Even after adjustment of the ATRplus, the crosshairs may not be positioned
exactly on the centre of the prism after an ATRplus measurement has been
completed. This outcome is a normal effect. To speed up the ATRplus measure-
ment, the telescope is normally not positioned exactly on the centre of the
prism. These small deviations/ATRplus offsets, are calculated individually for
each measurement and corrected electronically. The horizontal and vertical
angles are corrected twice: first by the determined ATRplus errors for Hz and V,
and then by the individual small deviations of the current aiming.
22.7.2
Details on Instrument Errors
Instrument errors occur, if the standing axis, the tilting axis and the line of
sight are not precisely perpendicular to each other.
008365_001
a
a
b
d
c
a
Tilting axis
b
Line perpendicular to tilting
axis
c
Horizontal collimation error
(c), also called line-of-sight
error
d
Line of sight
The Horizontal collimation error (c) is also called line-of-sight error. The error is
caused by the deviation between the optical line of sight, which means the
direction in which the crosshairs points and the line perpendicular to the tilting
axis. This error affects all horizontal readings and increases with steep sight-
ings.
☞
Definition
Horizontal collimation
error (c)
264
Settings - TS instrument
