This invention relates to a transmitter for providing a non-planar reference cone of electromagnetic radiation.
Electromagnetic radiation has been applied in the construction industry to provide a reference for leveling and alignment. It has been found particularly useful because it propagates along a straight line, provides a continuous reference over time, and can be provided in a portable unit. In many applications where two or more workers were required with prior aligning techniques, only one man is now necessary to perform the same task with equal or greater accuracy.
It has often been desirable to have an omni-directional leveling or aligning capability. For example, in hanging a ceiling, installing a computer floor, or in grading a field, it has been desirable to have each point in the ceiling, floor or field lie in a common, horizontal plane.
An omni-directional field of radiation can be generated in a plane to provide an omni-directional aligning capability. However, for leveling, the plane must itself be extremely close to level. This is because any error in the level of the plane is amplified by a factor proportional to the distance from the transmitter of the plane. For a reference measurement taken 100 feet from the transmitter, an error in the orientation of the plane of only one degree from horizontal results in the reference measurement being 21 inches off from the desired grade, which is usually not acceptable.
Moreover, it is not economically possible to meticulously level the radiation plane at the construction site to provide the desired degree of accuracy with respect to horizontal every different time the transmitter is used. Also, particularly with alignment applications of long distances, an alignment plane is not suitable. Because the earth's surface is curved, an alignment plane can be inaccurate and not appropriate for alignment purposes. Consider the use of a plane of light as an alignment tool at 1,000 ft. Due to the earth's curvature, the alignment error will be 0.284 inches. Instead of creating a horizontal plane, a descending reference cone of electromagnetic energy which substantially follows the earth's curvature may be desirable. Therefore, a need exists for a transmitter which can be quickly and easily set up at a construction site and which will produce a non-planar reference cone which provides alignment and substantially follows the curvature of the earth to make alignment even more accurate than reference planes.