Establishing control points
Lindblad Construction Company of Joliet Inc. in Joliet, Ill., sometimes employs a professional surveying firm to provide at least two control points before beginning a project when no established points exist on a site. A few years ago, the general contractor purchased its first total station unit followed by a robotic total station the next year, and is considering buying another one.
“We were skeptical at first so we rented one and tested its accuracy by conventional means and quickly discovered the benefits, and then bought one,” says Vice President Mark Stadalsky.
Three employees are trained to use the layout instruments to set points for structures, piers, footings, and locate anchor bolts — a major challenge in their business. Lindblad markets itself on its ability to precisely locate anchor bolts for machines and equipment. The general contractor also often sets control points for subcontractors as well.Working with a licensed surveyor
It's expensive to buy a 3D laser scanner and provide the necessary staff training. Contractors that can't afford this hire a company like SEC Group Inc., an HR Green Co. , in McHenry, Ill.
SEC Group uses 3D laser scanners, robotic total stations, laser levels, and GPS systems to establish control points, calculate excavation volumes, stake out points for mass grading, plot points for underground structures, lay out curbs and pavements, locate columns, perform anchor bolt surveys, and provide spot foundation surveys required by some municipalities. The firm also collects and interprets data for studies or record drawings and, depending on state law governing surveying and construction layout, performs some survey services that require licensed surveyors.
Mike Fischer, group leader of surveying, says the firm makes it a point to respond to client calls within 48 hours.
Although the relationship between contractors and surveyors is changing because of the influx of easier-to-use equipment, some functions are best handled by professional surveying consultants. A word of warning: Don't automatically assume that contractors' surveying divisions, which rarely employ licensed surveyors, can completely replace the industry's more experienced counterparts.
— Nasvik is senior editor of CONCRETE CONSTRUCTIONS, a sister magazine of PUBLIC WORKS. A longer version of this article is available here.