The transit (fig. 11-6) is often called the
universal survey instrument because of its uses. It
may be used for measuring horizontal angles and
directions, vertical angles, and differences in
elevations; for prolonging straight lines; and for
measuring distances by stadia. Although transits of
various manufacturers differ in appearance, they are
alike in their essential parts and operations.
The engineers transit contains several hundred
parts. For-descriptive purposes, these parts may be
grouped into three assemblies: the leveling head
assembly, the lower plate assembly, and the upper
many plate or alidade assembly (fig. 11-7).
Leveling Head Assembly
The leveling head of the transit normally is the
four-screw type, constructed so the instrument can be
shifted on the foot plate for centering over a marked
point on the ground.
Lower Plate Assembly
The lower plate assembly of the transit consists
of a hollow spindle that is perpendicular to the
Figure 11-6.-An engineers transit.