At a lofty altitude of 2500m above sea level, 20 wind turbines of 100 m height are to be built. These wind turbines will produce 60 GWh per year to power 15,000 households. The challenge however is twofold: with the construction site in the middle of the mountains, there are no roads to access it, nor is there any pre-existing detailed data for site planning of the wind park itself, which is 800 ha large.
This is the challenge Cavigelli Ingenieure AG faced in the Swiss Alpine valley of Lumnezia. While mapping and 3D modelling of large areas with high accuracy is a routine challenge in geospatial applications, the hilly terrain, high altitude and fast changing weather conditions in the mountains brought additional constraints. Keeping in mind the need for flexibility and low cost, the company turned to drone use.
Drone use in geospatial applications
Cavigelli is not alone in its decision to use a drone for data collection – the surveying industry has in fact been one of the early adopters of drone use and continues to be an avid user today. Engineers looking at commercial drone solutions often face a dilemma though: difficult terrains and limited spaces necessitate the use of multirotors. However, commercial multirotors – quadcopters and hexacopters – are also limited in their area coverage, because these drones tend to be inefficient in flight. Popular quadcopters can only cover an area of 40 ha in 25 minutes, for example.
On the other hand, though fixed-wings can fly longer and cover more area, they also complicate flight planning as they need wide open areas for take-off and landing. Further, as sensors can often get damaged during belly landings, fixed-wing drones typically carry inferior sensors when compared to multirotors.
This gap between usability, long range, and survey-grade imagery is what the Swiss drone company Wingtra aims to bridge. Introduced earlier this year, their VTOL WingtraOne drone takes off and lands vertically like a multirotor but tilts forward in flight to fly like a fixed-wing aircraft. Combining this with the capability to carry heavy sensors means that the WingtraOne can cover areas as large as 400ha – equivalent to 570 football fields – in a single flight of 55 minutes*.
Collecting aerial imagery in the heart of the Swiss Alps
This combination – VTOL capabilities to navigate through hilly terrain along with long flight range and accurate imagery – is exactly what the engineers at Cavigelli were looking for. For this particular application, they chose a WingtraOne with the full-frame 42MP Sony RX1RII. They then set out to collect aerial data.
The crew started the day with a one-hour hike to the site and planned four flights on site to take into account environmental challenges. All flights were planned at 500 m relative altitude, with a GSD of 3.5-4.5 cm/px. The engineers also used seven ground control points per flight for better accuracy. Each flight took up to 20 minutes of planning and 30 minutes of flying time. Together, these flights covered an area of 1100 ha, 200-300 ha per flight.
Turning information into insight
Finally, aerial data collected from the site was converted to 3D models that allowed visualization of planned roads and wind turbines in the wind mill park. The entire data collection workflow itself took a mere four hours with the WingtraOne – a process that could easily take days with traditional surveying methods. Use of high-end sensors ensure survey grade imagery and accuracy – in this particular example, the engineers obtained an accuracy of 3-4 cm.
“The transport, the flight preparation, the flight planning, the takeoff process and the data transfer were very easy and convincing,” says Thomas Arpagaus, engineer at Cavigelli. “The aerial survey has shown that it takes only a very short introduction/training for a successful completion of a project. For the implementation of the flight planning, the user is accompanied by the menu in a very structured way. The subsequent aerial photographs work (almost) completely automatically. The process has convinced me!”
While WingtraOne made its market entry earlier this year, and is already in use for various Geospatial applications in Europe, US, China and Australia, Wingtra’s origin lie in a research project at ETH Zurich 3 years ago. Wingtra has since grown to a 40 people strong team of engineers, creatives, and business professionals. Believing that data fuels the 21st century, it’s Wingtra’s mission to give people the tool to extract it easily, accurately and efficiently. And if projects like these are any indications, Wingtra is well on its way to fulfill its mission.
As Arpagaus added, “Thanks to the use of a drone, we were able to greatly reduce the costs for the surveying and evaluation of the original site for the design work. The tight project planning could be kept due to the fast and flexible data acquisition with the WingraOne.”
Collecting aerial data in an area as constrained as the Swiss Alps was one of the most complicated challenges that Wingtra undertook recently. Encouraged by its success, Wingtra will continue to pave the way for innovative, long-term solutions that work in harmony with various established industries and add great value to applications that might be far removed from drone use at first glance.