Surveying and inspecting safely from the air

无人机——无人机现在使用in many areas of surveying. This is not restricted to land surveys, but also includes open-cast mines, landfill sites and roads or buildings. In addition, these versatile little aircraft open up entirely new possibilities for the more efficient management of major construction sites. Before building work has even started, they can deliver a fast, low-cost aerial overview of local conditions and generate accurate and meaningful data for calculation and quotation purposes. Once building work has started, aerial photographs taken by UAVs provide regular documentary records of interim steps. Besides making it much easier to monitor construction progress, it also facilitates the control of internal processes. Once construction work has been completed, it is no problem for a UAV to carry out an inspection of the building and provide evidence that the work has been carried out as agreed and expedite final acceptance.

瑞士电力公司AXPO正在使用UAV AIBOT X6来调查和记录Glarus Alps地区的主要建筑项目“ Linthal 2015”。在最初的一步中，从空气中调查了整个林塔尔山谷，并生成了最高一厘米（0.4英寸）的点云。现在，该数据将构成计划施工过程后续步骤的基础。

The Swiss power company Axpo is building a new, underground pumped storage plant – the largest in the country – in the Canton of Glarus. In future, the plant will guarantee the future electricity supply to northeastern and central Switzerland. The plan is for the plant to pump water from Lake Limmernsee back up to Lake Muttsee – an altitude difference of 630 metres (2,070 feet) – where it can be used again to generate electricity when required. This large-scale project, which involves investment costs of around 1.85 billion USD (1.7 billion EUR) and is expected to take the best part of five years to complete, will employ up to 500 people at various construction sites. The plant should start to deliver electricity at the beginning of 2016.

Fast, flexible data collection
必须清除数十万立方米的土壤和岩石，以建造泵储存厂的隧道和洞穴。大部分这些损失将通过缆车将其运送到Muttenalp山，并用于建造大坝，该大坝长度超过一公里，最大高度为36米（118英尺）。其余材料将存放在现有的Limmern大坝前面。2014年10月，AXPO首次使用AIBOT X6来调查该区域，这被称为Limmerntobel惰性物质处理地点。由于周围的山脉阻止了卫星信号接收，因此飞机是手动飞行的，没有GPS导航。在飞行过程中以垂直角度拍摄地形的照片，以创建60％至90％重叠的处置地点的高分辨率图像。在飞行前，将14个地面控制点均匀地绘制在被调查区域的七个角度约50至80米（160至260英尺）的距离上，以便随后对图像进行地理参考。“这是Aibot X6第一次部署在2,000米（6,562英尺）的高度，但稀有气氛对其飞行特征没有不利影响，”飞行员Robert Lautenschlager解释说。

The 50,000 square metres (12.5 acres) of land was surveyed in two flights lasting ten minutes each. Agisoft photogrammetry software was used to process the data collected and a precise point cloud with an accuracy of up to one centimetre (0.4 inch) was generated. The whole evaluation processed lasted about 120 minutes. The point cloud was then integrated in the local coordinate system of the construction site, enabling Axpo’s surveyors to calculate the volume of the deposited material.

Periodic photographic records of the disposal site had previously been created using an external filming system suspended from a helicopter. Not only can high-precision geographical data be recorded within a short space of time using the Aibot X6, but it is also possible to create complete and seamless documentation of the current status of construction work. At any given moment, the UAV can give contractors an immediate overview of how building work is progressing, thus helping them to plan and control processes better.

Combination of surveying and inspection
The use of UAVs means that surveying and inspecting tasks can now be combined more and more frequently. The Axpo example is a perfect illustration of this: in future, the company intends to use the Aibot X6 not only for the creation of digital models of terrain for planning and building power plants, but also for vital inspection tasks. It will be possible to fly over existing dams and take photographs that will allow the condition of the concrete surfaces on the airside and waterside of the dam to be assessed in detail. In this case, the hexacopter will again be fitted with a digital camera and flown to locations where it will take high-resolution pictures of all critical areas, thus enabling even the smallest cracks and other anomalies to be detected.

The Aibot X6 can also be used to inspect electricity pylons. The hexacopter offers a number of advantages here, such as flexibility of deployment and availability at short notice in the event of a malfunction or defect. As the inspection is performed by a remote-control, unmanned aircraft, it is also safer and much cheaper than an inspection by helicopter or steeplejack, since it is not even necessary to switch off the current beforehand. In future, Axpo will also rely on unmanned airborne help in the environmental sector, where UAVs will be used to take pictures of mountain streams as part of residual water experiments.

Written by Friederike Nielsen and Robert Lautenschlager