RAIL SURVEYING
Surveying with GRP 1000 from Amberg Technologies: Collection of horizontal track location, top of rail elevation, gauge and super-elevation in one process.
U.S. distributor, to demonstrate the system, which is based on a three-wheeled instrument that rides along rails. The GRP is equipped with extremely precise sensors that continuously measure track gauge and super- elevation, as well as an odometer for relative stationing.
The horizontal and vertical alignment of the track is established by streaming position data (N, E, Z) to the GRP from either a Leica robotic total station or RTK GPS. All of the data are simultaneously managed in the onboard Amberg Rail software. In practice, the GRP is pushed along the track and in a single process, provides all track information.
Depending on how it is configured, the GRP System FX can also be used for real-time track adjustment in slab track construction (used in high-speed and light rail projects), tamping surveys for ballasted tracks, real- time clearance analysis and 3D mobile laser scanning. “The Kara Company provided training for the system,” says Dickey. “We trained four people—two field guys and two office guys—which took about a week. Once we learned the software, the field work went very efficiently.”
For this project, the GRP’s horizontal and vertical positioning was provided by RTK GPS. A Leica GX1230 receiver was connected via cellular modem to the California Surveying Virtual Survey Network (CSVSN). The CSVSN covered the SMART corridor and allowed CPI to start work each morning without setting up a base station or stopping every few miles to move the base station forward.
“Data was collected quickly enough to create a ratio of about 2:1, fieldwork to office work.”
The only GRP-specific set up needed was a daily calibration of the cant sensor, which measures the super-elevation of the track. The calibration takes only a
couple of minutes and works much like checking any level: the GRP is set on the track, a measurement is taken, then the GRP is turned the opposite direction (one person can do this) and a new measurement is taken and automatically evaluated by the on-board software.
Although the GRP only requires one person to operate, a two-man crew was used on this project for safety reasons. CPI had estimated the time required to complete this survey with traditional methods would have been three months. The GRP enabled CPI to cover five to nine miles a day and complete the fieldwork for the entire 60-mile corridor survey in just under two weeks.
Mike Jones, who handled the office part of the project, says data was collected quickly enough to create a ratio of about 2:1, fieldwork to office work. For deliverables, he exported points from the onboard Amberg data collector to a spreadsheet and then into AutoCAD—maps were simple, basically points and coordinates in parallel. With training, fieldwork, and office work, the entire project took about four weeks.
“The Amberg GRP saved us months of fieldwork,” says Dickey. “Plus, we could do more for our client. Since the GRP and GPS were gathering data more or less continuously, we were able to provide coordinates and track data at 25-foot stationing, rather than 100-foot. We now have all the data available to provide the track data at any other interval if requested by our client.”
Because it was new technology for CPI, Dickey made sure that spot checks were conducted with conventional equipment and found that the GRP consistently gave precise results.
rail technology magazine Dec/Jan 11 | 59
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