The mountain calls

KlöntalerSee坐落在海拔848米的海平面，早在1655年就开始启发，苏黎世艺术家康拉德·梅耶（Conrad Meyer）绘制了第一个现代的高山全景。该湖面由岩石滑坡（Rockslide）久久以前创建，并由2900毫米高的山地massifglärnisch创建，这对于游客和艺术家来说仍然是令人陶醉的美丽之美的令人惊叹的吸引力。但是，诗人和画家不仅认识到3.3平方公里的大型仅限的潜力，这是由周围的山溪（Klön）等周围的山溪喂养的。1908年，klöntalersee在罗丹伯格和萨克伯格之间的东边扣押了一个土墩，为周围的村庄和公司发电。

Due to the new 220-m-long and 21.5-m-high earth bulk dam, the lake can carry about 39.8 million cubic meters of water, which can be used to generate electricity if demand fluctuates and during peak times.

从空气到水

With their groundbreaking approach to combine hydrography and photogrammetry, the IngenieurTeam GEO GmbH planned to survey the area by using their sounding boat, Surveyor, Leica Geosystems industrial Unmanned Aerial Vehicle (UAV) solution as well as state-of-the-art positioning technology from Leica Geosystems in the Swiss canton of Glarus. The goal was to generate a 3D-model for accurate and inch-step precise calculation and simulation of the actual holding capacity.

在采取了所有准备措施之后，批准过程和计划已经完成，来自卡尔斯鲁希的专家带着他们的声纳船只到达220公里以上的湖泊进入瑞士阿尔卑斯山，以常规的水表绘制湖泊的污染状况。在瑞士国家坐标系统LV03中记录了船只和Leica Geosystems无人机所做的所有测量。

With 172 planned recording lines, the 6-meter-long vessel set sail to create a detailed picture of the lake’s soil using its Reson SeaBat 8101 Multibeam echosounder. The fathometer emits acoustic signals at an angle of 150 degrees and calculates the depth of the water by measuring the elapsed time of the echo. At 101 beams per ping at a frequency of 30 pings per second, the hydrographs receive high-precision data of the bed with a graticule of 3,030 single points per second. With an overlap of one-third of every measuring track, the experts ensure that an accuracy of less than 10 centimeters is achieved during their measurement.

但是在收集数据之前，必须精确校准测量系统，以避免干扰因素并正确确定结果。因此，必须在每次部署之前对传感器技术进行调整，以减去容器的线性运动以及围绕其车轴旋转以阻止任何伪造。水文图获得清晰详细的湖泊地面视图的另一个步骤是将水的声音速度考虑到计算中，这取决于温度和悬浮颗粒的变化，并且在藤水中变得尤为重要。

船推出和校准后，船员们以两个半小时的长时间巡游出海，以对湖泊的性格产生第一印象，并开始创建土壤的第一个声纳数据。遵循计划的路线并考虑了湖泊的深度和质地，测量师的高技能水文图收集了足够的信息，以创建134.837.653 X-Y-Z-Coordinates的点云。总而言之，观察船的船员在五天之内就记录了KlöntalerSee的所有2,855,204平方米。

Beyond limits

不仅快速多变的气候条件和好的e-chilling cold pushed man and machine to its limits, with the glaciated massif Glärnisch building the south embankment, the environment put the technology to the test. With its 2,900 m, the massif literally threw its shadow ahead. Through the massifs steep slopes in close vicinity to the riverside, the experts feared they might lose their GPS-stream due to signal opacity on the south side of the Klöntalersee. In this case, the determination of the boat’s position would have been carried out by tachymeters placed on the northern and eastern shore of the lake. Because of the lake’s long-drawn-out kidney shape, this would have led to serious problems to get accurate details of the boat’s position.

通过在测量师上使用Leica viva GS 16 GNSS天线，可以将具有多层声纳记录的数据分配给其坐标。凭借其内置的SmartLink技术，即使GSM网络的信号丢失了，机组人员仍然能够记录高精度数据并接收GNSS校正数据。多亏了550个频道，最先进的测量引擎和超现代RTK算法，无人机和船只的数据都可以精确地分配给测试结果。

Due their general design, bank situations are hard to capture for multibeam equipped vessels. In addition to that, the risk of damaging the sensitive and expensive sensor rapidly rises in shallow water and in the proximity of the shore. In order to still obtain exact results for the volume calculations and simulations, the engineers relied on their experience with their UAV and decided to capture the shores and embankments airborne via photogrammetry.

Precision from the sky

After the lake was measured at regular water level from the boat, the engineers began to plan the flights for the Leica Geosystems UAV solution. To capture the shore regions overlapping with the measurements taken by the boat, it was crucial to plan the following flights with the UAV at lower water levels. After the level of the Klöntalersee had been lowered seasonally, the survey with Leica Geosystems hexacopter began.

For this purpose, the experts of the Ing.Team GEO planned the flight with the in-house built flight planning software, set the waypoints for the following flights, and determined the parameters suitable for the survey, such as height, ground sampling distance (GSD), flight speed and overlapping of the data. To record the often angled and steep terrain of the bank area as precisely as possible, the experts decided to survey each area several times to increase the validity of their data. After the flight planning on the PC had been completed and the waypoints were loaded onto the UAVs internal storage, the ground control points (GCP) around the lake were measured with the Viva GS16 so first flights could begin.

Once again, the surveying of the alpine reservoirs presented its very own challenges for man and machine. In addition to average temperatures of less than 0 degrees Celsius, rapid weather changes and low clouds, once again the southern bank of the Klöntalersee with its steeply sloping mountain walls was the biggest challenge. The UAV had to be started and landed on a separate boat because the steep walls and the dense vegetation of the shore made it impossible for the pilot to operate from the land. In addition to the sensitive and reliable technology, the skills and the steady hand of the pilot were particularly important.

Despite the adverse conditions, the team from Karlsruhe was able to collect highly precise data in 18 flights, so the dry shore strip with a total length of more than 12 km was covered within two days. With a picture taken every two seconds and the drone moving with 4 m/s, the experts ensured that the data was recorded with the highest accuracy by the camera attached to the flying multisensor platform.

“由于无人机的快速数据可用性，我们能够评估现场的第一个结果。”

Combining technologies with accuracy

As with the recordings of the surveying boat, it was of immanent importance for the UAV-based results to accurately reference them. For this purpose, the experts of the Ingenieurteam GEO equipped the UAV with an special RTK / GNSS module and used in addition the Viva GS16 GNSS antenna, which was the perfect match to work under these difficult conditions to achieve an accuracy of 1-3 cm in georeferencing the collected data.

After all measurements had taken place, the surveying experts began to process the obtained data. The point clouds created by the multibeam sonar had to be fed into the PDS 2000 bearing software to manually edit and correct them from imprecision. In order integrate the data of the river banks into the volume calculation, all 4,400 high-resolution images created with the UAV had to be imported into flight planning software, where they were merged with the coordinates from the UAV’s log file. After that, the georeferenced data was edited in the post processing software AgiSoft PhotoScan Pro to create a 3D model as well as a point cloud. Subsequently, the two 3D models were combined in the Autodesk application AutoCAD® Civil 3D to generate an exact model of the lake's situation.

Using the data from the 3D model, the engineers generated a precise map with elevation lines for their client. By being able to generate such a precise result and to combine two completely different ways of surveying large and challenging areas, the engineers stood up to the game and used the most modern technology to get the job done. With the data generated by boat and UAV, the experts are able to fulfill their clients’ wishes of a detailed virtual 3D model and a metres long situation plan with contour lines printed out.

“The combination of the measurement results of our modern multibeam system and Leica Geosystems UAV allows us to generate high-precision data very quickly,” said Busse.

Once again choosing the flying multisensory platform by Leica Geosystems to rethink conventional ways of working was the right choice for the professionals to achieve the best results.