Figure 2-20. Centering with optical plummet.

TM 5-6675-312-14

STEP 1.

Install tripod (refer to figure 2-9).

STEP 2.

Center theodolite and tribrach assembly using plumbbob (refer to figure 2-19).

STEP 3.

Remove plumbob assembly by rotating bayonet socket one-quarter turn counter-

clockwise and pulling down.

STEP 4.

Level theodolite and tribrach assembly (refer to figure 2-21).

STEP 5.

Turn optical plummet eyepiece to focus cross hairs.

STEP 6.

Pull out or push in optical plummet eyepiece to focus station point.

STEP 7.

Loosen central fixing screw and move theodolite and tribrach assembly until cross

hairs coincide with station point. Do not rotate theodolite and tribrach assembly

in relation to tripod or level will be disturbed.

Tighten central fixing screw.

STEP 8.

Relevel theodolite (refer to figure 2-21).

STEP 9.

Repeat steps 4, 5, and 6.

STEP 10.

Release horizontal clamp, rotate theodolite 1800

STEP 11.

Loosen central fixing screw and move theodolite to take up one-half

of the deviation.

STEP 12.

Relevel theodolite (refer to figure 2-21).

STEP 13.

Centering is correct when, for a full rotation (3600) of the theodolite, the

cross hairs remain on the station point.

5-6675-31 2-14/2-20

Figure 2-20. Centering with optical plummet.

2-33

Index