Nikon DTM-502 Series Instruction Manual page 163

4-3. Optical Plummet
(Aligning the optical axis of the plummet with the vertical axis of the instrument)
1) Checking
(1) Place the instrument on the tripod. (No
leveling is necessary.)
(2) Place a thick sheet of paper marked
with an X on the ground just below
the instrument.
(3) Looking through the optical plummet,
adjust the leveling screws to bring the
image of the X to the center of the
reticle mark
(4) Rotate the alidade approximately
180°.
(5) If the marked image is seen in the
same position in the center of the
reticle mark, no adjustment will be
required.
If any displacement is detected, such
as that shown in Figure, refer to the
adjustment procedure below.
2) Adjustment
(1) Using the supplied hexagonal wrench,
turn the adjustment screws to align the
4
X marking with position P, as shown
in the Figure. Point P is the center
point of the line connecting the X
marking and the center of the reticle
mark .
(2) Recheck, following the checking steps
(3) to (5).
4-2
.