FOCUS 35 TOTAL STATION USER GUIDE
6 –
Instrument Technology
86
Correction for Trunnion Axis
The trunnion axis tilt error is the deviation of the trunnion axis of the telescope from its required
position at right angles to the plumb axis of the instrument.
In the Spectra Precision FOCUS 35 Total Station, perform a pre-measurement trunnion axis tilt test to
determine the trunnion axis tilt error. Angular measurements are observed in both instrument faces,
the trunnion axis tilt error is calculated, and the respective correction value is stored in the
instrument. The trunnion axis tilt correction value is then applied as a correction to the horizontal
angle value.
Carry out a trunnion axis tilt test in the following situations:
•
Whenever the instrument may have been roughly handled during transport.
•
When the ambient temperature differs by more than 10°C (18°F) from the previous collimation
test.
•
Immediately prior to high precision angle measurements in one face.
Trunnion axis
tilt error
