Located atop the 700-meter Corcovado Mountain, the Christ statue – with a 38-meter height and 28-meter arm span – towers over Rio de Janeiro.
Using the Aeryon unmanned aerial vehicle (UAV) platform for data acquisition and Pix4D’s image processing software for 3D reconstruction, the project team collected data for six consecutive mornings on-site in late October. The NEXT Lab of PUC University was in charge of project logistics, including special permission to fly UAVs at the site.
The main challenges were the changing weather and wind conditions, restricted hours (flights could only take place before and after visiting hours) and inconsistent lighting conditions (shadows in early morning and late afternoon). A total of 3,584 images were acquired during 19 10-minute flights. Another challenge was signal reflectance, which affected the geotag accuracy; as a result, the sub-projects were processed without geotags.
The team used 2,090 images in the Pix4Dmapper Pro desktop software to convert them into the 3D model. The reconstruction was divided into three main projects (statue, base and surrounding area) and nine sub-projects to help manage the variations in image capture.
Accurate 3D reconstruction has not been possible until today because technologies such as LiDAR cannot scan the complete statue because of its size, location, difficult accessibility and challenging weather conditions. All previous 3D models and replicas of the statue have been designed by hand, Aeryon says.
“This project took years of waiting by the NEXT Lab team and many months of planning and collaboration across several time zones to pull the technologies together in Rio,” says Dave Kroetsch, Aeryon’s president and CEO.
The final 3D model – available both as a point cloud of 134.4 million points (97.6 million for the statue, 30.7 million for the terrace and 6.1 million for the surroundings) and as a full, 3D-textured mesh of 2.5 million triangles with a texture of 16384px x16384px – will be used and presented by PUC University for upcoming projects in the near future.
An accompanying video can be found here.