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.
