Together with our partner 3DS-Scan, which offers software programs for surveying & GIS data, CAD plans and Revit models in highest quality, we digitally surveyed a dam reservoir with a DJI Zenmuse L1.
What is a dam reservoir:
A dam Reservoir or fill dam is the shut-off structure of a dam or impoundment consisting essentially of an earth or rock fill. As a rule, a dam blocks off a valley cross-section.
Why was measurement carried out / problem definition:
The purpose of the flight was to record the flood line in the reservoir of the Kronenburger See after the flood in NRW / Rhineland-Palatinate at the end of July.
In addition, the vegetation penetration of the Zenmuse L1 was to be tested to see whether a more accurate terrain model can be generated with it.
How drones can help with a survey:
Drones are not a replacement for proven traditional methods, but the right drones and payloads can complement existing efforts and expand capabilities.
Drones can provide a large amount of information at a faster pace.
Key uses and benefits of survey drones include:
- HIGH ACCESSIBILITY: Hard-to-reach areas can be flown safely. Surveyors on the ground do not have to put themselves in danger, construction work, machinery and equipment can work without interruption during a drone survey.
- PRECISE SURVEY: A GPS ground station combined with the latest drone technology and high-resolution cameras enables precise drone surveying of large areas.
- REPEATABILITY: The ease of repeatability of drone surveying allows for target/actual comparisons as well as accurate documentation of changes over time.
Surveying drone in use: dam reservoir project:
Matrice 300 RTK
This drone has everything you need for effective surveying. From a safe distance, you can survey and get a quick overview of the area. The 55-minute flight time means you can gather the information you need in just a few flights.
DJI Zenmuse L1
The Zenmuse L1 includes a Livox lidar module, a high-precision IMU, and a camera with a 1-inch CMOS on a gimbal stabilized on three axes. When used in conjunction with the Matrice 300 RTK and DJI Terra, the L1 forms a complete solution that provides real-time 3D data throughout the day. It captures the details of complex structures and delivers highly accurate reconstructed models.
- Flight at 100 m height with DJI Matrice 300 RTK with DJI Zenmuse L1
- RTK correction with Sapos NRW
- Automatic flight grid with calibration (start and end)
- Scanning Zenmuse L1 Linear RGB highest frequency with approx. 60 % overlap between flight paths
- Warm-up time L1 approx. 5 minutes
- Flight time total approx. 30 minutes
- Area approx. 40 hectares (lake with dam)
- DJI Terra (V3.1.2) with optimization of accuracy
- Target KBS (coordinate system) ETRS 89 / UTM 32N (epsg 25832)
- Point cloud format .las
- Analysis and visualization with CloudCompare (v 2.11)
- Conversion of ellipsoidal heights (WGS 84 resp. ETRS 89) into normal heights resp. use heights (DHHN2016)
- Filter scanangle from 35° to 30
- Comparison with terrain model from state survey (DTM 1 meter grid NRW)
- DGM (Digital Terrain Model) generation with Cloth Simulation Filter (CSF Filter).
- Fast acquisition with low effort and good georeferencing (+- 10 cm) without further processing
- Parallel acquisition of image data for e.g. additional photogrammetric analysis
- RGB point cloud (RGB interpolated from color images)
- High point density
- Water surfaces are captured
- Lowest cost Lidar sensor
- Low penetration of very dense vegetation (summer)
- Detection of only three lidar repeats
- Relative accuracy is about 10 cm, quite high point noise (due to lower sampling frequency probably slightly better results regarding point noise but also lower point density)
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