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The Future of Layout, Part 2: Rise of the Machines

A Robotic Total Station (RTS) allows layout to be completed by only one persone, rather than the classic layout team, and increases both efficiency and accuracy.

To begin construction layout, a tablet computer is loaded with a 2D drawing or 3D building model. Site survey points from on-site (e.g. a structural pillar) are identified in the model and are used to locate the RTS on the project site and in the model. Once the RTS is located, the person operating the RTS can view the model on the tablet computer in reference to the RTS position and select the points to be laid-out (hanger locations etc.). After selected, the RTS will tell the operator their precise distance from the point (if using a rod) and then guide the user to the point with directions indicating forward/backward or left/right movement. The operator then stakes the point and moves to the next one. A more dvanced RTS feature is Visual Layout, a Trimble patented technology, which marks the layout point with a highly-visible green laser (removing the need for the rod); the operator then only has to follow the laser to each point and mark the location. Basically, the RTS does all the work while the operator follows its laser, marking each point to within a distance of millimeters from the 2D/3D model point. This can be used for the accurate positioning of multiple trades at the same time, ensuring no delays on site.

So, why is this important?

EFFICIENCY The Trimble Robotic Total Station and software utilize the same 2D drawings or 3D building models as other trades involved in the project, making collaboration simpler and quicker. Layout coordinates can be accessed directly from the building model and changes to layout positions can be recorded at the time of layout and documented with reasons and photographs. This speeds-up the process of transferring data between ‘Model/Design/BIM and field’. It also ensures quality control for layout points as data is reported back to the office and all works are done ‘as designed’. Fewer mistakes are made as the RTS works directly from the building model. There are no manual measuring processes involved. Points to be laid out are extremely accurate and their purpose is referenced to the operator via their tablet device. Using the RTS on a job is a paperless process, meaning there is no risk of losing documents or spilling coffee on them. Because of the nature of the design files results are easily shared with other trades. Paperless work sites are becoming increasingly popular, with companies like QUALITY CONTROL Robotic Total Stations can be used as a sophisticated tool in a QA/QC process, both pre and post installation: Contractors using a RTS to site hangers, duct strap, sleeves, anchors etc. before or after concrete pours, have the added security of documented layout data against the original building design or model. These records can be accessed and presented against any claim of inaccuracy or deviation from model or plan. Reports a RTS user can produce include: daily layout summaries, deviation reports, field reports with photos of issues and progress, descriptions and exact coordinates of any issues, checking reports of embeds and anchor bolts prior to steel fabrication to eliminate costly site repairs, item locations, pre-pour, to ensure all are within wall cavities or chase areas where applicable.3 Following layout or installation, construction managers can also use a RTS to verify accuracy. They do this by referencing the as-built dimensional accuracy against the as-designed accuracy, this allows discrepancies to be easily spotted in work completed, hopefully avoiding costly rework. This method of quality control ensures both detailed documentation of works, BIM-to-field capabilities and a process of ensuring consistent similarity to the building design or model. Providing this similarity will avoid clashes and ensure future model reference is always accurate. BIM-TO-FIELD BIM is currently the most used and recognized in the planning and design stage. Companies looking to move their use of BIM strategy and technology into construction and operation etc. will need methods of completing tasks, such as field layout, direct from the model and in a manner integrated with office process. Adding elements to the model and having tools on-site which have a direct link to them are key to the success of a BIM-to-field strategy; an example of this is adding layout points to a model and uploading to a RTS and associated field software. The layout points become coordinates for the RTS and work can be started, recorded and updated in the field. Through this one data repository, and the use of intelligent field products like a Trimble Robotic Total Station, the site is always up-to-date and working as efficiently as possible, reducing delays and speeding-up progress.