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Mainstreaming surveying, layout work
National contractor Walsh Construction bought Trimble Tablets to go paperless while placing concrete for runway expansion at Chicago's O'Hare International Airport. Photos: Joe Nasvik
3D laser scanners. Able to shoot millions of points in every scan, the most expensive and technically sophisticated surveying tool. Imagine using a conventional total station or theodolite to lay out 10 or 15 points for a project. Now imagine setting up a 3D laser scanner, which looks very much like a robotic total station, and recording a million points in a few minutes. With this data, you can generate an infinite amount of information: locate any number of points needed, record information on a site to create CAD drawings, create as-built drawings, or generate accurate records of construction progress to use when job conflicts arise. Several large general contractors, as well as a few subcontractors, own these.
Once regarded as leading edge, robotic total stations are becoming increasingly common because unlike their predecessor — the total station — only one person is needed to plot points. An operator can stand at the instrument to shoot points and elevations for developing site information to help generate CAD drawings, saving time and obtaining information that might otherwise be dangerous to collect. These instruments also direct excavators and concrete placing equipment that require 3D contours. Total stations cost much less, but require two people to operate: one at the instrument and one at the rod.
Digital levels can be extremely accurate across long distances. They gather very precise elevations over long, level routes. Surveyors often use a rod with barcode lines that the level reads to determine elevation. Sometimes the rods used have barcodes instead of numbers, so the instrument reads the barcode to determine elevation.
Laser levels remain the construction industry's workhorse; just about every contractor uses them to set elevations or to guide equipment. Newer models automatically level themselves, are easier and faster to use, and are less expensive than earlier models.
Especially good for inside buildings or low-light conditions where the laser beam can easily be seen, small laser level systems establish level automatically and provide colored laser beams to help users lay out level, plumb, and square. Add a remote sensor to lock on the beam in bright light or outside conditions, and you also can easily plot points accurately up to about 100 feet. Inexpensive compared to other instruments, they're used for laying out floor tile, ceiling panels, or smaller forming applications.
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.
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