the
theodolite
with
the
foot
screws.
t u r n i n g foot screws B and C an equal distance in
(b) C h e c k t h e a d j u s t m e n t o f t h e c i r c u l a r
o p p o s i t e directions. When the plate level bubble is
level by completing the exact leveling of the
c e n t e r e d , turn the instrument 90 , centering the
theodolite with the
plate level (6, fig. 2-3) as
plate level over foot screw A. Adjust this foot screw,
described in (4) (a)
below. If the bubble is not
if required, to again center the plate level bubble.
centered in the black
reference circle of the circular
Now turn the instrument 180 . If the bubble
level vial window,
the circular level is out of
does not stay centered in the position, the plate level
alinement.
i s out of alinement.
(c) Mark the position of the bubble on the
level vial window with a grease pencil or other
(b) Leave the instrument in the last-named
p o s i t i o n . Correct one-half of the bubble error by
suitable marking device for glass. Remove the
a d j u s t i n g foot screw A.
theodolite from the tripod. Place the instrument on
a steady support so that the circular level housing
( c ) Insert an adjusting pin (4, fig. 2-7) in
t h e plate level adjusting screw (9, fig. 1-3 ), and
projects over the edge of the support. This will
c o r r e c t the other half of the error by moving the
provide access to the three circular level adjusting
adjusting
screw.
screws in the base of the level housing. Adjust the
level of the instrument with suitable shim material
(d) R e p e a t t h e o b s e r v i n g p r o c e d u r e s i n
( a ) t h r o u g h ( c ) , as may be required, until the
u n t i l the circular level bubble is alined with the
plate level bubble remains centered in any position
temporary reference mark placed on the vial
t o which the upper part of the theodolite may be
w i n d o w . Now adjust the three springloaded screws
turned.
i n the base of the circular level housing until the
b u b b l e is centered in the regular black circle.
(5) O p t i c a l
plumb.
(a) With the instrument securely mounted
NOTE
o n the tripod, carefully center and level it over a
The
three
adjusting
screws
should
not
be
s t a t i o n point (5, fig. 2-4) by using the plumb bob
tightened all the way. All of them should "float"
( 4 ) and plate level (6, fig. 2-3). Carefully remove
the level on the adjusting springs.
the plumb bob and observe if the station point
R e m o v e the temporary reference mark previously
r e m a i n s exactly in the center of the optical plumb
placed on the level vial window. Install the
reticle.
theodolite on the tripod and bring it to exact level
(b) I f t h e s t a t i o n p o i n t d o e s n o t r e m a i n
w i t h the plate level. Observe the position of the
c e n t e r e d in the optical plumb reticle, bring it to
circular level bubble. If it is centered in the black
c e n t e r by means of two adjusting screws. Remove
c i r c l e , the circular level is correctly alined. If the
the two cover screws (6, fig. 1-1), to the right and
bubble is not centered, repeat the above procedures
l e f t of the optical plumb eyepiece and adjust the
u n t i l the level bubble is correctly centered.
inner screws to center the optical plumb reticle on
(4) P l a t e l e v e l .
the station point. Remember that the adjusting
(a) L e v e l t h e t h e o d o l i t e e x a c t l y w i t h t h e
screws move the reticle in the opposite direction of
plate level (6, fig. 2-3 ). Loosen the horizontal clamp
the travel of the adjusting screws. Replace the cover
s c r e w (8, fig. 1-3). Turn the instrument until the
s c r e w s when the adjustment is completed.
longitudinal axis of the plate level is parallel to any
(6) V e r t i c a l c o l l i m a t i o n l e v e l m i r r o r . T h e
two of the foot screws, such as B and C, figure 2-8
c o l l i m a t i o n level mirror assembly (1, fig. 1-2) must
Adjust the position of the plate level bubble by
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