From the beginning of time, land surveying has been an essential part of civilization. First used to accurately divide land for the purpose of taxation, today, it is used in the construction industry to map and stake-out land. Since 1571, the theodolite—an instrument that looks like a small telescope mounted on a tripod—most commonly was used, until the total station was invented in the 1970s. There have been many advancements since. Understanding your job requirements will help determine what type of instrument to use.
What accuracy is needed?
Laser levels, now the standard in the industry, generate a laser beam, either as a static ray or through a rotating lens. It then is mounted and leveled on a horizontal axis to indicate all points of common elevation up to rated projection length of the instrument. All lasers have accuracy tolerances based on its design, range, and distance involved. Self-leveling lasers automatically find and maintain level within a specified range. Ken Shawler, segment manager of layout at Trimble, Sunnyvale, Calif., believes self-leveling lasers are more common today, as they provide more accuracy, are easier to operate, and cost less then they did several years ago.
Most self-leveling lasers offer a height alert warning so that the user knows that the instrument height has been changed and the user should check the setup.
Manual laser levels, on the other hand, typically are lower in cost. If used for a short period of time and for short distances, a manual laser lever is probably the route to take. Shawler explains that if the manual laser level were used for an extended period of time, the laser level would need to be frequently checked for accuracy. If an adjustment were needed, the user would need to rebench on the elevation hub. The time to continually check the accuracy of the instrument with previously set height measurements makes the additional cost of a self-leveling laser worth the investment.
What angles are you measuring?
Different types of laser levels can be used for different applications. According to Jason Becker, marketing manager for Stabila Inc., South Elgin, Ill., “It all depends on the application—whether it is indoors or outdoors,—and the distance of the measurement.”
Slope lasers allow the user to dial in the exact slope percentage between two points. Shawler explains that single-slope lasers can have a slope percentage entered in one axis while a dual-slope laser allows the user to enter slope in two axis, with the second axis commonly referred to as a cross-axis. This is the axis that is perpendicular to the main or primary slope axis.
Other options include rotating or straight-line laser levels. Straight-line lasers, or pointer lasers, are used for interior applications to establish a straight line between two points, create plumb points, and making sure that lines are at 90-degree angles.
Rotating lasers, according to Becker, work best with distances of 50 feet and longer. Used in conjunction with a laser detector, they are ideal for exterior applications because they offer high accuracy, long range, and the ability to quickly check level and elevation with one person.
Becker believes the most important advancement over the past couple of years is the durability of the equipment. Shawler adds, “The biggest advancement is not in the instrument itself, but in the software used with the instrument.”
Sharon J. Rehara