In the past, surveying firms provided nearly all the layout work for construction projects. This began to change when surveying equipment manufacturers recognized the potential of the contractor market and began to design according to their needs. Prior to that time, software for survey and layout instruments, such as total stations and robotic total stations, were designed for surveyors, which contractors had a hard time understanding. The market trend continues toward contractors buying into sophisticated surveying technologies.
A reason contractors were motivated to move in this direction because 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.
Layout equipment
There are several classes of layout instruments in service today.
3-D laser scanners are the most expensive and technically sophisticated surveying tools. Imagine using a conventional total station or theodolite to layout 10 or 15 points for a project. Now imagine setting up a 3-D 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, such as locate any number of points you might need, record information on a site to create computer-aided design (CAD) drawings, create as-built drawings required by many projects, or generate accurate records of construction progress that can be useful when job conflicts arise. Currently, several large general contractors, as well as a few concrete contractors, own 3-D laser scanners.
Robotic total stations, once regarded as leading edge, are now owned by many contractors because 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 3-D contours.
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.
Total stations are the predessor of robotic total stations. They cost much less to purchase and are widely used by contractors. Like robotic total stations, data collectors provide the information needed for plotting points. Total stations' primary drawback is that two people are needed to operate them: one at the instrument and one at the rod.
Digital levels still are used primarily by surveyors. They gather very precise elevations over long, level routes. Sometimes the rods used have barcodes instead of numbers, so the instrument reads the barcode to determine elevation.
Laser levels remain the workhorse of the construction industry and 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.
Small laser level products establish level automatically and provide colored laser beams to help you layout level, plumb, and square. They are especially good for inside buildings or low-light conditions where the laser beam can easily be seen. With the addition of a remote sensor to lock on the beam in bright light or outside conditions, you also can easily plot points accurately up to about 100 feet. These instruments are inexpensive compared to other instruments and are used for laying out floor tile, ceiling panels, or smaller forming applications.
