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Monday, April 12, 2010

Surveying new Sonoma-Marin Area Rail Transit

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Sonoma-Marin Area Rail Transit (SMART) is an overwhelmingly popular rail initiative in Northern California, according to an article in The American Surveyor. Measure Q had an amazing 70-percent support of the two-county (Sonoma-Marin) SMART District.

One reason for voter enthusiasm is that SMART promises to be relatively inexpensive. Planners estimate that the new commuter rail system can be built for about $7.1 million per mile, which compares very favorably to the cost of extending other local systems. The cost of extending Bay Area Rapid Transit (BART) to San Jose, for example, is projected to cost as much as $326.3 million per mile. 

Why does the SMART initiative cost so much less? The main reason is an existing Northwestern Pacific rail corridor that runs straight through both counties involved, from Cloverdale at the north end of Sonoma County to Larkspur in central Marin County. Most of this right-of-way is now owned by the SMART district. At Larkspur, commuters can transfer to the Golden Gate Ferry to get to San Francisco. By taking advantage of the existing right-of-way and using diesel-powered trains that don't require electrification or grade separation (grade separation requires tunnels or bridges at all road crossings) SMART avoids most of the expense commonly required by new railways. 

Taking advantage of this existing infrastructure will still require a lot of work, especially if SMART is to begin service in 2014, as projected. The Northwestern Pacific railway has been out of service since 1994. The right-of-way is overgrown in many areas, two existing tunnels will need to be refurbished, and the entire track will be redesigned and replaced.

One of the first steps in the redesign of the track is an accurate survey of the existing 70 miles of track. This means good coordinates at regular intervals on both rails. Planners and designers needed to know the location, super-elevation, gauge, location of switches, etc. This is a major undertaking.

"We worked on the railroad in the past, with SMART's lead consultant; HDR Engineering," says James M. Dickey, PLS, president of Cinquini & Passarino Inc. (CPI), a surveying firm based in Santa Rosa, Calif. "We knew from our previous experience that the top of rail survey could take months to complete with conventional surveying equipment." 

CPI was asked to provide details of track and crossing conditions for a northern 60-mile section of the SMART corridor, with rail information at 100-foot stations. With conventional RTK or optical surveying, the work goes slowly and it's hard to reliably get sufficient accuracy. Setting and plumbing the rod at consistent points on the rounded top surface of rails, is tedious. And, counting off stations along the track adds up as well. CPI wanted to work more efficiently, while providing higher density and more accurate information to their client.

The firm is known for innovative use of technology; for example, they won a 2010 American Council of Engineering Companies' small firm merit award for a project that combined RTK surveying and echo sounding to provide hydrographic data to the City of Napa, Calif. 

True to form, CPI came up with a better idea for the SMART corridor work.

"The project was qualifications-based and we had to figure out the best way to meet project goals. We were challenged with a very tight time schedule," Dickey explains. "We saw some information on the Amberg Technologies' GRP System FX track-surveying system in The American Surveyor [March 2009], and we thought it might work perfectly for this."

Amberg Technologies' (Regensdorf, Switzerland) rail and tunnel solutions are well established in Europe and Asia, but are just being introduced to the United States. Dickey asked the Kara Company, Inc. (Countryside, Ill.), Amberg's 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. 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. 

The only GRP-specific setup 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 onboard 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 that 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, PLS, CfedS, handled the office part of the project, and says that data was collected quickly enough to create a ratio of about two-to-one, fieldwork to office work. For deliverables, he exported points from the onboard Amberg data collector (based on a Panasonic ToughBook), 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. 

"This saved us months of fieldwork, plus, we could do more for our client," said Dickey. "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. Return on investment was substantial and the project has encouraged Cinquini & Passarino, Inc., to pursue more railroad work.