That's just what the underside of a bridge is, and Fujitsu wants to use drones with large wheels to scoot along them while checking for cracks and other wear and tear.
At a technology expo in Tokyo on Tuesday, the electronics maker showed off a prototype quadcopter that could help reduce bridge inspection and maintenance costs.
The drone looks a bit like a space station from science fiction. It consists of a central unit with four rotors, a high-definition camera and sensors including gyroscopes. On either side of this central unit are two large fiberglass wheels.
While it's aimed at streamlining maintenance, the drone's unique design could inspire new applications for unmanned aerial vehicles.
The wheels serve to protect the drone from pipes and other obstacles when it flies up the walls of bridge supports and along the undersides of bridges. They also help keep the drone a fixed distance from the surfaces it is video recording.
The fisheye camera can capture close-up views of bridges and capture cracks as small as 2mm wide. The imagery is relayed to tablets or remote servers and used to create detailed 3D models of bridge pillars and undersides for remote inspection by engineers. If they spot a worrisome crack, they can then check out the structure in person.
"This could be useful because Japan has 700,000 bridges over 2 meters high and the government stipulated that they must be inspected every five years," said Hiroshi Haruyama, a Fujitsu senior manager.
Weighing between 2 and 3 kilograms, the prototype was developed with the state-backed New Energy and Industrial Technology Development Organization and Nagoya Institute of Technology. The group plans to improve its 15-minute battery life and add more user-friendly control methods such as video game controllers.
Fujitsu plans to continue trials of the drone before commercialization, which would initially target expressway operators in Japan.
Tim Hornyak covers Japan and emerging technologies for The IDG News Service. Follow Tim on Twitter at @robotopia.