As the technology becomes more accessible and costs continue to decrease, Global Positioning Systems (GPS) are fast becoming an integral part of the process of designing and managing infrastructure, be it bridges and highways, water and sewer systems, telephone networks or electrical distribution grids.
      In fact, infrastructure management is now a major market for GPS technology providers. "Utilities represent one of our largest growth segments for GPS products," said John Herrgott, product marketing manager for the GIS Data Capture Unit at Trimble Navigation Limited, Sunnyvale, Calif. "The technology has become sophisticated enough to record, not just points but also lines and areas. It's flexible and can capture whatever data they require."
      The reasons utilities, highway departments and others are embracing GPS so enthusiastically are two-fold:
      Integration with most geographic information systems (GIS). GPS developers have created efficient data formats to download three-dimensional positions and a variety of descriptive features directly into the database of most GIS software packages.
      Efficiency and accuracy in data collection. Traditionally, data acquisition or conversion from paper to digital maps was the largest hurdle in implementing a GIS - accounting for 60 percent or more of the total project cost. With portable GPS mapping systems the speed and cost of acquiring and maintaining data has been substantially reduced and the accuracy of positions has improved.
      Consequently, users are finding that the marriage of GIS and GPS technologies saves them time, money and headaches.

A Case In Point
Take, for example, the Denton County Electric Cooperative (DCEC) in north-central Texas. After nearly a decade of double-digit growth - as high as 20 percent per year - this coop serves some 35,000 homes and businesses in the suburbs north of Dallas and Fort Worth, including Highland Village, Flower Mound, Allen, McKinney and Plano.
      Faced with a system that was more than doubling in size, Denton County first jumped into GIS in 1986. "We needed the ability to produce maps on demand," explained Curtis Trivitt, P.E., system engineer for DCEC. "When you're developing service for 2,000 to 3,000 new meters per year its important to have the ability to produce current, as-constructed, maps on a weekly and daily basis."
      DCEC took a pragmatic approach to its GIS implementation, eschewing the bells and whistles of some of the bigger, higher-cost systems and selecting a PC-based system called GeoBase STRINGS for graphics and dBase for the data storage. "The two packages weren't integrated," Trivitt said, "but they were affordable and easy to use."
      Although a limited and relatively generic mapping product, it gave Trivitt and his group a solution to their immediate problem. "We had the line department, operations and construction, even maketing coming to us daily needing maps for some purpose," he said.

Improving Accuracy
But automated mapping alone could only solve half of the Coop's problem. "We needed a way to collect information quickly, efficiently and accurately," Trivitt said. In 1991, the coop purchased a couple of Pathfinder GPS Basic Plusª receivers from Trimble Navigation, Sunnyvale, Calif.
      "We looked at conventional surveying methods and aerial photography," he added. "We found the task to be very costly until GPS came along. Now one man can collect location and attribute information at one time. Otherwise we needed at least two people, plus the aerial photography."
      He concedes the old manual maps were never fully accurate. But this was compounded by the rapid growth rate. Construction crews were installing cable in new subdivisions, sometimes before final drawings were available.
      Trivitt is certain there are cost savings using GPS over traditional surveying methods, although he never took the time to calculate them. Ease of use and accuracy were the driving factors behind their choice.
      "Using GPS is relatively easy. You don't have to be a registered surveyor to collect the data," Trivitt said. "GPS gives us the ability to accurately map our electric facilities with in-house engineering staff."
      In addition to inputing information on new construction, Trivitt outlines many other uses for GPS in the field:
      Perform field inventory. DCEC is collecting detailed data on poles, pole top assemblies and electric devices to be stored in a relational database. This data can then be queried to provide information for maintenance scheduling, construction budgets and assets accounting.
      Update road and development information. With the rapid growth, construction of new streets and roads is common. DCEC often must begin installing new services before maps suitable for digitizing are available. "It's easier, faster and more accurate for us to drive the new roads to obtain the locations. GPS becomes a mobile digitizer. It also can be used to obtain new subdivision parcel boundaries right off the surveyors' stakes," Trivitt said.
      Maintain accuracy from map to map. Trivitt said that only about one in 50 subdivision plats includes any kind of accurate geopositioning controls. "When dealing with large areas developing over several years in 30- to 60-acre phases, it is very important to position the first few phases accurately. Otherwise, when the area is fully developed, the map of the area may not be accurate in relation to other geographic features previously mapped," Trivitt said. "By establishing earth-coordinate control points our maps fit together like pieces of a puzzle."

Practicality in the Field
The DCEC crews have created a variety of techniques to deal with the survey needs of the power utility. For road surveying, they attach the GPS antenna to the roof of a vehicle and drive both sides of the road. For subdivisions, they collect the four corners to establish control. Then they determine the locations of poles, trenches, lines and other equipment.
      Of course, their most common GPS activity is mapping underground and overhead facilities. Not only can field crews establish precise location, they can also input attribute data, like ID number, pole top assemblies, equipment name-plate data, conductor size and types, age and maintenance or inspection notes.
      Total time for the inventory averages about three minutes per item. At the end of the survey, the data is downloaded from the data collector into a PC file. DCEC then uses Trimble's PFINDER software to differentially correct the GPS positions. Then data is output for use in the GIS software.
      "It all starts with the GIS," explained Trimble's Herrgott. "Since the information must be spatially-registered in the GIS, we provide software to build a 'data dictionary' - a list of objects and associated attributes - that is consistent with the GIS. This way the user can collect not just three-dimensional locations, but features and attributes - or descriptions - on each plant item as well."

Not All Wine and Roses
Trivitt cautions that using GPS requires more than just buying the box. "It's not just point and click," he said. "We've had times when we only got 40 percent of the points we surveyed. Whoever's collecting the data has to be aware of how it works. They have to be sure the satellites are positioned for accurate locations to be obtained. Sometimes a satellite may be obstructed by a building, hill or tree, or, at that time of day, an inadequate number of satellites are in view and you don't get the readings you want."
     For the new GPS user, Trivitt offers two pieces of advice. "First, you really need someone on staff that understands some basic cartography - mapping, earth coordinates, projection systems, etc.," he said.
      His second admonition: get proper training. "We sent our people out to Trimble to get first-hand training on the equipment," he said. "Adequate training is certainly worth the investment."
     With those caveats in mind, Trivitt said acceptance of the new technologies has been quick throughout the organization. "We started using computers and other advanced tools and equipment in the early 1980s to help us deal with the growth. Once the ease of use and benefits of GIS and GPS were demonstrated, our people took right to these tools," Trivitt said.
      "The line construction and maintenance personnel are also interested," he added. "They like the convenience, the ability to request a map and have it their hands 15 minutes later."
      He noted that, after three years, they are developing the discipline to keep their records updated continually. "It's gotten so easy to do, it's practically automatic," Trivitt said. "The next step is to provide the dispatchers with a computer terminal into the GIS. Then, with limited editing functions, they can note changes and updates for later entry into the permanent database and print special maps on demand."

Second-Generation GIS
Although DCEC's 15 to 20 percent growth rate had settled to about nine percent by 1994, the real number of new meters added to the system is actually greater today than in the mid-eighties. The cooperative stills adds more than 100 miles of new distribution line and about 2,000 to 3,000 new meters - mostly homes and retail businesses - to its system each year.
      Now DCEC is moving to the next phase of its GIS/GPS implementation, upgrading its GIS with two complementary software packages - ArcInfo Envision, by Environmental Systems Resource Institute (ESRI) of Redlands, Calif. and Envision Electric GIS, an ArcInfo application for Electric utilities developed by Envision Utility Software Corp., Santa Fe, New Mexico.
      The new system will give Trivitt and his crew the ability to integrate not only its graphic and attribute data, but also will directly accept GPS-collected data.
      As for GPS, Trivitt sees increasing uses in the years to come. "I'd like to outfit all of our staking crews with GPS and notebooks," Trivitt said, "so they can get locations in the planning phase of a new project."
      Eventually he even envisions outfitting all his line trucks. "That would give us real time vehicle tracking and dispatch for repair and construction crews," he said. "GPS makes a big difference in the efficiency, accuracy and even safety of our operations. That translates to more efficient operations and better customer service."

About the Author:
J.D. Wilson is a freelance writer in Denver, Colo., specializing in the GeoTechnologies. He may be reached at 303-751-7636.

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