Total Station is an equipment used in surveying, designed for measuring horizontal and vertical angles, inclusive of measuring sloping distance of object to the instrument. It is a combination of electronic theodolite and electromagnetic distance measuring (EDM) instrument. It also consists of a micro-processor with a memory unit which deals with recordings, readings, and the fundamental calculation of measurements.
Components of a Total Station
TotalStation is a compact instrument which weighs around 50 N to 55 N. It consists of a distance measuring instrument (EDM), an angle measuring instrument (Theodolite) and a simple microprocessor. The components used in Total station surveying are as follows:
- A tripod is used to hold the total station
- An electronic notebook used to record, calculate and even manipulate the field data
- Prism and prism pole which can measure lengths up to 2 km and up to 6-7 km can be measured with triple prism
Currently there are approximately more than 40 different models available. Total-station are currently the most used instrument in the surveying field. Cheapest instrument is available in the range of 2000$ to 2500$. Leica is one of the most famous total-station manufacturers.
Basic Steps involved in Totalstation surveying
Step-1: Setting up the of the instrument along with the tripod
Step-2: Levelling of the instrument approximately with the help of “bull’s eye bubble” and then verifying the levelling electronically
Step-3: Adjustment of reticle focus and image.
Step-4: Recording all the measurements
Step-5: Data Processing
Functions of Total-Station
To measure horizontal and vertical angles, the electronic theodolite of device is used with an accuracy of 2-6 seconds. For horizontal measurement of angles, any direction can be taken as reference. In case of vertical measurement of angles, upward direction is taken as reference.
Distance Measurement in TotalStation:
To measure the distance, Electronic Distance Measuring (EDM) instrument of total station is used with an accuracy of 5-10 mm per km. The range of EDM varies from 2.8-4.2 km.
Computation of horizontal distances along with X, Y, Z coordinates is done by the instrument called Microprocessor. Hence, if atmospheric temperature and pressure is applied, the microprocessor applies suitable correction to the measurements.
Various software are available in the market which can be used to post-process the outputs from the device. Usually manufacturers provide their software which lets you export the survey results into other formats. Thus, output can be imported to CAD application or software like MX Roads.
Advantages of Total Station
The first and foremost advantage of using a Totalstation is that it saves time of work on the field. It understands and supports all the local languages. Setting up of the instrument on the tripod can be done easily and quickly by laser plummet. The accuracy of measurements is much higher in comparison to other conventional surveying instruments.
Computerization of old maps can be achieved by Totalstation. The computed data can be saved and simultaneously transferred to the computer. No writing or recording errors can be detected since everything is computerized. With the help of data accumulated from Total-station, map making and contour plotting can also be done. Correction for temperature and pressure can also be made.
The working conditions of the totalstation should be checked beforehand by the surveyor before using it. The cost price of the instrument is higher than the other surveying instruments. Checking for errors or other things during the operation is slightly difficult for the surveyor. Essentially, skilled surveyors are required to handle it since it is a sophisticated instrument to operate.
Applications of Totalstation
- General purpose of angle and distance measurements.
- Plotting of contours
- Illustration of detailed maps
- Carrying out controlled surveys
- Archaeologists use total station to record excavations
- Police use it in crime scene investigations to take measurements of the scene
- Used to fix the missing pillars
- Remote Distance Measurement (RDM)
- Missing Line Measurement (MLM)
- Remove Elevation Measurement (REM)