Topcon GTS-823A - Manual (Page 26)

2-2
2 PREPARATION FOR MEASUREMENT
2.2 Setting Instrument Up For Measurement
Mount the instrument to the tripod. Level and center the instrument precisely to insure the best
performance. Use tripods with a tripod screw of 5/8 in. diameter and 11 threads per inch, such as the
Type E TOPCON wide- frame wooden tripod.
1. Setting up the Tripod
First, extend the extension legs to suitable lengths
and tighten the screws on their midsections.
2. Attaching the Instrument on the Tripod
Head
Place the instrument carefully on the tripod head
and slide the instrument by loosening the tripod
screw. If the plumb bob is positioned right over the
center of the point, slightly tighten the tripod
screw.
3. Roughly Leveling the Instrument by Using the Circular
Level
1 Turn the leveling screws A and B to move the
bubble in the circular level. The bubble is now
located on a line perpendicular to a line
running through the centers of the two leveling
screws being adjusted.
2 Turn the leveling screw C to bring the bubble
to the center of the circular level.
4. Centering by Using the Plate Level
1
Rotate the instrument horizontally by using
the Horizontal motion/clamp screw and place
the plate level parallel with the line connecting
leveling screws A and B, and then bring the
bubble to the center of the plate level by
turning leveling screws A and B.
2 Rotate the instrument 90° (100g) around its
vertical axis and turn the remaining leveling
screw or C to center the bubble once more.
3 Repeat the procedures 1 and 2 for each 90°
(100g) rotation of the instrument and check
whether the bubble is correctly centered for all
four points.
5. Centering by Using the Optical Plummet
Telescope
Adjust the eyepiece of the optical plummet
telescope to your eyesight.
Slide the instrument by loosening the tripod
screw, place the point on the center mark, and
then tighten the tripod screw. Sliding the
instrument carefully not to rotate that allows you
to get the least dislocation of the bubble.
6. Completely Leveling the Instrument
Leveling the instrument precisely in a similar way
to 4. Rotate the instrument and check to see that
the bubble is in the center of the plate level
regardless of telescope direction, then tighten the
tripod screw hard.
Leveling
screw A
Leveling screw C
Leveling screw B
Leveling
screw A
Leveling
screw B
90
Leveling screw C
Point
Center mark
Reference: Leveling and Centering the Instrument