Product Manual

61
Instrument Technology
Angle Measuring
Technology
The principles of angle measurement are based on reading an
integrated signal over two opposite areas of the angle sensor
and producing a mean angular value. This eliminates
inaccuracies caused by eccentricity and graduation.
In addition, the angle measurement system compensates for
the following automatic corrections:
• Instrument mislevelment (deviation of the plumb axis).
• Horizontal and vertical collimation error.
• Trunnion axis tilt. See Correction for Trunnion Axis Tilt on
page 62.
Correction for Mislevelment
The instrument automatically corrects for mislevelments up
to ±6 ’.
The instrument warns the operator immediately of any
mislevelments in excess of ±6 ’(±0.11 grads).
The instrument also utilizes SurePoint™ accuracy assurance
technology to automatically correct the pointing of the
telescope for all mislevelment and trunnion axis errors in real
time during operation.
Corrections for the horizontal angle, vertical angle, and slope
distance are calculated in the field application software and
applied to all measurements.
Correction for Collimation Errors
The horizontal collimation error is the deviation of the sighting
axis from its required position at right angles to trunnion axis.
The vertical collimation error is the difference between the
vertical circle zero and the plumb axis of the instrument.
Traditionally, collimation errors were eliminated by observing
angles in both instrument faces. In the FOCUS 50 total station,
a pre-measurement collimation test is performed to
determine the collimation errors. Angular measurements are
observed in both instrument faces, the collimation errors are
calculated, and the respective correction values are stored in
the instrument. The collimation correction values are then
applied to all subsequent angle measurements. Angles
observed in a single face are corrected for collimation errors,