Total Station in Surveying

In the world of construction and civil engineering, accurate surveying is essential for the success of any project. The total station has revolutionised surveying by combining electronic distance measurement (EDM), angle measurement, and data recording into a single device. This advanced instrument enables surveyors to perform tasks with precision and efficiency. In this blog, we will discuss the total station, its working principles, applications, and relevant IS codes for surveying in India.

What is a Total Station?

A total station is an integrated electronic instrument used for measuring angles, distances, and coordinates. It is equipped with a microprocessor, data storage, and processing capabilities, making it a versatile tool for both field and office work.

The total station replaces traditional surveying instruments like theodolites, dumpy levels, and measuring tapes, providing enhanced accuracy and convenience.

components of a total station

The components of a total station are as follows:

1. Telescope
   • Used for sighting the target.
   • Enables precise angle measurements and focusing on distant objects.
2. Electronic Distance Measurement (EDM)
   • Measures the distance between the instrument and the target using infrared or laser beams.
3. Levelling Head and Tribrach
   • Helps in levelling the total station using levelling screws.
   • Tribrach allows easy mounting and detachment from the tripod.
4. Horizontal and Vertical Circles
   • Measures horizontal and vertical angles electronically.
5. Data Storage and Processing Unit
   • Records all measurements digitally.
   • Includes a microprocessor for data calculations and storage.
6. Control Panel and Display Screen
   • Features a keypad and a display for input and output of data.
   • Provides user-friendly interaction for surveyors.
7. Battery
   • Powers the total station for field operations.
   • Usually rechargeable for convenience.
8. Plummet (Optical or Laser)
   • Used for centring the total station over a survey point accurately.
9. Reflector and Prism
   • Reflects the signal sent by the EDM for accurate distance measurement.
10. Tripod
    • Provides a stable platform for the total station during operation.
11. Communication Ports
    • USB, Bluetooth, or Wi-Fi connectivity for data transfer to external devices.

These components work together to provide accurate angle, distance, and coordinate measurements, making the total station an indispensable tool in surveying.

Features of a Total Station

• Angle Measurement: Horizontal and vertical angles are measured electronically.
• Distance Measurement: Uses EDM technology to measure distances with high accuracy.
• Data Storage: Records measurements digitally for easy processing.
• Integration with GPS: Some total stations integrate with GPS for advanced geodetic surveys.

Working of a Total Station

The total station operates in three primary steps:

1. Setting Up the Instrument

• Mount the total station on a tripod and level it using the levelling screws and spirit bubble.
• Centre the instrument precisely over the survey point using a plumb bob or laser plummet.

2. Measuring Angles and Distances

• Horizontal and Vertical Angles: The telescope of the total station is aimed at the target point, and the angles are recorded electronically.
• Distances: The instrument emits an infrared or laser beam towards a reflector, and the reflected signal is used to calculate the distance.

3. Data Recording and Processing

• Measurements are stored in the total station’s memory or an external device.
• The data can be transferred to a computer for further analysis using specialised software.

Steps for Surveying with a Total Station

1. Reconnaissance
   • Inspect the site and mark survey points based on the requirements of the project.
2. Station Setup
   • Set up the total station at a known point with proper levelling and centring.
3. Backsighting
   • Take a backsight reading to a reference point for orientation.
4. Measurement
   • Aim the telescope at the target points and measure angles and distances.
   • Record the readings electronically.
5. Data Processing
   • Transfer the recorded data to a computer and process it using software like AutoCAD or GIS.
6. Plotting
   • Use the processed data to generate plans, contours, or 3D models.

Formulas Used in Total Station Surveying

1. Horizontal Distance (D):

D=S⋅cos(θ)

           where:

• S = slope distance
• θ = vertical angle
  2.Elevation Difference (h):

h=S⋅sin⁡(θ)

          where:

• S = slope distance
• θ = vertical angle

  3.Coordinates of a Point (X,Y):

X=X₀+D⋅cos⁡(α)

Y=Y_0​+D⋅sin(α)

           where:

• X₀,Y₀​ = coordinates of the known point
• D = horizontal distance
• α = horizontal angle

Relevant IS Codes for Surveying in India

• IS 1892:1979: Code of practice for subsurface investigations.
• IS 4880 (Parts 1 to 5): Recommendations for underground construction in rock.
• IS 14858:2000: Standard for total station instruments and their calibration.

Applications of Total Station in Surveying

1. Topographic Surveys
   • Create detailed maps showing natural and man-made features.
2. Construction Layouts
   • Mark positions of foundations, columns, and other structures on-site.
3. Boundary Surveys
   • Establish property lines for legal documentation.
4. Road and Railway Projects
   • Align routes and determine gradients accurately.
5. Volume Calculations
   • Measure excavation or fill quantities for construction.

Advantages of Using a Total Station

• High Accuracy: Ensures precision in measurements.
• Time-Saving: Combines multiple functions in one device.
• Ease of Use: Stores and processes data automatically.
• Versatility: Suitable for various types of surveys.
• Reduced Human Error: Minimises manual calculations.

Limitations of Total Station

• Cost: Initial investment is high.
• Training Requirement: Operators must be skilled in using the instrument.
• Line of Sight: Requires an unobstructed view between the instrument and target.

Conclusion

The total station is an indispensable tool in modern surveying, offering unparalleled accuracy and efficiency. Whether it’s for topographic mapping, construction layouts, or boundary surveys, this instrument has become a cornerstone of civil engineering projects. By adhering to IS codes and proper surveying practices, engineers can ensure reliable and accurate results.

Frequently Asked Questions

1. What is the typical accuracy of a total station?
   • Total stations provide angular accuracy up to 1 second and distance accuracy up to 1 mm.
2. Which IS code covers total station instruments?
   • IS 14858:2000 outlines standards for total stations.
3. What software is commonly used with total station data?
   • Software like AutoCAD, GIS, and Leica Geo Office are widely used.