Illinois - Metra 7400/Vision-Metra/V2 Publisher: Modern Railways Deadline: None METRA--Railroad With a Vision by Michael W. Michelsen, Jr. With some right-of-way maps dating back to the 1920's, transportation planner John Arndorfer knew it was time for an update. Not that Northeastern Railroad Corporation (Metra, Chicago, Ill.), which serves commuter needs between the counties of Cook, DuPage, Lake, Will, McHenry, Kane and the city of Chicago, was any different than most other railroads. "Many of the railroads in this country have one problem in common--bad data," Arndorfer explained. "And that's easy to understand because almost none of the railways in this country have been mapped since they were built, more than 100 years ago in most cases. And in our case, the 1920s." But it was time to update the nearly 500 miles of rail condition data in the agency's geographic information system (GIS) database--and Arndorfer wanted it done economically. Corporate officials wanted to know more about the commuter line's railways, the locations of trackside features, and other information that would facilitate more informed decisions about route planning and other issues. Conventional surveys had always been the preferred method for this work, but the time required as well as the always-attractive opportunity to save money led officials to turn to GPSVision TM, a tool developed by Lambda Tech International [Waukesha, Wisc.] and the 7400MSi GPS receiver developed by Trimble [Sunnyvale, Calif.]. Arndorfer and his colleagues wanted to create a GIS basemap for a variety of applications. "There are all sorts of data we wanted to look at, but those data are either in a form not readily accessible or we can't get the data without looking at every inch of our tracks," he said. "We wanted to change that by actually going out and gathering data--about track conditions, corridors, yard configurations--all kinds of data that would be accessible throughout the agency for a variety of applications." Mapping with a Vision GPSVision combines 7400 GPS positioning technology, an Inertial Navigation System (INS), and digital imaging, allowing users to map streets, highways and even railways--at a fraction of the time and cost of traditional data collection techniques. GPSVision was developed by Lambda Tech International in 1994 to meet the need for a better way to map facilities. Lambda Tech International was founded by digital mapping professionals to help government agencies and a wide variety of private clients build interactive GIS databases to a level of accuracy never achieved before. Data imagery allows users to map visible features such as utility poles, traffic signs, buildings, trees, even potholes and more. "Anything you can see with the cameras we can locate with GPS coordinates, and we can do it faster and more accurately (submeter/horizontal) than in the past. We can map railways as easily as city streets. And after the data is collected the user can repeatedly go back to map additional features on an incremental basis. So it's flexible as well as accurate." said Lambda Tech's representative. The GPSVision mobile mapping equipment is a transportable unit mounted inside and atop a vehicle. This system can be installed in a vehicle without special tools in about four hours. The GPSVision mobile mapping system consists of four basic modules: Positioning: A highly accurate, inertial measurement unit (IMU) alongside the GPS receiver. Stereo Imaging: High resolution progressive scan digital color cameras. Digital Recording: A digital image and data storage system. P.C. Software: Full-function feature extraction software that allows the user to point at visible features, determine their position and attach attributes interactively. Heights, widths and areas can also be measured and recorded. How to Map a Railway According to Arndorfer, collecting data with the GPSVision product was as easy as a train ride. "We mounted the GPSVision unit onto a high-wheel vehicle--basically a Chevy Suburban with metal wheels that run up and down the rails," he said. "The GPSVision cameras fit on the top of the high-rail vehicle, just like a ski rack, and the supporting computer equipment fits in the cab. We captured all sorts of data: The locations of stations, bridges, grade crossings, and other major infrastructure points. The width of the visual swath was about 100 feet, so data outside that area, such as parking lots, had to be obtained by using digital aerial images and combining them with the data collected by GPSVision." Picture This "What's important is that not only are the pictures in stereo (one camera is mounted above the passenger compartment, the other above the driver), but we know the exact position and direction of every picture. We combine that with the camera lens parameters and a baseline to perform traditional photogrammetry at locations on those images." Picture this: A computer screen shows you the stereo images taken by the GPSVision vehicle. Let's assume also that in both images you see an object such as a railroad tie. By pointing your cursor to the object in each screen and clicking the mouse, the object's X, Y, and Z coordinates (accuracy is less than one meter) are immediately fed into the target GIS format. "Anything you can see in the images can be captured very accurately by the GPS receiver. Metra uses Microstation as its GIS hardware platform with ArcView software. The agency will soon convert to Intergraph MGE and Intergraph Office GIS. "We're changing our GIS software program to take advantage of our networking capabilities with other Metra departments," Arndorfer said. "The competing GIS programs all have translator mechanisms that are improving and getting more interchangeable. This helps us because we not only have data that we create ourselves, but we also get data from other regional agencies who might use other data formats." The 7400 Element "Trimble's 7400 GPS receiver is the positioning component for GPSVision," Greg Orvets, President of Lambda Tech explained. "We started this project using Trimble's Pro XL mapping system, differentially corrected to get the submeter accuracy. But we changed to the 7400 because as the other elements of GPSVision changed we wanted to increase accuracy. The 7400 gives us a data point every second and allows us to update our IMU on a regular basis." "The GPS part of the equation is critical," said Guangping He, PhD (Photogrametry), also a Vice President. "We need to know the precise location of the cameras so that we can transfer the positions of the infrastructure to the surface of the earth. Without great accuracy in this positional element, there would be no way to accurately measure anything in the system. The measurement of any image taken by the cameras would be relative to the accuracy of the GPS coordinates." Richard Hammersley, Vice President, emphasizes the importance of the system's measurement capability. "Not only can we position where things are, but the accuracy of the GPS positioning allows users to do accurate measurements," Hammersley said. "For example, measure the length of a track with a relative accuracy that is on the order of a quarter-meter or less, it's probably more like 15 centimeters in accuracy. We can do that very easily." A Matter of Results "We're pleased with the results we are getting from GPSVision," Arndorfer said. "Now we have a digital record from which we can extract a large variety of information for many different purposes. In the past, every time we needed data about our tracks, we would have to call in a consultant to gather that data. We can do all that in-house now, saving considerable time and money. And we have railroad professionals in-house who can use the data to a much greater extent than an outside consultant could." According to Arndorfer, GPSVision and the positioning capabilities allowed by the 7400 receiver has given METRA officials the ability to more accurately estimate the position of facilities not readily seen. "When utilities such as fiber optic companies or electric companies put down lines, they like to work with a handful of railroads that go through territories they want to serve as opposed to thousands of different landowners to negotiate the use of easements," he said. "These lines are positioned alongside or underneath our tracks. Now when we want to know where they are located we know-and to a degree of accuracy we never had before." Back to Projects Map Mobile Mapping for Right-of-way Engineering: Fast and Accurate "Build for me a rail right-of-way map, accurately position, inventory, station and offset the visible structures and deliver the data in AutoCAD format tomorrow" said Ben Osborne of C & S Contractors. He and his staff were under a condensed time frame to design, engineer and oversee the construction of multiple fiber optic cable projects when he called on Lambda Tech International of Waukesha, Wisconsin for help. With the use of Lambda's high-rail mounted GPSVisionTM mobile mapping system and PC software tools, the call for help was answered. After discussing the mapping strategy with the fiber cable owner's project manager, Alex Navarro, a pilot project along 27 miles of rail operated by Metra, Chicago's commuter railway was developed. According to Navarro, "the ability to quickly create a digital base map showing the position of signs, signals, road crossings, bridges, buildings and other visible features was something that needed to be tested." If it worked as planned, future fiber routes could be mapped faster and for less cost. Additionally, the digital stereo images used to create the maps could be used over and over again for maintenance, trouble analysis and inventory of additional features such as trees, stations, occupied buildings. According to Osborne, any item visible in the imagery would be positioned with a horizontal accuracy of one meter or less. The initial project included surveying the 27 miles of track with the high-rail mounted GPSVisionTM system. Since the GPSVisionTM system was designed to be transportable, moving it from a highway vehicle to the railroad vehicle was an easy process. A standard high-rail vehicle was outfitted with the camera system facing to the rear to provide an unobstructed a view of the rail right-of-way. To ensure that all field assets and required features would be visible, the vehicle traveled the route in both directions. The total time for data collection was less than four hours with an average speed was 35 mph. By comparison, a C & S survey crew of three can collect the positions of infrastructure and field assets at the rate of one mile per day in urban areas. When additional time for in-house down loading of field data and CAD mapping was considered, the total time from start to finish was reduced by more than 50% while saving actual dollars of 30%. After the digital imagery data was collected in the field and the GPS data differentially corrected and processed, it was transferred to CD format. Approximately 25 miles of imagery on each CD was now ready for feature extraction, tagging and positioning. Using a PC and the Feature Extraction software in the office, technicians produced data files containing the locations of rail assets and related features such as poles, trees, road crossings and bridges. Each feature was positioned with a horizontal accuracy of one meter or less. The production rate was approximately one mile mapped per hour. After the feature extraction process was completed, a technician produced the final AutoCAD maps at the rate of one mile per hour. Each AutoCAD map contained the track centerlines, the positions, names and attribute tags of required assets and features as well as the stationing from a known zero point. Offset distances from the track base line were also automatically calculated. A sample of the AutoCAD output product is shown here. The AutoCAD base map, along with the GPSVisionTM software and digital imagery, was used by C & S to lay out and engineer the location of the buried plastic conduits that housed the fiber cables. Because of the one meter positional accuracy of the maps, the GPS positions of actual conduit "as built" locations were layered into the original map quickly and without scaling problems. "The right-of-way engineering moved faster than with traditional methods. With the digital imagery in hand, our engineers and technicians avoided the costly effort of having to drive to the field to view a particular track condition or potential problem" said Osborne. In addition to the terrestrial imagery, aerial digital imagery with 6 inch pixel resolution flown at an altitude of 1000 feet was also collected. This data was used to view Metra assets outside of the right-of-way. The aerial imagery was georeferenced and rectified by using the GPSVisionTM data for ground control and alignment of the same point in the aerial image with the matching terrestrial point. The software used for this process, which runs on a PC with Windows, is part of the GPSVisionTM suite of processing tools. The final products delivered to the owner were the paper maps, AutoCAD files complete with attributes and GIS tags as well as all of the stereo imagery and GPSVisionTM software. Copies of the data were also delivered to John Arndorfer, Metra's project manager, for use with their CAD and GIS software. According to John, "the digital data and software allowed our planning department to begin developing a GIS data base for all departments to use." Continuing, "the project opened many eyes at Metra and prompted our organization to fund the imaging and mapping of all of our 240 miles of passenger routes in north eastern Illinois" said Arndorfer. The initial pilot project was so successful that the fiber owner decided to use the GPSVisionTM system on all of their new routes in Canada and the U.S. To date almost 2000 additional miles have been mapped with the system with another 6,000 waiting to be surveyed. (Update: over 7,000 contiguous miles were completed in 1999.) In addition to the fiber optic engineers, contractors and owners mentioned in this article, others such as telephone, electric and CATV enterprises as well as cities, counties, transportation departments and railways also use this technology. They all want to efficiently collect data once and use it over and over again for projects and other related programs. Back to Projects Map