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Delivering the Three Rs of Monitoring

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-4- Technology&more I t's been a long time coming. First envisioned shortly after World War II, Crossrail is a 118-km long (73-mi) railway serving the greater London area. Under construction since 2009, the £15-billion ($24-billion) project will provide passenger transportation for commuters and suburban residents and include direct passenger connections to Britain's Network Rail. The new line includes 42 km (26 mi) of new tunnels beneath central London. A critical part of constructing the tunnels is understanding how the work affects existing rail lines near the sites. Using blended geospatial technologies, a Crossrail construction contractor created a monitoring solution to provide timely, accurate information for project stakeholders. Protecting the Rails The contractor, Morgan Sindall plc, was awarded a roughly £100-million ($160-million) contract to link new Crossrail tunnels to the Network Rail infrastructure in the London Borough of Newham. The work includes construction of a tunnel portal and a new elevated Docklands Light Railway (DLR) station. The contract required Morgan Sindall to provide 24-hour monitoring to measure the impact of its cut-and-cover tunnel construction along an 860 m (2,800 ft) stretch of Network Rail and DLR track. The monitoring was needed to reliably detect movement and enable project teams to avoid the possibility of compromising passenger safety or project schedules. Morgan Sindall assigned Chief Land Surveyor Nick Giles to handle surveying and monitoring on the project. The requirements for the monitoring system were clear: It needed to be robust, reliable and repeatable to provide total confidence for those depending on it. Working with Monitoring Surveyor Pawel Owsianka, Giles developed a unique two-pronged approach to provide the required confidence. An optical system using total stations and monitoring software would monitor horizontal displacement. Simultaneously, several hundred wireless tilt meters attached directly to the track would monitor cant and twist. The two systems could provide constant checks for each other while reducing the number of trackside optical instruments. To provide optical monitoring, Giles selected 10 Trimble S8 total stations equipped with Trimble VISION™ technology. The instruments were installed at regular intervals along Network Rail and DLR tracks and controlled by Trimble 4D Control™ software (T4D) running on a central server. The team attached small prism targets directly to the tracks at 3-m (10-ft) intervals. Each total station had line-of-sight to up to 60 of the rail-mounted prisms. Providing Flexibility and Consistency The core of the monitoring system was in the T4D software, which the team used to create customized operation and analyses, including remotely managing the 10 total stations, all measurement cycles and communications. The system provided 24-hour coverage using a pre- programmed hourly cycle. Each instrument's cycle began with readings to fixed reference targets before measuring to the prisms attached to the rails. The T4D software Delivering the Three Rs of Monitoring A massive infrastructure project uses geospatial technologies to streamline essential construction processes technology&more technology&more technology&more

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