Equipment Review
Total stations are one of the most common
such as mapping software are able to deliver
surveying tools used today. They comprise
the
of an electronic theodolite and an electronic
measuring to mapping.
distance
metre/measurement
(EDM)
component. Robotic total stations are also
available which allow for single-person
operation by controlling the instrument using
a remote control.
Electronic
distance
measurement
1940, and was commercially available in the
1960s. The first total station (electronic
theodolite and EDM) was developed in the
late 1970s by Topcon.
Stations
surveying
package,
from
There are two methods of measuring
distance: the “prism” method, which uses a
reflective prism at the target measurement
point, and the “non-prism,” or “reflectorless,”
method that does not use a reflective prism.
equipment was initially developed around
Total
‘total’
use
With the “prism” method, a laser is beamed
at a reflective prism (also called a mirror)
placed at the measurement point, and the
distance is measured by the time it takes for
light to be reflected back from the prism.
Though this method is more accurate than
electronic
transit
the “reflectorless” method, it requires the
theodolites in conjunction with a distance
placing
meter to read any slope distance from the
measurement point, making it difficult to
instrument to any particular spot. They are
measure
hence two essential surveying instruments
diagonal surfaces, or inaccessible locations.
in one and when used with other technology
of
a
reflective
distances
to
prism
high
at
the
locations,
Total stations are not only used for
collecting surveys, but also for setting out
designs. Using a prism on a plumbing pole
(and usually an offsider), a surveyor can
determine where pegs need to be placed
using the instrument and the design which
would have been saved onto a storage
card/device by simply pointing at the
prism. Most total stations have set-out
features and can use loaded design
information to determine where the prism
is located with reference to the design
lines, and provide information on the offset
and chainage for the position of the prism
(therefore telling where the pole needs to
be moved to be in the correct position).
And did you know that a traditional
problem for surveyors is simply wet paper?