TOTAL STATION USES AND ITS ADVANTAGES
The Total station is designed
for measuring of slant distances, horizontal and vertical angles and
elevations,measurement results can be recorded into the internal memory and
transferred to a personal computer interface.
Angles and distances are
measured from the total station to points under survey, and the coordinates (X,
Y, and Z or northing, easting and elevation) of surveyed points relative to the
total station position are calculated using trigonometry and triangulation.
Data can be downloaded from the
total station to a computer and application software used to compute results
and generate a map of the surveyed area.
A total station is
an electronic/optical instrument used in modern surveying. It is also used by
archaeologists to record excavations as well as by police, crime scene
investigators, private accident Reconstructionists and insurance companies to
take measurements of scenes.
The total station is an
electronic theodolite (transit) integrated with an electronic distance meter
(EDM), plus internal data storage and/or external data collector.
The purpose of any survey is to
prepare maps, control points formed a basic requirement for the preparation of
these maps.
(i)
Distance measuring instrument (EDM).
ii) An angle measuring instrument (Theodolite).
iii) A simple microprocessor.
Instrumentation:
It consists of an EDM, Theodolite, Microprocessor combined into
one. It also has a memory card to store the data. It also consists
of battery socket which houses the battery. A fully charged battery works
for about 3 to 5 hrs continuously. 
Accuracy depending upon the
instrument and varies from instrument to instrument
1.The angular accuracy varies
from1″ to 20 ″.
2.Distance accuracy depends
upon two factors.
Instrumental error which ranges
from + / – 10mm to + / – 2mm.
Accuracy & Precision
• Precision is the
reproducibility of the measurement.
• Accuracy is how close the
measured position is to the actual location
Measurement
of distance is accomplished with a modulated microwave or infrared carrier
signal, generated by a small solid-state emitter within the instrument’s
optical path, and reflected by a prism reflector or the object under survey.
The modulation pattern in the returning signal is read and interpreted by the
onboard computer in the total station. The distance is determined by emitting
and receiving multiple frequencies, and determining the integer number of
wavelengths to the target for each frequency. Most total stations use
purpose-built glass Porro prism reflectors for the EDM signal, and can measure
distances to a few kilometers. Reflectorless total stations can measure
distances to any object that is reasonably light in color, to a few hundred
meters.
Principle:
Given
the co-ordinate of the instrument position and bearing of a backward station
the co-ordinates of any other point can be computed.
Total station can be used
When two points are given.
When only one co-ordinate is
given. In this case the coordinate of the back station is determined by any
suitable method.
When no co-ordinates were given
in which case arbitrary system of coordinates can be used.
These
devices, also called electronic Tachometers, can automatically measure
horizontal and vertical angles as well as slope distances from a single
set up. From these data they can instantaneously compute horizontal and
vertical distance components, elevations, and coordinates, and display the
results on LCD.
They
can also store the data, either on board or in external data
collectors. If the coordinates of the occupied station and a reference
azimuth are input to the system, the coordinates of the sighted point are
immediately obtained.
This
information can be directly stored in an automatic data collector, there by
eliminating manual recording.
These
instruments are of tremendous value in all types of surveying. Total
Stations offer many advantages for almost all types of surveying. They
are used for topographic, Hydrographic, cadastral, project and construction
surveys.
The EDM instrument component
installed in a Total Station is relatively small but still has distance ranges
adequate for most work. Lengths up to about 2 km can be measured with a
single prism, and up to about 6 to 7 km with triple prism.
The
angle resolution of available Total Stations varies from as low as a
half-second for precise instruments suitable for control surveys, up to 20″ for
instruments made specifically for construction stakeout .
Applications of Total Station
There are many other facilities
available, the total station can be used for the following
purposes.
Detail survey i.e., data
collection.
Control Survey (Traverse).
Height measurement (Remove
elevation measurement- REM).
Fixing of missing pillars (or)
Setting out (or) Stake out.
Resection.
Area calculations, etc.
Remote distance measurement
(RDM) or Missing line measurement (MLM).
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