18-7
18 CHECKS AND ADJUSTMENTS
4) Remove the optical plummet reticle cover.
5) Turn the 4 adjusting screws of the optical plummet to adjust
the remaining half of the deviation using hexagonal wrench
(1.3 mm) as shown below.
When the survey point is on the lower (upper) part of the
illustration:
Loosen the upper (lower) adjusting screw slightly, and
tighten the upper (lower) adjusting screw the same amount
to move the survey point to a point directly under the center
of the optical plummet.
(It will move to the line in the figure on the right.)
If the survey point is on the solid line (dotted line):
Loosen the right (left) adjusting screw slightly and, tighten
the left (right) adjusting screw by the same amount to move
the survey point to a point in the center of the optical
plummet.
6) Check to make sure that the survey point remains centered
on the reticle even if the upper part of the instrument is
rotated.
If necessary, perform the adjustment again.
7) Replace the optical plummet reticle cover by matching the
grooves on the cover with the grooves on the optical
plummet.
18.6 Additive Distance Constant
The additive distance constant K of the GM is adjusted to 0 before delivery. Although it almost never
deviates, use a baseline with a known distance precision to check that the additive distance constant K
is close to 0 several times a year and whenever the values measured by the instrument begin to
deviate by a consistent amount. Perform these checks as follows.
•
Errors in setting up the instrument and reflective prism or in sighting the target will influence the
additive distance constant. Be extremely careful to prevent such errors when performing these
procedures.
•
Set up so that the instrument height and the target height are identical. If a flat place is not
available, use an automatic level to make sure the heights are identical.
Cover
Adjusting screw
Groove
