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26. Check and Adjustment
26.1 The Instrument Constant
Ⅰ. Check
It is suggested to observe and compare the instrument with a testing baseline which is set
on stable ground with a particular accuracy, though error is not generally included in the
instrument constant. If the testing line is unavailable, you can select a flat place and set up
the instrument and a target in the same height.
1. Select a point B on the approximately horizontal line AC with about 100 meters long.
Measure the distances of lines AB , AC and BC .
2. The instrument constant can be calculated;
instrument constant =AB+BC-AC
3. Repeat steps 1 and 2 ten times, and get the average value for instrument const, if the
average value is within ±3mm, adjustment is unnecessary.
4. If the difference is over ±3mm after the preceding operations, it is necessary to reset
the instrument constant .
Ⅱ. Adjustment
If the instrument const is necessary to reset, please contact FOIF service representative to
perform that.
A B C
AB BC
AC