Measuring by Light Wave Devices
The light wave measuring device (fig. 12-25)
uses electro-optical instruments to measure
distances accurately. The device consists basically
of two units: the measuring unit (transmitter/
receiver) and the reflector unit (fig. 12-26). The
distance is measured by precise electronic timing
of a modulated LIGHT WAVE after it travels to,
and when it returns from, a reflector at the other
end of a course (fig. 12-27). When the instrument
receives the reflected light flash, it registers
readings that can be converted into the linear
distance between the instrument and the reflector
(with corrections made for atmospheric condi-
tions).
Like their microwave counterparts, the light
wave distance-measuring devices are capable of
first order base lines in triangulation and all orders
of traverse distance measurements. Most of these
instruments have a rated range of 200 to 50,000
meters.
These instruments, as all delicate scientific
equipment, are to be treated with proper care and
operator maintenance so that they may continue
to be available for use. Refer to the instrument
manufacturer’s manual for instructions on basic
operation, care, adjustments, calibrations, and
other details of the system.
FIELD PARTY SAFETY
A surveying field party is frequently working
its way through rugged terrain a long distance
away from any professional medical assistance.
Working through brush, felling trees, scaling
bluffs, and crossing streams are all hazardous.
Also, the use of such sharp-edged tools as
machetes, brush hooks, axes, and hatchets is
equally hazardous. Besides those dangers that are
inherent in the work itself, a party may be exposed
to a variety of natural dangers, such as those
created by weather conditions, by reptiles, by
insects, and by poisonous plants. Occasionally,
in some areas, there may be dangerous wild
animals or even dangerous domestic animals, such
as vicious dogs or angry bulls. When a party is
working along a thoroughfare on which vehicular
Figure 12-25.-A light wave distance-measuring device (Geodimeter, Model 2A).
12-26
