The design and construction of electric transmission lines is a very labor intensive and costly endeavor. Surveying and mapping activities are important elements of this endeavor that can also be costly and time consuming. Gulf Power’s use of aerial LiDAR and imaging surveys have proven to be cost-effective and optimize performance in the design and construction process of new transmission lines, and that asset and vegetation management also benefit greatly from the survey data.
Transmission Line Design and Construction
The design and construction of transmission lines involve land surveys for terrain studies and alternative route selection. Detailed designs of the selected routes face inevitable updating and revisions, affecting parameters of the selected route and power-line hardware. …all these issues add to the time, complexity and costs of the project.
“Imagine if you had to send crews out to survey every contingency …or potential scenario …it would be prohibitively expensive. But, by getting the LiDAR on the front end it allows us to use very high resolution, great quality survey data that can be shared by all the groups involved in the project,” said Sybelle Fitzgerald, transmission line supervisor, Gulf Power. “For the building and rebuilding of transmission lines …having LiDAR is great!”
Gulf Power, Pensacola, FL, was fortunate that other groups under The Southern Company, Atlanta, GA, umbrella have done LiDAR surveys. Southern Company has received numerous honors for the use of technology to “generate value to their business and doing the most interesting and relevant things.” according to IDG’s Computerworld and CIO Magazines. In conferring with various groups within the company, Gulf Power got an excellent perspective of the range of LiDAR products and suppliers.
“When we saw what GeoDigital could provide we were very impressed. The quality and array of products was outstanding,” said Gary Humrichouser, senior transmission analyst, Gulf Power. “We’ve seen LiDAR work from other companies …GeoDigital’s was outstanding!”
Aerial LiDAR/Imagery Survey
GeoDigital International Corp, Lompoc, CA., was contracted for the aerial LiDAR and imagery survey of 445 miles of 230kV lines, 92 miles of 115kV lines which included full PLS-CADD models, and 78 miles for new construction that included full PLS-CADD model.
“GeoDigital has a great service where they will collect all the data during one flight: The LiDAR, imagery (nadir and oblique, RGB ortho photos), and meteorological data all during the same flight survey. Then you pay as you go processing for value-added products,” said Humrichouser.
The Grid^Intel program provides the pre-processed high resolution data and when needed can be downloaded from archive on a segment by segment basis to allow “full-scope” LiDAR mapping and feature coding to support engineering, planning or construction applications such as re-rating, conductor replacement or construction, with deliverables typically being PLS-CADD files, plan and profile drawings.
The LiDAR data stored in the archive is now available for future processing at Gulf Power’s convenience and can be processed to provide survey accuracy mapping data.
The cornerstones of GeoDigital’s offering is their patented TCOR data acquisition systems, designed to meet the precision survey requirements of electrical utilities and engineering companies undertaking construction, re-rating vegetation and asset mapping projects. The systems provide the capability to acquire high-resolution LiDAR data, Ortho-images and high resolution oblique images of every structure and every inch of a power-line corridor in a single flight pass, reducing acquisition and processing time.
The helicopter-borne data acquisition systems are unique, both from a sensor integration perspective and from an engineering design perspective. No other company has taken the approach of integrating stabilized cameras and LiDAR system components into a self-contained, removable “pod” that can be attached to practically any helicopter.
“The generation of geospatial features is greatly facilitated by simultaneous LIDAR and multispectral image acquisition, saving up to 50% in acquisition costs,” said Alastair Jenkins, president and CEO of GeoDigital. “But, the real value is that each surface point possesses an accurate spectral signature assigned to its location, allowing the accurate classification of features.”
“Measurement overlap and optimal coverage of high-density LiDAR point-clouds provide a number of distinct advantages such as the ability to detect small linear-type objects and effectively identify transmission lines,” added Jenkins. “The LiDAR point cloud data allows the classification and vectorization of the data into detailed, accurate three dimensional information of transmission lines such as vegetation clearances, hazardous trees, encroachments, as well as pylon positions, cable fixations, attachment points, pylon center lines, lower cross arm edges, and line sag.
“LiDAR is not cheap …its not your bargain brand stuff …its expensive …that’s the only reason I can think of why not every utility is using this stuff,” said Humrichouser. “But we got what we paid for …it’s worth the money if you have to design transmission lines over miles and miles ….its much easier and cheaper to share the data than sending crews and different people all over the place.”
“Overall…our utilities perspective is to stay abreast of new technologies that make us more efficient and effective in our jobs,” said Fitzgerald. “In the past ….there has not been great growth in electric utility infrastructure construction ….but in the last few years we have seen a marked increase in construction and planning of new lines. Where in the past they were primarily small in scope …2-3 mile lines …now we are looking at planning, design and construction of new lines of hundreds of miles.”
“More construction means the need for more surveys but they have become too costly and difficult on such large projects …LiDAR is the best means to survey these projects … it provides the exact contours and terrain of the entire ROW plus the images and LiDAR data provide the foundation for the .bak files for PLS-CADD.”
The Grid^Intel program can be used to provide evidence that documents compliance with federal and state regulators and NERC standard FAC-003. “Our motivation was preventative for vegetation management … It was not required. But we want to be proactive to prevent any grow-ins. We had clearing scheduled for a 230 Kv ROW …forestry was able to look at what type of growth they may expect,” said Fitzgerald.
“The biggest advantage that GeoDigital offers …other than the superior quality of their data … is versatility,” said Humrichouser. “They provide so many options … LiDAR, PLS -CADD ready files, ortho imagery …very clear …very accurate snapshots of the system and entire ROW. Vegetation can plan clearing activities …it gives them an idea if they will have a heavy clear, or if it will be light …what type of equipment they will need and the size of crews.”
“We use the data everyday looking for encroachments. With only one encroachment/ROW specialist, we’re able to save human power … encroachment is really a big deal …it saves us a lot of time,” said Fitzgerald. “All encroachment points are identified …fences, gates, roads, dirt roads … we’re able to look at all that and plan for obstacles, livestock, buildings.”
“With the quality of imagery we are able to see everything …identify pole damage, look at maintenance issues such as woodpecker holes, cracked insulators. It is important know how many encroachments have occurred and how long have they been there.”
“I can load the data into my GIS and we can see encroachments, pull up the high-res imagery …overlay ROW boundaries, property parcels …that’s a real time saver. If a guy builds a metal shed on our ROW without permission ..we can see it!” said Humrichouser.
Gulf Power is able to realize performance optimization and cost-effectives by using aerial LiDAR surveys for transmission line design and construction, however, they are also experiencing real benefits everyday in asset and vegetation management from the use of the LiDAR and image data. “We really liked how GeoDigital worked with us …we could trust them because they delivered exactly what they promised …and if there were any misunderstanding, they responded directly to our needs. They don’t nickel and dime you. That means a lot …they deliver exactly what they say,” concluded Fitzgerald.