Performing a river survey with the Aibot X6 UAV: Having the feet on the ground, the eyes in the sky and the mind on the water.
The lower area of the Bavarian river Upper Alz, which was severely affected by a chemical accident in March 2012, is to be fully revitalised and regenerated. The measures include, among others, the demolition of parts of the existing bank development, so that the river again makes its natural way and can reclaim its natural structure.
In order to assess the success of the measure in one to two years, the Water Authority Traunstein needs an accurate terrain model of the affected river section. Engineers from Traunreut who were charged with the surveying used the modern multicopter Aibot X6, produced by the Kassel based company Aibotix, for data generation.
"For us, the fastest and best solution," says ing employee Markus Prechtl and explains: "A survey by GPS would not have worked because the satellite reception would have been shaded by the surrounding forest. A survey by tachymeter would have been necessary, which would have given us only individual cross sections and would also have taken at least three to four days to be completed. By contrast, with the Aibot X6 we could capture the whole site completely within a very short time."
With the hexacopter the entire route of 3.6 km was flown twice: once with a video and once with a digital camera.
"With the video, we get a complete documentation of the actual state at the time of the aerial survey," says Prechtl. "In two to three years, this can easily be compared with new recordings."
The geo-referenced images taken with the digital camera were processed after the flight to a detailed 3D model of the river section. River course and slope top are displayed in the model with a GSD of 2.5 cm. Prechtl explains:
"On the basis of the 3D model, changes in the river can be traced in detail in the course of time."
Technical data of the river survey:
- Camera: Nikon Coolpix A
- Sensor Resolution: 16.0 Megapixel
- Flight altitude: 100 m
- Image overlap: 60% in all directions (left, right, front, back)
- Ground resolution: 2.5 cm
- Synchronisation of the GPS information with the images shot by Aerial Image Manager for a fast post-processing
- Processing with photogrammetry software Agisoft
- Point cloud of high density
- 3D model with polygon view
- Highly accurate orthophoto