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The federal mandate for vegetation management is clear, and potentially harsh. Utility companies must eliminate the occurrence of all power outages caused by vegetation interference in power lines. Failure to meet this zero-outage mandate can result in fines of up to $1million per occurrence per day.

Because of this, vegetation management is now one of the largest maintenance functions of electric utilities, costing in excess of $2 billion annually. The new NERC standards are forcing virtually every utility to increase their expenditures on measuring, monitoring & dealing with vegetative threats and a few of the more progressive utilities have determined that the use of Light Detection and Ranging (LiDAR) and aerial imagery are invaluable tools for vegetation management.

Electric utilities establish LiDAR as invaluable tool for vegetation management.
LiDAR and image mapping surveys of power lines have been used for many years to provide high-precision engineering data of power line corridors and surrounding terrain for new line construction. With the right tools and expertise, utilities can now gain a wealth of additional information from these high-resolution, high-density data sets useful for vegetation management.

Applied correctly these technologies improve the efficiency and effectiveness of identifying danger trees and vegetation encroachments, they also aid in the predictive modeling of vegetation growth patterns, provide comprehensive geospatial GIS inventories of the right of way (ROW) and assist in engineering and overall asset management.

Hundreds of thousands of miles of electric transmission lines will need to be surveyed to validate FAC-003 vegetation clearances and other engineering requirements, much of it annually. Repeat surveys to address vegetation management issues associated with the new NERC requirements represent a unique challenge for LiDAR suppliers both in terms of reducing costs and improving timelines for data delivery which traditionally have been weeks or months after acquisition. To comply with applicable vegetation management standards using LiDAR and imagery data, it is necessary to automate the process of identifying vegetation clearances, hazard trees, vegetation encroachments, span lengths, sag distances and structure heights for integration into client supported Geographic Information Systems (GIS) and work management systems.

What LiDAR Provides
LiDAR surveys, when coupled with high resolution oblique and downward imagery, are able to provide invaluable information on transmission lines and transmission facilities such as right-of-way data, location of towers, buildings and roads to name a few. Additionally, LiDAR surveys provide accurate 3-D information on power lines such as catenary sags, pylon centre lines, cable fixations and attachment points, When coupled with appropriate software this allows the creation of cross and longitudinal sections created from the imagery and high-density point clouds that allow clearances to vegetation, ground and structures to be determined with an accuracy of a few inches.

Aerial LiDAR systems optimized for transmission line surveys typically generate LiDAR data point clouds, color and near infrared (NIR) image data, while associated systems collect information on the line, weather and current loading . These data are then processed into true-orthographic images, and Digital Elevation or Surface Models (DEM/DSM) in common file formats usable by Common Computer Aided Design (CAD) or GIS.

With this data individual power lines can be modeled in 3D and the sag of the line predicted when operating at maximum load under various weather conditions allowing clearances to vegetation and other objects to be predicted with high accuracy and confidence.

All LiDAR is Not Created Equal:
Good data in ...good info out; Bad data in ... bad final product!
Aerial LiDAR is accepted as the most efficient and cost-effective means of creating accurate digital elevation and terrain data. However, for the most part, how final deliverables such as those mentioned above are derived is a mystery to many LiDAR customers and data users.

This lack of understanding creates the situation where the LiDAR customer often does not have enough information to specify how they want their data processed. Therefore, the opportunity exists for some LiDAR vendors to, potentially, cut corners in their production process. And, because many LiDAR customers do not verify the accuracy and quality of their data, they may never discover the discrepancies until there is an issue.

It is important to keep in mind that when it comes to remote sensing technology there are no panaceas - no silver bullets. Results can vary widely between different LiDAR providers ... depending on the quality of their equipment, their production processes and the skill and talent of their LiDAR technicians. Remote sensing technology such as LiDAR is a tool, As with most trades no single tool provides the capability to entirely solve a particular problem: The solution invariably requires a combination of tools and the skills and talents of trained tradesmen to use the tools and materials to create the desired finished product. Remote sensing and LiDAR are no different.

Integration of multiple sensors, IMU, GPS is complicated...
Quality of sensors and components affects data quality.
To understand the issues related to the processing of LiDAR data and the production of various derived products, it is vital to understand the LiDAR mapping process. In an airborne LiDAR operation, a laser produces a light pulse projected to a mirror and is reflected out the bottom of a plane or helicopter. The light pulse travels down until it reaches an object and is then reflected back to the system. Since the speed of light is a constant, a standard mathematical equation can be used to determine the distance the light traveled in the recorded time interval.

Typically, these systems will incorporate LiDAR with global positioning systems to verify longitude and latitude providing the X and Y data points of a three-dimensional data set. The LiDAR provides the Z value. An inertial measurement unit (IMU) provides the pitch, yaw and roll information of the aircraft. These systems must all be custom integrated and are usually augmented with various natural color and multispectral imaging systems, thermal and imaging cameras.

The quality of components and their integration into a complete aerial LiDAR mapping system are critical to the quality and accuracy of the map and survey products which will be integrated into the final vegetation management tools. Effective operation requires much more than simply bolting a commercial camera and Laser to the bottom of a helicopter. The quality of components and the software used can vary widely and their integration is not trivial. And, these systems must be intricately engineered within an extremely stable, space-frame construction if they are to result in reliable data.

Art and science of processing LiDAR data key differentiator.
In reality, the creation of LiDAR information products is as much art as it is science. On the science side it is the integration of the LiDAR mapping system components and the software that facilitates pre-and-post processing of the various datasets and enables the entire project workflow from pre-flight planning to final deliverables.

A State of the Art LiDAR can collect more than 6,000,000 3-D points per minute but selection of flying height and speed can result in ground point densities varying from of one point every square meter to 40 or more points per meter with a wide range of relative and absolute accuracy. LiDAR data is collected from everything the light hits: the ground, buildings, trees, transmission lines, power poles, and so on. Now, imagine these 3 dimensional data points of light, floating in space as a 3D model. This is what is referred to in LiDAR vernacular as a "point cloud." When one views a LiDAR point cloud it is quite obvious that with too few points and without co-registered imagery the discrimination of exactly what the LiDAR beam bounced off is often not very obvious. Spatial analysis alone is often inconclusive when attempting to determine whether a LiDAR point has hit a small bush, tree, fire hydrant, boulder or a ground surface anomaly.

Therefore, it is critical to the success of a LiDAR project for the customer to know how the filtering of LiDAR data is done, how the system discriminates between vegetation, wires and other objects. Current commercial LiDAR processing software does not provide one single "magic" filter for all terrains, vegetation, buildings or other man-made structures. For this reason, after automated filtering, human editing typically needs to be done to ensure all the data anomalies have been removed or are corrected and this manual processing and quality assurance ultimately dictates the pace at which accurate data can be provided to the client.

It is the "Art" of processing the data, and the ability to add value to the information, that ensures customers obtain what they actually need. The processing of the data is the most critical element in the creation of final LiDAR products. Processing of LiDAR and image data on the part of the service provider is far from a commodity and should not be underestimated in any LiDAR vegetation management survey.

Experience Counts...
Not all suppliers are the same
While there are a lot of LiDAR companies operating in North America, most specialise in wide area and topographic mapping and only a few have chosen to specialise in meeting the needs of utilities. For companies like GeoDigital International Inc and their international partners meeting the needs of utilities has become their sole focus and has required them to develop highly specialized equipment and expertise. To date, this team has mapped over 200,000 miles of power line domestically and internationally and provided Engineering grade LiDAR for over 45,000 miles, more than any other group.

GeoDigital personnel have been involved in the development of many of the core technologies related to both airborne imagery and LiDAR for more than a decade, providing stabilization, Laser and imaging technologies to the US and other Governments for classified surveillance and reconnaissance programs. By leveraging tens of millions of dollars of investment by the US government they have developed a new generation of totally digital airborne data collection systems and advanced power line mapping software.

This advanced patented technology provides GeoDigital with the ability to acquire high-resolution LiDAR data, and stunning high resolution oblique images of every structure and of every inch of a power-line corridor in a single flight pass, reducing acquisition and processing time, and allowing them to offer clients the unique service of web delivery of initial critical vegetation clearance reports within hours of a survey rather than weeks or months - a capability considered impossible not long ago.

This unique service known as Grid^Intel generates detailed corridor and power-line models that can be used to predict current and future vegetation clearance issues and to effectively plan both urgent clearance work and subsequent cyclical maintenance activities while minimising the need for confirmatory ground survey activities. Since it does not have any affiliation with tree service companies, GeoDigital is solely focused on helping forestry professionals reduce their vegetation management expenditures. To this end, GeoDigital provides clients with an integrated software suite of custom, easy to use, viewing, mapping and work management tools that allow forestry professionals to plan, assign and manage both urgent and annual line clearance efforts and to track and maintain documentation for regulatory reporting.

By not compromising on the quality of the LiDAR data, GeoDigital is also able to offer, when required, fully detailed PLS-CADD line models to engineering standards, including the modeling of structures and transmission lines at the line rated temperature, and provide turnkey line rating services in cooperation with many of the leading Architectural & Engineering (AE) firms.

Conclusion
Electric energy has effectively become the very life-blood of society. To follow the metaphor, it appears just as self-evident that similar preventative and diagnostic efforts that avert a stroke or heart attack in humans need to be applied to preventing power blackouts and their devastating impact on human lives and economic activity.

LiDAR technology provides the critical information that improves an utility's ability to assess, plan, schedule, bid and audit vegetation management as well as adding intelligence to the grid in providing safe, secure and economic energy. The quality, accuracy and value of LiDAR derived information products are critically dependant on the experience of the LiDAR vendor and technology used. This experience is far from a commodity and should not be underestimated in any LiDAR vegetation management survey.

The key question for the Utility industry over the next few years is what will be the driver for the implementation of this technology. Will it be the significant improvements in the total cost of vegetation management made possible by allowing internal forestry professionals to accurately define the exact work that needs to be undertaken by the tree service companies, rather than letting them define their own activities. Or, will it be fear of NERC sanctions, public outcry, or simply a desire to provide the highest levels of reliability and service to a utility's customers.