||It has been suggested that this article be merged with Laser Machine Control. (Discuss) Proposed since August 2013.|
In surveying and construction, the laser level is a control tool consisting of a laser beam projector that can be affixed to a tripod, which is leveled according to the accuracy of the device and which projects a fixed red or green beam along the horizontal and/or vertical axis. A rotary laser level is a more advanced laser level in that it spins the beam of light fast enough to give the effect of a complete 360 degree horizontal or vertical plane, thus illuminating not just a fixed line, but a horizontal plane. The laser beam projector employs a rotating head with a mirror for sweeping the laser beam about a vertical axis. If the mirror is not self-leveling, it is provided with visually readable level vials and manually adjustable screws for orienting the projector. A staff carried by the operator is equipped with a movable sensor, which can detect the laser beam and gives a signal when the sensor is in line with the beam (usually an audible beep). The position of the sensor on the graduated staff, also known as a Grade Rod, or Story Pole, allows comparison of elevations between different points on the terrain. Most laser levels are used in the construction industry and can be explained here, http://www.engineersupply.com/Construction-Laser-Levels-Explained.aspx.
A tower-mounted laser level is used in combination with a sensor on a wheel tractor-scraper in the process of land laser leveling to bring land (for example, an agricultural field) to near-flatness with a slight grade for drainage.
The concept of a laser level has been around since at least the early 1970s, the original spinning-mirror design laser plane and line level was patented by the late 1980s, and the compact lens-based laser line level (as produced by many tool manufacturers today) was patented in the late 1990s.
Originally, the work required two persons to complete, one to control the laser and one carrying the staff or grade rod. More recently, technology has evolved to where one person can control the laser with a smart device from 1,200 feet away and complete the job, like the Smart Rotary from NWi as seen here http://www.nwismart.com/Smart_NRL800HT.html.