Johnson 40-6910 Manuel D'instructions page 11

7443H-All_Manuals 10/24/13 4:09 PM Page 11
5.7 Stadia Distance Measuring
Distance measuring can be done using the stadia hairs of the reticle.
The distance between the upper stadia hair and the lower stadia hair is
set at a 1:100 ration. So if the difference is 1 foot, the person holding
the grade rod is 100 feet away from the instrument.
5.8 Measuring Horizontal Angles
To measure or lay out an angle, set the instrument over a point and
level it up. Use a plumb bob with about six feet of string. Attach the
plumb bob string to the hook under the instrument by means of a large
loop fastened by a slipknot and adjust the plumb bob until it is clear of
the ground point. By shifting the entire instrument, set the tripod
(keeping tripod head as level as possible by estimation) so that the
plumb bob appears to be over the ground point. Next, press the legs of
the tripod into the ground and lower the plumb bob until its point is
about one-quarter inch above the point on the ground. The final
centering of the instrument can be made by loosening the tripod center
bolt and slowly shift the instrument until the plumb bob is directly over
the point on the ground. Then retighten the tripod center bolt and
re-level the instrument.
To measure horizontal angles, such as FIG (Fig. 8), center and level your
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