What is a Total Station?

Total station is a surveying equipment combination of Electromagnetic Distance Measuring Instrument and electronic theodolite. It is also integrated with microprocessor, electronic data collector and storage system. The instrument can be used to measure horizontal and vertical angles as well as sloping distance of object to the instrument.

Capability of a Total Station:

Microprocessor unit in total station processes the data collected to compute:

1. Average of multiple angles measured.
2. Average of multiple distance measured.
3. Horizontal distance.
4. Distance between any two points.
5. Elevation of objects and
6. All the three coordinates of the observed points.

Data collected and processed in a Total Station can be downloaded to computers for further processing.

Total station is a compact instrument and weighs 50 to 55 N. A person can easily carry it to the field. Total stations with different accuracy, in angle measurement and different range of measurements are available in the market. Figure below shows one such instrument manufactured by SOKKIA Co. Ltd. Tokyo, Japan.

Important Operations of Total Station:

Distance Measurement

Electronic distance measuring (EDM) instrument is a major part of total station. Its range varies from 2.8 km to 4.2 km. The accuracy of measurement varies from 5 mm to 10 mm per km measurement. They are used with automatic target recognizer. The distance measured is always sloping distance from instrument to the object.

Angle Measurements

The electronic theodolite part of total station is used for measuring vertical and horizontal angle. For measurement of horizontal angles any convenient direction may be taken as reference direction. For vertical angle measurement vertical upward (zenith) direction is taken as reference direction. The accuracy of angle measurement varies from 2 to 6 seconds.

Data Processing

This instrument is provided with an inbuilt microprocessor. The microprocessor averages multiple observations. With the help of slope distance and vertical and horizontal angles measured, when height of axis of instrument and targets are supplied, the microprocessor computes the horizontal distance and X, Y, Z coordinates.

The processor is capable of applying temperature and pressure corrections to the measurements, if atmospheric temperature and pressures are supplied.

Display

Electronic display unit is capable of displaying various values when respective keys are pressed. The system is capable of displaying horizontal distance, vertical distance, horizontal and vertical angles, difference in elevations of two observed points and all the three coordinates of the observed points.

Electronic Book

Each point data can be stored in an electronic note book (like compact disc). The capacity of electronic note book varies from 2000 points to 4000 points data. Surveyor can unload the data stored in note book to computer and reuse the note book.

 

ADVANTAGES OF TOTAL STATION:

1. Quick setup of the instrument on the tripod by utilizing the laser plummet.

2. Programmed with on board area computation for computing the area of a field.

3. It supports local languages.

4. It shows the graphical view of land and plots.

5. No recording and writing errors.

6.It gives more accurate measurements than other conventional surveying instruments.

7. Data can be saved and transferred to a PC.

8. It has integrated database.

9. Computerization of old maps.

10. All in one and multitasking instrument, from surveying to GIS creation by using the appropriate software.

11. Faster work, saves time, quick finishing off the job.

 

DISADVANTAGES OF TOTAL STATION:

1. The instrument is costlier than other conventional surveying instruments.

2. It might be troublesome for the surveyor to investigate and check the work when surveying.

3. Working with total station is not so easy, as more skilled surveyors are required to conduct a total station survey.

4. To check the survey work thoroughly it would be necessary to come back to the office and prepare the drawings by using the right software.