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In sloping terrain, the lower part of the staff should not be used, as refraction
close to the ground can cause errors.
In sunny weather an umbrella should be used to shelter the instrument to
ensure that the level is protected from the glare of the sun.
Procedure:
1. Sequence of measurements is the same as with normal height leveling
measurement.
2. When reading the staff, turn the micrometer knob until a graduation line is
centered between the wedge-shaped hairs of the reticule.
3. Centimeters are read from the staff and millimeters from the micrometer
scale.
4. Invar staffs have two sets of graduations. These are read alternatively
between foresight and back sight. This provides two independent results and
