Sokkia im-101 Operator's Manual page 206

9. Rotate the top of the instrument through 180° until the
displayed horizontal angle is 180° ±1' and [OK] is
displayed.
10.Wait a few seconds for the display to stabilize, then store
the automatically compensated angles X1 and Y1.
Press [YES] to store tilt angles X1 and Y1. The new
correction constant is displayed.
11. Confirm that the values are in the adjustment range.
If both correction constant are within the range ±180, select
[YES] to renew the correction angle. <Instr. const> is
restored. Continue to step 12.
If the values exceed the adjustment range, select [NO] to
cancel the adjustment and restore <Instr. const>. Contact
your local dealer to perform the adjustment.
PROCEDURE Rechecking
12.Press {ENT} at <Instr. const>.
13.Wait a few seconds for the display to stabilize, then read the
automatically compensated angles X3 and Y3.
14.Rotate the top of the instrument through 180°.
15.Wait a few seconds for the display to stabilize, then read the
automatically compensated angles X4 and Y4.
16.In this state, the following offset values (tilt zero point error)
are calculated.
Xoffset = (X3+X4)/2
Yoffset = (Y3+Y4)/2
When both offset values fall within the range ±20",
adjustment is completed.
Press {ESC} to return to <Instr. const>.
If one of the offset values (Xoffset, Yoffset) exceeds ±20",
repeat the check and adjustment procedures from the
beginning. If the difference continues to exceed ±20" after
repeating the check 2 or 3 times, have your local dealer
perform the adjustment.
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35. CHECKS AND ADJUSTMENTS
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