to urban management and planning like assessment of the efficacy of lighting systems, traffic simulation and sun view for solar panels installation. Finally, communication is a significant factor for the success of territory management and planning. 3D technology enables the visualisation of a project from different angles. Various stakeholders, from general public to investors and decision-makers, will be able to understand and to be aware of the effects and impact of a project. Strategic for decision-making and for explanation of the development to all involved people, 3D interactive supports projects through its promotion and communication all around the world. From 3D GIS models to virtual reality The advantages of this technology are numerous. This is a powerful tool enabling decision-makers to understand and explain in 3D the large urbanism and architecture projects, to analyse and validate a master plan, to assess territory risks, to communicate about the city and to let people discover it through Internet, to supply data to GIS applications, to have at your disposal data relevant for civil security, to create a urban database for consultancy of developers, town planners, architects, etc. Interactive 3D shows an architectural model at the same time in its environment and from different view angles. The two major benefits for architects and town planners are to explain the projects and to take decisions. Virtual reality prevents wrong interpretation and construction mistakes by offering a unique view of the project which the stakeholders can approve. Page 1 of 1
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