We start a series of articles exploring the applications of airborne laser scanning (ALS) technology for monitoring existing and designing new power lines (PL)
Power generating plants and transporting electricity are now one of the most important components that ensure the functioning of our civilization.
Every year electrical power becomes more and more popular, replacing other types of energy in many sectors of the economy.
It's no secret that the main peak of power line construction fell to the 70-80's of last century, and in many countries of the former Soviet Union this infrastructure has been in operation without any overhaul for over 30 years, using the margin of safety built during the construction of the Soviet era.
The task of a comprehensive monitoring of power transmission lines, determining the conditions, wear and tear of wires and contamination of insulators, detection of critical sagging, contact of wires with the ground and various objects is becoming more and more critical and important. Statistically, most of the damages of aerial power lines are short circuits and broken wires. The aerial survey and drone LiDAR survey allows us to solve these problems in a timely manner.
In this article we will show how TOPODRONE equipment can be used to monitor existing power lines, using the example of a power line laser scanning project with the new model TOPODRONE LiDAR 100 HDL, which is the most accurate and most advanced solution in our line of LiDAR systems.
Fig. 1. TOPODRONE LiDAR 100 HDL equipped with a high-precision GNSS receiver and a professional Honeywell inertial system.
TOPODRONE LiDAR 100 HDL is based on the Velodyne HDL32 sensor and has 32 factory well precalibrated lasers with viewing angles up to 30 degrees. That allows to obtain highly accurate and detailed three-dimensional models with a great level of detail. The sensor working range is up to 100 meters, and due to the use of a high-quality inertial system and GNSS receiver a point cloud can be obtained with an accuracy of up to 2-3 cm in XYZ.
TOPODRONE LiDAR 100 HDL can be mounted on DJI Matrice 200/210, DJI Matrice 300, DJI Matrice 600 as well as integrated with the newest TOPODRONE RGB 24 and TOPODRONE RGB 61 cameras which provide not only realistic coloring of highly detailed LiDAR clouds but also high resolution pictures showing the condition of insulators.
Fig. 2. TOPODRONE LiDAR 100 HDL on board of DJI Matrice 300.
Fig. 3. Possible option for integrating 61-megapixel camera with LiDAR system.
While performing aerial surveys of power lines it is necessary to use professional software for mission planning, which allows to prepare flight paths, taking into account the location of towers and the detailed terrain model. UgCS Expert was used for this project.
Fig. 4. Flight planning in UgCS Expert.
The powerline route was aerial surveyed in two passes at an altitude of 80 meters. A reference base station was installed in the immediate proximity of the work area, recording static GNSS measurements throughout the duration of the flights.
The next stage was the post-processing of GNSS measurements in TOPODRONE Post Processing software, which is a natural extension of TOPOSETTER and TOPOLiDAR software products, which are popular all over the world.
TOPODRONE Post Processing includes all essential modules for processing of static measurements and determination of base station coordinates, adjustment of drone paths, image georeferencing, generation of point clouds and supports a variety of coordinate systems and geoids.
In order to determine high-precision coordinates of the base station, we performed a calculation of static measurements in the Static Post Processing module.
Fig. 5. TOPODRONE Post Processing software.
At the next stage high-precision trajectory was calculated using GNSS and inertial data stored at 200 Hz rate (200 times per second), after that LiDAR point cloud generation was performed and within several minutes we started automatic classification and detection of wires, power line towers, vegetation and other objects.
It is necessary to underline the outstanding quality of the point cloud acquired by the TOPODRONE LiDAR 100 HDL without using any filtering or other noise reduction methods.
Figures 6-9 show examples of power line mapping, characterized by clarity and detail unavailable for other models, including solid-state sensors.
Fig. 6. Highly detailed point cloud obtained by TOPODRONE LiDAR 100 HDL.
Fig. 7. Highly detailed point cloud obtained by TOPODRONE LiDAR 100 HDL.
Fig. 8. Highly detailed point cloud obtained by TOPODRONE LiDAR 100 HDL.
Fig. 9. Highly detailed point cloud obtained by TOPODRONE LiDAR 100 HDL.
Figures 10-13 shows the results of automatic point cloud classification, highlighting poles, power lines, overhead cable, insulators and vegetation.
Fig. 10. Automatic point cloud classification. Power line towers, transmission lines, overhead wire, insulators, terrain and vegetation are highlighted.
Fig. 11. Automatic point cloud classification. Power line towers, transmission lines, overhead wire, insulators, terrain and vegetation are highlighted.
Fig. 12. Automatic point cloud classification. Power line towers, transmission lines, overhead wire, insulators, terrain and vegetation are highlighted.
Fig. 13. Automatic point cloud classification. Power line towers, transmission lines, overhead wire, insulators, terrain and vegetation are highlighted. Note that relief and vegetation are excluded from the visualization.
Based on the results of the point cloud classification, the location of wires and insulators was vectorized figures 14-15.
The next step is to analyze the existence of non-normative proximity of power lines with vegetation and other objects.
Fig. 14. Results of automatic vectorization of wires and insulators.
Fig. 15. Results of automatic vectorization of wires and insulators.
Using the results of the automatic point cloud classification it is possible to automatically search for objects in the non-normal proximity of power lines, to create a report, as well as to determine the angle of each pole, the sag of wires and the distance between them.
An example of this project shows the great potential of TOPODRONE equipment for real-time monitoring of existing power lines, which allows in time to get reliable information about their condition.
The application of LiDAR technology provides not only high accuracy and detail of created 3D models, but also outstanding operational efficiency of data acquisition within a few minutes after the flight.
At the same time we have to note the spectacular productivity of TOPODRONE airborne laser scanning systems, which allows to survey tens of kilometers of power lines with one set of equipment engaging one or two trained specialists extremely cutting expenses for field work and data processing.
