Through the telescope
The aim of this tutorial is to demonstrate how to read a levelling staff that conforms to British Standard 4484.
Check that the staff is vertical.
It
is essential that readings are taken when the staff is vertical. If the
staff is not vertical the reading will be larger than it should be, as
you are measuring a slope distance, and will give errors.
Some staffs are fitted with a spherical spirit level and handles to help the staff person keep it vertical. Even with a spirit level it is difficult to hold a staff vertical. This difficulty increases in wind.
Staff
leaning forward
reading high
To
read the staff when vertical the surveyor use the vertical reticule line
to direct the staff person to move the top of the staff left or right
of the sight line.
The staff person then slowly tilts the top of the staff towards and away from the instrument so that it will pass through the vertical. The staff will appear to move up and down in the telescope field. The lowest reading is recorded as this is the point at which the staff is vertical.
Staff
vertical
lowest reading
Staff
leaning back
reading high
Now check your knowledge:
