Using a laser system is faster than optical grade leveling and requires fewer workers. To use it correctly, though, you need to understand how the system works and how to keep it in calibration.
Laser leveling requires a transmitter, receiver, tripod, rod that attaches to the receiver, and only one worker. Photocells in the receiver sense the laser beam, and sight or sound signals alert the worker to the above-grade, below-grade, or on-grade position of the receiver. Transmitters project a laser plane that may range from 300 to 2,000 feet in diameter. Most transmitters need to be rough leveled to within the tolerances used on conventional optical leveling equipment since the transmitter is self-leveling within this range. Power sources range from alkaline batteries, to rechargeable NiCad batteries, to a 12-volt car battery.
LASER ACCURACY AND TOLERANCES
As with any measuring device, lasers are not perfectly accurate. The transmitter and receiver both have permitted variations (tolerances) on their leveling accuracy. The laser beam radiates from the transmitter as a vertical arc that increases in width the farther the beam travels. The beam width is small but can still change the elevation reading since the receiver may pick up the top or the bottom of the beam.