Plane table surveying is a graphical method of surveying that allows for simultaneous fieldwork and plotting. This method relies on a plane table and accessories to map topographic features, which are visible during the survey. Its efficiency in small-scale projects and unique suitability for certain environments make it a popular choice in surveying. Below, we explore the major advantages and disadvantages of plane table surveying.
Advantages of Plane Table Surveying
Plane table surveying offers several notable benefits that make it an effective choice for certain surveying projects:
1. Ideal for Small-Scale Mapping
This method is widely regarded as one of the most effective for creating small-scale maps, making it a preferred choice for local and specific area surveys.
2. Error Elimination
By performing surveying and plotting simultaneously in the field, the risk of human and machine errors is minimized. This direct approach avoids discrepancies that can arise from separate surveying and data recording processes.
3. Reliable in Areas with Magnetic Fluctuations
Unlike compass-based surveys, plane table surveying is not affected by magnetic interferences, making it suitable for regions with high magnetic fluctuations.
4. Cost-Effective
As plane table surveying does not rely on machinery, it is less expensive than many modern surveying methods. This simplicity makes it accessible for smaller or budget-limited projects.
5. Rapid Execution
This method is known for its speed, as the simultaneous plotting saves time compared to processes that involve separate fieldwork and office plotting.
6. Avoids Field Book Entry Errors
Errors that can occur during data entry in a field book are eliminated since plotting occurs directly in the field.
7. Accurate Representation
Contours and irregular features can be represented with high accuracy because the surveyor has a direct view of the landscape during mapping.
8. No Need for Skilled Personnel
Plane table surveys do not require highly trained personnel, as the plotting is straightforward and can be performed by individuals with basic training.
9. Error Checking Through Check Lines
Plotting errors can be identified and corrected in the field by using check lines, ensuring greater reliability in the results.
Disadvantages of Plane Table Surveying
While plane table surveying has its advantages, there are several limitations to consider:
1. Lengthy Shifting and Re-Orientation
Moving and re-aligning the plane table for each new location can be a time-consuming process, particularly for larger projects.
2. Weather Dependency
This method is impractical in rainy or windy conditions, as plotting is performed directly in the field and can be disrupted by adverse weather.
3. Portability Issues
The plane table and its accessories are bulky and difficult to transport, which can limit its use in remote or rugged terrains.
4. Lower Accuracy
Plane table surveying does not achieve the same level of accuracy as other modern surveying techniques, such as total station or GPS-based methods.
5. Challenges in Replotting or Scaling
Without field notes, replotting maps at different scales or computing specific quantities can be inconvenient and difficult.
6. Unsuitable for Large Areas
This method is not practical for surveying large areas due to the time and effort required to shift and re-orient the equipment.
7. Limited Use in Dense Forests
Dense forests present a significant challenge for plane table surveying because trees obstruct the view of critical components of the field.
8. Daylight Dependency
Plane table surveying can only be conducted during daylight hours, limiting its operational flexibility.
Conclusion
Plane table surveying is an efficient and cost-effective method for small-scale surveys, particularly in areas with magnetic disturbances or where contour representation is crucial. However, its limitations, including dependency on weather, portability challenges, and restricted accuracy, must be considered when choosing this method. Ultimately, plane table surveying is best suited for specific project types where its advantages outweigh its drawbacks. By understanding its strengths and weaknesses, surveyors can make informed decisions about its use in their projects.