Case Study: Riegl USA
Power Line Mapping with LiDAR
By Vladimir Kadatskiy and Peter Licari
These have been a trying few years, this goes without question. Our great nation has been fraught with conflict, economic destitution, and political controversy. Through this internal struggle we will continue to expand and move towards our unrivaled potential. This is not the time to halt our advancement. It is the time to march onward and pave the way for our future, to rejuvenate and reinvent the old as we work to prepare and create the new; the new world that awaits us tomorrow.
Today, the Power Transmission Industry is facing many challenges in providing and aiding our Nation in its growing demand for electricity. They are faced with reliability challenges that could lead to brownouts and blackouts, such as the ones encountered in 1965, 1977, 1996 and the most recent in 2003. In addition to reliability, vegetation incursions raise safety concerns for wildfires, which create even greater problems.
The reliability and safety of the Electric Power Transmission Industry in North America is regulated by the Federal Energy Regulatory Commission
(FERC) and North American Electric Reliability Corporation (NERC). Energy providers are obligated to fully comply with the orders of FERC (March 18 BAL-003-0) and NERC (March 18 TPL-002) that state, violators are subject to one million dollars per day in fines for non-compliance. In order to meet Federal Government requirements, power companies are periodically required to assess Bulk Transmission Systems that are comprised of transmission lines, towers and other small tower features. Due to a high volume of transmission lines that required assessment, power line companies turned to LiDAR technology to rapidly provide the most comprehensive and accurate assessment of power lines and their surroundings.
In order to undertake such a future-driven goal, they needed to utilize the most up to date and advanced equipment on the market. Such equipment needed to be precise, economical, efficient and unrivaled in the field in order to ensure the success of such a vital task. For this, they went to one company, the only company which could deliver the whole package: RIEGL USA.
In this particular case study, this ideology was acted out by the company Aerial Cartographics of America
. ACA’s mission was to assess the viability of acquiring 80 miles of LiDAR data with a minimum of 25 points per square meter density and meeting the requirement of +/-0.05m RMSE accuracy of ground truth within a week timeframe.
The system used to tackle this task, was comprised of a Riegl’s LMS-Q680i LiDAR scanner, Applanix
POS AV 510 INS/GPS, and Vexcel
digital camera which was mounted into a Cessna 208 aircraft. To meet the high accuracy standards, Riegl’s VZ400 3D laser scanner was used to precisely measure the lever arms between all of the sensor components. Furthermore, a boresight calibration flight was performed to calculate misalignment angles between IMU and the LiDAR scanner where a Planimetric Surface Matching Algorithm was utilized to reveal RPY angle biases.
The full-waveform LiDAR data was acquired at 400,000Hz from 1600ft AGL producing data of 266,000 points per second on the ground at a 60 degree field of view. The full-waveform feature of the LiDAR was critical when analyzing vegetation. The data was automatically pre-classified by Riegl’s Processing Software, RiProcess, into two different layers (Ground and Vegetation). Utilizing software by Terrasolid
the data was easily evaluated to show where the power lines encroached upon vegetation layers. All of the data processing, sensor boresight misalignment calculation, LiDAR’s data Geo-referencing, and QA/QC was performed in Riegl’s ALS (Airborne Laser Scanning) suite. The next step was LiDAR Point Classification and further processing by Terrascan, a Terrasolid product, for export to PLS-CADD™ by Power Line Systems Inc. for evaluation and analysis to the client.
To ensure trajectory accuracy each flight mission was planned to avoid spikes in Position Dilution of Precision. Furthermore a network of base stations was used to collect ground GPS ephemeris data for maximum precession.
After the LiDAR data was acquired and post processed it was QA/QC against a series of pre-established ground control points. The results of this case study by far outperformed expected results delivering 25-40 points per square meter at 0.018-0.05m RMSE to ground control truth. LiDAR technology has demonstrated that speed, high resolution and accuracy are benefits that can be used for transmission power line assessment. Previous case studies have been done where a rotorcraft platform was used in order to meet high point density requirements. ALS operated from a fixed wing aircraft provides dramatic cost savings to service provider allowing them to pass the savings onto the end user of the data.
In conclusion, this case study has demonstrated the benefits of using LiDAR for power line assessment and monitoring. It is proven that LiDAR is an effective tool that dramatically improves the efficiency of the current workflow used by power line companies. It was also revealed that using a fixed wing aircraft and high resolution LiDAR sensor can substantially lower operating costs while delivering incredibly dense and accurate full-waveform point cloud data.
The future is bright for our Nation and our glorious internal expansion is imminent. There are cities to be built, mines to be excavated, power lines to be revitalized, and an inherent interior beauty to analyze and preserve. There is work to be done. The technology of our present, such as the LMS-Q680i, is what will be the driving force into our tomorrow.
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