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Tilting-axis error (a)
Vertical index error (i)
Settings - TS instrument
b
a
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The deviation between the mechanical tilting axis and the line perpendicular to
the vertical axis causes the tilting-axis error (a).
This error affects horizontal angles. The effect is zero in the horizon and
increases with steep sights. To determine this error, it is necessary to point to
a target located significantly below or above the horizontal plane. To avoid
influences from the horizontal collimation error (c), the horizontal collimation
has to be determined prior to the tilting-axis error.
a
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A vertical index error (i) exists, if the 0° mark of the vertical circle reading does
not coincide with the mechanical vertical axis of the instrument, also called
standing axis.
a
Axis perpendicular to the ver-
tical axis
d
c
b
Mechanical vertical axis of the
instrument, also called stand-
ing axis
c
Tilting-axis error
d
Tilting axis
d
b
c
a
b
c
d
Mechanical vertical axis of the
instrument, also called standing
axis
Axis perpendicular to the vertical
axis
V = 90° reading in a specific face
Vertical index error
265
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