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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
2) Set the instrument at a point 2 m from point A. Take read-
ings a
and b
2
Leave the telescope sighted on point B.
Calculate
b
' = a
- (a
2
2
If b
' = b
2
no adjustment is necessary.
When b
2
as follows:
. (Fig.8.6)
2
- b
)
1
1
, the horizontal cross-line is normal and
2
' and b
are different, adjust the cross-line
2
and b
1
Fig.8.5
Fig.8.6
- 22 -
. (Fig.8.5)
1
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