Who has not at some time or other wandered through the streets of New York City, Tokyo or Paris on Google Maps? Recent advances in three-dimensional (3D) mapping and improvements in the quality of the photos gathered by Google Cars and aeroplanes now offer the general public a highly captivating immersive experience. However, giant 3D models can potentially be applied in cities in many more ways, such as examining a potential new town layout, studying urban networks, planning the installation of telecoms antennae and an increasing number of city authorities are getting interested in the digital twin concept.

Emulating Google, cities now want their own 3D model

In 2011, Google and outdoor advertising specialist JCDecaux created Paris Métropole 2020, an impressive digital model of the city of Paris that was exhibited at the Pavillon de L'Arsenal, the Paris Centre for architecture and urban planning. Now however, municipal authorities are looking to go beyond merely projecting their image and publicising their town with this type of modelling. They increasingly want to have real 3D working tools that will help them to make a better job of running their city. Sidewalk Labs, a subsidiary of Google parent company Alphabet, is working on this issue with Toronto City Hall. Meanwhile similar projects are starting up in many places as an extension of the local geographic information systems (GIS).

Regard d'expert

David Jonglez

Director Business Development

ERSI France 

Don't forget that cities began developing GIS systems over thirty years ago. Those mapping systems have now morphed into a full range of GIS services, which are today evolving further towards creating city 'digital doubles'.

 The Digital Twin is the natural evolution of GIS, argues David Jonglez, Director of Business Development at ESRI France, the world’s foremost GIS publisher, pointing out: Don’t forget that cities began developing GIS systems over thirty years ago. Those mapping systems have now morphed into a full range of GIS services, which are today evolving further towards creating city ‘digital doubles. Paradoxically, medium-sized cities have been the quickest to embark on this 3D mapping adventure. In France, for instance, the coastal towns of Cannes, Brest and Le Havre have been among the pioneers in this field, especially when it comes to major development projects such as the re-development of port installations at Cannes and Brest. In fact the huge amounts of data required to model an entire city have proved to be a major obstacle to creating digital twins of the very largest cities, but things are moving forward. The City of Paris authorities are aiming to have a digital twin up and running by early 2019, but the entire modelling project is scheduled to run until 2024. In addition to digitising streets and buildings, City Hall is also thinking about modelling what is happening underground, especially the sewerage network. In the same vein, the Ile-de-France (Greater Paris) region is looking at modelling the entire region, a gigantic undertaking, even though nowadays satellite photos, aerial photography and the deployment of drones make it somewhat easier to build up a three-dimensional  model of a city. While algorithms are able to generate 3D models automatically from a series of photos, there is still a colossal amount of processing and checking to be done. Moreover, once the model has been set up, it has to be updated on a regular basis. This means that the city authorities have to run fresh data-capture campaigns on a regular basis, every two years in some cases.

Digital twin: big brother to the Building Information Model (BIM)


Mixed Dimensions brings 3D modeling and printing to a wider public

Archive April 2014

An increasing number of cities are now launching initiatives to create digital twins, as these models bring benefits in many areas far beyond burnishing their brand image. David Jonglez explains: Going way beyond the pure publicity exercises that we used to see a few years ago, a digital twin brings significant gains as regards urban planning. In a re-development project like the one at Paris Saclay [southwest of Paris], 3D modelling creates new possibilities aside from the visual aspect. The Business Rules Engine enables you to simulate urban redevelopment with, say, 70% of the surface area reserved for the tertiary sector, 15% for commercial use and the rest for housing. So you can simulate the economic impact or the need for new transport services in these zones.  This type of analysis has been carried out by the city of Philadelphia. Using 3D modelling they have been able to simulate public transport requirements so as to work out the most convenient places to put the bus stops, to plan an extension of the tramline in order to provide a better service to local residents, and at the same time assess the economic impact of extending the line.

Gwenael Bachelot, Technical Sales Manager at US software specialist Autodesk, a company whose clients include a number of architectural practices and construction industry firms, sees wide scope for applying the digital twin approach beyond urban redevelopment impact studies. 3D modelling can also be used to assess the impact of road improvements, such as the construction of a new roundabout or bridge. You can also use the model to simulate climate events and to support decision-making,he points out.

Autodesk, which has a close involvement in the construction and public works sector, has teamed up with GIS mapping software developer ESRI in order to streamline interaction between its BIM solutions and ESRI’s GIS systems and exploit the obvious synergies.  It is very likely that in the near future city authorities will ask architects to send them the project BIM once construction has been completed so as to incorporate it into the digital twin. Software publishers working with the construction industry will therefore need to ensure they can incorporate a ‘light’ BIM system. Between the Cloud, mobile technologies, BIM and GIS, we’re now seeing an explosion in the amount of data being created, underlines Gwenael Bachelot, adding: “Clients expect far more than just a CAD [Computer Aided Design] file – they want to see their project in a wider context. So it’s vital for our clients to have a seamless flow of data between the GIS and BIM systems.”

Managing a city as you would the life-cycle of a manufactured product

Regard d'expert

Gérard Le Bihan


Images et Réseaux  

Compared to a more traditional Open Data portal, a 3D model of a city brings the added value of visualisation and decision-making support.

Meanwhile publishers of BIM and SIG software are now facing a new competitor in their market – French 3D design and engineering software company Dassault Systèmes. The firm, which is well-known for designing software that is widely used in the aeronautics and automobile sectors, is now planning to apply its manufacturing-based Product Lifecycle Management (PLM) approach to the Smart City. Its ‘3DExperiencity’ platform was set up following acquisition of the Rennes (Brittany)-based software company Archividéo, which specialises in 3D modelling of land areas, in 2013. "Dassault Systèmes’ aim was to combine the ability to manage land areas in 3D with project management using PLM techniques," explains Gérard Le Bihan, Head of Images et Réseaux, a competitiveness hub representing companies and laboratories in Brittany and the Loire Valley in western France, underlining:  Combining these two fields has given rise to a platform designed to host a digital twin of the land area.

In addition to the town planning and decision-making support aspects, the platform is also intended to serve as a tool for communicating with local people. This is precisely what happened in Rennes: a demonstration of the city’s digital twin was used when a call was put out for ‘industrial demonstration projects for a sustainable city’. The aim was to encourage innovation, with apps designed to sit on top of the platform feeding in and facilitating the use of data. Compared to a more traditional Open Data portal, a 3D model of a city brings the added value of visualisation and decision-making support. The 3D model itself is just a tool on to which application layers can be added. The more information stored in the model, the more relevant it becomes and the more it enables new use cases, stresses Le Bihan.


Rennes 2030

A channel for digital simulation

  • 1 min

All sorts of city-related data can be uploaded into the digital twin and, in addition, simulation algorithms can be used to visualise natural phenomena and make forecasts. Gérard Le Bihan explains what happens: On a given model, you can run a simulation and see the results of the calculation directly on the model. Among the first use cases of the model is the issue of power shortages. 3D modelling enables you to visualise the results across a whole building, and also floor-by-floor, which of course you can’t do in two dimensions. Research based on digital simulation – for calculating values for sun and shade, for the wind blowing around a building or even the growth of vegetation, plus simulating accidents such as explosions and natural disasters such as flooding – opens up a broad range of opportunities for future uses of digital twin technology. One example of these new approaches is the work being done by French 3D urban modelling and software developer Siradel, which specialises in  optimising radio connectivity between residents, objects and infrastructure  by, for instance, setting up simplified city models so as to optimise 4G antenna placement. Siradel was acquired in 2016 by French power and gas utility Engie, which was keen to apply its 3D modelling expertise to a variety of other uses. Engie has thus now entered the new digital twin market with a solution for storing administrative, economic, social and technical data on buildings, urban networks, public space WiFi coverage and geolocation of connected objects. Engie has drawn on the expertise provided by Siradel for its participation in the European ACCENT (‘Accompany cities in energy strategy’)project , which is being rolled out in Paris, Valencia in Spain and  the Italian towns of Reggio Emilia and Ferrara. The algorithm used for this initiative calculates potential gains when a given building in a city goes through an energy-oriented renovation process. The owners might opt to change the windows, install external insulation or apply other insulation solutions, and the algorithm will then put a figure on the savings they can expect so as to guide them towards the solution which offers the best cost/efficiency ratio.

Digital twin becoming a common benchmark for the IoT

the ‘virtual SINGAPORE’ project

One of the most cutting-edge cities in the world when it comes to applying the digital twin concept is Singapore. The Virtual Singapore initiative was launched in 2015 with a view to bringing together all relevant data in a single 3D model. George Loh, Programme Director at the National Research Foundation (NRF) in Singapore explains: “When it comes to town planning, Singapore has a number of challenges to face and researchers are now using simulation to look for answers. What we wanted to do was to set up a single 3D model of the city, and this is what drove us to launch the Virtual Singapore project. At the time of the project launch, Ng Siau Yong, Director of the GeoSpatial and Data Division at the Singapore Land Authority, declared: The aim was to achieve synergy between all the 3D modelling coming out of the various government agencies by placing them on a common platform so as to enable all public agencies to use the same 3D model of the city.

 “The aim was to achieve synergy between all the 3D modelling coming out of the various government agencies by placing them on a common platform so as to enable all public agencies to use the same 3D model of the city.”

Singaporeans are very much at the cutting-edge as regards one new use of the digital twin approach: linking the model with data flowing from connected objects. The NRF and the Ministry of Education jointly launched a first-ever experiment: 250,000 schoolchildren and students were enrolled in a huge data-gathering campaign with the aim of gathering data on the environment via connected objects embedded with sensors which they wore around their necks so as to collect data throughout the day. By 2017, 43,000 had already been equipped with a device called a Sensg. Explains Erik Wilhelm, a researcher at the Singapore University of Technology and Design: We measure the temperature, pressure, ambient humidity and luminosity, noise level, infrared rays, and also the wearer’s own level of physical activity – specifically the number of steps each wearer takes. This data is extremely useful for our analysts. It can be visually displayed directly on the 3D model and Virtual Singapore enables you to refine the research so as to answer specific questions and go into extremely fine detail.

Notwithstanding the growing number of Smart City projects in operation, city data seems to be increasingly stored in silos, each with its own technical providers, its own sensors and its own databases. Going forward, the digital twin approach seems to be the right way to bring all the information together in the same place and generate innovative solutions through data aggregation. The Smart City of tomorrow will surely not be able to do without its – virtual – double.
By Alain Clapaud
Independent journalist specialising in the new technologies