Environmental Engineering Reference
In-Depth Information
Fig. 2.11 An example of
rotating laser equipment,
which can be used by a single
person
is the difference between c and d. Therefore, absolute value of (a-b) should equal
absolute value (c-d). If they vary by more than a few mm, consider instrument
calibration prior to surveying.
2.3.2.3 Rotating Level Laser
A direct substitute for an autolevel is a rotating laser level (Fig.
2.11
). A rotating
laser level performs a similar function, but emits a laser (usually red) that can be
used to measure the vertical distance from a level plane created by the spinning
laser beam. The same notes and data are taken (e.g., HI, FS, and BS), and horizontal
control is still provided by the tape grid, but a rotating laser replaces the autolevel
on the tripod. Some rotating level lasers have self-leveling servo motors, while
others must be leveled by hand using an integrated bubble level and three leveling
screws. Once leveled, the rotating laser emits a laser beam from a lens that is
spinning about a vertical axis. The beam describes a horizontal plane that represents
HI. There is a laser sensor attached to the survey rod that emits a beeping sound
when the beam hits the sensor. The rod end is placed on the BM or wetland surface,
and the rod is telescoped up or down until the sensor cuts the laser. Then, the rod
reading gives the distance from HI to the ground surface as before.
