Sokkia B20, Operator'S Manual, Page: 52 / 60

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8.3 RETICLE CROSS-LINE (LINE OF SIGHT)
1) Set the instrument halfway between two points, A and B,
30 to 50m apart. Take readings a
1
and b
1
. (Fig.8.5)
Fig.8.5
2) Set the instrument at a point 2 m from point A. Take read-
ings a
2
and b
2
. (Fig.8.6)
Fig.8.6
Leave the telescope sighted on point B.
Calculate
b
2
’ = a
2
- (a
1
- b
1
)
If b
2
’ = b
2
, the horizontal cross-line is normal and
no adjustment is necessary.
When b
2
’ and b
2
are different, adjust the cross-line
as follows: