In the past, surveying firms provided nearly all the layout work for projects. This began to change when equipment manufacturers recognized the potential of the contracting and public markets and began to design according to the needs of these potential consumers. Before that time, software for survey and layout instruments was difficult for anyone other than a licensed surveyor to understand.
Contractors continue buying into sophisticated surveying technologies, which gives public agencies more options when outsourcing survey and layout work. As equipment becomes more user-friendly, more contractors are able to offer these services. This, in turn, could translate into more and less-expensive alternatives for your department or agency.
One reason contractors were motivated to move in this direction was that surveyor firms had large work backlogs that resulted in job delays and lost contractor time. Today many construction companies have their own survey divisions to conduct their layout work.
The size of the company and the type of project have a lot to do with how a contractor deals with surveying, layout, and machine control.
Here are two examples.
Correcting plan errors
As one of the largest construction companies in the nation that self-performs concrete work, Chicago's Walsh Construction assigns teams to projects, such as the runway expansion at the Chicago Department of Aviation's O'Hare International Airport, to provide layout and surveying.
Andrew Stover, a survey manager for Walsh, says the company provides all the construction layout work for the project, which includes support to subcontractors. They also generate and maintain all the as-built drawing requirements of Walsh contracts. “In a job of this size, there are many plan errors, so a major responsibility for us is finding them and making corrections, and sometimes offering other solutions,” he says.
Walsh places all runway concrete with a string-less paver guided by three robotic total stations. The survey team provides the elevations and manages the movement and control of the stations for the paver. They also supervise and load CAD files into the survey equipment to control earthmoving equipment, which includes a 3D motor-grader controlled by a robotic total station.
Walsh believes in keeping up with the latest technology developments to maintain a competitive edge. The company's survey group, for example, bought Trimble Tablets , a handheld computer that incorporates a cellular modem, laptop, GPS, and controller, to go paperless on projects. All CAD drawings can be loaded into the instrument and updated in real time via the Web or by downloading information from a computer. Each tablet also provides direction to any Trimble surveying tool used.
Stover says the paper savings alone on a project this size can exceed $100,000 if the entire project is paperless. In addition to the tablet data collectors, Stover and his team use 3D laser scanners, robotic total stations, digital levels, GPS surveying instruments, and laser levels.
|BRINGING IT ALL TOGETHER|
Data collectors, which are purchased separately, are the support tools that provide all the information for guiding GPS surveying instruments and the equipment pictured here.
They represent the very latest in technology and increasingly are easier to learn to use. Current high-end generations allow users to plug into a wide range of surveying instruments. As small computers, they can upload CAD drawings to direct surveying instruments to help crews plot points, store information, and control machines. They also record data from a jobsite to help build CAD drawings.
GPS surveying instruments establish location by receiving measurements from satellites and communicating with a known reference station. GPS units are used for plotting points and locations or for providing direction to equipment.