Unlocking New Perspectives: Mapping the Széchenyi Chain Bridge with Drone LiDAR Technology

This case study highlights how YellowScan utilized it’s Surveyor lidar sensor mounted on a drone to establish a baseline and document the condition of the Széchenyi Chain Bridge in Budapest prior to its restoration.

This initiative, spearheaded by our partner Ventus-Tech in Hungary, focused on documenting the bridge’s current state before restoration efforts commenced.

The initial scan will serve as a reference point for evaluating the bridge’s condition post-restoration, with a follow-up scan planned to assess the changes.

Ventus-Tech aimed to demonstrate the potential of advanced sensors and post-processing technologies to enhance construction workflows and promote awareness of Building Facts Modeling (BIM) solutions.

By seizing the chance to work on the Chain Bridge, a national emblem of innovation in Hungary, they sought to align with contemporary standards and develop a solution compatible with BIM systems.

What Challenges Were Faced?

To effectively survey the entire bridge, a variety of sensors and unmanned aerial vehicles were required.

A DJI M600 drone equipped with an RGB camera captured top and side views using RTK GPS, while the YellowScan Surveyor LiDAR sensor was deployed to map the structure.

Additionally, a static ground laser scanner and a robotic boat were utilized to capture RGB images of the bridge’s underside, complemented by multibeam sonar to scan the riverbed for ordnance and debris.

Conducting flights in the bustling city center posed meaningful challenges. Ventus-Tech had to secure special permissions from aviation authorities, which mandated maintaining a safe distance of 150 meters from the Carmelite Monastery (Prime Minister’s Office) and the Sandor Palace (President’s Office). They were also prohibited from flying over the Ministry of Interior. With these restrictions in mind, they meticulously planned their flight paths to comply with local regulations.

Proposed Solution

Implementing a LiDAR system was crucial for the success of this project. Ventus-Tech opted for the YellowScan Surveyor, marking their first acquisition of a LiDAR system.

This system was especially well-suited for the mission due to its versatility, user-friendly design, and 360-degree scanning capabilities.It is also ideal for urban surveys that must adhere to stringent flying regulations, necessitating lightweight payloads.

Mission Specifications

• Survey Dimensions: 60m x 420m
• Timeline: 30-day flight permit,2 days for aerial flights (LiDAR and photogrammetry),1 day for the boat,1 day for sonar,16 days for vectorization and post-processing
• Flight Count: 3 (1 LiDAR / 2 Photogrammetry)
• Flight Speed & Altitude: 4 m/s,40m above the road,55m above the water
• Equipment Used: DJI M600 Pro,YS Surveyor,RGB Sony a6400 camera with Zeiss Ventum 21mm lenses,and a static laser scanner
• Main Focus: the bridge itself (60m high by 40m long)

Outcomes

The project achieved a point density of 100 points/m² with an accuracy of less than 5cm,resulting in a highly detailed point cloud. Areas of the structure that were inaccessible via aerial scans were supplemented with terrestrial laser scanning, and the photogrammetry point cloud was refined based on the aerial laser scanning results.

Ventus-Tech reported that the quality of the data collected was exceptional,and they have since developed a workflow to integrate data from various sources seamlessly.

“The support from YellowScan has consistently been outstanding. We have a long-standing partnership and are thrilled to collaborate with them,” stated Balint Vanek, Chief Technology Officer at Ventus-Tech. “The Chain bridge is an iconic architectural landmark in Budapest, and both Ventus-Tech and Bimfra were proud to contribute to this project pro bono. It was a bonus that the construction firm handling the renovation took our findings seriously and considered incorporating the survey results into future projects, even during the bidding process. The value of a digital twin extends beyond a single construction phase; it can be leveraged during pricing, design, construction, and operational stages. Thanks to the YellowScan Surveyor,we successfully completed this project!”