| GPS/Mapping: A Ticket to Ride
Faced with the task of mapping thousands of miles of roads and close to a million utility poles, Bell Atlantic of West Virginia turns to mobile mapping technologies for its data collection.
By Fred Bennett and Day Shelmire Introduction
How does a telephone company begin to map tens of thousands of miles of roads and almost a million utility poles in a state the size of West Virginia? Bell Atlantic, faced with this question, chose Global Visions Inc. of Herndon, Va. to apply an emerging technology solution to the job. Global Visions, a mapping and data collection company, used its GPS Mobile Surveyor technology, an integrated vehicle equipped with GPS (Global Positioning System) receivers, inertial navigation systems, and video equipment to map 1,200 miles of road and 25,000 telephone poles in the first ever utility pole mapping application of this technology.
During the summer of 1995, Bell Atlantic took a major step in improving the management of its pole network in West Virginia by beginning a complete inventory of the utility poles that carry wire and fiber throughout their service areas, as well as the roads that provide access to them. The project was made more difficult by the fact that current and accurate digital maps of the state are non-existent. West Virginia is typical of the more rural states of the country in that it is poorly mapped. Conventional methods for mapping poles and roads would be extremely slow and time consuming in mapping such a large area. Existing maps such as those available thorough government agencies are inaccurate and out of date. Even the West Virginia Department of Transportation's maps are too out of date to be considered useful for Bell Atlantic's needs.
Bell Atlantic had a number of options for mapping poles in West Virginia including aerial photography, lasers, and hand held GPS. Aerial photography for the entire State of West Virginia would have been an expensive proposition. In order to map poles from the air, thousands of photos would have to be shot from low altitudes. The photography and digitization processes would have taken years and millions of dollars to complete. Both hand held GPS and lasers require stopping on the side of the road to collect position information one pole at a time, sometimes, in the case of hand-held GPS, for several minutes per pole. In addition, lasers and hand held GPS are options that would have provided only a partial solution to the problem, some other method would still be needed to generate the landbase.
Using the GPS Mobile Surveyor technology, Global Visions was able to map roads and poles just by driving past them at posted speeds. The GPS and video systems provided rapid mapping of roadside objects. Use of this technology allowed Bell Atlantic to create a full road and pole inventory, and when used as the base data for an AM/FM or GIS program, will allow them to manage their assets better than ever before. Mapping Alternatives
Data collection is often the major cost of any AM/FM or GIS project, and is also the most important to the outcome of the project. The decision must be made between low cost existing data and the higher cost of collecting new data. Existing data may be outdated or incomplete, and the new data must be customized for the use in mind. A balance between cost and accuracy is often what is needed.
Among the least expensive sources of data are existing records. Either from public sources, such as TIGER or state DOT maps, or from paper records kept internally, these sources are usually available at little or no cost. The disadvantage to these sources is currency and accuracy. The poor quality of internal paper documents is often what prompted the desire for a computerized system in the first place, and it is foolish to expect people to use digital versions of paper maps that they never found useful in the past. Costs may also be higher than what is expected. Conversion of paper maps can run into the millions for companies with large service areas.
TIGER or other public sources of data are often little better. Not known for accuracy, these maps usually do not have all the roads, and those that they do have are usually not placed to any level of accuracy. In the case of the Bell Atlantic project for instance, fully 30 percent of the roads mapped did not exist on any other map. Many more miles that were on those maps no longer existed.
The real costs start when people try to update these sources by a process known as field verification. This usually involves using existing data, and then sending crews into the field to verify and update them. In an attempt to reduce costs, crews who are normally in the field may be asked to take on mapping jobs as well. The disadvantage to this is that these crews are not usually trained in GPS or other mapping equipment, and so different crews will collect data differently, making standardization and accuracy of data collection difficult to achieve. The time spent mapping is also time not spent doing regular work.
Faced with the problems of low cost solutions, many organizations choose to collect data and perform a full inventory using aerial photography and dedicated field crews. While very accurate, aerial photography can become very expensive and take a long time, especially when dealing with large areas. To compound the problem, mapping of small features such as utility poles and lines require flying very low and taking many more images.
New technologies are now being used in the market which combine the accuracy of custom collected data, with the more reasonable costs that are needed in eras of competition and tight budgets. Using GPS and other inertial navigation equipment with video cameras in a moving vehicle constitute are what are known as mobile mapping technologies. Mobile mapping allows custom data collection simply by driving down the road at normal speeds. In this way both landbase and roadside features are collected very efficiently, and in only the time it takes to drive the roads.
While not perfect for every application, and often used in conjunction with other methods, mobile mapping technologies have advantages in the type of data collection that utility companies need in beginning an AM/FM or GIS project. Bell Atlantic saw the advantages, and choose this method for its data collection. Data Collection and Landbase Generation
For the Bell Atlantic project, the first step was to collect the data for generation of an accurate landbase. Landbases can take many forms, but a road centerline map was chosen as the most appropriate landbase because of the way Bell dispatches crews, and the fact that the majority of poles are along the roads. This is the application for which mobile mapping vehicles were designed.
By merely driving the road at normal speeds, GPS and inertial mapping information was collected and combined into map data. GPS in a differential mode provided accuracies of one to three meters which was within Bell accuracy requirements, while the inertial navigation systems allowed data collection to continue when satellite signals were blocked by trees, tall buildings and other obstructions. The usefulness of the inertial system is very important. Without a system to compensate for GPS being blocked, many roads would not have been mapped, and those that were mapped would not have been done so as accurately.
Data collection for 1200 miles of road took approximately 35 days, and a cleaned-up landbase was delivered less than one month later. The landbase included layers for road names, types and route numbers. Position data on roads is recorded in both a latitude, longitude and altitude coordinate system and by the logmile, and converted to the State Plane system for delivery to Bell. Data Processing and Utility Pole Inventory
During data collection, video images were collected and linked to the GPS map created. In this way, images are geocoded to the landbase. Cameras out the front and both sides of the vehicle provide a full view. Pole locations were recorded from the images using custom software, and loaded into a GIS. Information about the pole, including lead and line numbers were recorded in the field, and are tied to the pole during processing. The result was each pole accurately placed on the landbase, and information on the pole linked to it. Processing for approximately 25,000 poles took under 2 months to complete. In several wire centers, over 95 percent of all poles were estimated to have been mapped.
Digital and analog video collection provide a number of unique benefits. First, all data collected and delivered to the customer is processed from digital and analog video collected in the field. This means that data is collected only once and additional data that is needed by the customer such as pedestals or other information, is simply processed from the existing images without the costly process of redeploying the data collection equipment. Second, all data is collected from a vehicle moving at posted speed limits. This means that data collection is fast, efficient, and best of all, as safe as possible under the conditions. Data collection personnel do not have to stop and leave the vehicle on busy highways to calculate positions and measurements. Uses for the Data
The primary use of this information will be to update Bell Atlantic records of pole information with a complete inventory. Accurate locations of poles will allow crews to be dispatched more efficiently, and with the right equipment.
The final product that Global Visions delivered to Bell Atlantic is a current and accurate digital map showing the road system, road names and route numbers, pole locations and pole numbers and full video of the roads and poles dynamically linked to the map. Bell personnel are able to search for any pole on the map by pole number or location, click on that pole to display inventory information and maintenance history, as well as display the most efficient route to that pole from the nearest maintenance facility.
Bell also intends to track maintenance vehicles using this digital map system (each vehicle shows up as a blip on the screen) so that managers can track and dispatch vehicles more efficiently in both routine and emergency repair situations. Bell expects that these advanced management technologies will provide substantial savings in the years to come. In the future, Bell is looking into using mobile mapping technology in the rest of their service area. This project was just a portion of their operating area, and has proven itself a very efficient and cost effective way to collect data. For collection of road and pole information in other areas mobile mapping is now another tool that is at the disposal of Bell Atlantic. Conclusion
Surprisingly, many districts in even the largest utility companies are not accurately mapped. In the past these decisions were left to the individual districts. Companies such as the regional Bells are discovering to their dismay that while one district may have the latest in digital mapping technology, the neighboring district doesn't even have an accurate paper map of the roads and poles it has to manage. Utilities must manage and maintain thousands of utility poles and other assets. This requires detailed inventories and current and accurate maps. Mobile mapping technologies significantly reduces the time and effort it takes for these companies to make current and accurate inventories of all of the assets they manage.
While not perfect for every mapping application, mobile mapping technologies are able to provide certain data in much less time and at competitive costs compared to conventional methods of mapping. As another tool for data collection, mobile mapping technologies are a valuable method of collecting information on the roads, and roadside features.
In just a few months, Global Visions mapped what would have taken several times as long using conventional methods. With an increasingly competitive environment, as more utilities realize the benefits of digital mapping, the use of mobile mapping technologies will only increase. About the Authors:
Fred Bennett and Day Shelmir are founders of Global Visions Inc. They may be reached at 703-478-7287. Back |
