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12
3.2 Line of Sight
• Set the instrument at a point
halfway between point A and B,
spaced about 30-40m apart.
Take the readings of staff A and
B as “a1” and “b1” (fig. 12)
Calculate the real height
difference:
∆
H = a1-b1
• Adjust the rest half of error by using
the allen key (fig. 11).
• Repeat the above steps until the
bubble remains centered when the
telescope is pointed at any direction.
Fig. 11
Fig. 12