Inspecting dams for sustainable hydropower

作者：安妮·皮特卡宁（Anne Pitkaenen）

当您接近Lai da Nalps时，瑞士的Tujetsch，Grisons市政当局的水库时，高度为127米的大坝结构，宽度为480米，宽度已经从远处雄伟地打开。大型拱形大坝是为海拔近2,000 m的水力发电生产而设计的。水电被认为是当今瑞士电力供应高安全性的骨干。

Lai da Nalps靠近Gotthard隧道，附近的该水坝和其他大坝自动监测以进行急性运动和变化。除了详细的监测外，还可以在视觉上检查大坝建设，以记录长期了解大坝健康状况的状况。

The dam is operated by Axpo Group, the largest producer of electricity from hydropower in Switzerland. The company is also responsible for the inspection and development of the surrounding area with roads, bridges, a dam lake, the power plant and the dam.

The concrete construction of the dam is designed to withstand extreme loads, which only occur every 10’000 years. This will ensure it won’t risk the lives and livelihood of the people in the valley. However strongly built, the behaviour of the dam and its surroundings and the state of the construction is intensively observed by Axpo personnel.

Axpo has an inhouse team of surveyors, with three of them trained to use Leica Aibot for surveying tasks. Thorsten Zimmer, an engineering surveyor at Axpo, is responsible for the inspection project in Lai da Nalps.

“Using a UAV has widened our toolbox of available equipment technologies we can use for our daily tasks. Total stations, GNSS rovers and smaller UAVs are as common tools for us as it is the Leica Aibot,”齐默说。

Game changer technology in dam inspection

Before surveying with UAVs, one option for dam inspection purposes was to take images from below the dam and from the mountain walls surrounding it. For a dam of the size of the Lai da Nalps, the surveyor occasionally had to climb the surrounding hills, have the camera positioned correctly and take the photos, finally covering the entire wall. Another option was to move up and down along the outside of the dam, standing inside a basket or a gondola, and document everything from there. Even with precise planning and the perfect locations, these methods were very time-consuming, sometimes even dangerous, and couldn’t deliver as highly detailed images and quality results as the ones taken with a UAV facing the dam from an approximate 10 m distance.

Before owning a Leica Aibot, the Axpo team had already been a user of Aibotix Aibot X6, which they used for several years for surveying. Now it was the time to upgrade because flight time is started to be a challenge with the previous Aibot. Previously during large inspections - due to much shorter achievable flight times - one person was responsible just for recharging the batteries. With the new Leica Aibot surveyors can use more time and energy focusing on the inspection and not just keeping the system in the air.

Surveying with Leica Aibot

每一个大坝Axpo运作is planned to have a full UAV inspection every five years using the Aibot. The inspection of a large dam takes two to three days and approximately 10 hours of total flight time. During the flight, the Aibot takes automatic images every two seconds, enabling the pilot to focus just on flying the copter at a constant height and distance close to the wall. The inspection is a two-person job: one operates the UAV with a focus on the flying position, speed and height, while the other person observes the surroundings, focusing on the quality and overlap of the photos taken as well as the status of the batteries.

AXPO使用配备了Sonyα7RII传感器和55毫米镜头的Leica AIBOT AX20无人机溶液。42 MP和清晰的清晰图像确保数据和结果是准确的。为了创建准确可靠的点云，AXPO使用Leica Nova TS60总站来测量控制点以进行后处理。大坝有几个可见元素，可以用作控制点，以便能够定位和扩展点云。可以在飞行之前，之间或之后进行测量和记录控制点。

“由于庞大的大小或拱形大坝以及对GPS的访问权限，大坝的条件都具有挑战性。我们需要一个稳定的无人机，飞行员可以轻松运行，因为有时必须在没有GP的帮助下飞行，但仍将无人机保持在稳定且安全的位置。我们之所以使用Leica Aibot，是因为沿我们的大坝易于操作很容易且安全，并且因为我们能够拥有水坝外部面孔的高分辨率图像，这需要达到最终结果所需的细节水平和最后的3D模型”comments Zimmer.作为测量师，我们通常会选择适合该任务的解决方案：对于某些任务，例如，我们使用的某些任务，扫描仪或较小的无人机，尤其是室内检查，对于其他项目，AIBOT是正确的解决方案 - 甚至是所有人的组合”。

During the snowless time of the year surveyors are busy with the inspection on the dams. The collected data and images will be processed into a point cloud and analysed by geologists and surveyors during the winter. The results are part of the long-term analysis of the dam to plan if any preventative renovation is needed and when.

无限可能

测量无人机改变地理空间行业，并为测量师提供巨大的潜力。AXPO使用AIBOT检查几个活跃的大坝以及其他室内和室外测量项目。

1. The company uses Leica Aibot to inspect the inaccessible parts of the dam. Once water levels are low, the team inspects the structures of the dam that are usually under water. The visual inspection of the submerged structure is done by combining unmanned UAV inspection technology and manned inspection from the structure.
2. Flood modelling is also an interesting project for UAVs to mitigate risks related to dam spilling. Geologists investigate potentially risky masses of land and rock that could slide into the dam lake. Volumes of those are calculated and then used in careful what-if analyses.
3. Construction projects and the infrastructure that supports them are large surveying projects for Axpo which can also be supported by UAV captured data.
4. AXPO还使用AIBOT来记录河岸，沿着无法访问的区域飞行并出于某些计划目的。

“The Leica Aibot is a solution that fits our purposes, especially for large and detailed inspections of major dams. It is interesting to see how versatile the Leica Aibot is and in how many ways it can be used by our team,”concludes Zimmer.

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