1 NOMENCLATURE AND FUNCTIONS
1-6
It is clear from the table that dual axis compensation has the most benefit when
the elevation of the target is greater then 30
°
and the axis is tilted more than
10". The entries indicated in bold in the table show, in fact, that for many
common surveying applications i.e. target elevation <30
°
and axis error <10",
virtually no correction would be required. Dual axis compensation is especially
suited then for applications where the sights are very steep.
Even though the compensators can correct horizontal angles for vertical axis
errors,
it is still important to use care in setting up the instrument.
Centering error, for instance, cannot be corrected by the compensators. If the
vertical axis is tilted by 1' with the instrument 1.4 meters above the ground, a
centering error of approx. 0.4mm will result. The maximum effect of this error at
10m is about 8" of horizontal angle error.
In order to maintain the increased accuracy possible through dual axis
compensation, it is necessary to keep the compensators in proper adjustment.The
compensators must agree with the actual level condition of the instrument. Through
various environmental stresses, the agreement between the level condition sensed
by the compensators and the true level condition of the instrument may be
disturbed. In order to reestablish the correct relationship between the compensator
and the true level condition of the instrument, it is necessary to carry out the
vertical indexing procedure listed on chapter 8.4 "Adjustment of Compensation
Systematic Error of Instrument". This adjustment will both reset the vertical index
(cause a indirect zenith reading to the same elevation to equal 360
°
) and
zero the level reference for the horizontal compensator. While correct vertical
angles can be obtained by averaging direct and indirect reading even when the
index is improperly adjusted, the same is not true for horizontal angles. Since the
vertical axis error is fixed for a given setup, its effect cannot be removed by
averaging two readings.
For this reason, it is extremely important to maintain the vertical indexing
adjustment to insure proper correction of the horizontal angles.
Summary of Contents for GTS-710 Series
Page 1: ...GTS 710 GTS 710 GTS 711 GTS 712 GTS 713...
Page 9: ...1 NOMENCLATURE AND FUNCTIONS 1 9 1 1 1 BT 30Q Lower horizontal clamp Point guide type only 4A...
Page 76: ...11 CORRECTION FOR REFRACTION AND EARTH CURVATURE 11 68 Temprerature C Temprerature F...
Page 77: ...11 CORRECTION FOR REFRACTION AND EARTH CURVATURE 11 69 Temprerature F...
