Pole treatment GPS (OR 170,000 Points of light)
Michael J. Buri DMS Project Manager, Nashville Electric Service 1214 Church Street, Nashville, TN 37203 Abstract Nashville Electric Service (NES) is presently running a pole groundline treatment and GPS inventory program. It is believed that this is the first time a pole groundline treatment and inspection program has been combined with a comprehensive GPS data collection effort. The program was started to provide two services to NES simultaneously, mainly 1) the treatment and inspection of the entire physical plant, and 2) the GPS positioning of the plant for use in the GIS system. The program, started in July of 1996 and scheduled to finish in December of 1997, will log approximately 170,000 poles. Data collected for each pole during the program will include 1) all treatment information, 2) visual inspection information on pole mechanics, 3) quantity and characteristics of a variety of ‘pole attachments’, and 4) R.O. W. tree trimming information. Data collected during the program is being used to support an ARC/INFO GIS. Project management, using the GIS, will include 1) weekly data input, 2) field verification of collected attributes, 3) GIS comparison of known pole locations, and 4) GIS comparison of known pole attributes. Introduction In early 1996, NES was preparing to undertake a pole treatment and inspection program. GPS positioning was added to the program as an option. Due to the size and complexity of the undertaking, GPS was considered an important element, and believed to be capable of providing an expert tool for project management NES estimated inspection and treatment of 170,000 poles, covering 700 square miles. (Estimates for the number of poles came from a mainframe facilities accounting system.) This project would cover all wooden poles used by NES, including primary feeder poles and secondary service poles. An AutoCAD mapping system contained primary maps showed approximately 120,000 poles in the service area. Area maps for inspection personnel would be provided through a paper mapping system, covering both primary and secondary poles. After bids were returned and analyzed, Osmose Wood Preserving Company was awarded the contract. Requirements of the contract included that the successfid bidder 1) supply a GPS base station for use in the project, 2) provide field tested GPS equipment capable of sub-meter mapping, 3) train crew foremen in NES equipment and terminology, 4) supply all treatment chemicals, clean up materials, and safety training for crew performing treatment operations, 5) deliver field inspection information to NES in electronic form, and 6) report to NES immediately any dangerous conditions found by field personnel. Pole inspection, Treatment, & Repair Pole inspection entails visiting each pole, visually inspecting the pole for problems (rot, insects, vehicle damage, etc.), partially excavating poles suspected of groundline exterior decay, and testing the pole for interior decay through sounding and boring or an electrical shigometer. Treatment, depending on the problem encountered, entails injecting chemicals to fumigate the interior of the pole, or stripping off exterior decay and applying tar-like preservatives and protective wrap. Repair entails two separate conditions the first being pole repairs, the second being equipment repairs. Pole repairs, designed to strengthen a pole weakened through decay, include ‘C trussing’ (driving a steel support alongside the pole and banding it to the pole) and fiber wrapping (excavating around the pole and applying a fiber glass type wrap.) Equipment repairs include repairs to damaged or missing ground wires and guy markers. The main benefit of providing an inspection and treatment program is to extend the service life of wooden pole. By treating a pole, 10 or more years of service life maybe added to a pole. The cost involved in chemically treating a standing pole is generally a few percent of the cost of the pole. The cost of repairing a pole is generally well below half the cost of installing a new pole, with no interruption of service to the customer. Pole Data Attribute data to be captured in the program was identified by brainstorming with several groups of potential users. An attribute ‘wish list’ was compiled, edited and included in the final RFP (Request for Proposal). After the bid was awarded, NES and Osmose worked to identifi mechanisms to accurately collect and enter the pole data list. The final pole data list included well over 100 items related to the pole, pole conditions and treatment, equipment on the pole, items needing maintenance, and tree conditions around the pole. Some data items, while initially considered important, were eventually dropped from the list, due to operational problems in collecting the information. However, the final attribute list still contains over 100 data elements. A short list of the pole data collected is as follows: Pole tag (metal plate affixed to pole denoting ownership& location) as it exists in the field (correct or not) All treatment and condition information (decay, decay area, treatment types, previous treatments) Pole classification data (height, class, age, manufacture) Equipment located on the pole (including sizes and classifications where appropriate) Maintenance requirements (equipment repair or replacement) Tree trimming information (tree types, involvement in electrical lines) Attachment types and numbers (telephone, cable TV, fiber optic, traffic) Surprisingly, several initially important items were excluded from the attribute list. One of the items dropped was transformer phasing information (information as to which of three lines or ‘phases’ a transformer is connected). Phasing information is determined by tracing circuits exiting a substation and following that trace to each pole. Since the pole inventory and treatment program was to be a work of a point to point nature, line GPS work, such as tracing phasing, was pulled out of the program by NES. Phasing was considered too time consuming for quality control checking and having too high a potential for error during input. GPS Methods A portion of the RFP was written detailing GPS equipment requirements. NES wanted GPS equipment used for the pole inventory with a proven background. Osmose selected Trimble Navigation Pro XL mapping grade receivers and a Trimble base station for the project. Osmose was able to relay experience using several GPS products under harsh field conditions, and suggested the Trimble equipment as being ‘field proven’. This information coincided with information independently gathered in procuring a GPS for NES. Using the GPS equipment, NES and Osmose conducted a joint pole pre-inspection trial. Two crews with Telxon clipboard data recorders and GPS equipment inventoried two small sections of the service area. Details gathered from the trial enabled NES and Osmose to iirther fine tune data gathering. The NES mapping system is based on a detailed flyover from 1987. The mapping system is considered ‘few meter’ accurate and generally printed on 1:300’ maps (pole symbols being 10 feet across in printed size). NES chose the following approach to GPS: Record attribute data in the Telxon units as Osmose had done on past jobs. Use the Trimble GPS to capture location and positioning information. Generate a unique id number in each unit to tie the two data records together. (i.e., GPS location and attribute) Keep the Trimble unit next to the pole but no more than 1.5 feet from the pole (if necessary to clear obstacles from recording position data). Any poles Osmose would be unable to position, would be located by the NES mapping group using a laser and NES GPS equipment. GPS ‘quality’ data for each point would be recorded to allow for quality control (QC) checks by both NES and Osmose. It was decided that the above approach would allow NES to capture more data points in a shorter time frame and maintain a ‘few meter’ accurate, or better, system. This reduces the number of revisit points by the NES mapping group. Position quality data included mask settings for the GPS unit at time of capture and RMS error calculated by the number and position of points recorded by the unit during capture. Using the QC data allowed NES and Osmose to post process monitor crews afier data was returned to the field office. In one event, a GPS operator had left the GPS unit operating as he walked from one pole to another. The data pulled from the units showed a RMS error of 70 feet (most others being 1-2 feet). This allowed the Osmose office staff to identi~ the problem data record and remove it from the data transfer to NES. The end result of the QC controls is a pole location with a ‘quality of placement’. NES can qualify pole locations as being either sub-meter accurate (or equal in accuracy to the NES mapping system - few meter accurate), or 1-5 meter accurate. Data Transfer Data transfer from the crew gathering back to NES involves several steps:
Project Management QC Project management and quality control on the NES side has several different aspects and involves different personnel in several departments. The project manager for the pole treatment and inspection program performs a weekly field check using printed data from the pole attribute records. (A laptop using ARCView, NES mapping data, a GPS unit, and collected Osmose pole location and attribute data, will soon be available to the project manager to perform quicker QC work.) The project manager also is responsible for checking and signing weekly invoices. 675?The Distribution Management System (DMS) project manager provides QC assistance to the projects by being an advisor in data collection questions and providing answers for ‘how can we ‘?’ questions from within NES. The DMS project manager also provides GIS tools and dothis . . . . . services to graphically display, analyze, and disseminate information gathered from the project. GIS analysis will also include comparison of mapped pole locations to collected pole locations and comparison of stored pole attributes to collected pole attributes. Information Systems provides QC support by transferring data from a flat ASCII file to normalized Oracle tables. QC is also performed by matching records between attribute and GPS tables and by performing unique record checks on each data transfer. Oracle support is also given for GIS applications running against the data. Projcet value of GPS The value of GPS within this project is several fold. Perhaps the largest value GPS provides the project is a common reference point from which to talk. It is possible to talk about and understand the exact physical location of a particular pole. The location of the poles becomes ‘absolute’, it is a known point on top of a GIS background. Project management is strengthened by reference to ‘exact’ locations. There is a large difference between a table of attributed points and a map of points with attributes. QC can quickly check for faulty data, such as a pole that has been GPS located previously, or a pole with incorrect data attributes. Aside from the value within the project itself, GPS locations are expected to fill a large hole required for data cleansing. Presently, mapping data at NES resides in two main electronic mapping repositories- 1) the AutoCAD primary maps and 2) the mainframe mapping system. It is a goal of the DMS to reduce the number of disparate mapping systems into a single mapping system. The building of a single mapping system, or One Mapping System as it is referred to in the DMS project, will require a fair amount of data scrubbing. The mainframe contains pole number and pole attribute information. The AutoCAD system contains pole number and some pole attribute data. The pole inventory program will provide a bridge between conversion of the two data sets into a single data set. Location information from the pole inventory will be compared against location information from the AutoCAD system. A data checking program wrhten in ARC/INFO will be used to visually identi~ and list errors within the mapping system. Location errors will then be corrected by GIS personnel. Factors such as whether the GPS points is sub-meter or 1-5 meters, and the distance between the AutoCAD pole location and the GPS pole location can be used to determine whether differences in spatial location show up as an error. (i.e., show all pole pairs greater than 10 feet from each other, where the GPS pole is a sub-meter point). Where poles are not tagged in the field properly, tools sets will be created to enable a user to ‘tag’ a GPS pole with a correct pole number. Automatic data checking routines can locate unpaired poles, poles with duplicate tags, or poles with tags numbered outside an acceptable numerical range. Electronic and subsequent field tagging of non-tagged poles then becomes part of the maintenance items out of the pole inventory program. Attribute data will be compared in a three way match between AutoCAD, Mainframe, and GPS data. Records that match across the three data sources will be considered valid. Data matching across two sources will be considered as valid, and possibly merit a field check. Data that does not match across any of the data sets will be investigated and corrected by mapping personnel. (i.e., AutoCAD identifies a 25 kVA transformer, the mainframe identifies h as a 37.5 kVA transformer, and the GPS inventory could find no marking on the transformer.) Lessons Learned Perhaps the biggest lesson learned in the project was one which could be called ‘firm compromise’. Firm compromise refers to a company purchasing goods or services, encountering potential delivery problems of expected items and seriously reflecting upon the value of those items as individuals when compared with the whole of the goods or services, and thus being able to make compromises on lesser value items and standing firm on high value items. Firm compromise also refers to looking for alternate solutions to potential problems as opposed to ‘letting the supplier figure it out’. Firm compromise has roots within the ‘win-win’ business philosophy. Firm compromise was called into play soon after the pilot started. The contract and the proposal stated that pole attachment data would include identification of the owner of the attachment, and that a certain percentage of poles would be of sub-meter quality. Prior to starting the pilot, meetings were held to identi~ the data elements for capture. The issue of attachments soon became an apparent problem. Attachment data is stored on the mainframe with no spatial locations. Details of companies attached to NES poles were quite limited in providing ‘where’ these attachments were located. Further complicating the issue was the fact the companies attached to the poles did not use any cable markings to identifi ownership. It would be possible to produce limited maps showing the company’s service areas but bordering areas between companies would then be fraught with error within the returned GPS data. Using mainframe attachment data and the AutoCAD position data, a map was created showing where specific cable TV companies were attached to NES poles. Clear boundaries between company service areas could be identified. It was determined from this map that attachment data collection would not include company name, but simply type and number of attachments. An NES technician, experienced in attachments, using a GIS application will identi~ ownership of pole attachment using the previously created map as an electronic underlay. Border areas will be clarified by field visits to the border to accurately model the ownership of the pole attachments. An added benefit to this compromise is the removal of an attachment ownership QC step for the pole inventory project manager (The QC process now can quickly and accurately check number and type of attachments rather than ownership). In the pilot project, the percentage of pole locations in the sub-meter range was found to be about half of that expected. It was found that satellite number 20 had failed and the replacement schedule was unknown. Upon reflection the GPS position was decided to be an one of the important parts of the program and a ‘firm’ point. NES, while allowing for some impact of a missing satellite, worked with Osmose to arrange for improved GPS data recording. Rather than record GPS positions throughout the day, including low satellite availability time periods, Osmose agreed to ‘work the satellites’ and re-position crews work schedules to take advantage of the existing satellites. NES agreed to work with Osmose and monitor GPS positions for improvements each week. After a replacement satellite was in orbit h was agreed that the sub-meter percentages should much higher. After several weeks of work and with a new satellite # 20 in orbit, the efforts have been repaid with much higher percentage of sub-meter locations. Early Project Results Early results have started to indicate a picture of pole health. While inconclusive, due to the volume of the data, a picture has emerged. Pole inspection crews started in the northern area of the NES service area. After several weeks in the combination sparse rural and medium density urban environment, it was determined that pole health was quite good. This area of the NES territory had previously been treated in 1986 and the treatment appears to have been quite effective. Only a few poles were found to be below required strength. It was then decided to split the crew efforts and start half of the crews in the dense urban areas of Nashville, where the pole treatment project in 1986 had been halted. Not surprisingly, higher numbers of poles requiring treatment and strengthening were found. While not yet in numbers that are capable of making a definitive statement, h can be said that pole treatment is akin to car maintenance. A car owner may either pay small sums many times to maintain the car as it is used or pay a large sum once to buy a new car when the old one fails. By the end of the project it is expected there will be some definitive numbers related to the cost of pole maintenance vs. the cost of pole replacement. Early results have also confirmed the quality of the 1987 flyover data. Spatial location of poles is generally within the few-meter accuracy hypothesis. As new rural segments, added since the flyover, are GPS located h is expected that these will be farther from the modeled poles. A larger benefit has also been realized in the area of pole tagging. The GPS location of a pole and its associated tag have enabled direct comparisons of mapped vs. field data. In one instance it was determined that the 1987 flyover missed the first pole on a side street, each pole thereafter (or about ten poles) was off by one pole tag. Conclusions Pole treatment and inventory programs are large and complex undertakings. The use of GPS technology has the capability to both increase the power of the data collected and ease the quality control of the data as it is produced. Studying similar past projects can help smooth out problems before they appear. Prioritization (firm vs. compromise) of data items for capture can be a difficult task, however it can be the difference between a successful and a unsuccessful project. Imaginative use of technology, data resources and experienced personnel can streamline a cumbersome process and can greatly improve intended results. | ||
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