When it comes to surveying land, there are a variety of techniques available. One popular method is plane table surveying, but how does it compare to other methods? In this article, we’ll take a close look at how plane table surveying stacks up against techniques like total station and GPS surveying. We’ll dive into the advantages, disadvantages, and when it’s best to use each one.
By the end of this article, you’ll have a clear understanding of the different surveying methods and be able to decide which is best for your project. Let’s get started!
What Is Plane Table Surveying?
Plane table surveying is a method of surveying that uses a plane table, an instrument with a flat surface on which a sheet of paper or map is placed. The surveyor positions the plane table at various points on the land being surveyed and draws the features observed. The surveyor then uses a sighting device to measure angles and distances from each point.
This technique is most often used for small-scale surveys and is especially effective when working in areas where it’s difficult to use other methods, like dense forests or rough terrain.
How Does Plane Table Surveying Work?
Plane table surveying works by setting up the plane table at different stations across the land. Here’s how the process generally unfolds:
- Setting up the Table: The plane table is positioned at a survey station, typically a known location on the land.
- Drawing the Map: The surveyor aligns the table with the land’s features. A sighting device, like an alidade, is used to determine the direction of various points on the land. The surveyor then draws the features of the land based on the observations.
- Measuring Distances: Distances between points are usually measured using a chain or tape, and the angles between those points are measured using a theodolite or other similar device.
The process continues by moving the table to different stations until a full map or survey of the area is completed.
How Does Plane Table Surveying Compare to Other Surveying Techniques?
Now that we have a basic understanding of plane table surveying, let’s compare it with other common surveying methods, such as total station and GPS surveying.
1. Plane Table Surveying vs. Total Station Surveying
Total stations are modern instruments that combine electronic theodolites and electronic distance measurement (EDM) equipment. They offer a highly accurate way to measure distances, angles, and elevations. Here’s a breakdown of how they compare:
Advantages of Total Station Surveying:
- Accuracy: Total stations offer high precision when measuring angles and distances, even over long distances.
- Efficiency: The process is faster because data is recorded electronically and can be directly transferred to a computer for further analysis.
- Versatility: Total stations can be used for various types of surveys, including land, construction, and mining surveys.
Drawbacks of Total Station Surveying:
- Cost: Total stations are more expensive than plane tables, making them less ideal for small-budget projects.
- Training: Proper use of a total station requires specialized training and knowledge of the software and equipment.
Plane Table Surveying:
- Advantages: Plane table surveying is a more affordable option and is easier to set up, especially in rough terrain. It also provides immediate visual representation of the area.
- Drawbacks: The accuracy is generally lower than total station surveying, and it can be time-consuming, particularly for larger areas.
2. Plane Table Surveying vs. GPS Surveying
GPS surveying uses satellites to determine precise locations on Earth. This method is particularly useful for large-scale surveys where high accuracy is required, such as for mapping cities or highways.
Advantages of GPS Surveying:
- Global Coverage: GPS works anywhere on Earth, which makes it perfect for large-scale surveys.
- Ease of Use: GPS systems are user-friendly and provide real-time data.
- Accuracy: GPS surveying can achieve a very high degree of accuracy, especially when using differential GPS (DGPS) systems.
Drawbacks of GPS Surveying:
- Cost: High-accuracy GPS equipment can be expensive.
- Signal Issues: GPS accuracy can be compromised in dense forests, urban canyons, or mountainous regions where satellite signals may be blocked.
Plane Table Surveying:
- Advantages: Plane table surveying does not rely on satellite signals and can be used in areas with poor GPS coverage.
- Drawbacks: Plane table surveys are much slower and can be less accurate, especially over long distances.
3. Plane Table Surveying vs. Traditional Chain Surveying
Chain surveying is one of the oldest methods of surveying and involves measuring distances using a chain or tape measure. Angles are typically measured with a compass or theodolite.
Advantages of Chain Surveying:
- Simplicity: The technique is straightforward and doesn’t require complex equipment.
- Affordability: Chain surveying is one of the cheapest surveying methods.
- Accuracy: For small, relatively simple surveys, chain surveying can provide adequate accuracy.
Drawbacks of Chain Surveying:
- Limited to Small Areas: Chain surveying is not practical for large, complex areas due to the difficulty in measuring angles and distances accurately over long stretches.
- Labor Intensive: The process is slow and requires more manpower.
Plane Table Surveying:
- Advantages: Plane table surveying is a more detailed method compared to chain surveying and is better suited for mapping complex features.
- Drawbacks: It’s more time-consuming and requires the surveyor to manually sketch out the features of the land, which can be slow.
Benefits of Plane Table Surveying
While it may not be as precise as modern techniques, plane table surveying offers a unique set of advantages. Let’s take a look at the key benefits of this method:
1. Affordability
Plane table surveying is one of the most affordable surveying techniques available. The equipment is inexpensive compared to high-tech devices like total stations and GPS units, making it an attractive option for budget-conscious projects.
2. Simplicity
The setup and use of a plane table are relatively simple. This method does not require complicated software or electronic devices, which makes it easier for surveyors with less technical experience to use.
3. Immediate Results
With plane table surveying, surveyors can see results immediately. As the features are drawn in real time, there’s no need to wait for data to be processed or analyzed, which speeds up the overall process.
4. Adaptability in Difficult Terrain
Unlike some modern methods, plane table surveying doesn’t require a clear line of sight to satellites or advanced equipment. This makes it especially useful in challenging terrains, such as dense forests or remote mountain areas, where GPS and other high-tech methods might struggle.
Drawbacks of Plane Table Surveying
Despite its advantages, plane table surveying does have its limitations:
1. Limited Accuracy
Plane table surveying tends to have lower accuracy compared to total station or GPS surveying. The measurements of angles and distances are prone to human error, and the method is not ideal for large-scale or highly detailed surveys.
2. Time-Consuming
While the results are immediate, the process can be slow, especially for large areas. Each point must be drawn manually, and the surveyor must move the plane table to multiple stations, which adds to the time it takes to complete the survey.
3. Labor-Intensive
Plane table surveying requires more physical labor than other techniques. Surveyors need to carry and set up the plane table at each station, which can be tiring and slow down the overall process.
When Is Plane Table Surveying the Best Option?
While plane table surveying might not be suitable for every project, it does have some ideal applications:
- Small-Scale Surveys: Plane table surveying is perfect for smaller surveys where high precision is not a critical factor.
- Remote or Difficult Terrain: If you are working in a location where GPS or total station surveying may not be feasible, plane table surveying can be a useful alternative.
- Budget-Friendly Projects: If you’re working on a tight budget, plane table surveying offers a cost-effective solution.
Conclusion
Plane table surveying is a tried-and-true method with a long history in the world of surveying. While modern techniques like total station and GPS surveying offer more precision and efficiency, plane table surveying still holds value in certain situations, particularly for small-scale projects or difficult terrains.
If you’re deciding which surveying method to use, consider the size of your project, your budget, and the terrain of your area. For simple surveys, plane table surveying might be your best option. However, for larger projects requiring higher precision, a total station or GPS might be the better choice.
Remember, each method has its place, and knowing when to use each one will ensure the best results for your surveying needs!
FAQs
- What is the main advantage of plane table surveying?
- Plane table surveying is cost-effective and suitable for small-scale surveys and areas with difficult terrain.
- Is plane table surveying accurate?
- It offers lower accuracy compared to modern methods like total station and GPS surveying.
- How long does plane table surveying take?
- It can be time-consuming, especially for larger areas, as the surveyor must manually draw features.
- Can plane table surveying be used in urban areas?
- Yes, but it may be less efficient in urban settings where more advanced equipment is available.
- Is plane table surveying suitable for large-scale surveys?
- Not usually, as it lacks the precision needed for large-scale, detailed surveys.
- What equipment is used in plane table surveying?
- A plane table, alidade, chain or tape for measuring distances, and sometimes a theodolite for measuring angles.
- Can plane table surveying be done alone?
- Yes, but it’s more efficient with a team, especially when large areas are being surveyed.
- What type of surveys is plane table surveying best for?
- Small-scale or preliminary surveys, especially in challenging terrains.
- Does plane table surveying require GPS?
- No, it does not rely on GPS or satellites.
- How do you set up a plane table?
- Position the table at a survey station, align it with the land’s features, and use a sighting device to measure angles and distances.
