Australian researchers have created a 3D interior map of Italy’s famous Leaning Tower of Pisa by using a breakthrough mobile laser mapping system.
The work will contribute to preserving the cultural heritage of the site.
Developed by the CSIRO, Australia’s national science agency, the Zebedee technology is a handheld 3D mapping system incorporating a laser scanner that sways on a spring to capture millions of detailed measurements of a site as fast as an operator can walk through it. Specialised software then converts the system’s laser data into a detailed 3D map.
While the tower’s complex architecture has prevented previous mapping technologies from capturing its interior, Zebedee has enabled researchers to create the first comprehensive 3D map of the entire building.
“It can often take a whole research team a number of days or weeks to map a site with the accuracy and detail of what we can produce in a few hours,” said Dr Jonathan Roberts, research programme leader at CSIRO’s Computational Informatics Division.
“Within 20 minutes we were able to use Zebedee to complete an entire scan of the building’s interior. This allowed us to create a uniquely comprehensive and accurate 3D map of the tower’s structure and composition, including small details in the stairs and stonework.”
Zebedee’s primary sensing technology is lidar, in which an infrared laser measures ranges to surfaces in the environment. The system’s distinguishing feature is that the laser scanner is mounted on a spring, which converts the natural motions of the operator into a sweeping motion of the scanner, giving a wide field of view.
A low-cost inertial sensor provides rough measurements of the spring’s rotations. Specially developed software can convert the raw range and inertial measurements into a 3D map in less time than it takes to collect the data. The maps are represented as point clouds, millions of points expressed in a common coordinate frame.
The CSIRO team collaborated on the Pisa project with local Italian scientists from Scuola Superiore Sant’Anna.
“Our detailed record of the Leaning Tower of Pisa may one day be critical in being able to reconstruct the site if it was to suffer catastrophic damage due to natural disasters,” said Franco Tecchia, assistant professor at the SSSA’s Perceptual Robotics lab, PERCRO.