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World Heritage Site meets artificial intelligence

A connected AI video solution from Bosch protects Aachen Cathedral from fire, intrusion, and vandalism

Uwe B. Herrmann, Helmut Mainz and Ralf Wolters in Aachen Cathedra

A new fire protection and safety solution sets an example: together with the engineering firm plan ing, Bosch has developed and implemented an intelligent video solution for the cathedral site office – one that provides comprehensive protection for the World Heritage Site and helps preserve it.

Außenansicht des Aachener Doms am Abend

The Aachen Cathedral with its 1,200-year-long architectural history is a true masterpiece. It is regarded as the epitome of Carolingian architecture and assumes an important role in the architectural history of Europe. In 1978, the Aachen Palatine Chapel became the first building in Germany to be added to the list of UNESCO World Heritage Sites. A dome crowns the 31-meter-tall building where 365 days a year, visitors stream into the cathedral to attend services or marvel at the octagonal central structure and the choir hall, as well as the side chapels.

What is the best way to protect a structure like this?

This is one of the biggest challenges facing master builders responsible for cathedrals around the world. “Although we have a fire and smoke detection system in the trusses in the roof, including a fire extinguishing system from 1929, there was no reliable solution for the interior. The clerical areas with the works of art, the organs, altars, wooden sculptures, paintings, the wardrobes for liturgical clothing and choir robes, as well as the choir stalls, were not protected,” said Helmut Maintz, who was responsible for Aachen Cathedral as master builder for over 20 years and handed over the building to his successor Jan Richarz at the beginning of 2023. “Fire safety in the Aachen Cathedral has been an issue for a while now,” explains Ralf Wolters, whose engineering firm plan Ing has been providing support to the cathedral’s site office for several years. “However, the design of a cathedral makes it difficult to find a satisfying solution using traditional technologies like smoke detection systems or photoelectric sensors. After all, anything that works in open spaces quickly reaches its limits in an angular, religious structure subject to strict heritage laws. In Aachen, there’s also the problem that the aging electronics presented the greatest risk for fire, which meant they had to be removed first.” Modernizing the electrical installations provided an excellent opportunity for a complete overhaul of the fire safety concept. In Bosch Energy and Building Solutions, Wolters and Maintz found the perfect partner to make what had until then been impossible possible and, at the same time, to solve additional challenges when it came to theft protection and vandalism.


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Intelligent early fire detection protects both people and unique artistic treasures

At the center of the solution is the video-based early fire detection system AVIOTEC from Bosch. More than 50 cameras were installed in 16 rooms in the Aachen Cathedral, forming an ingenious video surveillance system. The IP cameras with an integrated video analysis function detect flames and smoke visually right where they first develop, allowing fires to be identified quickly.

The AI-supported video solution can do even more: at night, it can be used as an alarm system in the event of a break-in. During official opening hours, the system helps to protect the valuable works of art and relics in the cathedral from vandalism by issuing an alert when virtual off-limits zones surrounding the exhibits are breached. Special software with statistics functions analyzes the flow of visitor traffic and informs the cathedral verger (doorkeeper and caretaker of a Catholic church) by smartphone as soon as the maximum number of visitors to the cathedral has been reached, so precautionary measures can be taken. “A decisive argument in favor of the system was that it could handle all these different aspects, pooling them into a single device,” says Helmut Maintz. “Normally, to take care of all these requirements, several technologies would’ve needed to be installed: a motion sensor for motion detection and an alarm system with door contacts as well as accompanying fire detectors for the fire alarm system or air intake system,” says Uwe B. Herrmann, sales manager and project manager at Bosch Energy and Building Solutions. “AVIOTEC, however, gives us video cameras that handle all these challenges.”

  • Simulation with the Aviotec camera from Bosch in Aachen Cathedral The computer shows how the Aviotec camera from Bosch immediately detected the fire.
  • Simulation with the Aviotec camera from Bosch in Aachen Cathedral The computer shows how the Aviotec camera from Bosch immediately detected the fire.

Aachen is at the international top with its video solution. World Heritage Sites require special protection. It’s not enough just to preserve the stone, the interior must also be protected.

Jan Richarz, master builder of the cathedral

AVIOTEC makes work easier for the fire department

One major benefit of the solution being used in Aachen is a direct connection to the local fire department. If one of the cameras detects a fire that has broken out, an alarm is immediately sounded and a fire detection system alerts the Aachen fire department, having been integrated into its own system in accordance with the relevant standards. When the fire brigade arrives, it also receives live images from inside the cathedral on an on-site monitor, showing the exact location where the danger was identified. That saves valuable time. “The professionals at the fire department were impressed by the high technical standards of the AVIOTEC- system, which is why they agreed to a special alarm – as part of the overall solution – that is connected directly to the department’s own system,” explains Herrmann. AVIOTEC was the first system of its kind to receive a VdS certification in 2017. In order for the cameras to use the correct protocols for communication with the fire department, Bosch Rexroth created special interfaces. “A lot of companies do video, a lot do fire detection technology, but as far as I know, this is the first time that solutions for all these requirements have been successfully combined. And that in a structure like this! Everyone involved contributed to and supported the final system,” says Wolters.

Jan Richarz with a statue of Aachen Cathedral
Cathedral master builder Jan Richarz is very satisfied with the intelligent video solution
Uwe B. Hermann, Helmut Maintz and Ralf Wolters in Aachen Cathedral
Very satisfied with the result: Uwe B. Hermann from Bosch Energy and Building Solutions, Helmut Maintz retired Aachen Cathedral master builder and Ralf Wolters from the engineering firm plan ing (from right to left).
View of the interior of Aachen Cathedral
Due to the construction of the Aachen Cathedral, it has been difficult to find a satisfactory solution with conventional fire protection technology so far
Wooden benches in the choir hall of Aachen Cathedral
There was no suitable fire protection solution for the sacred area and the interiors
Aviotec camera detects fire at Aachen Cathedral
Extensive simulations were carried out in advance from various positions
View of the Aviotec camera screen
The camera immediately detects the fire set for the simulation and sounds the alarm. It can distinguish the fire from people.
Installed camera in Aachen Cathedral
Over 50 cameras were installed in Aachen Cathedral. In advance, the positions were calculated on the computer and marked on site.
Aachen Cathedral Chapel, interior view
The Bosch solution is also used in the chapels and outbuildings
Candlelight in Aachen Cathedral
The AVIOTEC cameras can distinguish candlelight in the dome from fire
Seated interior of Aachen Cathedral with view of the altar pendium
Over 1.2 million people visit Aachen Cathedral every year. It is open daily from 7 a.m. to 6 p.m.
Interior view, Aachen Cathedral
Sometimes up to 12,000 people stay in the cathedral on one day.
View of the Barbarossa chandelier in Aachen Cathedral, interior view
When it comes to counting visitors, the cathedral verger receive smart support from the Bosch solution

Exact 3D simulations, red adhesive dots and heritage listing

In order to find the ideal position for each camera, the space was recreated digitally. Exhaustive 3D simulations were then conducted with the help of special software. Red adhesive dots were used to mark the positions planned within the cathedral. Before the installation could begin, another essential step was required: coordination with the heritage council. As Helmut Maintz recalls, “We brought in the heritage council early and showed them what the cameras look like and where they would be positioned, as well as our cable system, which will be concealed to the extent possible. We wanted the best protection – and don’t want it to be visible. There are areas with marble cladding in the cathedral, as well as mosaic tiling and paintings. It isn’t possible to cut recesses for cables in those areas.” To overcome these particular obstacles, the team worked closely with the council, which required the expertise of all parties involved. In order to make the cameras less noticeable, Bosch even covered the cameras in a black foil and installed specially built brackets. Every camera was fitted with a mounting system with specially designed thread, and the holes were carefully prepared by a stonemason. During the installation phase, more than 30 craftspersons worked in tandem in the cathedral, installing electrical lines, lighting and the new video solution. “Work on a World Heritage Site is certainly something very special. Every day, we also held two Mass twice a day, and there were a lot of visitors and tours. I was really impressed with the great teamwork in this extremely limited space,” adds Maintz.

  • Bosch Aviotec camera being installed
  • Installed Aviotec camera from Bosch in Aachen Cathedral

The challenges of the structure showcase the strengths of artificial intelligence

Thanks to artificial intelligence, the video cameras are able to separate important data from the unimportant ones, despite the large number of visitors walking through the cathedral and the cameras’ field of vision every day. In order to increase the accuracy and the speed, the algorithms are being continually improved. “The cameras must be individually trained, even in the difficult and constantly changing light conditions in the cathedral, to ensure the electronic eye is able to distinguish candle light from a fire hazard, as an example,” explains Herrmann, who oversaw the project from day one. “I’m very happy that this technological solution allowed us to make a significant contribution to the preservation and security of this World Heritage Site.”
Visitors to Aachen Cathedral can feel safe when they visit the cathedral and the chapels. Cathedral master builder Jan Richarz is also visibly satisfied. Cathedral site offices have been the guiding hand responsible for preserving and maintaining cathedrals – for hundreds of years, which is why cathedral workshops were added to UNESCO’s list of Intangible Cultural Heritage in 2020. "Aachen is at the international top with its video solution. World Heritage Sites require special protection. It’s not enough just to preserve the stone, the interior must also be protected. This was only possible because the Karlsverein/Dombauverein and therefore many citizens of Aachen as well as the state of North Rhine-Westphalia supported us with great effort so that this innovative project could be realized."