7. CHECKS AND ADJUSTMENTS
19
1
Set the instrument halfway between two points, A
and B, 30 to 50m apart. Take readings a
1
and b
1
.
2
Set the instrument at a point 2 m from point A.
Take readings a
2
and b
2
.
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:
7.3 RETICLE CROSS-LINE (LINE OF SIGHT)