Height: how drones work at heights nobody should have to climb

At height, wind gets stronger first. Near the ground, buildings and trees slow it; higher up it is stronger and changes direction more easily. Next, the aircraft looks tiny, and its orientation and distance become hard to judge by eye. Close to a tall structure, the structure itself can block radio and satellite signals. And if something goes wrong, the fall is long: a dropped aircraft or part becomes more dangerous to people and equipment below the higher it falls from.

High-access inspection relies on cameras that capture from a distance, sensors that hold standoff from the structure, and automated flight along planned routes. High zoom lets you capture detail without moving into dangerous proximity. Range sensors and obstacle avoidance prevent approaching walls and members. Planned routes put the camera in the same place every time, which makes comparison easier.

Height is central to energy and building inspection: power lines, transmission towers, telecom towers, wind turbines, chimneys, office building facades, condominium facades and roofs, tall bridge piers, dam faces, elevated expressways, and high cut slopes. All have relied on scaffolding, rope access, gondolas or aerial work platforms.

• Choose the aircraft for the wind aloft: assume the wind at inspection height, not at ground level. Pick an aircraft with wind margin and set a stop criterion if it strengthens.
• Let the camera set the standoff: if zoom gives the required resolution, do not move closer. Proximity increases turbulence and contact risk.
• Add observers for line of sight: when the aircraft goes behind the structure, use an observer at another angle or a second camera to confirm its position.
• Control the area below: keep people and vehicles out from beneath the route and the area the aircraft could be blown into. Over roads or railways, coordinate with the operator.
• Set generous battery and return-altitude margins: a strong headwind aloft can consume more battery than expected on the way back. Trigger return at a higher remaining charge.

Under Japan’s Civil Aeronautics Act, flight in airspace 150 m or more above ground or water requires permission. However, airspace within 30 m of an object such as a tall building, tower or power line is excluded from that requirement even above 150 m (permission for flying over a densely inhabited district is still needed where it applies). Because inspection means flying close to structures, it often also needs approval as flight within 30 m of people or property. Under US Part 107 the basic limit is 400 feet above ground, but within a 400-foot radius of a structure an aircraft may fly up to 400 feet above the structure’s top.

Related: strong electromagnetic fields, magnetic disturbance, urban areas & people below, world regulations.

• Unreadable wind aloft: a ground anemometer says nothing about gusts aloft or in a structure’s wake. Easy on-site measurement of wind at height is still limited.
• Contact inspection: tapping, bolt-torque checks and thickness gauging still often need human hands at height. Contact-capable aircraft are being researched and trialled but are not yet common.
• Detecting thin wires: conductors, stays and guy wires are easy for both cameras and sensors to miss.
• Safety when flying over people: below tall facades and over roads, controlling access is hard. How to demonstrate safety, including fall mitigation, is still being worked out country by country.

Aircraft wait beside pylons and turbines, take off automatically on schedule, capture from last time’s viewpoints and return. People climb only once repair is known to be needed, and by the time scaffolding or a gondola goes up, everyone already knows what to fix. Fewer people work at height, and more human effort goes to judgement and repair. That is the editors’ outlook.