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Home arrow Archives   The American Surveyor     

Catching the Right Train Print E-mail
Written by Fulvio Bernardini   
Saturday, 20 August 2016

How an Italian surveyor unexpectedly entered the business of railway maintenance surveying.

A 3.951Mb PDF of this article as it appeared in the magazine—complete with images—is available by clicking HERE

At work in his ground floor office in full view of passers-by, Diego Callegari had no idea that his career would take a new turn that day in 2001. Pictures of a survey that Zenit Topografia--the surveying firm owned by Callegari and Nicola Rebora--had recently done were rotating on the screen of one the company's computers. The survey was for the construction of a new subway station in Genoa, a field in which the firm had just started working. The survey pictures caught the attention of a passer-by, who entered the office, introduced himself and asked if Zenit happened to do railway surveys as well.

Zenit Topografia had just entered the business of railway maintenance surveying.

Callegari began his career as a surveyor in the early 1990s. His enthusiasm for the work led him in 1998 to found Zenit Topografia, which initially focused mainly on construction and cadastral surveys. Since the day that passer-by entered the office, 80 percent of Diego Callegari and Zenit's work time has been spent doing surveys of the Italian railway system for Rete Ferroviaria Italiana (RFI), the managing institution of the Italian national railway system, or companies that have maintenance contracts with RFI.

"The entry into the railway surveying field was as unexpected for us as it was fortuitous," said Callegari. "We were lucky--but, truth to be told, we also had unwittingly created the conditions for this collaboration to take place ourselves. In fact, we had just equipped the firm with a Geodimeter 610 total station, the first to feature the Autolock™ function, and then a Trimble S6, enabling us to satisfy the client's need to carry out surveys at night."

In Italy, the railway maintenance field uses many resources. As for track maintenance, RFI's main challenge is making sure that the gradient of the railway track does not exceed certain limits. Any values outside the limits must be corrected. Design plans for "modern" segments of railway come with spatial information--a control network made of reference points of known coordinates--that prove to be very useful during maintenance surveys. Surveys are rather simple: maintenance teams collect points by setting a total station on each of the reference points and then set a prism pole with a rail shoe on both rails to define the centerline and the gradient of the track. The correction plan is sent almost in real time to the maintenance team who then corrects the gradient of the tracks. Callegari worked on segments of modern railways with his Trimble S6 total station and he also tested a Trimble GEDO rail measurement trolley with the intent of using the new equipment for future projects. "Using the GEDO together with the TSC3 controller allowed for an extremely efficient workflow. For each point collected, the correction was sent to the maintenance team who then had the correction plan in real-time."

However, Callegari often finds himself working on "traditional" railway segments. These are parts of the railway line that lack the spatial information on which the maintenance surveys should be based. So, before the maintenance survey is carried out, a control network needs to be established. Due to the problems for train transit this kind of work creates, RFI finds it justifiable only for long railway segments. For shorter segments (3 to 4 km or 1.9 to 2.5 mi)--with elevation being the most important information--RFI relies on surveying teams to create elevation profiles of the railway segments in just a few hours. Correction plans are then created off these profiles. "RFI technical departments are often unable to guarantee adequate productivity due to labor contracts that prohibit their technicians from working too many nights consecutively," said Callegari. "This is where I come in."

Railroad maintenance surveys are, in fact, done exclusively at night to avoid train traffic and to take advantage of the planned interruptions that only RFI can organize. Sometimes, however, windows of working time open unexpectedly, as for example due to a train cancellation. So the Zenit team (usually composed of Callegari and his partner) must be ready on short notice, equipped and focused on the task; and always, safety in the field is the main concern of RFI and the surveyors.

"Equipment is another fundamental aspect for us. The Trimble S series, for example, has a very practical case much like a backpack. It seems insignificant, but it is an important item for people like us who must walk for kilometers with the equipment," Callegari said. Working at night, the tripod with dual-lock and the active prism are also important to the team.

Callegari and his partner typically arrive on-site at around 3:00 a.m. and leave a few hours later. "Despite the early hour, we don't feel tired," explained Callegari. "We have too many things to do and not a lot of time. And we must keep alert as we are in a rather dangerous working environment." The team, along with the RFI staff, the Trimble S6 total station and safety equipment, must first walk along the entire length of the segment to begin the survey from the point furthest from the entrance to the work area. They then work back towards the exit. The survey is carried out manually, collecting points every 30 to 40 m (100 to 130 ft) in correspondence to the electric supply poles where the corrections for the maintenance team are marked. The survey speed depends on how complicated a railway segment is, i.e., the number of straight and curved sections. The team can typically cover between 1.2 to 2 km/hr (0.7 to 1.2 mi/hr). Back in his office, Callegari integrates the newly collected data and provides RFI with the elevation profile of the railway segment.

"Little by little, as the traditional lines are given coordinates, these kinds of operations will become obsolete," Callegari said. "This doesn't mean that Zenit's involvement will end. On the contrary, it will change, integrating new technologies and methods to optimize the workflow."

Callegari and Zenit's accidental introduction into the railway surveying field was more than just luck. It came about in part thanks to their initial investment in new surveying technologies. This foresight continues to invigorate Zenit's work and presents them with new opportunities in growing sectors such as railway infrastructure maintenance. "Surveyors today must pay attention to changes in the field and stay current on the most recent equipment and techniques," Callegari said. "Surveying is an ever-changing profession and so are the needs of their clients."

Fulvio Bernardini is a freelance writer based in Italy who specializes in the geospatial industry.

A 3.951Mb PDF of this article as it appeared in the magazine—complete with images—is available by clicking HERE

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