A Drone River Inspection For Underground Canals

Benefits In A Nutshell


With outdated 2D records as the only guide, the Elios 3 was flown at low tide to gain access to underground canals which had likely not been entered since construction. This enabled a safe drone river inspection.

Data Quality

The team got clear visual data including photos and videos as well as a LiDAR scan that impressed the client. Data collection was completed above and beyond the mission scope with no additional work.


Sending people into this environment is borderline impossible, as changing water levels and a strong current make it unsafe for human access. The Elios 3 was the only viable solution.


All data collection was completed within 1 day, rather than taking several days of planning and equipment installation as would be necessary with a traditional way of gathering this data. 

Urban water management includes not only sewage but also freshwater in the form of rivers, as well as grey water.

Rivers are channeled into canals to facilitate their management. These can be part of the city's infrastructure, as in Birmingham or Venice, or the water can be conveyed underground. However, when they are underground, the condition of the canals can influence whether construction work can be carried out above ground, but inspections are difficult to carry out. Divers are often unable to penetrate these spaces safely due to a number of unknown factors. Some aquatic ROVs can reach these spaces, but they may not be able to withstand the currents, or they may be trapped inside.

So what is the alternative?


Drones such as the Elios 3, pictured here, are rapidly becoming a popular tool for gaining access to complex or confined spaces more safely. 

Planning A Drone River Inspection For An Underground Canal

Sater is a specialist company based in northern France, west of Lille. Part of the SARP group, a subsidiary of Veolia, Sater operates in the field of water and wastewater management. With a 30-year history, Sater work on projects throughout France and currently employs a team of 115 people.

As specialists, Sater often carries out inspections in complex environments that traditional inspection methods can't reach. They often use remote-controlled cameras and similar devices to reach these challenging areas. Recognizing the value of using sewer drones to complete inspections in water management areas safely, the company acquired an Elios 3 to enhance its range of inspection tools.

The Elios 3 was in action at a recent project in Rouen where they needed to inspect underground canals ahead of a construction project. With the Elios 3 having many proven case studies in flying sewer and water networks to date, the Sater team were confident they could use their drone to get the results needed by the client. Thus, they started planning the drone river inspection. 

Inspecting Canals With Drones

At Rouen's Marché d'Intérêt National (MIN), a river runs beneath the buildings and associated streets and empties into the Seine. Some building work is being planned on the surface, and in order to make go ahead with the construction plans, it was necessary to check the current state of the water network and its structural integrity. 


2 parallel canals transport water underneath several structures, but their condition needed to be assessed with a drone river inspection before surface-level construction could go ahead

This type of inspection involves numerous hazards that make it impossible to use divers, and this particular project presented an additional challenge: the tide. The Seine is tidal up to the first lock at Amfreville-Poses (upstream from Rouen). This means that any inspection must take into account precipitation and tidal variations in water level, so the time of inspection must be carefully chosen. 

The structure itself is fairly simple, with 2 parallel pipes with diameters of 3 meters running from one side of the MIN to the other, at the junction with the Seine. Both tunnels must be inspected for the project to be considered a success. 

Sater's team knew that despite variations in water level, they would be able to use their Elios 3. They planned the mission to determine the optimal means of data collection and set the date for the mission.

Completing A Drone River Inspection Underground

The Sater team had only historical charts to work from, as the canal had never been inspected since its construction. The mission took place at the beginning of April, at precise times of the day, so that the pilots could fly the Elios 3 at the lowest possible tidal coefficient.

The opening of each pipe was only 2 x 3 meters, with manholes every 50 meters or so along the progress of the canal. In total, the canals traveled 540 meters underground.

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The Elios 3 drone pilot could navitage using the visual camera and LiDAR point cloud when the drone was out of sight, ensuring they brought the drone back safely

At low tide, the team flew the Elios 3 inside each pipe. The drone enabled them to reach areas not normally accessible, and obtain the data needed to solve a complex problem. An added benefit of this project was the ability to collect both LiDAR and visual data during the mission.

Impressing The Municipality With Results From The Drone River Inspection

This mission aimed to provide the customer with video images of the interior of the pipes. However, the LiDAR scans were also shared with the customer, who was pleasantly surprised by the additional information. The 3D model was accurate and clear, providing a complete visualization of the pipes without exposing personnel to risk during the inspection.

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The LiDAR scan of the drone's flight helped the team clearly visualize the area. Even though they only needed a visual inspection, this map can be used for future planning and updating existing records

In this way, Sater met the needs of the local authorities for this project and set itself apart from the competition. The mission also enabled Sater to push back the limits of the current use of its Elios drone, and to plan more ambitious projects for the future. It would not have been possible to collect this data safely without the Elios 3.




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