1. EXPLAIN
BASIC RULES IN PRACTICE WHEN CONDUCTING A LEVELING
BASIC RULES IN PRACTICE WHEN CONDUCTING A LEVELING
Levelling is the process of measuring the difference
in elevation between two or more points. In engineering surveying, levelling
has many application and is used at all stages in construction projects from the
initial site survey through the final setting out. In practice, it is possible
to measure heights to better than a few millimeters when levelling this precision is more than adequate for height measurement
on the majority of civil engineering project.
in elevation between two or more points. In engineering surveying, levelling
has many application and is used at all stages in construction projects from the
initial site survey through the final setting out. In practice, it is possible
to measure heights to better than a few millimeters when levelling this precision is more than adequate for height measurement
on the majority of civil engineering project.
The basic rules in practice when
conducting a levelling fieldwork should be adhered to if many of the sources of
error are to be avoided. Levelling should always start and finish at points of known reduced level so that
misclosures can be detected. When only one bench mark is available, levelling
lines must be run in loops starting and finishing at the bench mark.
conducting a levelling fieldwork should be adhered to if many of the sources of
error are to be avoided. Levelling should always start and finish at points of known reduced level so that
misclosures can be detected. When only one bench mark is available, levelling
lines must be run in loops starting and finishing at the bench mark.
Where
possible, all sights length should below 50m. The staff must be held vertically
by suitable use of a circular bubble or by rocking the staff and notong the
minimum reading. Backsight and fortsight length should be equal for each
instrument position. For engineering application, many intermediate sight
readings may be taken from each set- up. Under this circumstances it is
important that the level has no more than a small collimation error.
possible, all sights length should below 50m. The staff must be held vertically
by suitable use of a circular bubble or by rocking the staff and notong the
minimum reading. Backsight and fortsight length should be equal for each
instrument position. For engineering application, many intermediate sight
readings may be taken from each set- up. Under this circumstances it is
important that the level has no more than a small collimation error.
Reading
should book immediately after they are observed and important readings,
particularly at change points, should be checked. The rise and fall method of
reduction should used when heighting reference or change points and the HPR method ( height of
collimation) should be used for contouring , sectioning and setting out
applications.
should book immediately after they are observed and important readings,
particularly at change points, should be checked. The rise and fall method of
reduction should used when heighting reference or change points and the HPR method ( height of
collimation) should be used for contouring , sectioning and setting out
applications.
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