Precise Levelling - Leica NA2 User Manual

Precise levelling

Project:
Height difference of very high
accuracy.
invar levelling staffs.
should not be used, as
refraction close to the ground
can cause errors.
to shelter the instrument to
ensure that the level is
protected from the glare of the
sun.
NA2/NAK2-2.0.0en
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Procedure:
1. Sequence of measurements
is the same as with line
levelling. However, the best
Use the GPM3 parallel
observing length is approx.
plate micrometer and
25m.
2. When reading the staff, turn
the micrometer knob until a
In sloping terrain, the
graduation line is centred
lower part of the staff
between the wedge-shaped
hairs of the reticle.
3. Centimetres are read from
the staff and millimetres from
the micrometer scale.
In sunny weather an
4. Leica invar staffs have two
umbrella should be used
sets of graduations. These
are read alternatively
between foresight and
backsight. This provides two
independent results and
serves as a check.
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Example above:
Staff reading
GPM3 reading =
Height
19
.com
= 77 cm
0.556 cm
= 77.556 cm
Measuring
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