Level vials and leveling thumb screws to make the telescope level and parallel to a horizontal
line of sight.
Optical devices, such as crosshairs in a telescope to sight on a target.
Magnification lenses on the telescope to magnify a target.
Plumb bobs or optical plummets to align the instrument exactly over a selected point.
The surveying instruments that you will become familiar with are the one-minute theodolite, geodimeter
(total station), and levels. These items of equipment are needed to help you determine the angles and
elevations that are required for a construction survey.
a. One-Minute Theodolite. The one-minute theodolite is used to obtain both horizontal and
vertical angles. The theodolite is a compact, lightweight, dustproof optical-reading, directional-type
instrument (see Figure 5-1). It may also be used as a repeating-type instrument for measuring horizontal
angles by using the repeating damp. The scales are readable directly to the nearest minute and may be
illuminated by sunlight or artificial light. The surveying points are observed through the instrument and
the angles read through an optical microscope on horizontal and vertical scales inside the instrument.
There are two versions of this theodolite-the engineer version, which reads directly to one minute (more
commonly known as the T16) and the artillery version, which reads directly to 0.2 mil (more commonly
known as the T2).
EN0591
5-2
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