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Step 2: Turn the theodolite to Face Right, and
collimate the crosshair center in the collimator
until it is clear. Press OK to proceed to next step.
Step 3: The index difference will be shown. Press
OK to confirm to calibrate. Caution: If the
difference is too big, it will suggest resetting the
i angle. Press OK to continue, or Back to return
to calibrate again.
Tips: Repeat the calibration of i angle according
to 3 steps above if necessary.
9.2 Correction of Additive Constant
Caution: Do not change the constant if
unnecessary.
The additive constant is relatively stable. We
suggest inspecting it once or twice a year. You
can follow the following steps to do a quick
inspection and correction.
Inspection
Step 1: Set the instrument on a flat ground, mark
it as Point A. Along the vertical crosshair, mark
Point B and C with a space of 50m on the same
line. Set reflectors on Point B and C precisely.
Step 2: Set the temperature and air pressure in
the system, and measure the horizontal
distances of AB and AC accurately.
Step 3: Set the theodolite on Point B and level it
precisely. Measure the horizontal distance of BC
accurately.
Step 4: Now we can get the additive constant
by the following formula.
K=AC-(AB+BC)
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