Routine inspection of power transmission lines is critical for securing uninterrupted distribution of electricity. The traditional monitoring method relying on teams of surveyors conducting the inspection from the ground is labor-intensive and time-consuming. Besides it being inefficient, the work could be dangerous when traveling along high-voltage transmission lines and sometimes nearly impossible when the lines are inside deep wilderness and hazardous terrains.
In recent years, Airborne Laser Scanning (ALS) has emerged as an effective alternative to traditional methods for power line inspection and is becoming widely adopted by the industry as an important component in the monitoring and maintenance of the electricity networks.
In this article, we present a recent power line corridor survey project conducted by GreenValley International (GVI) to illustrate the effectiveness of an ALS-based method for power line inspection using the GVI LiAir Pro UAV LiDAR scanning system and GVI LiDAR360 software suite.
LiDAR360 is the flagship LiDAR data processing and analysis software suite by GVI. The latest version 1.5 contains three main modules: Terrain, Forestry, and Power Line, along with a comprehensive collection of LiDAR point cloud tools. Built on top of the proprietary .LiData format, LiDAR360 is capable of working with very large point cloud datasets (tested over 300GB).
Project Background and LiDAR Data Collection
The project was in Guizhou Province in Southwest China. The survey covered over 200 kilometers of transmission lines of varying voltages between 110 KV to 500 KV. This was a complex power line system located in the deep mountains with treacherous terrains, significant variation in elevation, and dense vegetation. Past inspection using traditional method was extremely difficult and costly.
Despite the difficult operating environment, GVI completed the data acquisition in 20 days using its most advanced UAV LiDAR scanning system, LiAir Pro.
Some specs can be seen below:
Positioning Accuracy: 0.05 - 0.10m
LiDAR Points p/sec: 500K
Speed Accuracy: 0.005m / s
Scanning Distance: 920m
Angle Measurement Resolution: 0.001°
Scanning Angle: 0 ° - 330°
Flight Height: 150m
Data Analysis in LiDAR360
The collection of 200-km power line corridor produced a huge amount of raw point cloud data.
Once converted to .LiData format, the raw point cloud was classified into Ground, Building, Vegetation, Low Points, Tower, and Power Line. LiDAR360 is able to make automatic classifications through initially manually inputting classification parameters. The classification was done automatically and refined and improved by thorough visual inspection and manual editing using LiDAR360’s built-in classification and editing tools.
This classification was not only critical for the immediate detection of Danger Points, it also provided necessary data for the accurate modeling of the impact of changes in environmental factors, such as temperature, precipitation, and wind pattern, on the safety of the electricity transmission system.
Danger point detection was performed on the classified point cloud based upon the customer’s defined parameters. Figure 5., shows the power line from both a bird's eyes view and profile, classified as power line and vegetation. The red triangle indicates the vegetation overgrowth areas. After careful verification of the detection results, a final project report was automatically generated using the built-in reporting tool. The report provided accurate maps of the hazardous points as well as detailed information on their associated vegetation location, height, and number. Based on this report, the customer could now effectively plan the necessary maintenance work.
The customer of this project was very satisfied with the result delivered. This project showcased an example of using airborne laser scanning for effective and efficient power line corridor survey. In fact, the utility of ALS goes much beyond just power line hazardous points detection. It is also a great tool for project site selection, vegetation removal and excavation volume estimation, timber growth monitoring, natural disaster mapping, and various types of change detection.
Going forward, many exciting new developments, such as the combination of airborne laser scanning and terrestrial laser scanning and the fusion of LiDAR point cloud with multispectral imagery, will bring more possibilities to the application of LiDAR technology. GreenValley International will continue to advance our scientific research and product development, and strive to become a leading company and contributor in this industry. For more info on our software tool and powerline toolset please visit tutorials
Authors: Kevin Ford, Leo Liu and LiJing