In field survey, use of electronics-based instruments is now so widespread that it would be difficult to imagine any contemporary site surveying without it.
The recent applications of electronics in surveying instruments have enabled surveyors to collect and process field data much more easily and to a higher precision than is possible using routine instruments.
Definition of Total Station
A total-station is an optical instrument used as a primary contrivance for modern surveying.
It is a combination of an electronic theodolite (transit), an electronic distance meter (EDM) and software running on an external computer known as a data collector.
When these instruments are combined and interfaced with EDMS and electronic data collectors, they become total-stations or electronic tacheometers (ET).
Methodology
With a total-station one may determine horizontal and vertical angles together with slope distances from the instrument to points to be surveyed.
With the aid of trigonometry and triangulation, the angles and distances may be used to calculate the coordinates of actual positions (X, Y, and Z or northing, easting and elevation) of surveyed points, or the position of the instrument from known points, in absolute terms. These are operated using a multi-function keyboard which is connected to a microprocessor built into the instrument.
The microprocessor in the total-station can not only perform a variety of matnematical operations-for example, averaging multiple angle measurements, averaging muitiple distance measurements, calculation of rectangular coordinates, calculation Slope corrections, distances between remote points, remote object elevations, atmospheric and instrumental corrections but in some cases, can also store observations directly using an internal memory.
Many total-stations also enabled with a GPS interface.
GPS technology has advantageously been used in total-stations.
The use of GPS enhances the capability of a total-station as the line of sight is not required between points to be measured, and as compared to a traditional total-station, high precision for the measurement is enhanced especially in the vertical axis compared with GPS. These reduce the consequences of each technology's disadvantages, ie, GPS for poor accuracy in the vertical axis and lower accuracy without long occupation periods, and total-station which requires line of sight observations and must be set up over a known point or within a line of sight of two or more known points.
Modern Technology
Most modern total-station instruments measure angles by means of electro-optical scanning of extremely precise digital bar-codes etched on rotation glass cylinders or discs within the instrument.
The best-quality total-stations are capable of measuring angles down to 0.5 arc-second.
The low-cost construction-grade total-stations can generally measure angles up to 5 or 10 arc-seconds. 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 bounced off of the object to be measured.
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 a purpose-built glass Porro prism as the reflector for the EDM signal, and can measure distances out to a few kilometers, but some instruments are reflectorless, and can measure distances to any object that is reasonably light in color, out to a few hundred meters.
The typical total-station EDM can measure distances accurate to about 3 millimeters or 1/100th of a foot. Moreover, some modern total-stations are 'robotic' allowing the operator to control tne instrument from a distance via remote control. This eliminates the need for an assistant staff member to hold the reflector prism over the point to be measured.
The operalor holds the reflector him-herself and controls the total-station instrument from the Observed points. Though a number of companies are manufacturing total-stations, to acquaint the reader, Leica TCA 1800 and Nikon C-100 total-stations.
The recent applications of electronics in surveying instruments have enabled surveyors to collect and process field data much more easily and to a higher precision than is possible using routine instruments.
Definition of Total Station
A total-station is an optical instrument used as a primary contrivance for modern surveying.
It is a combination of an electronic theodolite (transit), an electronic distance meter (EDM) and software running on an external computer known as a data collector.
When these instruments are combined and interfaced with EDMS and electronic data collectors, they become total-stations or electronic tacheometers (ET).
Methodology
With a total-station one may determine horizontal and vertical angles together with slope distances from the instrument to points to be surveyed.
With the aid of trigonometry and triangulation, the angles and distances may be used to calculate the coordinates of actual positions (X, Y, and Z or northing, easting and elevation) of surveyed points, or the position of the instrument from known points, in absolute terms. These are operated using a multi-function keyboard which is connected to a microprocessor built into the instrument.
The microprocessor in the total-station can not only perform a variety of matnematical operations-for example, averaging multiple angle measurements, averaging muitiple distance measurements, calculation of rectangular coordinates, calculation Slope corrections, distances between remote points, remote object elevations, atmospheric and instrumental corrections but in some cases, can also store observations directly using an internal memory.
Many total-stations also enabled with a GPS interface.
GPS technology has advantageously been used in total-stations.
The use of GPS enhances the capability of a total-station as the line of sight is not required between points to be measured, and as compared to a traditional total-station, high precision for the measurement is enhanced especially in the vertical axis compared with GPS. These reduce the consequences of each technology's disadvantages, ie, GPS for poor accuracy in the vertical axis and lower accuracy without long occupation periods, and total-station which requires line of sight observations and must be set up over a known point or within a line of sight of two or more known points.
Modern Technology
Most modern total-station instruments measure angles by means of electro-optical scanning of extremely precise digital bar-codes etched on rotation glass cylinders or discs within the instrument.
The best-quality total-stations are capable of measuring angles down to 0.5 arc-second.
The low-cost construction-grade total-stations can generally measure angles up to 5 or 10 arc-seconds. 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 bounced off of the object to be measured.
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 a purpose-built glass Porro prism as the reflector for the EDM signal, and can measure distances out to a few kilometers, but some instruments are reflectorless, and can measure distances to any object that is reasonably light in color, out to a few hundred meters.
The typical total-station EDM can measure distances accurate to about 3 millimeters or 1/100th of a foot. Moreover, some modern total-stations are 'robotic' allowing the operator to control tne instrument from a distance via remote control. This eliminates the need for an assistant staff member to hold the reflector prism over the point to be measured.
The operalor holds the reflector him-herself and controls the total-station instrument from the Observed points. Though a number of companies are manufacturing total-stations, to acquaint the reader, Leica TCA 1800 and Nikon C-100 total-stations.
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