but slightly larger than, the 1-min theodolite. The
WILD theodolite shown in figure 11-20 is
compact, lightweight, dustproof, optical reading,
and tripod-mounted. It is one spindle, one plate
level, a circular level, horizontal and vertical
circles read by an optical microscope directly to
1 sec (0.002 roil), clamping and tangent screws for
controlling the motion, and a leveling head with
three foot screws. The circles are read using the
coincidence method rather than the direct method.
There is an inverter knob for reading the
horizontal and vertical circles independently. The
essential parts of a l-see theodolite are very
similar to that of the 1-min theodolite, includ-
ing the horizontal and vertical motions, the
levels, the telescope,
the tribrach, and the
optical system shown in figure 11-21. The
main difference between the two types, besides
precision, is the manner in which the circles are
read.
The CIRCLE to be viewed in the 1-see
theodolite is selected by turning the inverter
knob on the right standard. The field of the
circle-reading microscope shows the image of the
Figure 11-21.-Circle-reading optical system.
11-25
